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Carbon-Negative Biofuels from Low-Input High-Diversity Grassland Biomass
Abstract
Biofuels derived from low-input high-diversity (LIHD) mixtures of native grassland perennials can provide more usable energy,
greater greenhouse gas reductions, and less agrichemical pollution per hectare than can corn grain ethanol or soybean biodiesel.
High-diversity grasslands had increasingly higher bioenergy yields that were 238% greater than monoculture yields after a
decade. LIHD biofuels are carbon negative because net ecosystem carbon dioxide sequestration (4.4 megagram hectare–1 year–1 of carbon dioxide in soil and roots) exceeds fossil carbon dioxide release during biofuel production (0.32 megagram hectare–1 year–1). Moreover, LIHD biofuels can be produced on agriculturally degraded lands and thus need to neither displace food production
nor cause loss of biodiversity via habitat destruction.
... where d is the duration of the experiment (70 days in this study); 44/12 is the conversion coefficient from carbon to CO 2 , where 44 is the molecular weight of CO 2 and 12 is the atomic mass of carbon. Different biofuel production methods capture varying proportions of bioenergy (Tilman et al., 2006). The energy output (EB) produced from biofuel production was calculated as follows: ...
... H is the calorific value. The total energy output of chemical wastes produced in the form of biofuel production is calculated based on the 18.5 MJ·kg-1 released when burned (Tilman et al., 2006). Above-ground biomass yield (AGB g·m −2 ) was used to estimate biofuel production, as only above-ground biomass can be harvested in the CWs microenvironment of the sand substrate. ...
... Sequestration of organic carbon in the substrate is another important carbon sink (Tilman et al., 2006). In this study, there was a difference in GWP CH4+CO2+N2O between the C. indica and O. javanica systems without the addition of earthworms (Fig. 4b). ...
Plant configuration and earthworms play an important role in water purification and greenhouse gas emissions in constructed wetlands (CWs). However, the impact of earthworm density on greenhouse gas emissions across different plant configurations has not been explored. In this study, four wetland plant species, Canna indica, Lythrum salicaria, Oenanthe javanica, and Typha orientalis, were selected for monocultures. Under each monoculture, three earthworm densities (control, low, and high densities) were conducted to explore the effects of earthworm density on greenhouse gas emissions in CWs with different plant configurations. The results showed that: (1) in systems without earthworms, the CO2 emission from O. javanica monoculture was 69.9% lower than that from C. indica monoculture; the CH4 emission decreased with the increasing earthworm density across all plant configurations, with high earthworm density resulting in negative CH4 emission. (2) In systems with low and high-density earthworms, C. indica exhibited the highest biomass among four monocultures. However, earthworm density did not significantly affect plant biomass under the same plant configuration. (3) In systems without earthworms, the substrate organic carbon (SOC) of O. javanica monoculture was 18.94% and 4.93% lower than that in T. orientalis and C. indica monocultures, respectively; For L. salicaria monoculture, the SOC was 35.69% and 40.59% lower in systems without earthworms compared to those with low and high-density earthworms, respectively. (4) In systems without earthworms, the global warming potential (GWP) value, including GWPCH4+CO2+N2O+SOC, GWPnon-CO2+AGB+SOC, and GWPCH4+CO2+N2O+AGB+SOC were lowest in L. salicaria monoculture among four monocultures. Moreover, in L. salicaria monoculture, the GWPnon-CO2+SOC of systems without earthworms was 36% and 40.7% lower than in systems with low and high-density earthworms by, respectively. These results indicate that adding high-density earthworms can reduce CH4 emissions in constructed wetlands with different plant configurations. L. salicaria monoculture without adding earthworms demonstrated a low global warming potential.
... Here, we report on several new results obtained from the experiment described in Juyal et al. 34 . Labeling the growing switchgrass plants with 13 C enabled detection and quantification of the newly added plant-derived C within the soil, in the microbial biomass, and in the emitted CO 2 . Thus, the focus of the current work is (i) on an in-depth exploration of the fate of new switchgrass-originated C added to the intact soil cores of different vegetation histories and topographies and (ii) on the relationships between the newly added C and soil pore characteristics. ...
... Both fumigated and non-fumigated samples were shaken with 25 mL of 0.05 M K 2 SO 4 solution for 15 min, centrifuged at 3000 rpm for 10 min, and filtered (Whatman no.3). The K 2 SO 4 extracts were freeze-dried for 13 C and total C analyses. Microbial biomass C was calculated as the difference in dissolved organic C contents between fumigated and non-fumigated soil extracts. ...
... Total C (A) and atom%13 C excess (B) of soils from multi-year monoculture switchgrass and restored prairie cropping systems in topographical slopes and depressions. Shown are means with error bars representing standard errors. ...
Monoculture switchgrass and restored prairie are promising perennial feedstock sources for bioenergy production on the lands unsuitable for conventional agriculture. Such lands often display contrasting topography that influences soil characteristics and interactions between plant growth and soil C gains. This study aimed at elucidating the influences of topography and plant systems on the fate of C originated from switchgrass plants and on its relationships with soil pore characteristics. For that, switchgrass plants were grown in intact soil cores collected from two contrasting topographies, namely steep slopes and topographical depressions, in the fields in multi-year monoculture switchgrass and restored prairie vegetation. The ¹³C pulse labeling allowed tracing the C of switchgrass origin, which X-ray computed micro-tomography enabled in-detail characterization of soil pore structure. In eroded slopes, the differences between the monoculture switchgrass and prairie in terms of total and microbial biomass C were greater than those in topographical depressions. While new switchgrass increased the CO2 emission in depressions, it did not significantly affect the CO2 emission in slopes. Pores of 18–90 µm Ø facilitated the accumulation of new C in soil, while > 150 µm Ø pores enhanced the mineralization of the new C. These findings suggest that polyculture prairie located in slopes can be particularly beneficial in facilitating soil C accrual and reduce C losses as CO2.
... In recent years, functional diversity has become a mainstream approach in studying plant diversity and ecosystem function (McGill et al., 2006). Recently, the understanding of the negative impacts of plant diversity loss on ecosystem functions has increased, including the understanding of net primary production (Liang et al., 2016;Duffy, et al., 2017), carbon sequestration (Tilman, Hill and Lehman, 2006) and nutrient cycling (Handa et al., 2014). However, how plant diversity loss affects Rs and its components remains uncertain. ...
... The components of total respiration Rs are plants' autotrophic respiration (Ra), which generates energy for water and nutrient acquisition, survival, and growth, and in contrast, heterotrophic respiration (Rh) from the activity of soil microorganisms that regulates nutrient cycling (Ryan and Law, 2005). Recently, there have been some significant advances in our understanding of the negative impacts of plant diversity loss on ecosystem functions, including net primary production (Liang et al., 2016;Duffy, Godwin and Cardinale, 2017), carbon sequestration (Tilman, Hill and Lehman, 2006) and nutrient cycling (Handa et al., 2014). However, how plant diversity loss affects Rs and its components remains uncertain (Chen and Chen, 2019). ...
The subject of the paper is the analysis of the relationship between spontaneous vegetation diversity and soil respiration in novel post-coal mine ecosystem. In the natural and semi-natural ecosystems, soil respiration process (Rs) is a crucial ecosystem function regulating terrestrial ecosystems’ carbon cycle. Soil respiration depends on the quality and quantity of the soil organic matter (SOM), the soil microbes’ activity, and root metabolism. The listed factors are directly related to the composition diversity of vegetation plant species (biochemistry). For many years, soil respiration parameters have been studied in natural and seminatural vegetation communities and ecosystems. However, there still need to be a greater understanding of the relationship between vegetation plant species diversity and soil respiration as a crucial ecosystem function. Plant species diversity has to be analysed through both the taxonomic diversity and the functional diversity. These approaches reflect the composition, structure, and function of plant species communities. We hypothesise that the diversity of the spontaneous vegetation species composition shapes the amount of soil respiration in a post-coal mine novel ecosystem. The soil respiration differs significantly along the vegetational types driven by habitat gradients and is significantly higher in highly functional richness and dispersion vegetation patches. Contrary to our expectation, soil respiration was the highest in the less diverse vegetation types – both taxonomical and functional evenness were non-significant factors. Only functional dispersion is weakly negative correlated with soil respiration level (SRL).
... Financially viable alternatives are needed to meet the multiple demands of 21st-century society, which include ecosystem services and biodiversity preservation in addition to food and energy production (Mishra et al., 2019;Schulte et al., 2022). Over the past two decades, lignocellulosic biofuels, especially biofuels from perennial grasses, have been pursued as a pathway to address this need (Gelfand et al., 2013;Hallam et al., 2001;Jarchow et al., 2015;Meehan et al., 2013;Schmer et al., 2008;Tilman et al., 2006). Ecosystem services associated with grassland systems provide widespread public benefits, such as climate regulation, water purification, and recreational services, some of which can be monetized (Johnson et al., 2012;Meehan et al., 2013;Mishra et al., 2019). ...
... Converting low-yielding cropland to grassland cover has the potential to improve the overall profitability of farm fields. The cost of grassland establishment and management can be favorable compared to the highly volatile production costs of row crops (Audia et al., 2022), and depending on local or regional market development, perennial grassland systems may outcompete annual grain systems in terms of profitability (Brandes et al., 2016;Gelfand et al., 2013;Manatt et al., 2013;Tilman et al., 2006). ...
Restoring native grassland vegetation can substantially improve ecosystem service outcomes from agricultural watersheds, but profitable pathways are needed to incentivize conversion from conventional crops. Given growing demand for renewable energy, using grassy biomass to produce biofuels provides a potential solution. We assessed the techno‐economic feasibility and life cycle outcomes of a “grass‐to‐gas” pathway that includes harvesting grassy (lignocellulosic) biomass for renewable natural gas (RNG) production through anaerobic digestion (AD), expanding on previous research that quantified ecosystem service and landowner financial outcomes of simulated grassland restoration in the Grand River Basin of Iowa and Missouri, United States. We found that the amount of RNG produced through AD of grassy biomass ranged 0.12–45.04 million gigajoules (GJ), and the net present value (NPV) of the RNG ranged −422 million, depending on the combination of land use, productivity, and environmental credit scenarios. Positive NPVs are achieved with environmental credits for replacement of synthetic agricultural inputs with digestate and clean fuel production (e.g., USEPA D3 Renewable Identification Number, California Low Carbon Fuel Standard). Producing RNG from grassy biomass emits 15.1 g CO2‐eq/MJ, which compares favorably to the fossil natural gas value of 61.1 g CO2‐eq/MJ and exceeds the US Environmental Protection Agency's requirement for cellulosic biofuel. Overall, this study demonstrates opportunities and limitations to using grassy biomass from restored grasslands for sustainable RNG production.
... Anthropogenic activities and associated changes in climate have triggered major declines in biodiversity (Isbell et al., 2023;Tilman et al., 2006), with implications for ecosystem function and service provision. Forest ecosystems regulate organic matter decomposition and plant growth, and support nutrient cycling and carbon sequestration (Augusto & Boča, 2022;Gamfeldt et al., 2013;Yuan et al., 2021) that contribute to the mitigation of effects of global climate change (Eisenhauer et al., 2013;Messier et al., 2022). ...
... Rapid losses in biodiversity have triggered studies of relations between measures of diversity and ecosystem function (Isbell et al., 2023;Tilman et al., 2006). Although the positive relationship between biodiversity and ecosystem functioning has been established mostly based on individual functions like primary productivity (Erskine et al., 2006;Huang et al., 2018;Liang et al., 2016), the patterns of ecosystem multifunctionality across tree diversity gradients and underlying drivers are less well studied in subtropical forest ecosystems (Schuldt et al., 2018). ...
Rapid biodiversity losses under global climate change threaten forest ecosystem functions. However, our understanding of the patterns and drivers of multiple ecosystem functions across biodiversity gradients remains equivocal. To address this important knowledge gap, we measured simultaneous responses of multiple ecosystem functions (nutrient cycling, soil carbon stocks, organic matter decomposition, plant productivity) to a tree species richness gradient of 1, 4, 8, 16, and 32 species in a young subtropical forest. We found that tree species
richness had negligible effects on nutrient cycling, organic matter decomposition, and plant productivity, but soil carbon stocks and ecosystem multifunctionality significantly increased with tree species richness. Linear mixed-effect models showed that soil organisms, particularly arbuscular mycorrhizal fungi (AMF) and soil nematodes, elicited the greatest relative effects on ecosystem multifunctionality.
Structural equation models revealed indirect effects of tree species richness on ecosystem multifunctionality mediated by trophic interactions in soil micro-food webs. Specifically, we found a significant negative effect of gram-positive bacteria on soil nematode abundance (a top-down effect), and a significant positive effect of AMF biomass on soil nematode abundance (a bottom-up effect). Overall, our study
emphasizes the significance of a multitrophic perspective in elucidating biodiversity-multifunctionality relationships and highlights the conservation of functioning soil micro-food webs to maintain multiple ecosystem functions.
... Existem variações significativas na capacidade das paisagens de sequestrar carbono, que dependem de diversos fatores como a diversidade de espécies (Tilman et al., 2006), a densidade das plantas (Fang et al., 2007;Matamala et al., 2008), a composição das espécies (Whittinghill et al., 2014), o clima (Matamala et al., 2008) e a morfologia das plantas (Rhoades et al., 2000). Dentro da paisagem urbana, os telhados verdes funcionam como sumidouros do carbono atmosférico (Getter et al., 2009;Pessoa et al., 2022). ...
O uso de gramíneas em telhados verdes, visando promover a sustentabilidade urbana e melhorar o desempenho ambiental dos edifícios, configura uma prática crescente nos centros urbanos. Neste contexto, o presente estudo objetivou levantar e sumarizar as principais características e resultados de pesquisas sobre o uso de gramíneas em telhados verdes, com ênfase nos aspectos de crescimento e desenvolvimento, ornamental, segurança, conforto térmico e benefícios ambientais. Os documentos científicos foram recuperados da base de dados Web of Science. Foram incluídos artigos publicados até julho de 2024, sem data inicial definida, com o intuito de abranger o máximo de material teórico disponível. Após aplicação dos critérios de seleção, um total de 37 artigos publicados entre 2008 e 2024 foram incluídos nessa revisão. Foram identificados 40 gêneros de gramíneas utilizadas em estudos sobre telhados verdes, com Festuca, Bouteloua e Zoysia sendo os mais representativos (17%, 7% e 7%, respectivamente). Festuca ovina destacou-se como a espécie mais citada. Diversos estudos destacam a importância das gramíneas em telhados verdes em função da adaptabilidade e eficiência. Essa eficiência está ligada a uma melhor cobertura do solo, à capacidade de reduzir a temperatura superficial do telhado e a uma estética aprimorada para a estrutura verde, por exemplo. Assim, a seleção adequada de gramíneas contribui significativamente para uma infraestrutura urbana mais sustentável e resiliente.
... The research article entitled "Carbon-negative biofuels from low-input, high-diversity grassland biomass" published in "Science" by Tilman et al. received the most citations (54). He explains the importance of eco-friendly and energy-rich switchgrass for biofuel production compared to corn grain-producing ethanol or soybean for biodiesel [45]. A detailed list of the top 5 co-cited articles is shown in Table 2. ...
Burning fossil fuels is a major contributor to global warming and climate change, threatening biodiversity and presenting challenges for scientists and policymakers. To address these issues and promote sustainable development, bioenergy is based on efficiently utilizing biomass resources such as biomass feedstock for energy. Moreover, intensified global changes adversely affect our environment, signifying the importance of biomass and energy conservation research as a re-emerging topic of scientific interest. This study aims to comprehensively review the existing research trends, knowledge gaps, and future research in this field. A scientometric analysis was conducted using CiteSpace based on 1177 articles retrieved from the Web of Science Core Collection from 2000 to 2021. The leading countries, authors, and institutions are the USA, the Chinese Academy of Science, and Prof. Dr. Mehdi Bidabadi, respectively. The “Biomass and Bioenergy” is a prominent journal. European and North American countries collectively contribute around 73% of the publications. While there has been an increasing trend in publications over time, effective cooperation among institutions and authors, especially in developing countries, remains weak. The current research hotspots include “metabolic pathway”, “Clostridium ljungdahlii”, “short-term harvesting”, “anaerobic digestion”, “environmental impacts”, and so on. Future research will focus on cutting-edge techniques, the potential of biomass feed stocks for bioenergy, and the role of biomass feed stocks in mitigating climate change. This review provide comprehensive and valuable information for researchers, institutions, and policymakers to develop an effective, environmentally friendly, and sustainable strategy to cope with global environmental issues
... Unsustainable practices, such as monoculture plantations for biofuel crops, can result in habitat destruction and the loss of native species. Conversely, when implemented responsibly-such as through the integration of agroecological practices-biofuel production can enhance biodiversity by fostering diverse cropping systems that support a variety of species (Tilman et al., 2009). This approach not only contributes positively to ecosystem resilience but also bolsters local economies by providing alternative sources of income. ...
This study aims to investigate the impact of emerging contaminants (ECs) and hazardous substances on environmental health, particularly in Africa. It seeks to identify sustainable fuel alternatives that align with the Sustainable Development Goals (SDGs) while addressing climate change challenges. A comprehensive literature review was conducted, focusing on recent studies regarding ECs in African water bodies and their implications for public health. Additionally, case studies on innovative biofuels and renewable energy sources were analysed to assess their viability as sustainable alternatives. The findings indicate a significant presence of ECs in various ecosystems across Africa, leading to adverse effects on biodiversity and human health. However, the research also highlights promising developments in biofuel technology, such as algae-based fuels and waste-to-energy systems, which can reduce reliance on fossil fuels while mitigating pollution. Addressing the dual challenges of emerging contaminants and hazardous substances is crucial for achieving sustainable development in Africa. Transitioning to new fuel sources not only supports environmental sustainability but also enhances resilience against climate change impacts. Collaborative efforts among governments, industries, and communities are essential to implement these solutions effectively.
... The availability, accessibility and diversity of plant genetic resources (PGR) are the basis for the adaptation of our crops to environmental challenges and human needs. PGR are pivotal for breeding towards increased biotic and abiotic stress tolerance, optimizing human and animal nutrition and efficient use of renewable resources, including for the energy, chemical and pharmaceutical industries (Grusak and Dellapenna, 1999;Hoisington et al, 1999;Metzger and Bornscheuer, 2006;Tilman et al, 2006;Qian et al, 2018). However, since the beginning of industrialization and the introduction of the targeted selection of advantageous local plant varieties -so-called landraces -PGR have steadily disappeared (Tanksley and Mccouch, 1997). ...
Over more than 80 years, the collections of the German Federal Ex Situ Genebank for Agricultural and Horticultural Crops have grown to around 152,000 accessions of 3,000 species preserved at three locations: Gatersleben, Groß Lüsewitz and Malchow/Poel. More than 96% of the material is stored as desiccation-tolerant orthodox seeds according to the active–base–safety (A-B-S) replicate approach at -18°C. Almost 70,000 freshly regenerated safety replicates are stored in the Svalbard Global Seed Vault. However, 4% of the material (2,000 field, 3,000 in vitro and 2,500 cryopreserved accessions) can only be maintained vegetatively, as no or few seeds or no true-breeding seeds are available. Most of the accessions are provided via the standard material transfer agreement (SMTA) and more than 1.2 million samples have been distributed since the genebank was founded. To guarantee the identity of the living plant material, reference samples comprising about 450,000 voucher specimens, 110,000 seed and fruit samples and 57,000 cereal spikes are used for comparisons. Genebank workflows are supported by the Genebank Information System (GBIS), which also manages workflow-independent data to describe the genebank accessions by passport, phenotypic and taxonomic data, thus allowing users to make targeted selections of material. The genebank-related processes, including acquisition, preservation, regeneration, documentation and material distribution, are certified for quality management in accordance with ISO 9001. Nowadays, the genebank is undergoing a transformation process to become a bio-digital resource centre to improve utilization of the genetic resources in research and breeding to address future challenges.
... Moreover, perennial plant system might increase SOC rather than annual plant system (Machmuller et al., 2015). Additionally, Tilman et al. (2006) illustrated increases in SOC storage as vegetation diversity increased. To that end, in southern US, forages such as barley Hordeum vulgare, wheat Triticum aestivum, and ryegrass Lolium multiflorum are utilized as cool season grasses for diversity to the benefit of increasing SOC and improving soil health (Sarkar et al., 2020). ...
Accurately accounting for soil organic carbon stocks is crucial in assessing the sequestration potential of arid and semi-arid rangelands. This study, conducted in the rangelands near Loving, southeastern New Mexico, aims to evaluate soil organic carbon stocks, assess the potential for soil organic carbon sequestration, and identify both biotic and abiotic factors influencing this process. To achieve these goals, soil samples were collected and subjected to analysis for soil particle size, bulk density, soil characteristic curve, as well as soil total carbon and inorganic carbon. Soil total carbon stock (STCS), soil organic carbon stock (SOCS), soil inorganic carbon stock (SICS), and soil total nitrogen stock (STNS) were determined. Soil depth, vegetation types, and coverages on each ranch were identified. Additionally, soil ion concentrations, soil cation exchange capacity (CEC), and soil sodium adsorption ratio (SAR) were assessed. The soil CEC ranged from 6 to 20 meq/100 g soil, and SAR from 0.02 to 0.58 cmol/kg^0.5. The concentrations of Na and Cl were 42 and 13 mg/l, at a depth of 0–20 cm, increasing to 74 and 34 mg/l at 20–32 cm depth, respectively. In October 2021, STCS measured 39 Mg/ha at 0–20 cm and 11 Mg/ha at 20–32 cm soil depth. SOCS ranged from 18 Mg/ha at 0–20 cm to 6 Mg/ha at 20–32 cm soil depth, while SICS ranged from 20 to 1 Mg/ha at 0–20 cm and 20–32 cm soil depth, respectively. STNS varied from 1 Mg/ha at 0–20 cm to 3.8 Mg/ha at 20–32 cm soil depth. In the 20 cm sandy loam soil depth, ranches 1, 7, 8, 9, and 11 exhibited the highest SOCS, increased with increasing clay content, particularly where honey mesquite was the dominant species. These findings emphasize the importance of exploring soil carbon storage fluctuations in southern New Mexico. The differences in SOCS among ranches under different vegetation underscore the considerable potential for storing soil organic carbon in the semi-arid rangelands of this region.
... While the cost of renewable energy technologies has been decreasing, the initial capital investment required for large-scale projects remains high. This includes the costs of technology acquisition, infrastructure development, and installation (Tilman, D., et al.,2006). Additionally, financing mechanisms and investment models need to be developed to support the deployment of renewable energy in both developed and developing regions. ...
This shift is not uniform, however, and varies significantly across different regions due to diverse economic, environmental, and policy contexts. In advanced economies like the European Union and the United States, renewable energy adoption is largely driven by robust policy frameworks, technological advancements, and a high degree of public awareness about climate change. For instance, the European Union's Green Deal and the United States' Inflation Reduction Act exemplify ambitious policy commitments aimed at reducing greenhouse gas emissions and accelerating the deployment of renewable technologies. These regions benefit from well-established infrastructure, substantial financial investments, and a relatively high level of technological innovation, which collectively support the integration of renewable energy into existing energy systems. While these regions often have significant untapped renewable resources—such as abundant solar and wind potential—they may encounter barriers such as limited financial resources, and less mature regulatory frameworks.
... For example, switchgrass (Panicum virgatum) is a perennial North American native grass with several varieties that have been bred specifically for bioenergy applications. Reconstructed prairies emulate biodiverse native grasslands characteristic of the US Midwest prior to Euro-American colonization and have been proposed as an alternative to annual and/or monoculture sources of bioenergy (Tilman et al., 2006). Empirical studies have found that the introduction of strips of perennial vegetation into cropland can significantly improve the biodiversity and delivery of key ecosystem services of the cropland (Kemmerling et al., 2022;Schulte et al., 2017). ...
... Additionally, the use of fertilizers and pesticides in growing biofuel crops can lead to soil and groundwater pollution. A study by Tilman et al. (2006) illustrates that these practices can result in soil degradation and groundwater contamination, harming agricultural ecosystems and affecting environmental quality. ...
... CCS are subjected to progressive SOC depletion (Crème et al., 2016;Francaviglia et al., 2017) and raise several concerns regarding pest and weed management, soil nutrient depletion and agroecosystem resilience which rely upon complex interactions between biotic and abiotic components (Altieri and Toledo, 2011). On the other hand, biodiversity in ecosystems is a factor positively affecting C absorption (Lal, 2004;Tilman et al., 2006), therefore improved crop rotations and intercropping represent feasible solutions to improve biodiversity and soil health, while preventing land-degradation (McDaniel et al., 2014). Data (n = 5) on ΔSOC ABS provided by this review for improved crop rotations are insufficient to determine if the crop rotations only can increase the C sink (median ΔSOC ABS = 0 in the 0-90 cm profile). ...
Carbon farming has been recently proposed as an effective measure for climate change mitigation through carbon (C) sequestration or C emissions reduction. In order to identify and estimate the climate change miti- gation potential of carbon farming practices on European croplands we conduct a systematic review on both relative and absolute annual soil organic carbon (SOC) stock change (ΔSOCREL; ΔSOCABS) related to single and combined agroecological practices tested on mineral soils at a minimum of 0–30 cm and up to 150 cm soil depth whenever data were available. We used the term ΔSOCREL for SOC stock changes determined by the paired comparison method and the term ΔSOCABS for those calculated using the SOC stock difference method. We compiled a dataset with more than 700 records on SOC change rates representing 12 carbon farming practices. Mean ΔSOCREL in Mg C ha−1 yr−1 at 0–30 cm soil depth were collected for cover crops (0.40 ± 0.32), organic amendments (0.52 ± 0.47 and 0.38 ± 0.37 when the control is respectively unfertilized or liquid organic amendment), crop residue maintenance (0.14 ± 0.06), improved rotations (0.21 ± 0.16), reduced soil distur- bance (0.24 ± 0.34), silvoarable systems (0.21 ± 0.08), organic (0.9 Mg ± 0.25) and conservation management (0.78 ± 0.62), set-aside (0.75 ± 0.68 and −0.39 ± 0.50 when the control is respectively cropland or pasture/ grassland), cropland conversion into permanent grassland (0.79 ± 0.47), poplar plantations (0.25 ± 0.68 and −0.85 ± 0.53 when established on cropland or pasture/grassland). SOC sequestration was detected only for organic amendments, cover crops, poplar plantations, conservation management, organic management, and combined carbon farming practices for which we estimated a median ΔSOCABS ranging between 0.32 and 0.96 Mg C ha−1 yr−1 at 0–30 cm. The ΔSOCABS observed at 0–30 cm soil depth from cropland conversion into short rotation forestry resulted in an increase of C, while negative values were observed when the control was grassland. Cropland conversion into permanent grassland or pasture showed positive ΔSOCREL at 0–30 and 0–90 and 0–100 cm soil depth. Reduced soil disturbance full soil profile assessment at 0–50 cm soil depth completely counterweighted any SOC stock increase found in topsoil at 0–30 and 0–40 cm soil depth, therefore resulting in no net climate benefit. Conservation management, organic management, and combining cover crops with organic amendments are the most effective strategies shifting arable land from C source to net sink, with median ΔSOCABS at 0–30 cm soil depth of 0.63, 0.91 and 0.96 Mg C ha−1 yr−1, respectively. Permanent grasslands and pastures were negatively affected by any type of land-use change, at least in topsoil. Natural ecological successions after cropland abandonment (20-year set-aside), or arable land conversion into poplar plantations and grassland promote relative SOC stock annual increase by 1.08, 0.77 and 0.33 at 0–30 cm respectively, while the net climate benefit remains unclear when subsoils are assessed
... ex. Hodkinson et Renvoize), and biomass from agricultural grasslands, early successional fields, and prairies (Gelfand et al., 2013;Meserszmit et al., 2022;Sanford et al., 2016;Tilman et al., 2006;U.S. Department of Energy, 2011). ...
Though corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are widely grown and readily accepted into commodity markets and biofuel facilities, heavy reliance on seeds of those two crops for bioenergy production has been linked to environmental degradation, including nutrient discharge to water, and to constraints on food production. Alternative biofuel feedstock systems might better address this “food–energy–environment trilemma.” Using data from a 9‐ha field experiment in Iowa, we evaluated yields from a 14‐year period for four bioenergy feedstock systems: stover harvested from corn grown with and without an unharvested rye cover crop, and prairie vegetation grown with and without fertilizer. We also assessed sub‐surface drainage flows and NO3‐N concentrations and discharges in leachate from those cropping systems. The continuous corn systems produced mean grain yields of 11.0–11.5 Mg ha⁻¹ year⁻¹, while also yielding about 4 Mg ha⁻¹ year⁻¹ of stover. Mean harvested biomass from the fertilized prairie was 83% greater than from the unfertilized prairie and was superior to stover production in the two corn treatments in 11 out of 14 years. Nitrate‐N losses in drainage water from the corn systems averaged 12–14 kg NO3‐N ha⁻¹ year⁻¹, whereas both the fertilized and unfertilized prairie systems almost eliminated NO3‐N loss. Cover cropping with rye reduced NO3‐N loss in only one out of 13 years and had variable effects on corn yield. Adoption of prairie‐based biofuel systems might be driven by placing perennial feedstocks on environmentally sensitive sub‐field areas and by government policies that favor perennial feedstocks over annual crops like corn.
... The main factor influencing the amount of methane yield that can be obtained under favorable process conditions in biogas plants is the choice of plant species [23]. Tilman et al. [24] concluded that biofuels derived from low-input native perennial grasses can produce more useful energy and reduce greenhouse gas emissions and agrochemical pollutants compared to arable crops such as maize or soya. ...
Methane fermentation, which is one of the key processes in biogas production, plays an important role in the conversion of biomass to energy. During this process, changes occur in the chemical composition of organic feedstocks, including the chemical composition of grasses. The assessment of these changes is crucial for the efficiency and productivity of biogas production. The material for this study comprised fully mature grass blades with leaves and inflorescences and was collected from extensively used meadows and pastures, as well as cultivated and set-aside areas in the Wielkopolskie Voivodeship, the communes of Białośliwie and Trzcianka, Poland. The aim of this study was to compare methane fermentation efficiency in nine grass species and identify the biomass component involved in biogas production. The results indicate that the fermentation process, as expected, changed the cellulose content. The lignin content of the grasses before fermentation varied more than the cellulose content. The content of holocellulose (sum of carbohydrate components) in the grasses ranged from 59.77 to 72.93% before fermentation. Methane fermentation significantly reduced the carbohydrate content in the grasses, with a low degree of polymerization. Grassland biomass-based biogas production is a viable alternative to conventional fossil fuels.
... (www.preprints.org) | NOT PEER-REVIEWED | Posted: 1 May 2024 doi:10.20944/preprints202405.0057.v111 ...
Driven by mounting environmental apprehensions stemming from the over dependence on fossil fuels in energy and transportation sectors, extensive exploration into alternative energy sources, particularly biomass, has stimulated profound research on harnessing the potential of computational and mathematical techniques. This comprehensive survey delves into optimal models and strategies, unveiling their pivotal role in the design of biomass gasification processes.of hydrogen through biomass gasification. In this study, we aim to provide a comprehensive overview of the computational and mathematical techniques employed in optimizing biomass gasification processes, with a specific focus on enhancing hydrogen yield. Through an extensive literature review, various models and strategies will be examined, including thermodynamic analysis, kinetic modeling, reactor design, and process optimization. By uncovering the power of these techniques, we aim to contribute to the advancement of sustainable and efficient biomass utilization for the hydrogen-based future economy.This paper aims to provide an updated and comprehensive coverage of the investigations conducted on the potential of producing hydrogen from biomass through gasification. To achieve this, we incorporate the latest works that have utilized numerical modeling, simulation, optimization techniques, process heat integration, and co-generation in their studies. By encompassing these aspects, we aim to offer a broader and more in-depth re-appraisal of the subject matter. This will ensure that readers gain a holistic understanding of the advances made in the field and the potential for sustainable hydrogen production of biomass gasification.Through a meticulous re-appraisal and analysis of each subject, we can identify their respective strengths and areas that require further research effort. By thoroughly examining numerical modeling, simulation, optimization techniques, process heat integration, and co-generation, we can assess their effectiveness and applicability in the context of biomass gasification for hydrogen production. This analysis shed light on the areas where these techniques excel, as well as pinpoint limitations or gaps in current understanding. By identifying these areas, we can highlight the need for further research and development, enabling us to make significant advancements in biomass gasification processes and pave the way for a sustainable and efficient hydrogen-based future economy..
... Cellulose and hemicellulose, which make up the structural components of the plant cell wall, are the top two most abundant organic substances on earth. There is great motivation to convert these renewable resources into biofuels and chemicals as it is sustainable, carbon neutral, and provides an opportunity to be carbon negative (Canadell and Schulze, 2014;Tilman et al., 2006;Field et al., 2020). However, overcoming plant biomass (i.e., lignocellulose) recalcitrance is key to achieving economic production of bioproducts from these feedstocks (Himmel et al., 2007;Lynd et al., 2008) and various approaches have been explored (Hoffman et al., 2021;Chen et al., 2012;Xiaowen Chen et al., 2016). ...
... Biodiversity plays a key role in providing essential ecosystem services, contributing to clean water, carbon sequestration (Harrison et al., 2014;Tilman et al., 2006), soil maintenance, pest control, and pollination on which agricultural production depends (Brussaard et al., 2007;Karp et al., 2018;Kennedy et al., 2013;Tamburini et al., 2020). However, despite our awareness of its importance, biodiversity is declining globally, with land-use change and management intensificationlargely for agricultural productioncurrently being the leading drivers of losses (e.g., Díaz et al., 2019;Butchart et al., 2010;Lambertini, 2020). ...
... Marginal agricultural lands have low crop productivity due to inherent topographic, edaphic, or climatic limitations, magnified by agricultural intensification (Csikós and Tóth, 2023;Kang et al., 2013). Often, marginal lands are suitable for grasses, trees, or other perennial vegetation with persistent roots that are better adapted to unfavorable growth conditions (Arneth et al., 2021;Tilman et al., 2006). Replacing crops with perennial vegetation in these areas can improve a farms' provisioning of several ecosystem services, including soil erosion control, soil fertility, water availability, and water quality (Arneth et al., 2021;Barral et al., 2015;Mosier et al., 2021), and presumably, the achievement of positive agroecological outcomes. ...
... Gasification of biomass has shown great promise, surpassing conventional combustion concerning energy conversion efficiency [4]. It involves the thermal conversion of biomass feedstocks into combustible gases, mainly composed of hydrogen, carbon monoxide, and hydrocarbon gas, suitable for a range of applications like biofuels, energy storage, and power generation [5][6][7][8]. Extensive research in techno-economic analysis has strongly supported the economic feasibility of degrading biomass through gasification technologies [9,10]. ...
... Taborianski and Pacca [52] found that the introduction of a photovoltaic system could potentially reduce carbon emissions significantly. Tilman et al. [53] demonstrated that biofuels provide more usable energy and reduce greenhouse gas emission. ...
Carbon offset projects play a crucial role in tackling the global challenge of climate change. However, there is limited understanding of the factors contributing to the success of a carbon offset project. In this study, we utilize the latent Dirichlet allocation method to extract topics from the descriptions of carbon offset projects sourced from the Gold Standard Foundation. Our findings reveal that projects encompassing both safety and efficient energy solutions for households command higher prices. These results imply that an effective carbon offset project should mitigate individual household emissions while enhancing safety. Our research carries significant implications for stakeholders involved in carbon offset projects and can serve as a foundation for policy formulation and standard regulations.
... biomass were observed at a C/N ratio of 5 (Fig. S4b, c). This result is consistent with the findings of the positive response of aboveground biomass (slope = 2.90) in Tilman et al. (2006) and belowground biomass (slope = 28.77) in Ravenek et al. (2014) to SR. Some studies have shown that plant biomass in CWs can be used as biofuel to replace fossil fuels to alleviate GWP and turn it from a C source to a carbon sink (Liu et al. 2012;Du et al. 2018). ...
Treating wastewater with low carbon-to-nitrogen (C/N) ratios by constructed wetlands (CWs) is still problematic. Adding chemicals is costly and may cause secondary pollution. Configuring plant diversity in substrate-based CWs has been found to be a better way to treat low-C/N wastewater, but wastewater treatment in floating CWs needs to be studied. In this study, wastewater with C/N ratios of 5 and 10 were set in simulated floating CWs, and 9 combinations with plant species richness (SR) of 1, 3, and 4 were configured. The results showed that (1) increasing SR improved the total N mass removal (NMR) by 29% at a C/N ratio of 5 but not 10; (2) the presence of Oenanthe javanica in the microcosms increased the NMR by 13% and 20% with C/N ratios of 5 and 10, respectively; (3) increasing SR mitigated the net global warming potential (GWP) by 120% at a C/N ratio of 5 but not 10; and (4) a Hemerocallis fulva × O. javanica × Echinodorus parviflours × Iris hybrids mixture resulted in a high NMR and low net GWP. In summary, assembling plant diversity in floating CWs is an efficient and clean measure during the treatment of wastewater with a C/N ratio of 5.
The excessive population growth and growing energy demand in recent years have led to increased usage of fossil fuels, which contribute to climate change and global warming. This is primarily due to the greenhouse gas emissions from these types of sources. Sustainable biofuels, particularly biodiesel, are preferred as a substitute for fossil fuels to fulfil energy demands. Microorganisms are a vital subject of study in several scientific disciplines. They are everywhere in most environments on Earth, and their use contributes to a minor but notable technological advancement. Microorganisms are being used to produce lignocellulose-derived ethanol for biofuels, a mixture of cellulose, hemicellulose, and lignin found in plant cell walls. Biodiesel from microbes is widely considered due to its advantages, including a short life span, easy access to various environments, and the capacity to remediate several polluted environmental conditions. Presently, the purpose of this chapter is to provide an overview of the different microbial species that are used to produce biofuel.
This chapter characterizes sustainability by discussing the sustainability, ecological, economic, and social principles and environment. Systemic approaches include sub-systems, sustainable systems, and sustainability policies. The reference values provide a quantitative threshold distinguishing sustainable from unsustainable systems. Sustainability approaches (life cycle analysis (LCA), life cycle sustainability analysis (LCSA), net primary production (NPP), human appropriation of net primary production (HANPP)) and landscape, hemeroby, and naturalness indicators provide a quantitative assessment of sustainability.
The catalytic hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethylfuran (DHMF) represents a promising pathway for the valorisation of lignocellulosic-derived biomass feedstock. This study investigates the use of Ru–PNP complexes as (pre)catalysts to achieve efficient and highly selective hydrogenation of HMF in ionic liquids (ILs) as green reaction media under mild reaction conditions. Our results indicate that iPrRu-MACHO leads to excellent conversion and yield (up to 99%) of HMF to DHMF using 1-butyl-3-methylimidazolium acetate (BMIM OAc). The analogous cationic Ru–PNP complex bearing acetonitrile as ancillary ligand and hexafluorophosphate (PF6⁻) as counterion also shows high catalytic activity (up to 99% conversion) in BMIM OAc under mild reaction conditions. Interestingly, the IL seems to prevent HMF polymerization to humins. Furthermore, the recyclability and reusability of the ionic liquid are systematically investigated.
Hydrothermal liquefaction (HTL) of biomass for biocrude production constitutes an imperative domain within the renewable energy sector, and the co-liquefaction of different types of biomasses (co-HTL) represents a promising strategy for its potential to minimize logistics expenses and maximize synergistic enhancement in biocrude yield and quality. The investigation of co-HTL of carbohydrate-rich, protein-rich and ash-rich feedstocks has unearthed complex interactions among single components of biomass, which result in varying degree of synergistic and antagonistic effects. These co-liquefaction effects dependent on factors such as mixing ratios and temperature, demand a comprehensive understanding of underlying mechanisms. The exploration of co-HTL of biomass single model components (e.g., protein, carbohydrate, lipid) has facilitated advanced insights into these mechanisms. Maillard reaction between protein and carbohydrate, and amidation between protein and lipid, have been extensively observed. Further research efforts are needed to examine carbohydrate and lipid interactions and the variation induced by ash presence. The co-HTL of biomass with various types of plastics has recently shown promising results. Synergistic effects on oil yield and improvements in oil quality have been observed, even though additive effects have been noted as well. There is a necessity for additional research endeavors to investigate the co-HTL of biomass model components in conjunction with plastics and their corresponding monomers, with the aim to elucidate the underlying mechanism more explicitly and ultimately achieve more efficient feedstock selection and process design. These combined findings present co-HTL as the vital areas for future HTL research, reflecting not only its complexity but also its substantial promise in renewable energy and waste management advancements.
Shallow arable soils (<35 cm depth) are classified as marginal for common agriculture but may still support biomass production from industrial crops like fiber hemp, which has a low indirect land-use change risk. However, little is known about hemp’s performance under such conditions. Therefore, this study investigated the biomass yield and quality of fiber hemp and other crops on a shallow (<35 cm), stony (>15% stone content), and clay-rich (>50% clay content) soil at 800 m above sea level in Southwest Germany (2018–2021). A randomized field trial tested different row widths and nitrogen (N) fertilization levels to assess low-input options for the given type of marginal land. Across years and row widths, hemp achieved average grain dry matter (DM) yields of 1.3 Mg/ha at a fertilization rate of 40 kg N/ha and 1.6 Mg/ha at 120 kg N/ha (with on average 30.9 ± 1.4% crude fat content across treatments). The average stem DM yields accounted for 5.11 Mg/ha (40 kg N/ha) and 6.08 Mg/ha (120 kg N/ha), respectively. Reduced N fertilization (40 kg/ha) lowered DM yields by up to 16% compared to full fertilization (120 kg/ha), but the effect was not significant and weaker at wider row spacing (45 cm). Additionally, maize reached acceptable DM yields (>17 Mg/ha). These findings suggest that shallow soils classified as marginal require reassessment, as they may offer viable opportunities for sustainable industrial hemp cultivation and contribute to a bio-based economy.
Buku ini berisikan bahasan tentang konsep, peran guru dan orang tua serta karakter dalam pembentukan karakter pada anak usia dini.
Emerging low-emission production technologies make ethanol an interesting substrate for yeast biotechnology, but information on growth rates and biomass yields of yeasts on ethanol is scarce. Strains of 52 Saccharomycotina yeasts were screened for growth on ethanol. The 21 fastest strains, among which representatives of the Phaffomycetales order were overrepresented, showed specific growth rates in ethanol-grown shake-flask cultures between 0.12 and 0.46 h−1. Seven strains were studied in aerobic, ethanol-limited chemostats (dilution rate 0.10 h−1). Saccharomyces cerevisiae and Kluyveromyces lactis, whose genomes do not encode Complex-I-type NADH dehydrogenases, showed biomass yields of 0.59 and 0.56 gbiomass gethanol−1, respectively. Different biomass yields were observed among species whose genomes do harbour Complex-I-encoding genes: Phaffomyces thermotolerans (0.58 g g−1), Pichia ethanolica (0.59 g g−1), Saturnispora dispora (0.66 g g−1), Ogataea parapolymorpha (0.67 g g−1), and Cyberlindnera jadinii (0.73 g g−1). Cyberlindnera jadinii biomass showed the highest protein content (59 ± 2%) of these yeasts. Its biomass yield corresponded to 88% of the theoretical maximum that is reached when growth is limited by assimilation rather than by energy availability. This study suggests that energy coupling of mitochondrial respiration and its regulation will become key factors for selecting and improving yeast strains for ethanol-based processes.
Biodiesel has evolved as a viable and environmentally friendly substitute for traditional diesel fuel derived from petroleum. Biodiesel is a fuel that is produced from many sources such as vegetable oils, animal fats, and cooking oil. It provides a cleaner and more eco-friendly alternative for transportation and other energy requirements. This chapter delves into the complexities of biodiesel, covering its manufacturing methods, selection of raw materials, fuel characteristics, uses, and economic and environmental factors to be considered. The book chapter analyses the chemical conversion of feedstock into biodiesel using transesterification, investigating several techniques and their influence on the quality of the fuel. The analysis focuses on important fuel characteristics, including cetane numbers, cold flow, and oxidative stability, and how they affect engine performance and emissions. Moreover, it examines the economic feasibility of producing biodiesel, considering government subsidies, production expenses, and market dynamics. The environmental advantages of biodiesel are emphasized, such as its capacity to decrease greenhouse gas emissions , enhance air quality, and alleviate reliance on fossil fuels.
The banana value chain produces over 4 tonnes of waste biomass for every tonne of bananas harvested, including leaves, pseudostems, peels, rejected fruits, rhizomes, and empty fruit bunches. With rising fossil fuel costs and environmental concerns, these wastes present opportunities for alternative biofuel production through thermochemical processing and densification. This review examines the properties of various banana plant wastes, their pretreatments, and suitability for processes like pyrolysis, torrefaction, and hydrothermal carbonization, as well as briquetting. Banana plant wastes vary in physico-chemical properties depending on the biomass type. Their high volatile matter content (70.5–89.1%db) makes them better suited for bio-oil and gas production rather than biochar. Pretreatment methods such as water-washing, alkaline treatment, drying, pressing, chopping, grinding, and milling may be needed before thermochemical conversion of the wastes. Among conversion routes, pyrolysis is the most studied, followed by hydrothermal carbonization and dry torrefaction. The hydraulic press is the most commonly used technology for briquetting banana plant wastes. Depending on factors such as binder-to-biomass ratio, dwell time, and compaction pressure, this method can produce briquettes with compressive strength ranging from 1.33 to 38.39 MPa, which exceeds the minimum acceptable level of 0.38 MPa. However, these briquettes can have ash content as high as > 20%db, which can reduce their calorific value, increase the risk of ash slagging and fouling in combustion systems, as well as lead to increased emission of particulate matter during combustion. While thermochemical conversion and briquetting of banana plant wastes may incur significant costs, these could be offset by the low cost of the raw materials, improved fuel properties, and better handling, transportation, and storage. Research efforts should focus on ascertaining the emission potential of thermochemical conversion and briquetting of banana plant wastes, which could encourage wider acceptance of these technologies, especially considering growing awareness about the need for environmental protection.
Graphical abstract
Nanoclusters have emerged as promising candidates for CO2 electroreduction catalysts. The electroreduction of CO2 offers a pathway to sustainable clean fuel production by closing the carbon cycle, yet it requires...
It is still a great challenge to achieve high selectivity of ethanol in CO 2 electroreduction reactions (CO 2 RR) because of the similar reduction potentials and lower energy barrier of possible other C 2+ products. Here, we report a MOF‐based supported low‐nuclearity cluster catalysts (LNCCs), synthesized by electrochemical reduction of three‐dimensional (3D) microporous Cu‐based MOF, that achieves a single‐product Faradaic efficiency (FE) of 82.5 % at −1.0 V (versus the reversible hydrogen electrode) corresponding to the effective current density is 8.66 mA cm ⁻² . By investigating the relationship between the species of reduction products and the types of catalytic sites, it is confirmed that the multi‐site synergism of Cu LNCCs can increase the C−C coupling effect, and thus achieve high FE of CO 2 –to–ethanol. In addition, density functional theory (DFT) calculation and operando attenuated total reflectance surface‐enhanced infrared absorption spectroscopy further confirmed the reaction path and mechanism of CO 2 –to–EtOH.
It is still a great challenge to achieve high selectivity of ethanol in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials and lower energy barrier of possible other C2+ products. Here, we report a MOF‐based supported low‐nuclearity cluster catalysts (LNCCs), synthesized by electrochemical reduction of three‐dimensional (3D) microporous Cu‐based MOF, that achieves a single‐product Faradaic efficiency (FE) of 82.5 % at −1.0 V (versus the reversible hydrogen electrode) corresponding to the effective current density is 8.66 mA cm⁻². By investigating the relationship between the species of reduction products and the types of catalytic sites, it is confirmed that the multi‐site synergism of Cu LNCCs can increase the C−C coupling effect, and thus achieve high FE of CO2–to–ethanol. In addition, density functional theory (DFT) calculation and operando attenuated total reflectance surface‐enhanced infrared absorption spectroscopy further confirmed the reaction path and mechanism of CO2–to–EtOH.
We present the counterpart to Chap. 4 in Chap. 5, where we focus on the role of “permanent” exceptions and their importance in scientific knowledge and biology. These exceptions can be analyzed at any scale and are often not appreciated beyond anecdotal mentions. They can be aberrant or teratological groups, taxonomic groups unique for some features of their biology, “intermediate exceptions” with minorities of species or clades with certain characteristics compared to the majority, or organisms with exceptional distributions in space or time. In this chapter, we reviewed groups that have been difficult to classify because of their rarity, rarities that can be used for human benefit, exceptional groups that make us rethink phylogenetic relationships, rare and incredible biological phenomena, and evolutionary and ecological aspects of rare species. Our goal is to vindicate rarities and minorities, to highlight their importance for the understanding of evolution, and to begin to make these cases visible and treasured in the teaching of biology.
The global economy depends on one of the important constituents of life i.e., energy Globalization and industrialization in the world have led to increases in petroleum-based fuel and global oil prices, henceforth biofuel research is considered a hot topic due to the increasing demand for global energy which presently seems to be the alternative source of energy for sustainable development considering the environmental aspects. The development of different methods for biofuel production using plants and microbes has gained considerable attention. Inexhaustible biological resources are available in the form of agricultural biomass and various biological wastes which can be transformed into liquid biofuels. However, the conversion process is very expensive and not worthwhile for large-scale production of biofuel for commercial use, therefore a lot of research needs to be done for the efficient, economical, effective and sustainable production method. The present chapter aims to discuss the microbial mechanism for the production of biofuel with the advancement in metabolic engineering for new organisms and to improve biofuel production. We also discuss the economic viability of various approaches used in biofuel production.
Plant diversity effects on community productivity often increase over time. Whether the strengthening of diversity effects is caused by temporal shifts in species-level overyielding (i.e., higher species-level productivity in diverse communities compared with monocultures) remains unclear. Here, using data from 65 grassland and forest biodiversity experiments, we show that the temporal strength of diversity effects at the community scale is underpinned by temporal changes in the species that yield. These temporal trends of species-level overyielding are shaped by plant ecological strategies, which can be quantitatively delimited by functional traits. In grasslands, the temporal strengthening of biodiversity effects on community productivity was associated with increasing biomass overyielding of resource-conservative species increasing over time, and with overyielding of species characterized by fast resource acquisition either decreasing or increasing. In forests, temporal trends in species overyielding differ when considering above- versus belowground resource acquisition strategies. Overyielding in stem growth decreased for species with high light capture capacity but increased for those with high soil resource acquisition capacity. Our results imply that a diversity of species with different, and potentially complementary, ecological strategies is beneficial for maintaining community productivity over time in both grassland and forest ecosystems.
The sustainable development scenario (SDS) framework offers the most desirable human and global safety scenario in the long term, whereby nations work together to address energy access, limit air pollution, and mitigate climate change impact by transforming the energy mix towards a low carbon economy. Biofuels from biomass have brought worldwide attention to their potential to resolve various environmental problems, including climate change concerns and simultaneously help rural economy and livelihood aligning with the goals of the SDS. Most biomass-derived biofuel is oxygenated fuel, meaning it contains oxygen that provides more efficient combustion while reducing air pollutant gases. It has been highlighted that the global progress towards biofuel production and SDGs goals could significantly help to achieve a low carbon transition in the global energy supply. However, biofuels from biomass still have many challenges in large-scale production. The present review highlights the role of various types of biofuel production technologies advances, major challenges, and benefits in adapting biofuel to mitigate environmental pollution, worldwide carbon dioxide emissions reduction initiatives, and different biofuel policies adopted by different countries to achieve Sustainable Development Scenario (SDS) goals.
Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears able to obtain N from sources that other crops cannot tap. The N removed in harvested biomass is often greater than the amount of N applied. In areas with sufficient rainfall, sustainable yields of ∼15 Mg ha yr may be achievable by applying ∼50 kg N ha yr. Harvesting biomass once per season—after plants have senesced and translocated N into perennial tissues—appears to allow plants to maintain an internal N reserve. Two harvests yr may increase yields in some cultivars, but a single annual harvest maximizes yields in many cases. If two harvests are taken, more N must be applied to compensate for the N removed in the midseason harvest. Taking more than two harvests yr often adversely affects long-term productivity and persistence. Switchgrass has potential as a renewable fuel source, but such use will likely require large infrastructural changes; and, even at maximum output, such systems could not provide the energy currently being derived from fossil fuels.
Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use
change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term
field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing
on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained
diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed
by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically
stressed grasslands enhanced biodiversity.
Declining biodiversity represents one of the most dramatic and irreversible aspects of anthropogenic global change, yet the ecological implications of this change are poorly understood. Recent studies have shown that biodiversity loss of basal species, such as autotrophs or plants, affects fundamental ecosystem processes such as nutrient dynamics and autotrophic production. Ecological theory predicts that changes induced by the loss of biodiversity at the base of an ecosystem should impact the entire system. Here we show that experimental reductions in grassland plant richness increase ecosystem vulnerability to invasions by plant species, enhance the spread of plant fungal diseases, and alter the richness and structure of insect communities. These results suggest that the loss of basal species may have profound effects on the integrity and functioning of ecosystems.
1] We quantified the effects of repeated, seasonal fires on soil organic carbon (SOC), black carbon (BC), and total N in controls and four fire treatments differing in frequency and season of occurrence in a temperate savanna. The SOC at 0–20 cm depth increased from 2044 g C m À2 in controls to 2393–2534 g C m À2 in the three treatments that included summer fire. Similarly, soil total N (0–20 cm) increased from 224 g N m À2 in the control to 251–255 g N m À2 in the treatments that included summer fire. However, winter fires had no effect on SOC or total N. Plant species composition coupled with lower d 13 C of SOC suggested that increased soil C in summer fire treatments was related to shifts in community composition toward greater relative productivity by C 3 species. Lower d 15 N of soil total N in summer fire treatments was consistent with a scenario in which N inputs > N losses. The BC storage was not altered by fire, and comprised 13–17% of SOC in all treatments. Results indicated that fire and its season of occurrence can significantly alter ecosystem processes and the storage of C and N in savanna ecosystems., Soil organic carbon and black carbon storage and dynamics under different fire regimes in temperate mixed-grass savanna, Global Biogeochem. Cycles, 20, GB3006, doi:10.1029/2005GB002670.
There are major expectations that bioenergy will supply large amounts of CO2 neutral energy for the future. A large-scale expansion of energy crop production would lead to a large increase in evapotranspiration appropriation for human uses, potentially as large as the present evapotranspiration from global cropland. In some countries this could lead to further enhancement of an already stressed water situation. But there are also countries where such impacts are less likely to occur. One major conclusion for future research is that assessments of bioenergy potentials need to consider restrictions from competing demand for water resources.
Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the relationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are structured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain. Based on our review of the scientific literature, we are certain of the following conclusions: 1)Species' functional characteristics strongly influence ecosystem properties. Functional characteristics operate in a variety of contexts, including effects of dominant species, keystone species, ecological engineers, and interactions among species (e.g., competition, facilitation, mutualism, disease, and predation). Relative abundance alone is not always a good predictor of the ecosystem-level importance of a species, as even relatively rare species (e.g., a keystone predator) can strongly influence pathways of energy and material flows. 2)Alteration of biota in ecosystems via species invasions and extinctions caused by human activities has altered ecosystem goods and services in many well-documented cases. Many of these changes are difficult, expensive, or impossible to reverse or fix with technological solutions. 3)The effects of species loss or changes in composition, and the mechanisms by which the effects manifest themselves, can differ among ecosystem properties, ecosystem types, and pathways of potential community change. 4)Some ecosystem properties are initially insensitive to species loss because (a) ecosystems may have multiple species that carry out similar functional roles, (b) some species may contribute relatively little to ecosystem properties, or (c) properties may be primarily controlled by abiotic environmental conditions. 5)More species are needed to insure a stable supply of ecosystem goods and services as spatial and temporal variability increases, which typically occurs as longer time periods and larger areas are considered. We have high confidence in the following conclusions: 1)Certain combinations of species are complementary in their patterns of resource use and can increase average rates of productivity and nutrient retention. At the same time, environmental conditions can influence the importance of complementarity in structuring communities. Identification of which and how many species act in a complementary way in complex communities is just beginning. 2)Susceptibility to invasion by exotic species is strongly influenced by species composition and, under similar environmental conditions, generally decreases with increasing species richness. However, several other factors, such as propagule pressure, disturbance regime, and resource availability also strongly influence invasion success and often override effects of species richness in comparisons across different sites or ecosystems. 3)Having a range of species that respond differently to different environmental perturbations can stabilize ecosystem process rates in response to disturbances and variation in abiotic conditions. Using practices that maintain a diversity of organisms of different functional effect and functional response types will help preserve a range of management options. Uncertainties remain and further research is necessary in the following areas: 1)Further resolution of the relationships among taxonomic diversity, functional diversity, and community structure is important for identifying mechanisms of biodiversity effects. 2)Multiple trophic levels are common to ecosystems but have been understudied in biodiversity/ecosystem functioning research. The response of ecosystem properties to varying composition and diversity of consumer organisms is much more complex than responses seen in experiments that vary only the diversity of primary producers. 3)Theoretical work on stability has outpaced experimental work, especially field research. We need long-term experiments to be able to assess temporal stability, as well as experimental perturbations to assess response to and recovery from a variety of disturbances. Design and analysis of such experiments must account for several factors that covary with species diversity. 4)Because biodiversity both responds to and influences ecosystem properties, understanding the feedbacks involved is necessary to integrate results from experimental communities with patterns seen at broader scales. Likely patterns of extinction and invasion need to be linked to different drivers of global change, the forces that structure communities, and controls on ecosystem properties for the development of effective management and conservation strategies. 5)This paper focuses primarily on terrestrial systems, with some coverage of freshwater systems, because that is where most empirical and theoretical study has focused. While the fundamental principles described here should apply to marine systems, further study of that realm is necessary. Despite some uncertainties about the mechanisms and circumstances under which diversity influences ecosystem properties, incorporating diversity effects into policy and management is essential, especially in making decisions involving large temporal and spatial scales. Sacrificing those aspects of ecosystems that are difficult or impossible to reconstruct, such as diversity, simply because we are not yet certain about the extent and mechanisms by which they affect ecosystem properties, will restrict future management options even further. It is incumbent upon ecologists to communicate this need, and the values that can derive from such a perspective, to those charged with economic and policy decision-making.
During the next 50 years, which is likely to be the final period of rapid agricultural expansion, demand for food by a wealthier and 50 % larger global population will be a major driver of global environmental change. Should past dependences of the global environmental impacts of agriculture on human population and consumption continue, 10 9 hectares of natural ecosystems would be converted to agriculture by 2050. This would be accompanied by 2.4to 2.7-fold increases in nitrogen- and phosphorus-driven eutrophication of terrestrial, freshwater, and near-shore marine ecosystems, and comparable increases in pesticide use. This eutrophication and habitat destruction would cause unprecedented ecosystem simplification, loss of ecosystem services, and species extinctions. Significant scientific advances and regulatory, technological, and policy changes are needed to control the environmental impacts of agricultural expansion. During the first 35 years of the Green Revolution, global grain production doubled, greatly reducing food shortages, but at high environmental cost (1–5). In addition to its effects on greenhouse gases (1, 6, 7), agriculture affects
This study explores the range of future world potential of biomass for energy. The focus has been put on the factors that influence the potential biomass availability for energy purposes rather than give exact numbers. Six biomass resource categories for energy are identified: energy crops on surplus cropland, energy crops on degraded land, agricultural residues, forest residues, animal manure and organic wastes. Furthermore, specific attention is paid to the competing biomass use for material. The analysis makes use of a wide variety of existing studies on all separate categories. The main conclusion of the study is that the range of the global potential of primary biomass (in about 50 years) is very broad quantified at 33−1135EJy−1. Energy crops from surplus agricultural land have the largest potential contribution (0–988EJy−1). Crucial factors determining biomass availability for energy are: (1) The future demand for food, determined by the population growth and the future diet; (2) The type of food production systems that can be adopted world-wide over the next 50 years; (3) Productivity of forest and energy crops; (4) The (increased) use of bio-materials; (5) Availability of degraded land; (6) Competing land use types, e.g. surplus agricultural land used for reforestation.It is therefore not “a given” that biomass for energy can become available at a large-scale. Furthermore, it is shown that policies aiming for the energy supply from biomass should take the factors like food production system developments into account in comprehensive development schemes.
During the next 50 years, which is likely to be the final period of rapid agricultural expansion, demand for food by a wealthier and 50% larger global population will be a major driver of global environmental change. Should past dependences of the global environmental impacts of agriculture on human population and consumption continue, 10(9) hectares of natural ecosystems would be converted to agriculture by 2050. This would be accompanied by 2.4- to 2.7-fold increases in nitrogen- and phosphorus-driven eutrophication of terrestrial, freshwater, and near-shore marine ecosystems, and comparable increases in pesticide use. This eutrophication and habitat destruction would cause unprecedented ecosystem simplification, loss of ecosystem services, and species extinctions. Significant scientific advances and regulatory, technological, and policy changes are needed to control the environmental impacts of agricultural expansion.
Plant diversity and niche complementarity had progressively stronger effects on ecosystem functioning during a 7-year experiment,
with 16-species plots attaining 2.7 times greater biomass than monocultures. Diversity effects were neither transients nor
explained solely by a few productive or unviable species. Rather, many higher-diversity plots outperformed the best monoculture.
These results help resolve debate over biodiversity and ecosystem functioning, show effects at higher than expected diversity
levels, and demonstrate, for these ecosystems, that even the best-chosen monocultures cannot achieve greater productivity
or carbon stores than higher-diversity sites.
Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate
problem for the next half-century. A portfolio of technologies now exists to meet the world's energy needs over the next 50
years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond
the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although
no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is
large enough that not every element has to be used.
Land use has generally been considered a local environmental issue, but it is becoming a force of global importance. Worldwide
changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter
to more than six billion people. Global croplands, pastures, plantations, and urban areas have expanded in recent decades,
accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity.
Such changes in land use have enabled humans to appropriate an increasing share of the planet's resources, but they also potentially
undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate
and air quality, and ameliorate infectious diseases. We face the challenge of managing trade-offs between immediate human
needs and maintaining the capacity of the biosphere to provide goods and services in the long term.
Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more efficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides sufficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.
• corn
• soybean
• life-cycle accounting
• agriculture
• fossil fuel
We used two independent methods to determine the dynamics of soil carbon and nitrogen following abandonment of agricultural fields on a Minnesota sand plain. First, we used a chronosequence of 19 fields abandoned from 1927 to 1982 to infer soil carbon and nitrogen dynamics. Second, we directly observed dynamics of carbon and nitrogen over a 12-yr period in 1900 permanent plots in these fields. These observed dynamics were used in a differential equation model to predict soil carbon and nitrogen dynamics. The two methods yielded similar results. Resampling the 1900 plots showed that the rates of accumulation of nitrogen and carbon over 12 yr depended on ambient carbon and nitrogen levels in the soil, with rates of accumulation declining at higher carbon and nitrogen levels. A dynamic model fitted to the observed rates of change predicted logistic dynamics for nitrogen and carbon accumulation. On average, agricultural practices resulted in a 75% loss of soil nitrogen and an 89% loss of soil carbon at the time of abandonment. Recovery to 95% of the preagricultural levels is predicted to require 180 yr for nitrogen and 230 yr for carbon. This model accurately predicted the soil carbon, nitrogen, and carbon : nitrogen ratio patterns observed in the chronosequence of old fields, suggesting that the chronosequence may be indicative of actual changes in soil carbon and nitrogen. Our results suggest that the rate of carbon accumulation was controlled by the rate of nitrogen accumulation, which in turn depended on atmospheric nitrogen deposition and symbiotic nitrogen fixation by legumes. Our data support the hypothesis that these abandoned fields initially retain essentially all nitrogen and have a closed nitrogen cycle. Multiple regression suggests that vegetation composition had a significant influence on the rates of accumulation of both nitrogen and carbon; legumes increased these rates, and C-3 grasses and forbs decreased them. C-4 grasses increased the C:N ratio of the soil organic matter and thereby increased the rate of carbon accumulation, but not nitrogen accumulation.
Information on optimal harvest periods and N fertilization rates for switchgrass (Panicum virgatum L.) grown as a biomass or bioenergy crop in the Midwest USA is limited. Our objectives were to determine optimum harvest periods and N rates for biomass production in the region. Established stands of ‘Cave-in-Rock’ switchgrass at Ames, IA, and Mead, NE, were fertilized 0, 60, 120, 180, 240, or 300 kg N ha⁻¹ Harvest treatments were two- or one-cut treatments per year, with initial harvest starting in late June or early July (Harvest 1) and continuing at approximately 7-d intervals until the latter part of August (Harvest 7). A final eighth harvest was completed after a killing frost. Regrowth was harvested on previously harvested plots at that time. Soil samples were taken before fertilizer was applied in the spring of 1994 and again in the spring of 1996. Averaged over years, optimum biomass yields were obtained when switchgrass was harvested at the maturity stages R3 to R5 (panicle fully emerged from boot to postanthesis) and fertilized with 120 kg N ha⁻¹ Biomass yields with these treatments averaged 10.5 to 11.2 Mg ha⁻¹ at Mead and 11.6 to 12.6 Mg ha⁻¹ at Ames. At this fertility level, the amount of N removed was approximately the same as the amount applied. At rates above this level, soil NO3–N concentrations increased.
Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © 2002. American Society of Agronomy . Published in Agron. J.94:413–420.
Elucidating the role of pyrogenic carbon (Cpyr) as a global pool for CO2 sequestration in temperate ecosystems requires information on the contribution of Cpyr to soil organic carbon (SOC) across different climatic regions. We investigated the effect of climate and basic soil properties on the accumulation of Cpyr in surface soils across the native North American prairies. Topsoil samples (0-10 cm) of 18 native grassland sites along temperature and precipitation transects from central Saskatoon, Canada, to south Texas, USA, were analyzed for benzenecarboxylic acids as molecular markers for Cpyr after nitric acid oxidation in the bulk soil (
Short-rotation woody crops (SRWC) along with other woody biomass feedstocks will play a significant role in a more secure and sustainable energy future for the United States and around the world. In temperate regions, shrub willows are being developed as a SRWC because of their potential for high biomass production in short time periods, ease of vegetative propagation, broad genetic base, and ability to resprout after multiple harvests. Understanding and working with willow's biology is important for the agricultural and economic success of the system.
Changes in the plant community and ecosystem properties that follow the conversion of agriculture to restored tallgrass prairies are poorly understood. Beginning in 1995, we established a species-rich, restored prairie chronosequence where 3 ha of ag-ricultural land have been converted to tallgrass prairie each year. Our goals were to examine differences in ecosystem properties between these restored prairies and adjacent agricultural fields and to determine changes in, and potential interactions between, the plant community and ecosystem properties that occur over time in the restored prairies. During the summers of 2000–2002, we examined species cover, soil C and N, potential net C and N mineral-ization, litter mass, soil texture, and bulk density across the 6-to 8-year-old prairie chron-osequence and adjacent agricultural fields in southern Minnesota. We also established ex-perimentally fertilized, watered, and control plots in the prairie chronosequence to examine the degree of nitrogen limitation on aboveground and belowground net primary production (ANPP and BNPP). Large shifts in functional diversity occurred within three growing seasons. First-year prairies were dominated by annuals and biennials. By the second growing season, perennial native composites had become dominant, followed by a significant shift to warm-season C 4 grasses in prairies 3 yr old. Ecosystem properties that changed with the rise of C 4 grasses included increased BNPP, litter mass, and C mineralization rates and decreased N mineralization rates. ANPP increased significantly with N fertilization but did not vary between young and old prairies with dramatically different plant community composition. Total soil C and N were not significantly different between prairie and ag-ricultural soils in the depths examined (0–10, 10–20, 20–35, 35–50, 50–65 cm). We com-pared the results from our species-rich prairie restoration to published data on ecosystem function in other restored grasslands, such as Conservation Reserve Program (CRP) and old-field successional sites. Results suggest that rapid changes in functional diversity can have large impacts on ecosystem-level properties, causing community-and system-level dynamics in species-rich prairie restorations to converge with those from low-diversity managed grasslands.
To determine the long-term impact of elevated CO2 on primary production of native tallgrass prairie, we compared the responses of tallgrass prairie at ambient and twice-ambient atmospheric CO2 levels over an 8-year period. Plots in open-top chambers (4.5 m diameter) were exposed continuously (24 h) to ambient and elevated CO2 from early April to late October each year. Unchambered plots were monitored also. Above-ground peak biomass was determined by clipping each year in early August, and root growth was estimated by harvesting roots from root ingrowth bags. Plant community composition was censused each year in early June. In the last 2 years of the study, subplots were clipped on 1 June or 1 July, and regrowth was harvested on 1 October. Volumetric soil water content of the 0–100 cm soil layer was determined using neutron scattering, and was generally higher in elevated CO2 plots than ambient. Peak above-ground biomass was greater on elevated CO2 plots than ambient CO2 plots with or without chambers during years with significant plant water stress. Above-ground regrowth biomass was greater under elevated CO2 than under ambient CO2 in a year with late-season water stress, but did not differ in a wetter year. Root ingrowth biomass was also greater in elevated CO2 plots than ambient CO2 plots when water stress occurred during the growing season. The basal cover and relative amount of warm-season perennial grasses (C4) in the stand changed little during the 8-year period, but basal cover and relative amount of cool-season perennial grasses (C3) in the stand declined in the elevated CO2 plots and in ambient CO2 plots with chambers. Forbs (C3) and members of the Cyperaceae (C3) increased in basal cover and relative amount in the stand at elevated compared to ambient CO2. Greater biomass production under elevated CO2 in C4-dominated grasslands may lead to a greater carbon sequestration by those ecosystems and reduce peak atmospheric CO2 concentrations in the future.
Corn stover is the residue that is left behind after corn grain harvest. We have constructed a life‐cycle model that describes collecting corn stover in the state of Iowa, in the Midwest of the United States, for the production and use of a fuel mixture consisting of 85% ethanol/15% gasoline (known as “E85”) in a flexible‐fuel light‐duty vehicle. The model incorporates results from individual models for soil carbon dynamics, soil erosion, agronomics of stover collection and transport, and biocon‐version of stover to ethanol.
Limitations in available data forced us to focus on a scenario that assumes all farmers in the state of Iowa switch from their current cropping and tilling practices to continuous production of corn and “no‐till” practices. Under these conditions, which maximize the amount of collectible stover, Iowa alone could produce almost 8 billion liters per year of pure stover‐derived ethanol (E100) at prices competitive with today's corn‐starch‐derived fuel ethanol. Soil organic matter, an important indicator of soil health, drops slightly in the early years of stover collection but remains stable over the 90‐year time frame studied. Soil erosion is controlled at levels within tolerable soil‐loss limits established for each county in Iowa by the U.S. Department of Agriculture.
We find that, for each kilometer fueled by the ethanol portion of E85, the vehicle uses 95% less petroleum compared to a kilometer driven in the same vehicle on gasoline. Total fossil energy use (coal, oil, and natural gas) and greenhouse gas emissions (fossil CO 2 , N 2 O, and CH 4 ) on a life‐cycle basis are 102% and 113% lower, respectively. Air quality impacts are mixed, with emissions of CO, NOx, and SOx increasing, whereas hydrocarbon ozone precursors are reduced.
This model can serve as a platform for future discussion and analysis of possible scenarios for the sustainable production of transportation fuels from corn stover and other agricultural residues.
The generation of electricity, and the consumption of energy in general, often result in adverse effects on the environment. Coal-fired power plants generate over half of the electricity used in the U.S., and therefore play a significant role in any discussion of energy and the environment. By cofiring biomass, currently operating coal plants have an opportunity to reduce the impact they have, but to what degree, and with what trade-offs? A life cycle assessment has been conducted on a coal-fired power system that cofires wood residue. The assessment was conducted in a cradle-to-grave manner to cover all processes necessary for the operation of the power plant, including raw material extraction, feed preparation, transportation, and waste disposal and recycling. Cofiring was found to significantly reduce the environmental footprint of the average coal-fired power plant. At rates of 5% and 15% by heat input, cofiring reduces greenhouse gas emissions on a CO2-equivalent basis by 5.4% and 18.2%, respectively. Emissions of SO2, NOx
, non-methane hydrocarbons, particulates, and carbon monoxide are also reduced with cofiring. Additionally, total system energy consumption is lowered by 3.5% and 12.4% for the 5% and 15% cofiring cases, respectively. Finally, resource consumption and solid waste generation were found to be much less for systems that cofire.
Perennial grasses display many beneficial attributes as energy crops, and there has been increasing interest in their use in the US and Europe since the mid-1980s. In the US, the Herbaceous Energy Crops Research Program (HECP), funded by the US Department of Energy (DOE), was established in 1984. After evaluating 35 potential herbaceous crops of which 18 were perennial grasses it was concluded that switchgrass (Panicum virgatum) was the native perennial grass which showed the greatest potential. In 1991, the DOE's Bioenergy Feedstock Development Program (BFDP), which evolved from the HECP, decided to focus research on a “model” crop system and to concentrate research resources on switchgrass, in order to rapidly attain its maximal output as a biomass crop. In Europe, about 20 perennial grasses have been tested and four perennial rhizomatous grasses (PRG), namely miscanthus (Miscanthus spp.), reed canarygrass (Phalaris arundinacea), giant reed (Arundo donax) and switchgrass (Panicum virgatum) were chosen for more extensive research programs. Reed canarygrass and giant reed are grasses with the C3 photosynthetic pathway, and are native to Europe. Miscanthus, which originated in Southeast Asia, and switchgrass, native to North America, are both C4 grasses. These four grasses differ in their ecological/climatic demands, their yield potentials, biomass characteristics and crop management requirements. Efficient production of bioenergy from such perennial grasses requires the choice of the most appropriate grass species for the given ecological/climatic conditions. In temperate and warm regions, C4 grasses outyield C3 grasses due to their more efficient photosynthetic pathway. However, the further north perennial grasses are planted, the more likely cool season grasses are to yield more than warm season grasses. Low winter temperatures and short vegetation periods are major limits to the growth of C4 grasses in northern Europe. With increasing temperatures towards central and southern Europe, the productivity of C4 grasses and therefore their biomass yields and competitiveness increase.Since breeding of and research on perennial rhizomatous grasses (PRG) is comparatively recent, there is still a significant need for further development. Some of the given limitations, like insufficient biomass quality or the need for adaption to certain ecological/climatic zones, may be overcome by breeding varieties especially for biomass production. Furthermore, sure and cost-effective establishment methods for some of the grasses, and effective crop production and harvest methods, have yet to be developed.This review summarizes the experience with selecting perennial grasses for bioenergy production in both the US and Europe, and gives an overview of the characteristics and requirements of the four most investigated perennial rhizomatous grasses; switchgrass, miscanthus, reed canarygrass and giant reed.
Fischer–Tropsch (FT) diesel derived from biomass via gasification is an attractive clean and carbon neutral transportation fuel, directly usable in the present transport sector. System components necessary for FT diesel production from biomass are analysed and combined to a limited set of promising conversion concepts. The main variations are in gasification pressure, the oxygen or air medium, and in optimisation towards liquid fuels only, or towards the product mix of liquid fuels and electricity. The technical and economic performance is analysed. For this purpose, a dynamic model was built in Aspen Plus®, allowing for direct evaluation of the influence of each parameter or device, on investment costs, FT and electricity efficiency and resulting FT diesel costs. FT diesel produced by conventional systems on the short term and at moderate scale would probably cost 16 €/GJ. In the longer term (large scale, technological learning, and selective catalyst), this could decrease to 9 €/GJ. Biomass integrated gasification FT plants can only become economically viable when crude oil price levels rise substantially, or when the environmental benefits of green FT diesel are valued. Green FT diesel also seems 40–50% more expensive than biomass derived methanol or hydrogen, but has clear advantages with respect to applicability to the existing infrastructure and car technology.
The global annual potential bioethanol production from the major crops, corn, barley, oat, rice, wheat, sorghum, and sugar cane, is estimated. To avoid conflicts between human food use and industrial use of crops, only the wasted crop, which is defined as crop lost in distribution, is considered as feedstock. Lignocellulosic biomass such as crop residues and sugar cane bagasse are included in feedstock for producing bioethanol as well. There are about of dry wasted crops in the world that could potentially produce of bioethanol. About of dry lignocellulosic biomass from these seven crops is also available for conversion to bioethanol. Lignocellulosic biomass could produce up to of bioethanol. Thus, the total potential bioethanol production from crop residues and wasted crops is , about 16 times higher than the current world ethanol production. The potential bioethanol production could replace of gasoline (32% of the global gasoline consumption) when bioethanol is used in E85 fuel for a midsize passenger vehicle. Furthermore, lignin-rich fermentation residue, which is the coproduct of bioethanol made from crop residues and sugar cane bagasse, can potentially generate both of electricity (about 3.6% of world electricity production) and of steam. Asia is the largest potential producer of bioethanol from crop residues and wasted crops, and could produce up to of bioethanol. Rice straw, wheat straw, and corn stover are the most favorable bioethanol feedstocks in Asia. The next highest potential region is Europe ( of bioethanol), in which most bioethanol comes from wheat straw. Corn stover is the main feedstock in North America, from which about of bioethanol can potentially be produced. Globally rice straw can produce of bioethanol, which is the largest amount from single biomass feedstock. The next highest potential feedstock is wheat straw, which can produce of bioethanol. This paper is intended to give some perspective on the size of the bioethanol feedstock resource, globally and by region, and to summarize relevant data that we believe others will find useful, for example, those who are interested in producing biobased products such as lactic acid, rather than ethanol, from crops and wastes. The paper does not attempt to indicate how much, if any, of this waste material could actually be converted to bioethanol.
Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed
by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning
of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined;
more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species
on Earth have been driven to extinction. By these and other standards, it is clear that we live on a human-dominated planet.
We used two independent methods to determine the dynamics of soil carbon and nitrogen following abandonment of agricultural fields on a Minnesota sand plain. First, we used a chronosequence of 19 fields abandoned from 1927 to 1982 to infer soil carbon and nitrogen dynamics. Second, we directly observed dynamics of carbon and nitrogen over a 12-yr period in 1900 permanent plots in these fields. These observed dynamics were used in a differential equation model to predict soil carbon and nitrogen dynamics. The two methods yielded similar results. Resampling the 1900 plots showed that the rates of accumulation of nitrogen and carbon over 12 yr depended on ambient carbon and nitrogen levels in the soil, with rates of accumulation declining at higher carbon and nitrogen levels. A dynamic model fitted to the observed rates of change predicted logistic dynamics for nitrogen and carbon accumulation. On average, agricultural practices resulted in a 75% loss of soil nitrogen and an 89% loss of soil carbon at the
Four different continuous process flowsheets for biodiesel production from virgin vegetable oil or waste cooking oil under alkaline or acidic conditions on a commercial scale were developed. Detailed operating conditions and equipment designs for each process were obtained. A technological assessment of these four processes was carried out to evaluate their technical benefits and limitations. Analysis showed that the alkali-catalyzed process using virgin vegetable oil as the raw material required the fewest and smallest process equipment units but at a higher raw material cost than the other processes. The use of waste cooking oil to produce biodiesel reduced the raw material cost. The acid-catalyzed process using waste cooking oil proved to be technically feasible with less complexity than the alkali-catalyzed process using waste cooking oil, thereby making it a competitive alternative to commercial biodiesel production by the alkali-catalyzed process.
To study the potential effects of increased biofuel use, we evaluated six representative analyses of fuel ethanol. Studies
that reported negative net energy incorrectly ignored coproducts and used some obsolete data. All studies indicated that current
corn ethanol technologies are much less petroleum-intensive than gasoline but have greenhouse gas emissions similar to those
of gasoline. However, many important environmental effects of biofuel production are poorly understood. New metrics that measure
specific resource inputs are developed, but further research into environmental metrics is needed. Nonetheless, it is already
clear that large-scale use of ethanol for fuel will almost certainly require cellulosic technology.
Roughly 43 percent of Earth's terrestrial vegetated surface has diminished capacity to supply benefits to humanity because of recent, direct impacts of land use. This represents an approximately 10 percent reduction in potential direct instrumental value (PDIV), defined as the potential to yield direct benefits such as agricultural, forestry, industrial, and medicinal products. If present trends continue, the global loss of PDIV could reach approximately 20 percent by 2020. From a biophysical perspective, recovery of approximately 5 percent of PDIV is feasible over the next 25 years. Capitalizing on natural recovery mechanisms is urgently needed to prevent further irreversible degradation and to retain the multiple values of productive land.
The components of social costsincluded in the supply analysis are cashoutlays and opportunity costs associated withharvest and alternative residue uses, potentialenvironmental damage that is avoided byexcluding unsuitable land, and costs in movingresidues from farms to processing plants. Regional estimates account for the growingconditions and crops of the main agriculturalareas of the United States. Estimates includethe main U.S. field crops with potential forresidue harvest: corn, wheat, sorghum, oats,barley, rice and cane sugar. The potentialcontribution of residues to U.S. energy needsis discussed. Copyright Kluwer Academic Publishers 2003
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Supported by grants from the University of Minnesota's Initiative for Renewable Energy and the Environment, the NSF (grant DEB 0080382), and the Bush Foundation. We thank
- S Polasky
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Supported by grants from the University of Minnesota's
Initiative for Renewable Energy and the Environment, the
NSF (grant DEB 0080382), and the Bush Foundation. We
thank S. Polasky, J. Fargione, E. Nelson, P. Spath,
E. Larson, and R. Williams for comments.