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Bioenergy from plants and the sustainable yield challenge
New Phytologist
Abstract
Bioenergy from plants, particularly from perennial grasses and trees, could make a substantial contribution to alleviation of global problems in climate change and energy security if high yields can be sustained. Here, yield traits in a range of key bioenergy crops are reviewed, from which several targets for future improvement can be identified. Some are already the focus of genetically modified (GM) and non-GM approaches. However, the efficient growth strategies of perennial bioenergy crops rely on newly assimilated and recycled carbon and remobilized nitrogen in a continually shifting balance between sources and sinks. This balance is affected by biotic (e.g. pest, disease) and abiotic (e.g. drought) stresses. Future research should focus on three main challenges: changing (photo)thermal time sensitivity to lengthen the growing season without risking frost damage or limiting remobilization of nutritional elements following senescence; increasing aboveground biomass without depleting belowground reserves required for next year's growth and thus without increasing the requirement for nutrient applications; and increasing aboveground biomass without increasing water use.
... This makes it a renewable energy source, as long as the production and consumption of biomass are managed sustainably (Yuan et al. 2008). Using fossil fuels has long-term environmental impacts, including land degradation and the desertification of productive soils (Karp and Shield 2008), while biofuel helps to reduce greenhouse gas emissions and combat climate change (Wang et al. 2012b;Kim et al. 2013). In the transportation sector, biofuels serve as a lower-carbon substitute for fossil fuels, reducing vehicle emissions and facilitating the switch to more environmentally friendly modes of transportation (Malla et al. 2023). ...
... In the transportation sector, biofuels serve as a lower-carbon substitute for fossil fuels, reducing vehicle emissions and facilitating the switch to more environmentally friendly modes of transportation (Malla et al. 2023). Using fossil fuels has long-term environmental impacts, including land degradation and desertification of productive soils (Karp and Shield 2008). Biofuel crop production for bioenergy has become a promising solution for sustainable and renewable energy sources. ...
... N content is highest aboveground mid-season, but as plants senesce, nitrogen is translocated to the crown, rhizomes, and roots. Mature switchgrass forms a closed canopy and allocates a significant portion of photosynthetic products to maintain its large, active root system (Karp and Shield 2008). Under low N application, higher planting density in maize is associated with increased nitrogen use efficiency . ...
Biofuel crops play an important role in bioenergy production, providing a renewable and eco-friendly alternative to conventional fossil fuels. Minimal inputs are used to grow biofuel crops (sorghum, maize, sugarcane, poplar, and other grasses like panicum and miscanthus) on marginal and degraded land to avoid competition with arable crops. The high biomass production potential of these crops can be converted into biofuels like ethanol and biodiesel. Fast canopy capture with a profuse root system and photosynthetically efficient biofuel crops are reliable sources for bioenergy production. This chapter investigates the most recent research findings and advancements related to the comprehension and optimization of morpho-physiological traits for high bioenergy production in biofuel crops. Moreover, this chapter explains how biofuel crops attain heightened bioenergy yields and how morpho-physiological traits contribute to the production of substantial biomass. Overall, understanding these traits is crucial for harnessing the potential of biofuel crops for ideal bioenergy production.
... Bioenergy crops are pivotal in transitioning towards sustainable energy systems, offering renewable and carbon-efficient alternatives to fossil fuels. Among these, Miscanthus (Miscanthus × giganteus) and Willow (Salix spp.) stand out due to their high biomass yields and adaptability to various climatic conditions [1], and they have been subject to extensive recent breeding efforts [2][3][4]. Miscanthus, a perennial grass native to Asia and Africa, is recognised for its substantial biomass production and low input requirements. ...
... These areas provide consistent precipitation and optimal temperatures, which are crucial for robust growth. Similarly, Willow shows high productivity in tropical and subtropical regions, though with slightly lower maximum yields, reaching up to approximately 30 t ha −1 [1]. Despite this, Willow's ability to adapt to various climatic conditions is evident, as it performs well in temperate regions such as parts of Europe and the southeastern United States, much like Miscanthus [34]. ...
... Willow follows a similar pattern, with reduced productivity found in areas with medium to low suitability, such as parts of North America and Europe, where environmental factors are less ideal. The lowest productivity for both crops is observed in desert or arid environmental regions, areas of high latitudes, and mountainous ranges, underscoring their sensitivity to harsh environmental conditions [1,5]. The comparison between Miscanthus and Willow under current climate conditions highlights that while both crops can thrive in tropical and subtropical regions, Miscanthus generally demonstrates higher productivity. ...
Miscanthus (Miscanthus × giganteus) and Willow (Salix spp.) are promising bioenergy crops due to their high biomass yields and adaptability to diverse climatic conditions. This study applies the MiscanFor/SalixFor models to assess the sustainability of these crops under current and future climate scenarios, focusing on biomass productivity, carbon intensity (CI), and energy use efficiency (EUE). Under present conditions, both crops show high productivity in tropical and subtropical regions, with Miscanthus generally outperforming Willow. Productivity declines in less favourable climates, emphasising the crops’ sensitivity to environmental factors at the regional scale. The average productivity for Miscanthus and Willow was 19.9 t/ha and 10.4 t/ha, respectively. Future climate scenarios (A1F1, representing world markets and fossil-fuel-intensive, and B1, representing global sustainability) project significant shifts, with northern and central regions becoming more viable for cultivation due to warmer temperatures and extended growing seasons. However, southern and arid regions may experience reduced productivity, reflecting the uneven impacts of climate change. Miscanthus and Willow are predicted to show productivity declines of 15% and 8% and 12% and 7% under A1F1 and B1, respectively. CI analysis reveals substantial spatial variability, with higher values in industrialised and temperate regions due to intensive agricultural practices. Future scenarios indicate increased CI in northern latitudes due to intensified land use, while certain Southern Hemisphere regions may stabilise or reduce CI through mitigation strategies. Under climate change, CI for Miscanthus is projected to increase by over 100%, while Willow shows an increase of 64% and 57% for A1F1 and B1, respectively. EUE patterns suggest that both crops perform optimally in tropical and subtropical climates. Miscanthus shows a slight advantage in EUE, though Willow demonstrates greater adaptability in temperate regions. Climate change is expected to reduce EUE for Miscanthus by 10% and 7% and for Willow by 9% and 6%. This study underscores the need for region-specific strategies to optimise the sustainability of bioenergy crops under changing climate conditions.
... Such root systems are highly resistant to flooding, saturated soil, and a lack of oxygen (Karrenberg et al. 2002;Krasny et al. 1988). Salix can reproduce vegetatively and produce biomass (Carlson 1950;Karp and Shield 2008;Labrecque et al. 1997; Thomas et al. 2012). Furthermore, it is resistant to air and soil pollution and has an excellent ability to remediate contaminated soil by selectively absorbing cadmium (Cd) (Aronsson and Perttu 2001;Klang-Westin and Eriksson 2003;Labrecque et al. 1995). ...
... Because of these advantages, Salix is widely used as an ecosystem restoration material, such as disturbed landscape and riverbank stabilizer, and as a cost-effective material for biomass production (Kuzovkina and Quigley 2005;Kuzovkina and Vietto 2014). Salix is used for biomass production in Sweden, Canada, and the US, and various strategies such as breeding programs, cultivar development, and hybrid breeding are being studied to increase biomass productivity (Karp and Shield 2008;Kuzovkina and Vietto 2014;Smart and Cameron 2008;Smart et al. 2005;Serapiglia et al. 2013;Stanton et al. 2014;Volk et al. 2006). ...
The Salix genus of the Salicaceae family has advantages such as rapid initial growth, a high germination rate, and asexual reproduction; therefore, it is used as a short-rotation energy crop for biomass production. The National Institute of Forest Science created new interspecific hybrid cultivars with superior biomass production by artificially interbreeding Salix caprea L. and Salix gracilistyla Miq. Identifying these hybrids during the seedling stage is challenging because their separate reproductive and vegetative growth stages necessitate prolonged observation of their morphological characteristics. Consequently, a reliable identification method is required to overcome these limitations. This study aimed to develop nuclear DNA markers to distinguish between S. caprea , S. gracilistyla , and their interspecific hybrids. An evaluation of 35 nuclear simple-sequence repeat (nSSR) markers in the Salix genus revealed two markers that distinguish these parent species and their hybrids. A sequence analysis confirmed the presence of insertion-deletion (InDel) regions within the nSSR markers that differed between S. caprea and S. gracilistyla . To effectively identify hybrids, a primer set comprising the InDel region, which exhibited only interspecies differences and no intraspecies differences, was developed. The results of this study will facilitate the genetic resource management of interspecific hybrids between S. caprea and S. gracilistyla , thus allowing for early identification and improved management of hybrids.
... Biofuel produced from lignocellulosic biomass of plants, particularly perennial grasses and trees, is a promising and sustainable alternative to fossil fuels (McLaughlin et al., 2002;Karp & Shield, 2008). It has been projected that 30% of current US petroleum consumption will be replaced with bioethanol by 2030. ...
... For a successful biofuel production system, high biomass yield and processing quality with minimal and sustainable inputs of water, fertilizers, and other chemicals are desirable (Karp & Shield, 2008). Increases in switchgrass biomass production potential have been achieved via classical breeding (Sanderson et al., 2006), while transgenic and plant-microbe symbiotic approaches show promise in this regard (Ghimire et al., 2009;Fu et al., 2012). ...
... These harmful gases lead to long-term climate changes like acid rains, shift in temperatures, soil acidification contributing to the degradation of land, and also desertification of fertile soils. Hence, the fundamental reasons for alternative energy sources can be stated as climate change and the non-renewability of fossil fuels (Karp & Shield, 2008). For ages, plants have been serving various needs of the human population, being the primary producers in the food chain, and are irreplaceable and used as fuel (wood) for cooking and heating purposes, although fossil fuels and other sources (hydropower plants, nuclear power plants) of energy have replaced their role as fuel providers up to some extent. ...
... For ages, plants have been serving various needs of the human population, being the primary producers in the food chain, and are irreplaceable and used as fuel (wood) for cooking and heating purposes, although fossil fuels and other sources (hydropower plants, nuclear power plants) of energy have replaced their role as fuel providers up to some extent. But due to the nonrenewable nature of these other sources of energy and their harmful effects on the environment, once again, attention has shifted toward plants as a source of energy (Karp & Shield, 2008). Therefore, using bioenergy crops for energy production could be a possible alternative for fulfilling future energy needs. ...
Alternative sources of energy are the need of the hour since we are dependent upon traditional resources like fossil fuel for fulfilling our energy demands, but how long? The time has come when traditional sources of energy are depleting day by day and we are getting out of stock in terms of our energy. Using plants for the production of energy can be a good and efficient alternative that will be ecologically sustainable as well as financially stable for the ever-increasing population. This chapter focuses on such types of bioenergy crops, which can be the heroes of the coming generation in terms of energy production. Energy generated using bioenergy crops will be cleaner and cheaper, produce fewer greenhouses gases, and also help in carbon sequestration. Based on the roles played, the bioenergy crops can be divided into first generation, second generation, third generation, dedicated plants, and halophytes. Along with the multifaceted benefits like climate change, carbon sequestration, reduction in nitrous oxide emission and nitrate leaching, and restoration of ecological balance, there can be some challenges also in growing bioenergy crops. The challenges that we might be facing in growing bioenergy crops can be the competition for land and water with our main food crops, instability of the market for bioenergy crops, less economic incentives to produce and transport the bioenergy crops, and also the socioeconomic impacts. Despite the challenges associated, growing bioenergy crops can be beneficial in fulfilling the energy requirement of future generations.KeywordsEcosystemFossil fuelsBiofuelClimate changeCarbon sequestration
... However, due to growing political, social, and environmental concerns, both academic and industry groups have seen a large increase in recent years in research into significant energy [1]. Bioenergy is a viable substitute for conventional energy (fossil fuel) obtained from biological sources such as wood, crops, or animal feces [2]. According to the European Biogas Association's (EBA) most recent statistical report on the state of European biogas, published in 2021, the total number of biogas facilities operating in Europe was 18,774 and biogas is expected to account for 30-40% of total gas consumption in Europe by 2050 to reduce the dependency on conventional energy and the reduction of conventionally produced energy, i.e. fossil fuels [3]. ...
... This allows the correction for differences in initial element concentrations between mesophilic and thermophilic experiments originating from the inoculum ( Table 2) and the final evaluation of the element enrichment in reactors resulting from temperature changes. Additionally, based on the measured element concentrations in the dried digestate (Table 2) and final amounts of biomass in the fermenters, amounts of after digestion were calculated according to (2). ...
This study investigated the effect of mesophilic (37°C) and thermophilic (55°C) digestion on the enrichment and fractionation of plant nutrients (P, Mn, Fe), potentially toxic elements (Cd, Cr, Pb, As, Cu, Ni, Co, Zn) and economically valuable elements (Ge, rare earth elements REE). Batch experiment was conducted with the substrates of Phalaris arundinacea and inoculum for 40 days and the latter digestate was collected for further analysis. Diges-tate from selected reactors was filtered through 0.2 μm syringe filters to separate dissolved elements from the particulate. The solid digestate was extracted with ammonium acetate (pH 7 and pH 5) to determine the extraction of mobile/exchangeable and acid soluble elements, respectively. In fresh digestate, element concentration increased by more than 20-100% especially Ge (94%) and REEs (119%) and pH (6.5-7.9) was significantly higher compared to mesophilic (6.1-7.5). In dried digestate, thermophilic digestion showed increased enrichment of Fe, Co, Cu, Zn, Cr, As, Cd, Pb and especially Ge (193%) and REEs (90%) compared to mesophilic indicating a strong enrichment in thermophilic digestion. Considering both operating conditions 5% of elements were present in the liquid, less than 30% were exchangeable and acid soluble and more than 70% were stabile bound into solids. Thermophilic conditions significantly increased the portion of dissolved and labile-bound elements in the digestate. Reactor temperature offers a promising way to use digestate as a secondary raw material for element recovery in the spirit of phytomining, which contributes to a "cascade use" of digestate in the circular economy .
... Second-generation biofuels are expected to be gotten for the most part from lignocellulosic plant fabric, broadening the assortment of conceivable feedstocks past the restricted number of feedstocks utilized in first-generation biofuels (Somerville et al., 2010). The indicators in Table 1 can be used to help select feedstock generation frameworks that are most likely to be ecologically economical (Davis et al., , 2013Karp & Shield, 2008). To be steady with Dale et al. measurements of natural sustainability for biofuels, we classified these markers. ...
... Because geography can determine features of soil; the ability to refill groundwater; far from water sources; also the far from the biorefinery where the raw materials are grown (Dale et al., 2010) Index (Davis et al., 2011(Davis et al., , 2013Karp & Shield, 2008) is another aspect of sustainability. Through nutritive terms, habitat change, and/or greenhouse gas emissions, all of the features can impact the processes of ecology (Dale et al., 2010;Davis et al., 2013). ...
... Second-generation biofuels are expected to be gotten for the most part from lignocellulosic plant fabric, broadening the assortment of conceivable feedstocks past the restricted number of feedstocks utilized in first-generation biofuels (Somerville et al., 2010). The indicators in Table 1 can be used to help select feedstock generation frameworks that are most likely to be ecologically economical (Davis et al., , 2013Karp & Shield, 2008). To be steady with Dale et al. measurements of natural sustainability for biofuels, we classified these markers. ...
... Because geography can determine features of soil; the ability to refill groundwater; far from water sources; also the far from the biorefinery where the raw materials are grown (Dale et al., 2010) Index (Davis et al., 2011(Davis et al., , 2013Karp & Shield, 2008) is another aspect of sustainability. Through nutritive terms, habitat change, and/or greenhouse gas emissions, all of the features can impact the processes of ecology (Dale et al., 2010;Davis et al., 2013). ...
Environmental Sustainability of Biofuels: Prospects and Challenges provides a comprehensive sustainability analysis of biofuels based on lifecycle analysis and develops various multi-dimensional decision-making techniques for prioritizing biofuel production technologies. Taking a transversal approach, the book combines lifecycle sustainability assessment, lifecycle assessment, lifecycle costing analysis, social lifecycle assessment, sustainability metrics, triple bottom lines, operational research methods, and supply chain designs for investigating the critical factors and critical enablers that influence the sustainable development of biofuel industry. This book will be a valuable resource for students, researchers and practitioners seeking to deepen their knowledge of biofuels as an alternative fuel.
It will equip researchers and policymakers in the energy sector with the scientific methodology and metrics needed to develop strategies for a viable sustainability transition.
... Second-generation biofuels are expected to be gotten for the most part from lignocellulosic plant fabric, broadening the assortment of conceivable feedstocks past the restricted number of feedstocks utilized in first-generation biofuels (Somerville et al., 2010). The indicators in Table 1 can be used to help select feedstock generation frameworks that are most likely to be ecologically economical (Davis et al., , 2013Karp & Shield, 2008). To be steady with Dale et al. measurements of natural sustainability for biofuels, we classified these markers. ...
... Because geography can determine features of soil; the ability to refill groundwater; far from water sources; also the far from the biorefinery where the raw materials are grown (Dale et al., 2010) Index (Davis et al., 2011(Davis et al., , 2013Karp & Shield, 2008) is another aspect of sustainability. Through nutritive terms, habitat change, and/or greenhouse gas emissions, all of the features can impact the processes of ecology (Dale et al., 2010;Davis et al., 2013). ...
Biofuels are one of the most promising approaches for reducing CO2 emissions in the transportation industry. However, due to numerous fundamental restrictions, such as a lack of raw materials, a low CO2 mitigation effect, a blending wall, and poor cost competitiveness, traditional plant-based biofuels (e.g., biodiesel, bioethanol) had a relatively low fraction of total transportation-fuel usage in 2016, under 4%. Advanced biofuels, such as drop-in, microalgal, and electro biofuels, especially those derived from inedible biomass, are seen as a possible answer to the problem of meeting rising biofuel demand. Recent advances in oxy-free hydrocarbon conversion via catalytic deoxygenation processes, oleaginous microalgae selection and lipid content increase, electrochemical biofuel conversion, and the diversification of useful products from biomass and intermediates are discussed in this study. Although the United States and the EU have different financial and approach motivating forces for biofuel production, markers of environmental sustainability have evolved from the updated research across the boundaries of politics. We categorized mentioned markers into six already set up characteristics of natural supportability, advertising depictions for each and connecting them to proposed universal guidelines for progressed biofuels. If ideal feedstock choice, administration, generation, and fuel transformation criteria are particularly sought after, progressed biofuel improvement can be a step toward naturally economic vitality. Even though devices for surveying natural supportability exist, they have not however been connected to progressed biofuels in a standardized way.
... Konversi biomassa dari tanaman pascafitoremediasi menjadi bioenergi dapat menjadi salah satu langkah keberlanjutan fitoremediasi. Tanaman sejatinya dapat dikonversi menjadi berbagai macam jenis bioenergi seperti dalam bentuk bahan bakar padat (briket dan arang), bahan bakar gas (biogas) dan bahan bakar cair (misalnya bioetanol, biodiesel) (Karp & Shield, 2008). ...
Phytoremediation is a promising technology to reduce water and soil pollution problems. Phytoremediation has proven to be an economical and environmentally friendly technology. However, phytoremediation techniques contribute a large amount of contaminated materials to the environment and create further pollution problems. The biomass produced after phytoremediation is quite a lot and will become biological waste which is classified as hazardous and toxic waste. Therefore, it must be managed and handled properly. This review paper will review the methods of utilizing biomass after phytoremediation. Research that has been done on the conversion of biomass into bioenergy and compost is considered quite effective and efficient. In addition, this method will also increase the economic value of plant biomass after phytoremediation. Then the compaction method is considered more economical but produces contaminant residues that must be reprocessed. Synthesis of nanomaterials from contaminated biomass can also be an alternative, but this method is very complicated and quite expensive. Further research and life cycle assessment are needed to be able to choose the right and efficient technology in biomass management and review the effects produced after phytoremediation which aims to implement environmentally friendly and sustainable phytoremediation technology.
... An anticipated rise in demand for forest products, including woodbased products and energy (Karp and Shield, 2008;Zhou et al., 2011), is expected to create a significant increase in demand for forest production (Nepal et al., 2019;Korhonen et al., 2021). Short-rotation forestry (SRF), with intensive and innovative silvicultural practices, may help meet this demand (Mitchell et al., 1999;Tullus et al., 2013;Schulze et al., 2017). ...
Short rotation plantation forestry (SRF) is being widely adopted to increase wood production, in order to meet global demand for wood products. However, to ensure maximum gains from SRF, optimised management regimes need to be established by integrating robust predictions and an understanding of mechanisms underlying tree growth. Hybrid ecophysiological models, such as potentially usable light sum equation (PULSE) models, are useful tools requiring minimal input data that meet the requirements of SRF. PULSE models have been tested and calibrated for different evergreen conifers and broadleaves at both juvenile and mature stages of tree growth with coarse soil and climate data. Therefore, it is prudent to question: can adding detailed soil and climatic data reduce errors in this type of model? In addition, PULSE techniques have not been used to model deciduous species, which are a challenge for ecophysiological models due to their phenology. This study developed a PULSE model for a clonal Populus tomentosa plantation in northern China using detailed edaphic and climatic data. The results showed high precision and low bias in height (m) and basal area (m2·ha–1) predictions. While detailed edaphoclimatic data produce highly precise predictions and a good mechanistic understanding, the study suggested that local climatic data could also be employed. The study showed that PULSE modelling in combination with coarse level of edaphic and local climate data resulted in reasonably precise tree growth prediction and minimal bias.
... Bioenergy crops are well-known to be used in power generation like electricity, heat, and liquid fuels. 65 In this study, the seeds of switchgrass and sorghum were sterilized by washing them with 70% ethanol for 2 min, and then they were washed twice with distilled water. The concentrations of multiwalled CNTs chosen in their study were 50 and 200 μg mL −1 . ...
The prevailing agricultural system has become deeply ingrained and insufficient due to outdated practices inherited from the Green Revolution, necessitating innovative approaches for sustainable agricultural development. Nanomaterials possess the potential to significantly improve the efficient utilization of resources while simultaneously encouraging sustainability. Among these, carbonaceous nanomaterials have found diverse applications in agriculture, exhibiting remarkable capabilities in this domain. Notably, using biowaste to produce these materials makes them both cost-effective and environmentally friendly for seed priming. Seed priming is a technique that can potentially enhance germination rates and stress tolerance by effectively regulating gene pathways and metabolism. This review provides a comprehensive summary of recent progress in the field, highlighting the challenges and opportunities of applying carbonaceous materials in seed priming to advance sustainable agriculture practices. The existing reviews provide a general overview of using carbonaceous materials (graphene and derivatives) in agriculture. Yet, they often lack a comprehensive examination of their specific application in seed-related contexts. In this review, we aim to offer a detailed analysis of the application of carbonaceous materials in seed priming and elucidate their influence on germination. Furthermore, the review shows that crop response to carbonaceous nanomaterials is linked to material concentration and crop species.
... Poplar is used as a source of timber, fiber, and biomass energy (Perry et al. 2001). Recently, hybrid poplars have been considered bioenergy fuels because of their fast-growing ability and high cellulose and low lignin levels (Deckmyn et al. 2004;Karp and Shield 2008;Nassi o Di Nasso et al. 2010). Poplars have attracted worldwide attention for their carbon sequestration potential because of their fast-growing traits. ...
Climate change is a major global concern that has increased the frequency and intensity of extreme drought. Severe drought stress negatively affected tree survival and growth. Poplars are fast-growing trees that can effectively sequester atmospheric carbon dioxide, the most important greenhouse gas. Recently, poplar has attracted attention as a bioenergy fuel source, owing to its fast-growing traits and abiotic stress tolerance. However, the molecular mechanisms underlying drought tolerance in poplars remain uncertain. Therefore, we compared the transcriptomes of P. davidiana and its hybrid with Populus alba grown under drought stress. Before drought stress, genes related to root development processes were up-regulated, and aboveground tissue development genes were down-regulated in P. davidiana compared to P. alba × P. davidiana. After 6 days of drought treatment, P. alba × P. davidiana showed susceptibility to drought stress, whereas P. davidiana exhibited a resistant phenotype. At the transcriptional level, cell wall and lignin biosynthesis genes were up-regulated on day 6 of drought treatment. We concluded that P. davidiana showed more resistance to drought stress than its hybrid and that cell wall biosynthetic processes contributed to drought tolerance by preventing xylem damage. These results could provide valuable information for poplar breeding to improve drought stress tolerance.
... The cultivation of Salix spp. (willows) as short rotation coppice (SRC) has emerged as a promising approach to sustainably produce renewable biomass [45,46], with the largest cultivated areas found in China and Argentina, followed by Europe [47]. These production systems are characterized by short growth cycles of 2-5 years, after which the stems are harvested and shoots regrow rapidly from the stumps left in the soil [47]. ...
Soil organic matter (SOM) is essential for nutrient cycling and soil carbon (C) accumu-lation, both of which are heavily influenced by the quality and quantity of plant litter. Since SOM dynamics in relation to plant diversity are poorly understood we investigated the effects of willow variety and mixture, and site on the soil C stocks, SOM chemical composition and ther-mal stability. Using pyrolysis-field ionization mass spectrometry we analysed the top 10 cm of soil from two 7-year-old experimental sites in Germany and Sweden, with monocultures and mixtures of two willow varieties (Salix spp.) belonging to different species. Overall, site had the strongest effect on SOM quality. Results showed significant variability across sites for willow identity and mixture effects on C accumulation and SOM chemistry. In the German site (Ros-tock), yearly soil C accumulation was higher (p < 0.05) for variety ‘Loden’ (1.0 Mg C ha-1 year-1) compared to ‘Tora’ (0.5 Mg C ha-1 year-1), whilst in the Swedish site (Uppsala), both varieties ex-hibited similar soil C accumulation rates of around 0.6 Mg C ha-1 year-1. Willow variety identity significantly affected SOM quality at both sites, while mixing had minor effects. Our findings emphasize the significance of site-specific context and variety or species identity in shaping soil C accumulation in willow plantations.
... The cultivation of Salix spp. (willows) as a short-rotation coppice (SRC) has emerged as a promising approach to sustainably produce renewable biomass [45,46], with the largest cultivated areas found in China and Argentina, followed by Europe [47]. These production systems are characterized by short growth cycles of 2-5 years, after which the stems are harvested and shoots regrow rapidly from the stumps left in the soil [47]. ...
Soil organic matter (SOM) is essential for nutrient cycling and soil carbon (C) accumulation, both of which are heavily influenced by the quality and quantity of plant litter. Since SOM dynamics in relation to plant diversity are poorly understood, we investigated the effects of willow variety and mixture, and site on the soil C stocks, SOM chemical composition and thermal stability. Using pyrolysis-field ionization mass spectrometry (Py-FIMS), a method of stepwise thermal degradation in ultrahigh vacuum combined with soft ionization in a high electric field, followed by mass-spectrometric separation and detection of molecular ions, we analyzed SOM in the top 10 cm of soil from two 7-year-old experimental sites in Germany and Sweden. Monocultures and mixtures of two willow varieties (Salix spp.) belonging to different species were grown at the experimental plots. Overall, site had the strongest effect on SOM quality. The results showed significant variability across sites for willow identity and mixture effects on C accumulation and SOM chemistry. In the German site (Rostock), yearly soil C accumulation was higher (p < 0.05) for variety ‘Loden’ (1.0 Mg C ha⁻¹ year⁻¹) compared to ‘Tora’ (0.5 Mg C ha⁻¹ year⁻¹), whilst in the Swedish site (Uppsala), both varieties exhibited similar soil C accumulation rates of around 0.6 Mg C ha⁻¹ year⁻¹. Willow variety identity significantly affected SOM quality at both sites, while mixing had minor effects. Our findings emphasize the significance of site-specific context and variety and species identity in shaping soil C accumulation in willow plantations.
... Poslednjih godina raste interesovanje istraživača za korišćenje višegodišnjih energetskih useva za fitostabilizaciju zemljišnih i tehnogenih površina zagađenih PTE (10). Višegodišnji energetski usevi ne pripadaju grupi biljaka za proizvodnju hrane, te kao takvi imaju potencijal za održivu proizvodnju bioenergije [11]. Pored većih energetskih dobitaka, njihovim gajenjem značajno je smanjeno emitovanje gasova sa efektom staklene bašte u odnosu na biogoriva prve generacije. ...
Mediteranska trska (Arundo donax L.) je brzorastuća, rizomatozna višegodišnja C3 trava. Smatra se vodećim usevom za proizvodnju biomase na marginalnim i degradiranim zemljištima pod različitim nepovoljnim uslovima gajenja kao što su zaslanjenost, suša, dugotrajno zadržavanje vode, visoke i niske temperature i povišene koncentracije potencijalno toksičnih elemenata (PTE). Flota-ciona jalovina koja nastaje u procesu obrade ruda metala predstavlja tip tehnosola koji se odlikuje brojnim nepovoljnim fizičkim i hemijskim odlikama, koje ograničavaju i često potpuno onemogućav-aju rast i razvoj biljaka. Jalovina predstavlja i potencijalnu opasnost za životnu sredinu, budući da je izuzetno podložna eolskoj i fluvijalnoj eroziji, zbog čega velika količina PTE može lako dospeti u životnu sredinu. Cilj ovog istraživanja je bio da se ispita mogućnost zasnivanja i održivosti useva mediteranske trske na odlagalištu flotacione jalovine rudnika Pb, Zn i Cu radi fitostabilizacije nje-gove površine. Ogled je postavljen 2019. godine. Nakon sadnje je izvršena fertilizacija sa dozom od 650 kg/ha NPK đubriva (15:15:15) i usev je gajen bez navodnjavanja. Nakon 3 godine od zasnivanja usev se održao, a u biljnom materijalu i u supstratu ispitane su koncentracije sledećih elemenata: N, K, Cd, Cu, Fe, Mn, Ni, Pb, Zn. Najveći sadržaj makrohraniva izmeren je u listovima. Biljke su najveći deo PTE zadržale unutar korena, osim Mn i Zn i na taj način delimično sprečile njihov transport u nadzemne delove, a time i potencijalno negativni uticaj na različite fiziološke procese. Rezultati pokazuju da je moguće zasnovati samoodrživ usev mediteranske trske na podlozi poput flotacione jalovine i predstavljaju osnov za buduća detaljnija istraživanja. Na osnovu ovih preliminarnih re-zultata smatramo da A. donax, kao biljna vrsta zaslužuje pažnju u smislu daljih detaljnih istraživanja fitostabilizacije tehnosola nastalih radom u procesnoj industriji. Ključne reči: Arundo donax; flotaciona jalovina; fitostabilizacija; potencijalno toksični ele-menti Giant reed (Arundo donax L.) is a fast-growing, rhizomatous, perennial C3 grass. It is considered a leading crop for biomass production on marginal and degraded soils with numerous unfavorable conditions such as high salinity, drought, water retention, high and low temperatures and high
... The most common coppice rotations are from every 2 to every 4 years. Shorter rotations can adversely affect the following growth rate, especially for poplars, which are negatively affected by short rotation coppicing; longer periods of growth can be more suitable for them, depending on the clone [11,12]. Rotation length affects the total cultivation period, which is an important economic parameter [13]. ...
Background
Phytoextraction belongs to environmentally well-accepted remediation technologies to remove metals from contaminated soils. Due to long-time requirement, sufficient data for proper phytoextraction evaluation are missing. Four clones of fast-growing trees: two willow species (S1), Salix viminalis L. (Salix schwerinii E.L.Wolf × S. viminalis) × S. viminalis) and (S2)—Salix smithiana (Salix × smithiana Willd.), and two poplar clones (P1), Populus Max-4 (Populus nigra L. × Populus maximowiczii A. Henry) and (P2) Wolterson (P. nigra L.) were cultivated under field conditions at medium-to-high Cd and Pb, and low Zn soil contamination to assess trees’ long-term ability of biomass production and removal of potentially toxic elements (PTEs). The biomass yield and PTE uptake were measured during 8 years of regular growth under three rotation lengths: four harvests following 2-year periods (4 × 2y), two harvests in 4-year periods (2 × 4y), and one harvest representing 8 years of growth (1 × 8y).
Results
In most cases, the highest annual dry biomass yield was achieved with a 2 × 4y rotation (P1 = 20.9 t ha⁻¹ y⁻¹, S2 = 18.4 t ha⁻¹y⁻¹), and the yield decreased in order 2 × 4y > 1 × 8y > 4 × 2y of harvesting periods. Only clone S1 showed a different pattern. The differences in biomass yield substantially affected the PTE phytoextraction. The greatest amount of Cd and Zn was removed by willow S2, with the highest biomass yield, and the strongest ability to accumulate PTEs. With 2 × 4y rotation, S2 removed a substantial amount of Cd (9.07%) and Zn (3.43%) from the topsoil horizon (0–20 cm) and 5.62% Cd and 2.04% Zn from horizon 20–40 cm; phytoextraction rate was slightly lower for 1 × 8y rotation. The poplar P1 removed the most Pb in the 1 × 8y rotation, but the overall Pb phytoextraction was negligible. The results indicated that lignin and cellulose contents increased, and hemicellulose content decreased with increased concentrations of Cd, Pb and Zn in poplars wood.
Conclusions
The data confirmed that phytoextraction over longer harvest periods offered promising results for removing Cd from medium- to high-level contaminated soils; however, the ability of Pb removal was extremely low. The longer harvest period should be more economically feasible.
Graphical Abstract
... This underlying genetic basis implies that structurally robust plants can be bred in agricultural systems and that tissue toughness in many natural plant populations may adapt to environmental conditions. Specifically, in agricultural settings, stem lodging (i.e., stem bending near ground level) can reduce plant productivity and crop yields (Foulkes et al., 2011); in biofuel crops, stronger leaves are more likely to remain attached to the stem and contribute to biomass yield (Karp and Shield, 2008). In natural systems, this genetic basis means that in many species tissue toughness will be related to biotic pressures, such as herbivory, or abiotic pressures (Pérez-Harguindeguy et al., 2003;Moles et al., 2011). ...
Premise
Leaf tensile resistance, a leaf's ability to withstand pulling forces, is an important determinant of plant ecological strategies. One potential driver of leaf tensile resistance is growing season length. When growing seasons are long, strong leaves, which often require more time and resources to construct than weak leaves, may be more advantageous than when growing seasons are short. Growing season length and other ecological conditions may also impact the morphological traits that underlie leaf tensile resistance.
Methods
To understand variation in leaf tensile resistance, we measured size‐dependent leaf strength and size‐independent leaf toughness in diverse genotypes of the widespread perennial grass Panicum virgatum (switchgrass) in a common garden. We then used quantitative genetic approaches to estimate the heritability of leaf tensile resistance and whether there were genetic correlations between leaf tensile resistance and other morphological traits.
Results
Leaf tensile resistance was positively associated with aboveground biomass (a proxy for fitness). Moreover, both measures of leaf tensile resistance exhibited high heritability and were positively genetically correlated with leaf lamina thickness and leaf mass per area (LMA). Leaf tensile resistance also increased with the growing season length in the habitat of origin, and this effect was mediated by both LMA and leaf thickness.
Conclusions
Differences in growing season length may promote selection for different leaf lifespans and may explain existing variation in leaf tensile resistance in P. virgatum . In addition, the high heritability of leaf tensile resistance suggests that P. virgatum will be able to respond to climate change as growing seasons lengthen.
... However, these non-renewable energy sources are scarce, with estimations lasting 41 years (oil), 64 years (natural gas), and 155 years (coal) (British Petroleum, 2006). This scenario raised the need for new matrices and the conversion of biomass to electricity (gasification and pyrolysis) and liquid fuels (bioethanol, biodiesel, and bio-oil from pyrolysis) (Karp & Shield, 2008). ...
Despite the need for a sustainable energy resource, bioenergy gained its spotlight in the 2000s. Sugarcane is a significant crop in terms of sugar and energy capacity, and it can be an alternative energy source to mitigate the effects of climate change. Bioenergy production from sugarcane in Brazil is one of the most efficient. This production lends a centrality to biofuels' importance in confronting the effects of climate change. The present article reviews the Brazilian history of this crop as a biofuel source. We highlight the historical changes related to scientific, technological, industrial, and environmental advances since the beginning of the 20th century. We describe how creating governmental institutes and disseminating scientific knowledge strengthened public policies that led Brazil to occupy leadership positions in producing, distributing, and using bioenergy throughout the country. The compiled data shows the improvement and the new approaches needed in ethanol sugarcane. We developed a bibliometric analysis to evaluate Brazilian science's contribution to this process compared to other countries. Brazil's history of science and investments in sugarcane biofuel development for transportation may be divided into two phases: ethanol-only and flex-fuel cars. A third phase is starting, which is the ethanol-to-hydrogen era.
... However, these non-renewable energy sources are scarce, estimated to last 57 years (oil), 49 years (natural gas), and 139 years (coal) [7]. This scenario raised the need for new matrices and the conversion of biomass to electricity (gasification and pyrolysis) and liquid fuels (bioethanol, biodiesel, and bio-oil from pyrolysis) [8]. ...
Despite the recent need for sustainable energy resources, bioenergy gained its spotlight in the 2000s. Sugarcane is a significant crop in terms of sugar and energy capacity, and it can be an alternative energy source to mitigate the effects of climate change. Bioenergy production from sugarcane in Brazil is one of the most efficient options. This production lends a centrality to biofuels’ importance in confronting climate change effects. The present article reviews the Brazilian history of this crop as a biofuel source, focusing on plants as a biomass. We highlight the historical changes related to scientific, technological, industrial, and environmental advances since the beginning of the 20th century. We describe how creating governmental institutes and disseminating scientific knowledge strengthened public policies that led Brazil to occupy leadership positions in producing, distributing, and using bioenergy throughout the country. The compiled data show the improvements and the new approaches needed to improve ethanol sugarcane use. We performed a bibliometric analysis to evaluate Brazilian science’s contribution to this process compared to other countries. Brazil’s history of science and investment in sugarcane biofuel development for transportation may be divided into two phases: ethanol-only and flex-fuel cars. A third phase is starting, directed to the SAF and ethanol-to-hydrogen era.
... Additionally, generating electricity through nuclear fission requires extensive infrastructure and carries potential risks to the environment and human health (Gresshoff et al. 2017). The long-term consequences of fossil fuel usage, including land degradation and desertification of fertile soils, are becoming more evident (Karp and Shield 2008). The global impacts of these practices, such as climate change, severe weather events, and the rise of diseases linked to environmental pollution, highlight the urgent need to explore alternative energy sources (Yadav et al. 2019). ...
Our world is experiencing an unprecedented surge in energy demand due to rapid economic growth and population expansion. This escalating need for energy poses a significant challenge as reliance on fossil fuels leads to severe environmental pollution. Consequently, the exploration of renewable energy sources, such as biofuels, emerges as a prudent solution to mitigate the energy crisis. The cultivation of novel crops and the implementation of advanced cultivation systems are gradually gaining traction, aiming to minimize dependence on depleting fossil fuel reserves and foster resilience to global climate change. These promising biological resources hold immense potential as bioenergy feedstocks, offering a versatile and sustainable means to meet the energy requirements of modern society on a daily basis. Biotechnology, in particular, can play a critical role in developing superior genotypes of energy crops, specifically tailored for efficient bioprocessing and subsequent utilization. By applying cutting-edge molecular techniques, a wide range of important traits can be enhanced, encompassing total biomass yield, production, quality, and resistance to different biotic and abiotic stresses. These advancements have the potential to significantly improve the efficiency, cost-effectiveness, and environmental benefits of biofuels. This comprehensive review aims to evaluate the potential of biotechnological applications in the development of advantageous bioenergy crops, spanning from feedstock enhancement to sustainable biofuel production. Furthermore, it provides compelling examples of cutting-edge research in the field, showcasing the prospects of energy crop innovation.
... Beans and tomatoes were selected for two reasons: they are important vegetable crops and they are functionally distinct, as beans are in the legume family and have different nutritional requirements. Hybrid willow was chosen because it is a fast-growing woody plant, often used for remediating damaged land and as a source of biofuel (Karp and Shield, 2008). Each plant type was grown in the same organic planting mix (peat moss and vermiculite) subjected to four distinct levels of biochar (0, 3, 9 and 26% by dry weight). ...
Positive relationships have been documented between the amount of biochar added to soils and various aspects of plant growth and fertility such as root, shoot, and fruit production. However, these effects depend on biochar source materials, soil characteristics and species of plant examined. This makes it impossible to systematically compare and generalize findings across previous studies that have used different soils and biochar. We conducted a novel investigation to assess the effects of a single source of biochar (hazelnut wood), in a constructed organic soil, on the different plant tissues in three functionally distinct species: tomatoes (Solanum lycopersicon), green beans (Phaseolus vulgaris), and willow (Salix sp.). Five levels of biochar soil amendment were assessed: 0% (control), 3, 9, and 26% by dry weight. We found a highly significant positive relationship between biochar concentration and total plant biomass (roots + shoots + fruits) in all species, with no significant difference in total biomass response among species. Fruit production increased with increased biochar in both beans and tomatoes. However, tomatoes exhibited significant differences in response among plant tissues; fruit production and shoot biomass increased significantly with biochar, but root tissue did not. Bean germination success increased significantly with biochar concentration. Date of first flowering was earlier with increasing soil biochar in beans but not in tomatoes. Control over both sources of biochar and soil composition in this experiment enables us to conclude that biochar addition can have different impacts on different plants and, in some cases, species-specific impacts on different plant tissues and other measures of fertility. Our results are contrary to prior research that found inhibiting effects of biochar at levels comparable to our 26% treatment. Biochar impacts on soil properties such as CEC and percent base cation saturation do not explain our findings, leading us to conclude that microbial interaction with biochar is an important factor that may explain the positive impacts of soil biochar on plant fertility observed. Further research that repeats this experiment in other soil types, with other biochar sources, and with other plant species is necessary to determine the generalizability of these important findings.
... A great deal of research has led to the creation of new fields of plant breeding called "plant biotechnology" and "genetic engineering," which are based on cellular totipotency or the capacity to regenerate entire flowering plants (Ranabhat et al.). It might take years for some trees and plants to blossom and produce seeds, which makes improving them challenging (Karp and Shield, 2008). A few crops, such as sugarcane, bananas, apples, cassava, and yams, reproduce vegetatively, particularly the entirely sterile ones that lack seeds. ...
... As a result, combining both the first-and second-generation transfer approaches should increase both economic and environmental advantages (Joelsson et al. 2016). Sugarcane biomass is composed of lignin and cellulosic components (Karp and Shield 2008). Lignin is a recalcitrant component in the release of biofuels from plant biomass. ...
Purpose: Bagasse, the residue left after extracting juice from sugarcane stalks, is rich in lignocellulosic
biomass. The lignin present in this plant biomass is the key factor that hinders the efficient
extraction of ethanol from the bagasse. In the current study, c-irradiated sugarcane mutants were
evaluated for variation in lignin content and its corresponding caffeic acid-O-methyl transferase
(COMT) gene.
Materials and methods: The acetyl bromide method was used to estimate lignin content in sugarcane
mutants. PCR-based cloning of the COMT gene was performed in low lignin mutants as
well as control plants in E. coli (strain DH5a) to understand the mechanism of variation at the
molecular level. The Sanger sequencing for cloned gene was performed to check variation in gene
sequence.
Results: In comparison to the control (21.5%), the mutant plants’ lignin content ranged from 13
to 28%. The Sanger sequencing revealed approximately the same length of the gene from
mutants as well as a control plant. In comparison to the reference gene, the mutated gene
showed SNPs and indels in different regions, which may have an impact on lignin content.
Conclusions: Therefore, c-irradiated mutagenesis is an acceptable approach to develop novel
mutants of sugarcane with low lignin content to enhance bioethanol production from waste
material using bioprocess technology
... The requirement to reduce the emission of greenhouse gas and use more bioenergy, rather than relying on fossil fuels, has increased interest in bioenergy crop cultivation. Willow (Salix spp.) is considered as a short-rotation coppice (SRC) for the bioenergy, biofuel and bioproduct industries [1][2][3]. Meanwhile, willows are considered a highly promising tree species for soil remediation, due to their exceptional ability to hyperaccumulate soil pollutants such as petroleum hydrocarbons, polychlorinated biphenyls, and cadmium [4][5][6][7]. ...
Shrub willows are widely planted for landscaping, soil remediation, and biomass production, due to their rapid growth rates. Identification of regulatory genes in wood formation would provide clues for genetic engineering of willows for improved growth traits on marginal lands. Here, we conducted an expression quantitative trait locus (eQTL) analysis, using a full sibling F1 population of Salix suchowensis, to explore the genetic mechanisms underlying wood formation. Based on variants identified from simplified genome sequencing and gene expression data from RNA sequencing, 16,487 eQTL blocks controlling 5505 genes were identified, including 2148 cis-eQTLs and 16,480 trans-eQTLs. eQTL hotspots were identified, based on eQTL frequency in genomic windows, revealing one hotspot controlling genes involved in wood formation regulation. Regulatory networks were further constructed, resulting in the identification of key regulatory genes, including three transcription factors (JAZ1, HAT22, MYB36) and CLV1, BAM1, CYCB2;4, CDKB2;1, associated with the proliferation and differentiation activity of cambium cells. The enrichment of genes in plant hormone pathways indicates their critical roles in the regulation of wood formation. Our analyses provide a significant groundwork for a comprehensive understanding of the regulatory network of wood formation in S. suchowensis.
... Subramani [53] summarized the conversion of syngas to higher alcohols by various catalytic pathways. Karp [54] reviewed the yields of a range of key bioenergy crops and suggested targets that could be improved. Edwards [55] and Song [56] presented the current status, technical challenges and development forecasts for hydrogen cells, fuel cells and other advanced batteries. ...
The field of energy security is an important, complex and evolving field with important implications at the international, national and regional levels. Considering that no scholars have conducted bibliometric studies on the current energy security field, the authors of this study chose to use a bibliometric approach to conduct a search on the Web of Science using “energy security” as the keyword, and they conducted a systematic review of 5236 papers published between 2005 and 2022 to determine the current status and development of research in the field of energy security by addressing the following six questions: (1) What are the characteristics of the types of literature in the field of energy security? (2) What are the annual publication and citation frequency trends in the field of energy security? (3) What is the distribution of source journals, countries/regions, institutions, scholars and topics in the field of energy security? (4) What are the research hotspots in the field of energy security in the recent development history? (5) What are the most influential studies and the most disruptive studies in the field of energy security? (6) What are the characteristics of the different levels of cooperation networks in the field of energy security? Finally, we concluded the following: (1) In terms of publication dynamics, the number of annual publications and the citation frequency in the field of energy security maintain an upward trend, with a large number of source journals and a wide range of topics. The number of countries, institutions and scholars involved in research in the field of energy security keeps increasing, but the cooperation is fragmented and geopolitical. (2) From the perspective of research themes, research in the field of energy security has both strong technical characteristics and is associated with social science research themes. The contradictions between energy security and social, economic, environmental, land and climate issues, the interplay between energy supply systems and complex geopolitical and international relations issues and the important role of renewable energy and related technologies in maintaining national/regional energy security are the main issues of concern to researchers. (3) In terms of research centers, although the UK and the US still retain a first-mover advantage in this field, China has gradually overtaken and has become the country with the largest output of literature in recent years. The center of research in the field has also gradually shifted from Europe and the US to the East and South Asia regions. Overall, the governance of energy security issues still requires a combination of policy, economic and technological aspects. The results will help scholars systematically understand the current status of research, research frontiers and future trends in the field of energy security.
... Moreover, the energy which is produced from nuclear fission needs huge infrastructure and it also leads to hazardous effects on the environment in addition to human health (Gresshoff et al. 2017). Many long-term effects on the environment are related to the use of fossil fuels which include desertification and degradation of fertile soil (Karp and Shield 2008). The consequences of increased usage of fossil fuels are noticeable as diseases associated environmental pollution and drastic changes in climate such as torrential rains. ...
The mandate for energy has upsurged with the increase in population worldwide. Exploiting fossil fuels for energy has directed the exhaustion of fossil fuel assets. Thus, substitute sources of energy are required. Biomass is a renewable source and an alternative feedstock for providing eco-friendly and sustainable energy. Biofuels obtained from different biomass are grouped into three distinct groups: first-generation biofuels (obtained from wheat, sugarcane, barley, potato, soybean, corn, coconut, and sunflower), second-generation biofuels (produced from lignocellulosic materials like cassava, switchgrass, Jatropha, straw, and wood), third-generation biofuels (obtained from algae). The biofuel produced with the help of first-generation energy crops poses threat to biodiversity and food supply. But the use of lignocellulose as a biofuel does not contend with that of food production as it is nondigestible for humans. The principle advantage of algal biomass is higher oil production and it can convert all of the feedstock energy into various kinds of biofuels. Apart from this, it is useful for amputation of CO2 from the industrial chimney (algae bio-fixation), food products, animal feed, and energy cogeneration after extraction of oil and treatment of wastewater. Thus, it is one of the world’s most valuable, renewable, and sustainable source of the fuel which also helps in controlling environmental pollution. Thus, bioenergy crops and biofuels are considered as sustainable sources of energy production as waste products such as forest waste and agricultural residues, manures, industrial waste, and municipal solid waste are used for producing biofuels and bioenergy.
... Miscanthus is sensitive to pests and diseases in the areas of Asia, where it occurs naturally. In Europe, there were no reports of plant pests and diseases that significantly limit the productivity of Miscanthus (Cosentino et al., 2012), which is more favourable than the situation with forest crops of short rotation, such as willow and poplar (Karp and Shield, 2008). Potentially, the risk can be pathogenic fungus infections, virus diseases, leaf lice, common rural moths, larvae of ghostly moths, plant lice and parasite nematodes. ...
Second-generation biofuel production systems are significantly better than first-generation systems. However, the size of areas in which the energy crops are grown depends on public support, and it decreases if public support is missing. Despite all the environmental and economic benefits, perennial energy crops do not currently play a significant role. It is believed that available land areas will be a basic limiting factor for cultivating biofuel crops in the EU. On the other hand, there is significant untapped potential for bioenergy production in abandoned and marginal land in Southeast Europe. At the same time, perennial energy crops are investments with certain risks. Economically viable production of dedicated energy crops will be difficult to achieve on most lands classified into V-VIII land capability classes. In terms of the risk of farming investments, maize has an advantage over all perennial energy crop systems. We have identified 10 types of risks for successful production of energy crops: (1) Crop water supply; (2) Weed infestation in crops; (3) Risks of frost damages; (4) Crop lodging; (5) Crop diseases and pests; (6) Short harvest periods and variable yields; (7) Economic viability of cultivation on land areas of lower land capability class; (8) Influences of agricultural practices and agro-ecological conditions on biomass quality; (9) Storage of harvested biomass and fire hazard; and (10) economic sanctions, war, and war surroundings. Although the cultivation of perennial energy crops has a perspective, it must be systematically planned and further improved.
The genus Salix is a common component of the Northern Hemisphere dendroflora with important ecological and economic value. However, taxonomy and systematics of Salix is extremely difficult and relationships between main lineages, especially deep phylogenies, remain largely unresolved. In this study, we used genome-skimming, plastome assembly, and single-copy orthologs (SCOs) from 66 Salix accessions, along with publicly available plastome and sequence read archive (SRA) datasets to obtain a robust backbone phylogeny of Salix, clarify relationships between its main lineages, and gain a more precise understanding of the origin and diversification of this species-rich genus. The plastome and SCO datasets resolved Salix into two robust clades, with plastome-based phylogenies lacking inner resolution and SCO offering fully resolved phylogenies. Our results support the classification of Salix into five subgenera: Salix, Urbaniana, Triandrae, Longifoliae and Vetrix. We observed a significant acceleration in the diversification rate within the Chamaetia-Vetrix clade, while Salix exhibited increased rates of diversification spanning from the early Oligocene to the late Miocene. These changes coincided with contemporaneous tectonic and climate change events. Our results provide a foundation for future systematic and evolutionary studies of Salix. Additionally, we showed that genome skimming data is an efficient, rapid, and reliable approach for obtaining extensive genomic data for phylogenomic studies, enabling the comprehensive elucidation of Salix relationships.
The growing international need for petroleum-based fuel and the related environmental issues, such as greenhouse gas emissions, global warming, and change in the climate, have redirected global focus towards the development of sustainable, eco-friendly, and renewable fuels derived from energy crops. The production of biofuel utilizing fast-growing and very effective bioenergy crops is becoming a dependable substitute for fossil fuels. Bioenergy crops refer to specific plants that are cultivated and managed at reduced expenses for the purpose of producing biofuels. Among these, globe artichoke and sweet sorghum are significant bioenergy crops that can expedite the shift towards a low-carbon economy. Both plants are important crops that serve multiple purposes as food, animal feed, and bioenergy sources. Moreover, they are highly adaptable to harsh conditions. The potential for ethanol production from sweet sorghum is a minimum 6000 L per hectare. Globe artichoke, on the other hand, has high biomass and energy production even with limited external management sources. These traits make them highly desirable as bioenergy plants. This review demonstrates the potential of global artichoke and sweet sorghum as bioenergy sources. An improved understanding of the bioenergy potential of globe artichoke and sweet sorghum will better allow us to exploit these crops.
Biomass serves as a crucial indicator of plant productivity, and the development of biomass models has become an efficient way for estimating tree biomass production rapidly and accurately. This study aimed to develop a rapid and accurate model to estimate the individual aboveground biomass of Salix suchowensis. Growth parameters, including plant height (PH), ground diameter (GD), number of first branches (NFB), number of second branches (NSB) and aboveground fresh biomass weight (FW), were measured from 892 destructive sample trees. Correlation analysis indicated that GD had higher positive correlations with FW than PH, NFB and NSB. According to the biological features and field observations of S. suchowensis, the samples were classified into three categories: single-stemmed type, first-branched type and second-branched type. Based on the field measurement data, regression models were constructed separately between FW and each growth trait (PH, GD, NFB and NSB) using linear and nonlinear regression functions (linear, exponential and power). Then, multiple power regression and multiple linear regression were conducted to estimate the fresh biomass of three types of S. suchowensis. For the single-stemmed plant type, model M1 with GD as the single parameter had the highest adj R², outperforming the other models. Among the 16 constructed biomass-estimating equations for the first-branched plant type, model M32 FW = 0.010371 × PH1.15862 × GD1.250581 × NFB0.190707 was found to have the best fit, with the highest coefficient of determination (adj R² = 0.6627) and lowest Akaike Information Criterion (AIC = 5997.3081). When it comes to the second-branched plant type, the best-fitting equation was proved to be the multiple power model M43 with PH, GD, NFB and NSB as parameters, which had the highest adj R² value and best-fitting effect. The stability and reliability of the models were confirmed by the F-test, repeated k-fold cross-validation and paired-sample t-tests. The models developed in this study could provide efficient tools for accurately estimating the total aboveground biomass for S. suchowensis at individual tree levels. The results of this study could also be useful for optimizing the economic productivity of shrub willow plantations.
Non-structural carbohydrate reserves of stems and roots underpin overall tree fitness and productivity under short-rotation management practices such as coppicing for bioenergy. While sucrose and starch comprise the predominant stem carbohydrate reserves of Populus, utilization for fitness and agricultural productivity is understood primarily in terms of starch turnover. The tonoplast sucrose transport protein SUT4 modulates sucrose export from source leaves to distant sinks during photoautotrophic growth, but the possibility of its involvement in remobilizing carbohydrates from storage organs during heterotrophic growth has not been explored. Here, we used PtaSUT4-knockout mutants of Populus tremula × P. alba (INRA 717-1B4) in winter (cool) and summer (warm) glasshouse coppicing experiments to assess SUT4 involvement in reserve utilization. Conditions preceding and supporting summer sprouting were considered favorable for growth, while those preceding and supporting cool temperature sprouting were sub-optimal akin to conditions associated with coppicing as generally practiced. Epicormic bud emergence was delayed in sut4 mutants following lower temperature ‘winter’, but not summer coppicing. Winter xylem hexose increases were observed in control but not sut4 stumps after coppicing. The magnitude of starch and sucrose reserve depletion was similar in control and sut4 stumps during the winter and did not explain the sprouting and xylem hexose differences. However, winter maintenance costs appeared higher in sut4 based partly on Krebs cycle intermediate levels. In control plants, bark accrual of abundant defense metabolites, including salicinoids and condensed tannins, was higher in summer than in winter, but this increase of summer defense allocations was attenuated in sut4 mutants. Temperature-sensitive trade-offs between growth and other priorities may therefore depend on SUT4in Populus.
Lignocellulosic biomass comes from different sources: waste from industry or agriculture or dedicated production. The plant species used for this dedicated production must primarily meet the expectations of high yields and can also have varied compositions which can be more or less suitable to certain uses. Furthermore, in addition to variations in the quantity and quality of biomass produced between species, there are variations of composition and yield between different genotypes within each species. Thus, beyond the impacts of environmental factors, genetics is one of the factors which acts on the variation in yield and composition of lignocellulosic biomass within a species. This opens the way to the selection of genotypes suitable for industrial processes without losing their agronomic abilities. This chapter illustrates both the genetic and genomic approaches and the results obtained in different species used for the production of lignocellulosic biomass, such as salicaceae (poplar, willow) and C4 grasses (maize, sorghum, Miscanthus).
Our world is experiencing an unprecedented surge in energy demand due to rapid economic growth and population expansion. This escalating need for energy poses a significant challenge as reliance on fossil fuels leads to severe environmental pollution. Consequently, the exploration of renewable energy sources, such as biofuels, emerges as a prudent solution to mitigate the energy crisis. The cultivation of novel crops and the implementation of advanced cultivation systems are gradually gaining traction, aiming to minimize dependence on depleting fossil fuel reserves and foster resilience to global climate change. These promising biological resources hold immense potential as bioenergy feedstocks, offering a versatile and sustainable means to meet the energy requirements of modern society on a daily basis. Biotechnology, in particular, can play a critical role in developing superior genotypes of energy crops, specifically tailored for efficient bioprocessing and subsequent utilization. By applying cutting-edge molecular techniques, a wide range of important traits can be enhanced, encompassing total biomass yield, production, quality, and resistance to different biotic and abiotic stresses. These advancements have the potential to significantly improve the efficiency, cost-effectiveness, and environmental benefits of biofuels. This comprehensive review aims to evaluate the potential of biotechnological applications in the development of advantageous bioenergy crops, spanning from feedstock enhancement to sustainable biofuel production. Furthermore, it provides compelling examples of cutting-edge research in the field, showcasing the prospects of energy crop innovation.
C 4 perennial bioenergy grasses are an economically and ecologically important group whose responses to climate change will be important to the future bioeconomy. These grasses are highly productive and frequently possess large geographic ranges and broad environmental tolerances, which may contribute to the evolution of ecotypes that differ in physiological acclimation capacity and the evolution of distinct functional strategies. C 4 perennial bioenergy grasses are predicted to thrive under climate change—C 4 photosynthesis likely evolved to enhance photosynthetic efficiency under stressful conditions of low [CO 2 ], high temperature, and drought—although few studies have examined how these species will respond to combined stresses or to extremes of temperature and precipitation. Important targets for C 4 perennial bioenergy production in a changing world, such as sustainability and resilience, can benefit from combining knowledge of C 4 physiology with recent advances in crop improvement, especially genomic selection.
Expected final online publication date for the Annual Review of Plant Biology, Volume 75 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Perennial nectar‐producing wild plant species (WPS) cultivation for biogas production helps improve ecosystem services such as habitat functioning, erosion mitigation, groundwater protection, and carbon sequestration. These ecosystem services could be improved when WPS are harvested in late winter to produce pellets and briquettes as solid energy carriers for heat production. This study aims for gaining first insights into the use of WPS biomass as resource for pellet and briquette combustion with focus on two perennial WPS common tansy (Tanacetum vulgare L.) and mugwort (Artemisia vulgaris L.), and two biennial WPS yellow melilot (Melilotus officinalis L.) and wild teasel (Dipsacus fullonum L.). All WPS are found economically viable for pellet combustion. The main drivers are i) low cultivation costs, ii) subsidies, and iii) low pellet production costs due to low moisture contents. However, high ash contents in WPS biomass justify the need of i) blending with woody‐biomass or ii) supplementing with additives to attain international standards for household stoves. This approach appears technically feasible providing a research field with significant potential impacts. As 70% of the pellet market is demanded as household level, public concern about the legal framework of alternative plant biomass pellets must be overcome to develop this market.
Purpose: Bagasse, the residue left after extracting juice from sugarcane stalks, is rich in lignocellulosic biomass. The lignin present in this plant biomass is the key factor that hinders the efficient extraction of ethanol from the bagasse. In the current study, c-irradiated sugarcane mutants were evaluated for variation in lignin content and its corresponding caffeic acid-O-methyl transferase (COMT) gene.
Materials and methods: The acetyl bromide method was used to estimate lignin content in sugarcane mutants. PCR-based cloning of the COMT gene was performed in low lignin mutants as well as control plants in E. coli (strain DH5a) to understand the mechanism of variation at the molecular level. The Sanger sequencing for cloned gene was performed to check variation in gene sequence.
Results: In comparison to the control (21.5%), the mutant plants’ lignin content ranged from 13 to 28%. The Sanger sequencing revealed approximately the same length of the gene from mutants as well as a control plant. In comparison to the reference gene, the mutated gene showed SNPs and indels in different regions, which may have an impact on lignin content.
Conclusions: Therefore, c-irradiated mutagenesis is an acceptable approach to develop novel mutants of sugarcane with low lignin content to enhance bioethanol production from waste material using bioprocess technology.
This study reports the results of an evaluation of the techno-economic feasibility of a biorefinery with an annual lactic acid production capacity of 100,000 metric tons using lignocellulosic biomass. Corn stover and miscanthus were considered as model feedstocks, and three different fermentation pathways involving bacteria, fungi, and yeast were compared with respect to their ability to convert biomass feedstocks to lactic acid. Equipment, raw materials, utilities and labor requirements, and lactic acid production costs were estimated. The minimum selling price (at a 10% internal rate of return) per metric ton of lactic acid produced from different feedstocks for lactic acid bacteria, fungi, and yeast-based pathways were in the range of USD 1243–1390, USD 1250–1392, and USD 993–1123, respectively, with lower costs for miscanthus. Lactic acid production using genetically engineered yeast strains can eliminate the need for the simultaneous neutralization and recovery of lactic acid, resulting in lower equipment, chemical, and utility requirements and lower lactic acid production costs. Lactic acid production costs were highly sensitive to the conversion rates of sugars into lactic acid, feedstock cost, production plant size, operation hours, and acid hydrolysis reactor costs. Improvements in process conditions and efficiencies and lower costs of equipment and consumables are necessary to utilize lignocellulosic biomass for lactic acid production at lower costs while remaining cost-competitive with respect to first-generation and petroleum-based feedstocks.
The escalating human population all over the globe has posed serious threats such asa limited supply of resources (non-renewable), increasing environmental pollution, global warming, food, and energy insecurities, and diminishing petroleum resources. To overcome these problems, much progress has been made in successful one-pot synthesis reactions in combination with the exploitation of advantages of chemoselectivity, regioselectivity, and stereoselectivity of biocatalysts or enzyme promiscuity. In the recent decades, various novel startegies and approaches have been developed intending to address above-mentione global issues. Among various sustainable platforms, one-pot tandem catalytic reactions are reported to be used extensively for synthesizing biofuels such as first generation-, second generation from end-use products which are derived from renewable biomass feedstocks. Further, this one-pot tandem catalytic conversion reaction has surfaced as a sustainable strategy to produce value-added environmentally safe products. Hence, a potential green approach toward the chemical industries. In this contribution, this review discusses the emergence of nanocatalysts for producing renewable energies, an explanation of tandem catalysis and one-pot synthesis, and further the production of biofuels via one-pot tandem catalysis with supportive examples and most important economic aspects and challenges associated with a promising novel approach.
Maize is important for the biofuel and bio-based products. Building a clean maize production system could minimize the environment pollution from the N loss from the sloping land and achieve the industrial sustainable development. As a nitrogen-rich source, melamine could be used as a slow-release nitrogen (N) fertilizer, which provides a route for the recycling of melamine waste and the combatting of N loss from fertilizers. Model N release of melamine was compared with urea, sulfur(S)-coated urea via N loss in leaching column under intermittent leaching and under the ploughing fertilizer in the farmland soil. Only 7.12 % of the total nitrogen (TN) was lost from the 21 irrigation events, while the loss of TN from urea reached 77.28 %. TN from urea would be release totally in soil within 14 days in the ploughing fertilizer experiment, but 62 % of melamine was remained after 144 days. In order to evaluate the efficacy of melamine as an N fertilizer, plot experiments with an N rate of 180 kg ha-1 were carried out using pure melamine, urea and S-coated urea as well as mixed melamine/urea at 2:8, 1:1 and 7:3 by the N ratio. Melamine fertilization alone was unable to satisfy the N demand of maize, but the melamine/urea mixture (1:1) was comparable to the commercial S-coated urea in both years in terms of the grain yield (2217 kg ha-1 in 2019, 2368 kg ha-1 in 2020), total aboveground dry matter (5076 kg ha-1 in 2019, 4815 kg ha-1 in 2020), aboveground N uptake (36 kg ha-1 in 2019, 48 kg ha-1 in 2020), partial factor productivity of nitrogen (12.32 kg kg-1 in 2019 and 13.16 kg kg-1 in 2020) and net return (1474 USD in 2019, 1606 USD in 2020). Melamine accumulation in the maize grain measured from ELISA (enzyme-linked immunosorbent assay) ranged from 0.24 to 1.8 mg kg-1. The valorization of the melamine waste into N fertilizer by blending with urea was a possible way of reducing melamine pollution, alleviating N loss in hilly area and building a recyclable agriculture system.
Sugarcane (Saccharum spp.) is the main feedstock for bioethanol production in Brazil. Recently, some breeding programs have focused on energy cane for the enhancement of bioenergy yield in mills operating in the production of second-generation ethanol (2 G-ethanol). However, information on yield, nutritional and chemical composition of energy cane genotypes is still insufficient. Therefore, the objective of this study was to evaluate the biomass production and the amount of nutrients removed by energy cane genotypes under Brazilian field conditions. Between 2016 and 2018, trials were carried out under field conditions in the state of São Paulo, Brazil, throughout the plant cane and first ratoon growing seasons. The experiment was set up in a randomized block design containing 26 energy cane genotypes and two commercial sugarcane varieties. Agronomic and industrial characteristics related to the aboveground biomass (fresh and dry), chemical (sucrose, fiber, Brix, total recoverable sugar, extractives, ashes, lignin, cellulose, and hemicellulose), and nutritional (macro- and micronutrients) composition were evaluated. Some energy cane genotypes presented higher dry biomass yield (∼25%), fiber (∼40%), ashes (∼50%), lower sucrose, total recoverable sugar (∼60% and 50%, respectively), and lower extractives in stalks (∼50%) compared to sugarcane genotypes. The average nutrient requirement per unit of fresh biomass produced (in kg per megagram) for energy cane of two growing seasons was 1.7 N, 0.35 P, 4.2 K, 0.45 Ca, 0.47 Mg, and 0.41 S, while for sugarcane it was 1.3 N, 0.25 P, 3.2 K, 0.28 Ca, 0.30 Mg, and 0.44 S, respectively. For more productive energy cane genotypes, those differences in nutritional demands are even greater. Therefore, higher amounts of fertilizers are required for energy cane genotypes. Moreover, since energy cane genotypes produce less sucrose, its use in industry will only be beneficial as long as their higher fiber content is fully converted into 2 G-ethanol or used for electricity cogeneration.
Field experiments with N2-fixing Acetobacter diazotrophicus, Herbaspirillum spp., and Azospirillum lipoferum in association with vesicular arbuscular mycorrhiza (VAM) on South Indian commercial sugar cane varieties which were not associated with A. diazotrophicus naturally, indicated promising prospects for limiting the use of inorganic N fertilizer from 140 kg ha-1 to the recommended dose of 275 kg N ha-1. The results also confirmed that the use of these microbes as biofertilizers would support sugar cane yields equivalent to or greater than yields supported by the recommended chemical N fertilizers.
In the period 1996-1999 field trial was performed in Obory near Kwidzyn on heavy textured Fluvisols. The experiment was aimed to determine yield, chemical composition, heat value of wood of six genotypes of willow coppice in relation to cutting frequency and on determining the costs and profitability of willow production on arable land for purposes of energy generation. Yield of wood dry matter in one-year cutting cycle amounted to 14.09 t.ha-1.year-1 and significantly increased to 16.05 and 21.55 t.ha-1.year-1 when harvesting was performed in two and three years cycle, respectively. The highest yield was found for Salix viminalis 082 form cut in three years cycle and it amounted to 26.44 t.ha-1.year-1. Stems of Salix sp. cut every three years showed the lowest water content (46.05%), high heat value 19.56 MJ.kg-1 dry matter and the highest content of cellulose (55.94%), lignins (13.79%) and hemicelluloses (13.96%). High yielding potential of Salix sp. and high content of cellulose and lignin in wood make this crop very prosperous as a feedstock for bioenergy production. The highest profit from the willow plantation was obtained in case of harvest every three years at 578.76 EUR.ha-1.year-1.
Understanding the changes underlying past breeding progress may help to focus research efforts and accelerate future genetic gains. The major abiotic stress affecting maize production on a worldwide basis is drought. We addressed the improvements in drought tolerance over a 50-year period of hybrid breeding by evaluating, under targeted stress conditions, a set of 18 Pioneer-brand hybrids that had been released during the 1953-2001 period. Stress treatments were designed as overlapping windows of water deficit covering the pre-flowering to late grain filling development stages. Data were collected on grain yield, yield components and anthesis-silking interval (ASI), and were analyzed using a linear mixed model approach. Genetic gain was measured as the slope of the regression of the trait on the year of hybrid release. Significant, positive genetic gains of varying magnitude were observed for grain yield in all windows of stress evaluated. The largest genetic gains for grain yield were observed under conditions of full irrigation and severe flowering stress. ASI and barrenness, especially under stress at flowering, were significantly reduced by selection. Though flowering remains the most susceptible stage to drought in maize, selection has reduced its negative effects, and susceptibility during early grain filling is now of similar importance in many modern hybrids. Yield under drought at flowering has more than kept pace with the increase in yield potential because of the emphasis breeders have placed on improved floral synchrony.
This paper addresses the question of whether there has been an increase in yield potential of maize (Zea mays L.) hybrids released in the north-central United States since the advent of the “Green Revolution” that began in the late 1960s. Because there are few published data about hybrid growth rates and yield-determining plant traits when grown at yield potential levels, we attempt to address this issue indirectly by evaluation of maize breeding efforts, changes in plant traits of commercial hybrids, and by comparison of statewide average yield trends and yield trends in sanctioned yield contests. On the basis of these sources of information and a definition of yield potential as the yield that can be achieved with an adapted hybrid when grown without obvious stress of any kind, we found that there is conflicting evidence to support the hypothesis that maize yield potential has increased. We recommend experimental approaches to quantify and investigate the determinants of maize yield potential in the north-central United States and for use in breeding hybrids with greater yield potential.
Crop productivity in the UK still falls well short of the potential of the UK's fertile environment. Because the industry does not detect the main changes being made by breeders in the major species, crop management strategies are not adjusted to fully exploit the potentials of new varieties. Crop growth can be seen in three phases: a foundation period which sets shoot numbers, a crop construction period (in which final crop structure is determined), and a yield forming period. These coincide roughly with winter, spring and summer. New research indicates that, from the 1960s to the 1990s, successive wheat varieties showed improvements primarily during the crop construction period: with increases in ear fertility, soluble stem carbohydrates, photosynthetic efficiency, fertiliser N recovery and total biomass, in addition to the well known decrease in height and increase in harvest index. Flowering dates did not change, but there is evidence of decreased rooting and less uptake of deep soil N. Modern wheat crops are probably still 'sink-limited', so they can withstand modest late stress, but as a consequence, they often fail to fully exploit good grain-filling conditions. The productivity of new varieties may be best exploited by restricting excess tillering, boosting ear fertility, and matching late N availability to the variety's grain protein demands. No similar studies have been made of changes in oilseed rape varieties, although breeding effort has been active, with frequent adoption of new varieties. Despite this, there has been no increase in farm yields over the past 20 years. Physiological factors associated with the restricted oilseed rape yields appear to be a short yield-forming period, over-dense pod canopies, and low photosynthetic efficiency of the pods. Low yields may also have arisen through the spread of sulphur deficiency, and over-early crop establishment. As with wheat, it appears that crop managers should aim to constrain growth in the foundation period, so that, during the construction phase, the potential for setting large pods with many seeds is fully exploited.
This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
The use of the 15N natural abundance technique to
quantify contribution of biological nitrogen fixation (BNF) to any plant is
based on the observation that N derived from soil is generally slightly
different [usually higher in 15N abundance
(δ15N‰)] than that of the air. Plants
or micro-organisms growing solely on BNF generally accumulate N with
15N isotopic abundance lower than that of the air (i.e.
δ15N‰ is negative), while plants obtaining
all N from the soil generally show a positive δ15N‰ signal. The
technique is applied by estimating the 15N abundance of
the putative ‘N2-fixing’ crop and analysing
the 15N abundance of neighbouring
non-N2-fixing reference plants. However, often there are
such large variations in the N derived from the soil by different
non-N2-fixing plants that in natural ecosystems it is
often impossible to even distinguish plants that are benefiting form BNF, let
alone quantity this contribution. The reasons why soil derived N can vary so
widely, especially in natural ecosystems, are briefly discussed and a sampling
strategy is described to assess possible BNF inputs to sugar cane plants in
commercial plantations in Brazil. The results suggest that in nine of the 11
sites studied, BNF inputs were significant ranging from 25 to 60% of N
assimilated.
Biomass represents an abundant carbon-neutral renewable resource for the production of bioenergy and biomaterials, and its
enhanced use would address several societal needs. Advances in genetics, biotechnology, process chemistry, and engineering
are leading to a new manufacturing concept for converting renewable biomass to valuable fuels and products, generally referred
to as the biorefinery. The integration of agroenergy crops and biorefinery manufacturing technologies offers the potential
for the development of sustainable biopower and biomaterials that will lead to a new manufacturing paradigm.
A range of free-living and endophytic N2 fixing bacteria have been isolated and used as inoculants on non-legume plants in attempts to maintain or increase yield while reducing the need for fertiliser N. Here, the literature on inoculation of dryland graminaceous crops with N2 fixing bacteria in temperate and tropical agricultural systems is reviewed and the progress made, mechanisms of action of the bacteria and future potential of this approach, assessed. Firstly, we consider the use of Azotobacter spp. in Russia in the 1940s and 1950s and Azospirillum spp. worldwide in the 1970s and 1980s. In both cases, effects on yield were inconsistent.
Maize (Zea mays L.) pollen production has been found not to limit kernel set, but there is scarce information on pollen production of modern hybrids and the effect that breeding for reduced tassel size has had on this trait. Our objectives were to study genotypic differences in pollen production and flowering dynamics, and to estimate pollen availability per exposed silk. Four F1 hybrids were grown at different plant densities (between 2.5 and 12.5 plants m-2) in two distinct environments (cool Midwest USA and temperate Argentine Pampa). Pollen availability was also modified by delayed plantings and detasseling treatments. We measured the dates of anthesis and silking of individual plants, the anthesis-silking interval (ASI), the number of exposed silks per apical ear, the number of pollen grains per square meter (PGM), and kernel number per ear. The number of pollen grains produced per tassel (PGT) and per exposed silk were estimated. Increased plant density promoted an increase in ASI, matched by an enhanced interplant variability in this parameter, and a reduction in PGT. The latter was reduced from 10.3 × 106 or 11 × 106 at 2.5 plants m-2 to about 3 × 106 at 12.5 plants m-2 (USA), and from 9.7 × 106 or 11.3 × 106 at 3 plants m-2 to 4 × 106 or 3.6 × 106 at 9 plants m-2 (Argentina). We estimated two thresholds beyond which kernel set could be affected: (i) 227 pollen grains cm-2 d-1 at the end of pollen shedding and (ii) two pollen grains per exposed silk. Some cropping conditions were closer to the second threshold than others.
Miscanthus spp. are high-yielding perennial C4 grasses, native to Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high biomass yields with good combustion qualities. Good biomass combustion quality depends on minimizing moisture, ash, K, chloride, N, and S. To this end, field trials at five sites in Europe from Sweden to Portugal were planted with 15 different genotypes including M. × giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis hybrids. Yield and combustion quality at an autumn and a late winter/early spring harvest were determined in the third year after planting when the stands had reached maturity. As expected, delaying the harvest by three to four months improved the combustion quality of all genotypes by reducing ash (from 40 to 25 g kg⁻¹ dry matter), K (from 9 to 4 g kg⁻¹ dry matter), chloride (from 4 to 1 g kg⁻¹ dry matter), N (from 5 to 4 g kg⁻¹ dry matter), and moisture (from 564 to 291 g kg⁻¹ fresh matter). However, the delayed harvest also decreased mean biomass yields from 17 to 14 t ha⁻¹ There is a strong interaction among yield, quality, and site growing conditions. Results show that in northern regions of Europe, M. sinensis hybrids can be recommended for high yields (yielding up to 25 t ha⁻¹), but M. sinensis (nonhybrid) genotypes have higher combustion qualities. In mid- and south Europe, M. × giganteus (yielding up to 38 t ha⁻¹) or specific high-yielding M. sinensis hybrids (yielding up to 41 t ha⁻¹) are more suitable for biofuel production.
Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © 2003. American Society of Agronomy . American Society of Agronomy
Miscanthus is a genus of high-yielding perennial rhizomatous grasses with C4 photosynthesis. Extensive field trials of Miscanthus spp. biomass production in Europe during the past decade have shown several limitations of the most widely planted clone, M. ? giganteus Greef et Deu. A 3-yr study was conducted at five sites in Europe (Sweden, Denmark, England, Germany, and Portugal) to evaluate adaptation and biomass production potential of four acquisitions of M. ? giganteus (No. 1?4) and 11 other genotypes, including M. sacchariflorus (Maxim.) Benth. (No. 5), M. sinensis Andersson (No. 11?15), and hybrids (No. 6?10). At each site, three randomized blocks containing a 5- by 5-m plot of each genotype were established (except in Portugal where there were two blocks) with micropropagated plants at 2 plants m?2 In Sweden and Denmark, only M. sinensis and its hybrids satisfactorily survived the first winter following planting. Mean annual yields across all sites for all surviving genotypes increased each year from 2 t ha?1 dry matter following the first year of growth to 9 and 18 t ha?1 following the second and third year, respectively. Highest autumn yields at sites in Sweden, Denmark, England, and Germany were 24.7 (M. sinensis hybrid no. 8), 18.2 (M. sinensis hybrid no. 10), 18.7 (M. ? giganteus no. 3), and 29.1 t ha?1 (M. ? giganteus no. 4), respectively. In Portugal, where irrigation was used, the top-yielding genotype produced 40.9 t ha?1 dry matter (M. sinensis hybrid no. 7). Highest-yielding genotypes in Sweden and Denmark were among the lowest yielding in Portugal and Germany, demonstrating strong genotype ? environment interactions.
Greenhouse gas (GHG) emissions constitute a global problem. The need for agricultural involvement in GHG mitigation has been widely recognized since the 1990s. The concept of C sinks, C credits, and emission trading has attracted special interests in herbaceous and woody species as energy crops and source of biofuel feedstock. Bioenergy crops are defined as any plant material used to produce bioenergy. These crops have the capacity to produce large volume of biomass, high energy potential, and can be grown in marginal soils. Planting bioenergy crops in degraded soils is one of the promising agricultural options with C sequestration rates ranging from 0.6 to 3.0 Mg C ha yr. About 60 million hectares (Mha) of land is available in the United States and 757 Mha in the world to grow bioenergy crops. With an energy offset of 1 kg of C in biomass per 0.6 kg of C in fossil fuel, there exists a vast potential of offsetting fossil fuel emission. Bioenergy crops have the potential to sequester approximately 318 Tg C yr in the United States and 1631 Tg C yr worldwide. Bioenergy crops consist of herbaceous bunch-type grasses and short-rotation woody perennials. Important grasses include switchgrass (Panicum virgatum L.), elephant grass (Pennissetum purpureum Schum.), tall fescue (Fetusca arundinacea L.), etc. Important among short-rotation woody perennials are poplar (Populus spp.), willow (Salix spp.), mesquite (Prosopis spp.), etc. The emissions of CO2 from using switchgrass as energy crop is 1.9 kg C Gj compared with 13.8, 22.3, and 24.6 kg C Gj from using gas, petroleum, and coal, respectively. Mitigation of GHG emissions cannot be achieved by C sinks alone, a substantial reduction in fossil fuel combustion will be necessary. Carbon sequestration and fossil fuel offset by bioenergy crops is an important component of a possible total societal response to a GHG emission reduction initiative.
As molecular biologists are realising the importance of physiology in understanding functional genomics of quantitative traits, and as physiologists are realising the formidable prospects for improving their phenotypic models with information on the underlying gene networks, researchers worldwide are working on linked physiological–genetic models. These efforts are in their early methodological stage despite, or because of, the availability of many different types of models, the problem being to bring together the different ways that scientists see the plant. This paper describes some current efforts to adapt phenotype models to the objective of simulating gene-phene processes at the plant or crop scale. Particular emphasis is given to the models’ capacity to simulate genotype × environment interaction and the resulting phenotypic plasticity, assuming that this permits the defining of model parameters that are closer to specific gene action. Three different types of approaches are presented: (1) a generic, mathematical-architectural model called GREENLAB that simulates resource-modulated morphogenesis; (2) an ecophysiological model of peach tree fruit development and filling, parameterised for a mapping population to evaluate the potential of plugging quantitative trait locus (QTL) effects into the model; and (3) the new model Ecomeristem that constructs plant architecture and its phenotypic plasticity from meristem behaviour, the principal hypothesis being that resource limitations and stresses feed back on the meristems. This latter choice is based on the fact that gene expression happens to a large extent in the meristems. The model is evaluated on the basis of preliminary studies on vegetative-stage rice. The different modelling concepts are critically discussed with respect to their ability to simulate phenotypic plasticity and to operate with parameters that approximate specific gene action, particularly in the area of morphogenesis.
Phenotypic plasticity enables plants to adjust their morphology and phenology to variable environments. Although potentially important for crop breeding and management, the physiology and genetics of plasticity traits are poorly understood, and few models exist for their study. In the previous paper of this series, the structural–functional model EcoMeristem was described and field validated for vegetative-stage rice. This study applies the model to an experimental study on phosphorus deficiency effects on two morphologically contrasting rice cultivars, IR64 and Azucena, grown in controlled environments under hydroponics culture. Phosphorus deficiency caused severe biomass growth reductions in the shoot but not in the root, thus increasing the root / shoot weight ratio. It also inhibited tiller formation and leaf elongation, prolonged the phyllochron, and increased carbohydrate reserve pools in the plant. Analysis aided by the model identified inhibition of leaf extension and tillering as primary effects of the stress. Physiological feedback probably led to longer phyllochron, greater reserve accumulation and root growth stimulation. The main effect of P deficiency appeared to be a reduction in demand for assimilates in the shoot while photosynthetic radiation use efficiency remained nearly constant, resulting in spill-over of excess assimilates into reserve compartments and root growth. The results are discussed in the light of future applications of EcoMeristem for phenotyping and genetic analyses of phenotypic plasticity.
Sugarcane was first introduced into Brazil in 1532, in São Vicente (São Paulo State) by the Portuguese. Since the first cane selection and breeding programs started in Brazil, both local and introduced material were used. In none of the breeding programs were large amounts of nitrogen fertilizer utilized, and this may be the reason why today the best materials have little demand for nitrogen fertilizer, and an effective association has developed between endophytic nitrogen-fixing bacteria and the plant. In some cases high inputs of associated biological nitrogen fixation have been observed. The oil crisis also played a role in the sugarcane story, since the alcohol-from-cane-juice (PRO-ÁLCOOL) program installed to find a substitute for gasoline in cars, stimulated the selection of highly efficient varieties with low nitrogen fertilizer input. The recent promising results involving the inoculation of micropropagated sugarcane plants with endophytic diazotrophic bacteria, along with the ongoing Brazilian sugarcane plant and bacterial genome programs, suggest that the success of the Brazilian sugarcane business may continue for many years to come, considering the potential to be exploited.
A model for forage yield with adequate details for leaf area, biomass, nutrients, and hydrology would be valuable for making management decisions. The objectives of this study were to develop Alamo switchgrass (Panicum virgatum L.) parameters for the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model and demonstrate its accuracy across a wide range of environments. Derived plant parameters included potential leaf area index (LAI), potential biomass growth per unit intercepted light, optimum nutrient concentrations, and growth responses to temperature. The model's simulated yields accounted for 79% of the variability in measured yields for one-cut and two-cut harvest systems from six diverse sites in Texas in 1993 and 1994. Simulated yields for three locations differed in sensitivity to potential LAI, heat units to maturity, radiation use efficiency (RUE), and soil depth. The ALMANAC model shows promise as a management tool for this important forage and bioenergy crop.
Populus is a genus of extremely fast-growing trees originating in the northern hemisphere, with potential as a source of renewable, biomass energy. The aim of this work was to physiologically characterize genotypes of hybrid poplar, informing future selection, breeding and the development of process-based yield models. Two experiments – a short rotation coppice field trial at two contrasting UK sites and a glasshouse experiment – were conducted on five different genotypes of Populus. The field trial experiment showed that stemwood yields varied between 5.8 and 11.8 t ha?1 a?1 and that the genotype, Hoogvorst (Populus trichocarpa × P. deltoides) was the most productive. This production was characterized at a physiological level by rapid rates of leaf expansion and slow rates of leaf production and, at a cellular level, by the largest epidermal cell number per leaf. The glasshouse experiment confirmed the superior productivity of Hoogvorst, with this genotype producing the largest individual leaf areas (P 0.005) that were highly correlated with biomass production (R2 = 0.7). There was no correlation between leaf-level photosynthesis measurements and total biomass production. In general, leaf level photosynthetic characteristics were less able to differentiate between the most productive and less productive genotypes than morphological traits.
Energy crops currently contribute a relatively small proportion to the total energy produced from biomass each year, but the proportion is set to grow over the next few decades. This paper reviews the current status of energy crops and their conversion technologies, assesses their potential to contribute to global energy demand and climate mitigation over the next few decades, and examines the future prospects. Previous estimates have suggested a technical potential for energy crops of?400?EJ?yr?1 by 2050. In a new analysis based on energy crop areas for each of the IPCC SRES scenarios in 2025 (as projected by the IMAGE 2.2 integrated assessment model), more conservative dry matter and energy yield estimates and an assessment of the impact on non-CO2 greenhouse gases were used to estimate the realistically achievable potential for energy crops by 2025 to be between 2 and 22?EJ?yr?1, which will offset?100-2070?Mt?CO2-eq.?yr?1. These results suggest that additional production of energy crops alone is not sufficient to reduce emissions to meet a 550??mol?mol?1 atmospheric CO2 stabilization trajectory, but is sufficient to form an important component in a portfolio of climate mitigation measures, as well as to provide a significant sustainable energy resource to displace fossil fuel resources. Realizing the potential of energy crops will necessitate optimizing the dry matter and energy yield of these crops per area of land through the latest biotechnological routes, with or without the need for genetic modification. In future, the co-benefits of bioenergy production will need to be optimized and methods will need to be developed to extract and refine high-value products from the feedstock before it is used for energy production.
Field trials were established at four different sites in 1994, setting out plants of Miscanthus sinensis, cv. Gigantheus produced from tissue cultures. The influence of soil and weather conditions was studied with respect to plant wintering over the first winter season, the effects of differentiated N rates (0, 50, 100 kg.ha(-1)) on the yield of Miscanthus dry biomass were investigated at the experimental sites in the particular years. The survival of plants in the first winter with respect to the soil and weather conditions at the sites ranged between 10% on shallow and poor-in-nutrients Cambisol in cold conditions and 100% on Orthic Luvisol and Chernozem in warmer conditions. The yields of dry biomass increased every year, average yields amounted to 6.15 t.ha(-1) at Lukavec, 17.89 t.ha(-1) at Ruzyne, 28.19 t.ha(-1) at Troubsko in the third year after planting. Miscanthus yields were substantially influenced by N application rates at Lukavec site with less favorable soil and climatic conditions, and at Troubsko site. Application rates of 100 kg.ha(-1) N at Lukavec increased dry biomass yields from 3.0 t.ha(-1) without N fertilizing to 9.32 t.ha(-1) in the third year after planting. At Troubsko, the best site for Miscanthus productivity, N application rates of 50 kg.ha(-1) increased dry biomass yields by 6.9% on average over the whole period of observation, while the N rate of 100 kg.ha(-1) increased yields by 18.2% against the variant without fertilizing. The results obtained at Ruzyne site in the separate years do not allow to determine explicitly any significant effect of differentiated N rates on yield increase.
The grain and straw yields and nitrogen contents of an old and a modern winter wheat cultivar were compared on a series of plots on the Broadbalk wheat experiment at Rothamsted Experimental Station, England, over a three year period. The plots had received amounts of fertilizer nitrogen ranging from 0 to 288 kg ha-1 and, except for one, all had received ample amounts of phosphorus, potassium and magnesium fertilizer. In each plot, the plants in a 2.0 × 2.0 m area were supported to prevent lodging, those in the remaining area being non-supported. Different sections of the experiment allowed rotational and agrochemical treatments, and their interactions with plot, i.e., nitrogen fertilization, and cultivar, to be assessed.
The use of the 15N natural abundance technique to quantify contribution of biological nitrogen fixation (BNF) to any plant is based on the observation that N derived from soil is generally slightly different [usually higher in 15N abundance (δ15N‰)] than that of the air. Plants or micro-organisms growing solely on BNF generally accumulate N with 15N isotopic abundance lower than that of the air (i.e. δ15N‰ is negative), while plants obtaining all N from the soil generally show a positive δ15N‰ signal. The technique is applied by estimating the 15N abundance of the putative 'N2-fixing' crop and analysing the N abundance of neighbouring non-N2-fixing reference plants. However, often there are such large variations in the N derived from the soil by different non-N2-fixing plants that in natural ecosystems it is often impossible to even distinguish plants that are benefiting form BNF, let alone quantity this contribution. The reasons why soil derived N can vary so widely, especially in natural ecosystems, are briefly discussed and a sampling strategy is described to assess possible BNF inputs to sugar cane plants in commercial plantations in Brazil. The results suggest that in nine of the 11 sites studied, BNF inputs were significant ranging from 25 to 60% of N assimilated.
Experiments in three dry seasons (1993/94, 1994/95, 1995/96) on a loamy medium sand at ADAS Gleadthorpe, Nottinghamshire, England tested responses of green area, radiation interception, water uptake and above-ground dry matter growth of six wheat cultivars to irrigation. Cultivars differing in date of introduction (Haven 1987, Maris Huntsman 1969, Mercia 1983, Rialto 1991, Riband 1985 and Soissons 1989) were chosen for contrast in flowering time and maximum green area. Maximum soil moisture deficit (SMD) exceeded 140 mm in all years, with large deficits (> 75 mm) from early June in 1994 and more prolonged large deficits in 1995 and 1996. Restricted water availability first affected canopy expansion at a SMD of 74 mm (50% available water capacity; AW), and canopy senescence at 95 mm (64% AW). Decreases in biomass at harvest were larger with prolonged droughts in 1995 and 1996 (4245·7 g/m2/mm. The susceptibility of Haven to drought was possibly due to restricted water uptake, depression of radiation use efficiency (RUE) and accelerated senescence. The cultivars differed in flowering by up to 9 days but date of flowering correlated poorly with biomass response to irrigation. Early flowering was, however, correlated with favourable distribution of seasonal water use with respect to the grain filling period. The maximum green area index (GAI) of cultivars varied from 4·4 to 5·3 (P < 0·01), but differences were countered by shifts in the extinction coefficient (K), such that season-long radiation interception varied little. Green area index maxima did not therefore relate to the pattern of growth or water use, and they were correlated poorly with the biomass responses. Cultivars did not differ in their maximum depth of water extraction; they all extracted water to 1·65 m depth in each year. It is concluded that early flowering and high WUE might offer scope for improving drought resistance in the UK's temperate climate, but that small maximum GAI seems less useful.
The effects of nitrogen fertilization (100, 200 kg N ha(-1) per year) and soil properties on mycorrhizal formation on Salix viminalis were investigated at three short rotation plantations on Gleysols and Cambisols (Abbachhof (ABB) and Wildeshausen (WIL) in Germany. Ultuna (ULT) in Sweden). During 3 years the ectomycorrhizal colonization, the composition of ectomycorrhizal morphotypes and the VAM spore density in the soil were analyzed. The ectomycorrhizal colonization was significantly altered due to N-fertilization at all sites. The quality and magnitude of the fertilization effects on mycorrhizal formation on Salix viminalis varied due to the soil properties, i.e. soil texture, soil N content and pH. The WIL site was characterized by sandy soil (low pH. high soil N content), whereas the ABB site was characterized by clayey soil (high pH, low N content). The ULT site was characterized by clayey soil (high pH. high N content). In the unfertilized control plots
Over ten times more CO2 is fixed by plants into biomass, and annually released by decomposers and food chains, than is emitted to the atmosphere due to the burning of fossil fuels. Human activity is already directly and indirectly affecting almost half of the terrestrial biological C cycle. Management of even a small fraction of the biological C cycle would make a major contribution to mitigation of this greenhouse gas.Electric power generation is responsible for roughly one third of fossil CO2 emissions. Direct CO2 mitigation processes are those that reduce fossil CO2 emissions from specific power plants. Direct biological CO2 mitigation processes include the cultivation of microalgae on flue-gas or captured CO2, and the cofiring of wood with fossil fuels. Indirect biological processes, such as growing trees for C storage or for fueling dedicated biomass power plants, recapture CO2 that already has entered the atmosphere. Indirect and direct CO2 mitigation processes have the same overall effect in reducing global warming potential.Reducing global CO2 emissions from forest destruction and unsustainable agricultural and land use practices is one of the most cost-effective, and environmentally beneficial actions that can be taken now to arrest global climate change. Another near-term option is to enhance the substitution of fossil fuels with biofuels. Biofuels are a major source of fuel for the power half of mankind. Globally, biofuels could replace a substantial fraction of current fossil fuel usage.Cofiring biomass wastes and residues with coal is one of the lowest-cost, nearest-term options for reducing fossil CO2 emissions at existing power plants. Long-term demonstrations of biomass cofiring are required at full-scale coal-fired power plants to document efficiencies, ash characteristics, biomass preparation and feeding, and other technical issues. Biomass fuel resources for cofiring can be expanded in the near-term through greater recovery of wastes and residues in forestry and agriculture, and in the mid-term through systems that produce biomass specifically for use as fuels (energy crops).
A robust fusion of the agricultural, industrial biotechnology, and energy industries can create a new strategic national capability for energy independence and climate protection. In his State of the Union Address (Bush 2006), President George W. Bush outlined the Advanced Energy Initiative, which seeks to reduce our national dependence on imported oil by accelerating the development of domestic, renewable alternatives to gasoline and diesel fuels. The president has set a national goal of developing cleaner, cheaper, and more reliable alternative energy sources to substantially replace oil imports in the coming years. Fuels derived from cellulosic biomass - the fibrous, woody, and generally inedible portions of plant matter - offer one such alternative to conventional energy sources that can dramatically impact national economic growth, national energy security, and environmental goals. Cellulosic biomass is an attractive energy feedstock because it is an abundant, domestic, renewable source that can be converted to liquid transportation fuels. These fuels can be used readily by current-generation vehicles and distributed through the existing transportation-fuel infrastructure. The Biomass to Biofuels Workshop, held December 7-9, 2005, was convened by the Department of Energy's Office of Biological and Environmental Research in the Office of Science; and the Office of the Biomass Program in the Office of Energy Efficiency and Renewable Energy. The purpose was to define barriers and challenges to a rapid expansion of cellulosic-ethanol production and determine ways to speed solutions through concerted application of modern biology tools as part of a joint research agenda. Although the focus was ethanol, the science applies to additional fuels that include biodiesel and other bioproducts or coproducts having critical roles in any deployment scheme. The core barrier is cellulosic-biomass recalcitrance to processing to ethanol. Biomass is composed of nature's most ready energy source, sugars, but they are locked in a complex polymer composite exquisitely created to resist biological and chemical degradation. Key to energizing a new biofuel industry based on conversion of cellulose (and hemicelluloses) to ethanol is to understand plant cell-wall chemical and physical structures - how they are synthesized and can be deconstructed. With this knowledge, innovative energy crops - plants specifically designed for industrial processing to biofuel - can be developed concurrently with new biology-based treatment and conversion methods. Recent advances in science and technological capabilities, especially those from the nascent discipline of systems biology, promise to accelerate and enhance this development. Resulting technologies will create a fundamentally new process and biorefinery paradigm that will enable an efficient and economic industry for converting plant biomass to liquid fuels. These key barriers and suggested research strategies to address them are described in this report. As technologies mature for accomplishing this task, the technical strategy proceeds through three phases: In the research phase, within 5 years, an understanding of existing feedstocks must be gained to devise sustainable, effective, and economical methods for their harvest, deconstruction, and conversion to ethanol. Research is centered on enzymatic breakdown of cellulosic biomass to component 5- and 6-carbon sugars and lignin, using a combination of thermochemical and biological processes, followed by cofermentation of sugars to specified endproducts such as ethanol. Processes will be integrated and consolidated to reduce costs, improve efficacy, reduce generation of and sensitivity to inhibitors, and improve overall yields and viability in biorefinery environments. The technology deployment phase, within 10 years, will include creation of a new generation of energy crops with enhanced sustainability, yield, and composition, coupled with processes for simultaneous breakdown of biomass to sugars and cofermentation of sugars via new biological systems. These processes will have enhanced substrate range, temperature and inhibitor tolerance, and the capability to function in complex biorefining environments and over time scales that are economically viable. The systems-integration phase, within 15 years, will incorporate concurrently engineered energy crops and biorefineries tailored for specific agroecosystems. Employing new and improved enzymes for breaking biomass down to sugars as well as robust fermentation processes jointly consolidated into plants or microbes, these highly integrated systems will accelerate and simplify the end-to-end production of fuel ethanol. In many ways, these final-phase technologies will strive to approach theoretical conversion limits. The new generation of biotechnologies will spur engineering of flexible biorefineries operable in different agricultural regions of the country and the world.
Energy crops are fast-growing species whose biomass yields are dedicated to the production of more immediately usable energy forms, such as liquid fuels or electricity. Biomass-based energy sources can offset, or displace, some amount of fossil-fuel use. Energy derived from biomass provides 2 to 3% of the energy used in the U.S.A.; but, with the exception of corn-(Zea mays L.)-to-ethanol, very little energy is currently derived from dedicated energy crops. In addition to the fossil-fuel offset, energy cropping might also mitigate an accentuated greenhouse gas effect by causing a net sequestration of atmospheric C into soil organic C (SOC). Energy plantations of short-rotation woody crops (SRWC) or herbaceous crops (HC) can potentially be managed to favor SOC sequestration. This review is focused primarily on the potential to mitigate atmospheric CO2 emissions by fostering SOC sequestration in energy cropping systems deployed across the landscape in the United States. We know that land use affects the dynamics of the SOC pool, but data about spatial and temporal variability in the SOC pool under SRWC and HC are scanty due to lack of well-designed, long-term studies. The conventional methods of studying SOC fluxes involve paired-plot designs and chronosequences, but isotopic techniques may also be feasible in understanding temporal changes in SOC. The rate of accumulation of SOC depends on land-use history, soil type, vegetation type, harvesting cycle, and other management practices. The SOC pool tends to be enhanced more under deep-rooted grasses, N-fixers, and deciduous species. Carbon sequestration into recalcitrant forms in the SOC pool can be enhanced with some management practices (e.g., conservation tillage, fertilization, irrigation); but those practices can carry a fossil-C cost. Reported rates of SOC sequestration range from 0 to 1.6 Mg C ha yr under SRWC and 0 to 3 Mg C ha yr under HC. Production of 5 EJ of electricity from energy crops—a perhaps reasonable scenario for the U.S.A.—would require about 60 Mha. That amount of land is potentially available for conversion to energy plantations in the U.S.A. The land so managed could mitigate C emissions (through fossil C not emitted and SOC sequestered) by about 5.4 Mg C ha yr. On 60 Mha, that would represent 324 Tg C yr—a 20% reduction from current fossil-fuel CO2 emissions. Advances in productivity of fast-growing SRWC and HC species suggest that deployment of energy cropping systems could be an effective strategy to reduce climate-altering effects of anthropogenic CO2 emissions and to meet global policy commitments.
The optimum plant density for total grain yield increased from old to more recent hybrids, but the increase in optimum plant density did not continue for hybrids from the 1970s era to hybrids of the 1980s era. Approximately one-third of the genetic gain in machine-harvestable grain yield can be attributed to reduced stem lodging. A comparison of the oldest and most recent hybrids indicates that approximately 15% of the genetic gain in total grain yield can be attributed to increased harvest index. Consequently, increase in total dry matter accumulation attributed 85% to the genetic gain in total grain yield
The genetic structure of Salix viminalis L. for different growth traits and bud flush has been studied. The aim was also to study differences in the genetic structure due to geographic origin and type of trait. Two incomplete factorial crossings with parental clones originating from Poland and Sweden were used. Growth traits showed a high amount of dominance genetic variance independent of parental origin. It is suggested that inbreeding depression found in S. viminalis could be a biological cause of the high levels of dominance as an alternative to overestimation due to epistasis. There were significant differences in amount of dominance genetic variance between the two origins for three of the nine growth traits. The higher number of characters influenced by dominance in the pedigree with Swedish origin can possibly be explained by linkage disequilibrium, since S. viminalis in Sweden has been introduced from Germany and Poland, and no sexual propagation of the species in Sweden has been reported. Bud flush showed high additive genetic variance in contrast to the growth traits. In the breeding for biomass production of S. viminalis, the high amount of dominance has to be taken into consideration.
In 1995, a short-rotation plantation (2.5 hectares) was established in the mining region of Welzow-Süd in southern Brandenburg, Germany, on a clayey, sandy, lignite- and pyrite-free substrate in order to study the potentials of fast-growing tree species (e. g. balsam poplar). In this study, special emphasis was placed on yield aspects as well as on the interaction between soil and plant, especially with regard to plant and soil water relations. So far the results indicate that the cultivation of fast-growing tree species in short-rotation plantation is an adequate tool for establishing sustainable land use systems in post-mining landscapes. Above-ground biomass increments ranged from 7 to 20 tons of dry matter per hectare at age 4. Investigations on the leaf water potential of two poplar clones (low-yielding clone Androscoggin and high-yielding clone Beaupré) showed different stomatal behaviour. Whole-shoot hydraulic conductivity as well as conductivity of diameter classes and transpiration rate were significantly higher in the high-yielding clone. The tendency of drought stress-induced embolism was significantly lower in the fast-growing clone Beaupré. By modelling the soil water regime for the experimental plots, it was found that transpiration and water-use efficiency were higher in the clone Beaupré than in the clone Androscoggin. The deep percolation rate was also higher at the clone Beaupré site than at the experimental field grown with the clone Androscoggin-Standort.
Previous studies have shown that both photoinhibition and low temperature impairment of leaf development occur in C4 species growing in temperate climates. These result in reductions in the maximum quantum efficiency (φ) and the light-saturated
rate of CO2 uptake (Asat). The perennial C4-grass Miscanthus × giganteus has been shown to attain high productivity in northern Europe. This study examines and analyses the seasonal variation in
photosynthetic gas exchange of M. × giganteus grown in southern England. Although the crop was exposed to chilling temperatures at the start of the season neither Asat nor φ were impaired, when assessed at a measurement temperature of 24°C. Between May and July the mean values of Asat and φ were 34 μmol m−2 s−1 and 0.067, respectively, declining to 20 μmol m−2, s−1 and 0.045 in October. In the field, on clear days between May and July, the typical midday rates of CO2, uptake ranged between 20–27 μmol m−2 S−1, although in late-June a peak mean value of 35 μmol m−2 s−1 was attained. The study shows that under the cool temperate conditions of southern England, M. × giganteus, unlike all C4 species previously examined, is able to realize the photosynthetic potential of the C4 process without suffering any apparent low temperature impairment, except possibly at the very end of the growing season.
Quantification of effects from factors known to modify vegetative development and growth in grasses is important in modeling biomass yield. The objective of this study was to measure the effects of increasing levels of N on leaf appearance (LAR) and lamina extension rates (LER) in switchgrass (Panicum virgatum L.) under field and controlled environmental conditions. Five nitrogen (N) fertilizer rates (0 to 268 kg N ha) were applied to a stand of “Alamo” switchgrass at Dallas, TX, and to potted plants (0 to 400 ppm) in a controlled environment. Quadratic regression models best described these responses to increasing rates of fertilizer N in both the field and controlled environment. In the field, LAR decreased to a minimum of 241 growing degree days (GDD) leaf at 163 kg N ha and LER increased to a maximum of 0.188 cm GDD at 164 kg N ha. In the controlled environment, LAR decreased to a minimum of 155 GDD leaf at 90 ppm N and LER increased to a maximum of 0.272 cm GDD at 156 ppm N. Results demonstrate that LAR and LER are significantly affected by fertilizer N. Lamina extension rate responded to increasing levels of N in a manner typical of a classic yield response curve and was strongly correlated to plot yields, confirming its value as a potential indicator of yield.
The broad spectrum fungicide mancozeb was applied to monocultured sugarcane soils affected by the growth constraint known as sugarcane yield decline. The constraint is associated with the long-term monoculture of sugarcane and has been shown to decrease sugarcane growth by 20% in commercial crops in Queensland. The fungicide was shown to decrease root colonization by soil fungi, particularly dematiaceous sterile fungi. Higher doses of mancozeb (up to 400 mg kg-1) sometimes led to increased populations of Penicillium spp. The fungicide greatly improved plant growth and root health when applied at doses of 100 mg kg-1 and above. Results suggest that the role of dematiaceous sterile fungi in sugarcane yield decline should be further examined.
This paper is concerned with a comparative study of the energy sustainability of the production of biodiesel from oleaginous plants (rape and sunflower), of bioethanol from sugar crops (sugar beet and sweet sorghum) and of electricity from lignocellulose materials (miscanthus and short rotation forestry poplar). The results show the lignocellulose feedstock to perform best in terms of both net energy produced per unit area of cultivated land, from around 184 GJ/ha to more than 434 GJ/ha, and of energy ratio between energy produced and energy consumed, in the order of 12–19. Biodiesel and bioethanol production were found to be less advantageous in terms of energy sustainability, especially when residues and by-products are not used as feedstock. For bioethanol production, sweet sorghum exhibited the higher energy ratio of around 5.2, due mainly to the heat recovered from residue in cogeneration plants. As for biodiesel production, neither the rape nor the sunflower proved to be particularly sustainable with an energy ratio of around 1.3–1.4, but performance can be improved using the agricultural and industrial processing residues to produce energy, increasing energy ratios up to 3.4–4.2.
Field experiments were conducted during 1991 and 1992 to identify the effect of wheat breeding on crop biomass production and its physiological determinants, i.e. radiation interception and radiation-use efficiency. To address this objective, biomass accumulation and its physiological attributes of seven cultivars (including a commercial hybrid) released between 1920 and 1990 were compared in fertilised and irrigated plots. Weeds, pests, diseases and lodging were controlled or prevented. Crop radiation interception was calculated from measurements of incident and transmitted radiation at different times after sowing. Above-ground dry matter was determined at particular stages of development of the cultivars. Radiation-use efficiencies and crop growth rates were calculated for each cultivar for pre-anthesis (in both years) and post-anthesis (in 1992) periods.Biomass at anthesis tended to be less in most recently released cultivars than in older materials. Accumulated intercepted radiation at similar developmental stages also differed between cultivars. These differences, as well as the trend of biomass at anthesis, were caused by differences in the length of developmental phases between cultivars rather than by changes in the architecture of the canopies. The most recently released cultivars had shorter seedling emergence-anthesis periods than older cultivars. Moreover, all cultivars had similar canopy light extinction coefficients (k), pre-anthesis radiation-use efficiencies, and crop growth rates.After anthesis, the two oldest cultivars accumulated the least biomass and their radiation-use efficiencies and crop growth rates were smaller than those of modern cultivars. Remarkably, modern cultivars maintained during post-anthesis almost the same levels of crop growth rates and radiation use efficiencies reached during the pre-anthesis period.
The C4 perennial grasses Miscanthus x giganteus and Spartina cynosuroides are potential biomass crops. Evaporation and growth rates of 3-year-old rainfed and irrigated stands were measured over one growing season in southeast England. Leaf gas exchange provided an independent measure of instantaneous water use efficiency. Total water use was similar in both species, in each treatment. However, due to the higher productivity of M. x giganteus, the above ground biomass formed per unit of water loss (‘water use efficiency’) was higher in M. x giganteus than S. cynosuroides. In irrigated crops the values were 9.1 and 7.4gkg−1, respectively and in rainfed crops 9.5 and 8.2gkg−1, respectively. When normalized by the daily maximum vapour pressure deficit, the values for both crops were comparable with typical values for C4 crops in a range of environments; 7.3–9.4gkPakg−1. Soil water deficits reduced the crop coefficient (the ratio of water loss from the crop to Penman potential evaporation) in rainfed stands by ca. 50%. The crop coefficient of irrigated crops exceeded 1.5 in mid-season. Difficulties in making comparisons between values of water use efficiency derived from different measurements of leaf gas exchange and crop growth are discussed.
A commercial breeding programme of willows was started by Svalöf Weibull AB in 1987. Since willow is a novel crop when it comes to breeding for biomass production, rapid progress has been made in terms of improved yield, erect growth, resistance to leaf rust and insects and tolerance to frost. Seven varieties have been released up to now. Material collected in Europe, central Russia and Siberia constitutes the main gene pool in the breeding population. Data are presented on relative yields, rust and gall midge susceptibility, and pest resistance.
A comparative overview is made of a suite of characteristics related to physiological processes of development, growth and productivity of three functionally related genera, namely eucalypt (Eucalyptus), poplar (Populus) and willow (Salix). The approach provides basic information for top-down as well as bottom-up models, with particular reference to coppice growth and productivity. Eucalypt, poplar and willow are similar in many aspects but differ in others. All three genera have similar indeterminate shoot growth, leaf life span and biomass development patterns. Information on the development of leaf area index is central to current models of biomass production. However, there are very few data in the literature on the time-course of leaf area development for short-rotation crops, particularly after coppicing. There is considerable evidence that coppicing schedules affect the spatial and temporal development of canopy structure. More information is needed on how canopy development in coppice regrowth differs from that in plantations of seedlings or first-rotation cuttings, if comparative assessment of the three genera in a longer term silvicultural context is to be meaningful. Key components are leaf size and photosynthetic rates during sprouting, in relation to carbohydrate status of the stool. The longer term responses must take into account the interaction between coppicing schedules and the susceptibility of new shoots to herbivory and disease.
An experiment was set up at three sites in the UK representing a range of soil types and annual rainfall. Three poplar clones, Populus trichocarpa×P. deltoides “Beaupré”, Populus trichocarpa×P. deltoides “Boelare” and Populus trichocarpa “Trichobel”, were used to examine the effects of spacing and cutting cycle on yield production. Two spacings 1.0×1.0 m and 2.0×2.0 m were examined factorially with two and four year cutting cycles.The highest yield of 13.6 oven dry tonnes per hectare per year was achieved by the clone Populus trichocarpa×P. deltoides “Boelare” at the wettest site with the best soil moisture retention on a four year cutting cycle at the 1.0×1.0 m spacing. The 1.0×1.0 m spacing produced higher yields than the 2.0×2.0 m spacing. At the most productive site the annual yield from a four year cutting cycle was significantly greater than that from the two year cutting cycle. This finding was not repeated at the other two sites. However when the combined yield from the two two-year cutting cycles was compared with the four year yield, the four year yield was higher on all occasions. This was significant for all clones at two sites but not significant for two clones at the third site. This finding has strong economic implications for the grower as longer cutting cycles will increase yield and reduce harvesting costs.
The Growth Processes activity had four participating countries, Finland, Sweden, UK and USA. The overall objective of the activity was to investigate growth processes of greatest importance in species used and leading to improvement and sustainability in short rotation forestry biomass production. The areas of interest agreed by the participants as topics for further research and information exchange were: canopy dynamics, mixed clonal plantations, coppice biology with root/shoot interactions, water-use efficiency in coppice and growth models of coppice growth processes and systems. The activity arranged four meetings during four years, each with a separate theme in agreement with the programme of work. The meetings were joint meetings with other IEA-activities and also with other organisations such as FAO/IPC and IUFRO. A number of scientific presentations from the activity meetings were published in peered journals. A separate study on water-use efficiency and drought tolerance in selected willow clones was undertaken in co-operation with the University of Toronto. A research collaboration on translocation of nutrients and carbon allocation in coppice was carried out with the USDA Forest Service in Rheinlander, WI., USA to provide data for a growth model of physiological processes in coppice systems presently under development as an international/IEA co-operation project. Two literature reviews have also been carried out, one dealing with the importance of reserve nutrients for resprouting in willows and the other reviewing existing growth models of fast-growing trees that served as a basis for a modelling workshop held as a joint meeting of this activity, SUAS and New Cultural Treatments and Yield Optimisation activity.
The investigation of the PAR variability in a willow forest requires a detailed description of architecture at the leaf, branch, stem and canopy levels. Due to the great variability of the object under study, parameters of the architecture should be considered as stochastic quantities and expressed by their probability density functions (PDF). Establishment of correlations between different architectural parameters enables a reduction in the great number of phytometrical measurements. A statistical phytometrical methodology, describing plantation architecture during the first three growing years, has been elaborated and applied for a willow (Salix viminalis) coppice. The whole canopy was divided into three layers. The upper foliage layer consists of foliage cylinders (current year shoots and branches with leaves) with given geometrical characteristics. The lower foliage layer consists of previous year stems and branches as well as current year shoots and can be modelled as horizontally homogeneous turbid plate medium. The lower leafless layer consists of nearly vertical stems only. The dynamics and development of these layers was analyzed during the years 1994–1996. The vertical distribution of leaf area density for the whole canopy is not uniform; but can be approximated by a normal distribution. At the relative coppice height 0.6–0.7 leaf area density reaches its maximum value of 23m2 leaf area per m3 canopy volume. In the years 1994, 1995 and 1996 at the end of July the leaf area index reached maximum values 1.2, 2.6 and 4.2, respectively. The leaf inclination angle distribution is not uniform, the maximum being located between 20 and 40 degrees.
Two energy crops (switchgrass and reed canary grass) have been processed using ball mills and divided into two size fractions (90μm sample. Two laboratory scale techniques, thermogravimetric analysis (TGA) and pyrolysis–GC–MS (py–GC–MS), were used to study the significance of these differences in thermal conversion. In py–GC–MS of reed canary grass, and switchgrass to a lesser extent, the amounts of cellulose and lignin decomposition products were higher for the larger particle size fraction. The differences in cellulose contents were also apparent from the TGA studies, where different mass losses were seen in the cellulose decomposition region of the two size fractions. From the results of these two techniques it was concluded that the differences in ash, and therefore catalytic metal contents, between the two size fractions, resulted in lower pyrolysis temperatures, lower char combustion temperatures, and higher yields of catalytic pyrolysis decomposition products for the smaller size fractions. The implications of the results are discussed in terms of the bio-oil quality in fast pyrolysis and the predicted behaviour of the ash in combustion. It is suggested that pre-treatment by milling is one route that might be used routinely as a feedstock quality improvement strategy in integrated biomass conversion processes.
The conversion of primary energy from natural sources and the subsequent utilisation of secondary forms of energy are basically related to the development of our society with its continuous change of requirements. Consequently the consumption of primary energy resources rose drastically especially during the last five decades. However, the increasing awareness of environment pollution from the use of, e.g. fossil fuels, the limitation of the availability of such sources as well as market considerations and costs forces governments to re-orientate their energy policy in order to ensure a sustainable supply for the future of their societies.The paper will start with an overview of the energy market development in general and by comparing certain key areas in the world. In particular, the situation in Europe will be discussed and the consequences for political actions and technological needs for the future energy supply will be highlighted.