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Life cycle assessment of biomass densification systems
Abstract
Several recent life cycle assessments (LCA) of biomass densification have been carried out. This paper reviews data from 19 sources with 48 case scenarios to assess the current status of LCA of biomass densification. It describes the specific units in a reference “gate-to-gate” LCA in relation to the existing studies, and summarises key differences between them. Finally, it provides a qualitative analysis of the associated sources of uncertainty.
Existing LCA studies of biomass densification were found to provide insufficient and inconsistent information for full transparency and comparability, due to different choices in system boundary, functional unit, allocation procedure, densification technology and biomass residues. Most of the reviewed studies attributed most of the energy use and greenhouse gas (GHG) emissions to transportation, drying and densification. The energy and GHG emissions of the gate-to-gate densification system were highly sensitive to the technology, feed material used in densification and scale of production.
Apart from one study with zero energy consumption as a result of the use of manual operations, the normalised values of energy consumption for the reviewed studies ranged from 20 to 900 kJ MJ⁻¹. Neglecting three outlier values, GHG emissions as mass of CO2-eq for the reviewed studies ranged from 600 t MJ⁻¹ to 50 g MJ⁻¹. Similar variations in result and outlier cases have beesn reported for other bioenergy processes, by other authors. Assuming that the biggest impact of densification processes is on transport fuel use, and based on 5 studies that reported densification ratios, the net energy and GHG emissions savings resulting from densification ranged from 200 to 1000 kJ MJ⁻¹ and 9 to 50 CO2-eq (g MJ⁻¹), respectively. On this basis, it can be concluded that biomass densification is a worthwhile addition to the biomass energy conversion system.
There is a need for more transparent reporting and analysis of uncertainty in the modelling, to better understand the wide variation in outcomes.
... 1. Storage of raw and densified biomass: densifiable biomass requires a large area and specific infrastructure (silos and warehouses) for the temporary storage of the material and to reduce the risk of microbiological damage. This last aspect is vital since these microbial actions can compromise the calorific value of the prod-uct, significantly reducing its usefulness (Muazu et al. 2017). To keep them in proper condition without risk of degradation, it is necessary to use mechanical means of drying (fans and heaters). ...
... The pellets usually have a smaller dimension and are generally manufactured by extrusion, whereas the briquettes have a larger size because they are produced by compaction (Dias et al. 2012). Generally, the most used equipment in this phase is the pellet press, briquette press, mechanical piston press, hydraulic piston press, roller press, extruder screw press, conical screw press, press with cylindrical screw and heated die, and double screw press (Bajwa et al. 2018;Muazu et al. 2017). This type of equipment consumes a considerable amount of energy due to the energy requirements needed for extrusion or compaction. ...
... It can be observed that the choice of densification technology plays an important role. However, the compaction requirement according to the nature of the biomass must be evaluated (Muazu et al. 2017). 4. Cooling: the densified material usually suffers an increase in temperature due to the heating resulting from shearing between the particles (surface temperature above 200 °C) (Dias et al. 2012). ...
A systematic review of the state of the art of LCA biomass densification for energy purposes has been conducted. The aspects analyzed in the studies were: the temporal and geographical scope; type of raw material; densification technology, function, and functional unit; system boundary; allocation approach; impact assessment method; impact categories; sensitivity analysis; and uncertainty. Finally, a process contribution analysis with the environmental impacts is provided. Based on the results, wood fuels correspond to 56% of the biomass analyzed. The pelletizing technology represents 79% of the studies. A significant percentage of the life cycle assessments (88%) explicitly state the functional unit; however, 12% of these studies do not present it straightforwardly. Different functional units are used in the analyzed studies, with one MegaJoule (1 MJ) being the most common (in 33% of the studies). The most commonly used approach was from Cradle-to-grave, representing 54% of the studies. In this review, 54% of the studies applied allocation, 27% mass allocation, 17% market value allocation, and 4% combined. The typically employed life cycle impact assessment methods in the revised studies were ReCiPe, CML, and IPCC, representing 23, 21, and 19%, respectively. The most frequent impact categories among the studies are global warming (96.15%), acidification (58%), eutrophication (50%), ozone depletion (46%), and photochemical ozone formation (42%). The critical point most highlighted in the studies is the densification process, dominated by the use of machines, usually with high energy consumption, resulting in emissions of CO2 and CH4.
... Fig. 7.5A and B demonstrates the contribution of different life-cycle stages of densification systems and their components to the overall GHG emissions and energy consumption, respectively. Muazu et al. (2017) conducted a comprehensive review study focused on LCA studies for densification of various feedstocks, including the olive husk, corn stover, sawdust, wood chips, etc. (Fig. 7.6). The results obtained from 19 different studies were analyzed and valuable conclusions were made. ...
... Life cycle greenhouse gas emissions in CO 2 equiv. (g/MJ) for a reference gate-to-gate biomass densification system (Reproduced with permission fromMuazu et al., 2017). ...
... Possible sources of uncertainty in fuel densification life cycle assessment-Predensification (Reproduced with permission fromMuazu et al., 2017). ...
In the context of climate change and raising concerns regarding negative impacts on the environment, there is a growing interest in moving away from fossil energy to renewable options such as bioenergy produced from biofuels. These biofuels can be produced from biomass following a number of production processes. This chapter describes the technologies involved in such processes to produce the two most widely used biofuels: biogas and bioethanol. Additionally, it presents the life cycle assessment (LCA) methodology to calculate the environmental impact of biofuels over their entire life cycle and compare it with that of conventional fuels. The main key performance indicators used in LCA studies of biofuels are also explained and illustrated with results from previous studies. Finally, the product environmental footprint is described, and its potential to guide LCA studies of biofuels is discussed.
... Fig. 7.5A and B demonstrates the contribution of different life-cycle stages of densification systems and their components to the overall GHG emissions and energy consumption, respectively. Muazu et al. (2017) conducted a comprehensive review study focused on LCA studies for densification of various feedstocks, including the olive husk, corn stover, sawdust, wood chips, etc. (Fig. 7.6). The results obtained from 19 different studies were analyzed and valuable conclusions were made. ...
... Life cycle greenhouse gas emissions in CO 2 equiv. (g/MJ) for a reference gate-to-gate biomass densification system (Reproduced with permission fromMuazu et al., 2017). ...
... Possible sources of uncertainty in fuel densification life cycle assessment-Predensification (Reproduced with permission fromMuazu et al., 2017). ...
The environmental impacts of different types of battery storage have been widely investigated by considering a part of their life cycle. These investigations assisted in augmenting the environmental performances of the battery storage in many ways. However, so far, little research is conducted on assessing the probable environmental effects of batteries considering their lifespan, from raw material extraction to end-of-life disposal. Therefore, this work considers the environmental profiles evaluation of lithium-ion (Li-ion), sodium chloride (NaCl), and nickel-metal hydride (NiMH) battery storage, considering the whole lifetime. The impacts of these batteries are estimated using Impact 2002+, EcoPoints 97, and cumulative energy demand methods. The environmental effects are evaluated under many indicators like carcinogens, noncarcinogens, respiratory inorganics, ionizing radiation, ozone layer depletion, aquatic ecotoxicity, land occupation, mineral extraction, nonrenewable energy, terrestrial ecotoxicity, respiratory organics, and global warming. The impacts are also assessed for the end-point categories of human health, ecosystem quality, climate change, and resources. Moreover, the overall metal emissions such as mercury, zinc, cadmium, lead, copper, and greenhouse gas emissions such as carbon dioxide, nitrogen oxide, sulfur oxide, and ammonia are also estimated by the authors for Li-ion, NaCl, and NiMH battery storage. All the findings are compared to realize, which options are superior concerning the environment. The results reveal a significant environmental impact caused by NiMH batteries compared to Li-ion batteries. These impacts are the amount of toxic chemical elements present as a constituent of NiMH batteries. It can be anticipated that a better environmental performance can be achieved through optimization, especially by cautiously picking the constituents, taking into account the toxicity aspects, and minimizing the impacts related to these chemicals.
... This study only considered European regions and North America providing a descriptive analysis (qualitative synthesis) and a meta-analysis (quantitative analysis) of global warming potential as the environmental impact category [9]. Another literature review on the current situation of LCA of densified biomass (briquettes and pellets) was carried out by Muazu et al. [25] and considered 19 studies with 48 different scenarios in which they described and compared systems using a "gate to gate" approach. They included a qualitative and quantitative analysis of LCA reviewed studies of biomass densification and concluded that there is a need for more transparent reporting and analysis of uncertainty in the modeling to better understand the wide variation in the results. ...
... For instance, a FU combined with an impact indicator such as gCO 2eq /MJ [64]. It was found that "FU of output" was the most employed, which is consistent with what has been reported in previous reviews [9,22,25]. MJ and KWh were the most representative energy FUs (Ener) used for both thermal (th) and electrical (elec) applications. Mass was the second most utilized category with ton as the most frequent functional unit. ...
... This situation was frequently detected among the studies reviewed and hindered comparison of results. Inconsistencies have been reported before by many authors [9,24,25]. ...
Life cycle assessments conducted in the last decade on forest-derived solid biofuels contain key insights to assess the environmental impact of such fuels under different contexts. This paper reports on the results of a systematic review of 87 studies that applied life cycles assessment on five types of solid biofuels: firewood, charcoal, wood chips, briquettes, and pellets. By considering the particularities of the countries in which the studies were conducted, biomass sources, end-uses and life cycle methodological choices, and key insights were derived about the global distribution of studies and what existing works can contribute to general understanding of the sustainability of wood-based fuels. First, most life cycles assessment focus on modern solid biofuels in developed countries, only 13% were on traditional solid biofuels such as firewood and charcoal in developing countries. Secondly, there are remarkable inconsistencies across studies in how they report and define their system boundaries. Thirdly, global warming potential is the most widely applied impact category. A meta-analysis of a subset of the studies (N = 26) revealed that, in general, forest-derived solid biofuels have lower global warming potential than fossil-based alternatives. Given the global imbalance of life cycle assessment efforts on forest-derived solid biofuels, there is need to mobilize capacities in order to increase applications in developing nations. However, persistent low uptake of standardized application and reporting in life cycle assessment studies perpetuates oft-mentioned limitations for cross-study comparisons. An approach to standardize system boundaries is proposed to partially address these limitations.
... The additional energy and cost have raised concerns over the sustainability and importance of biomass briquetting. Previous literature review of assessments of the life cycle environmental impacts of biomass briquetting [4] found significant variations in the outcomes. More recent studies also showed similar variations in the LCA outcomes of biomass briquetting [5][6][7]. ...
... Figure 5 shows a screenshot of the user input tab. Other authors [e.g., 4,6] have used a similar approach in LCA modelling. An "input model" tab is provided to also serve as an interface between the user input and main calculations. ...
... 7.3E−3 kg SO 2 -eq for AP, 1.3E−1 to 1.5E−1 kg 1,4-DBeq for HT, 2.6E−8 to 2.8E−8 kg CFC-11-eq for ODP, and 2.8E−5 to 3.1E−5 kg 1,4-DB-eq for ET. LCA results are widely different [4], and the values obtained in this study fall within a realistic range of values 0.007 kg CO 2 -eq for GWP and 0.01 kg 1, 4-DB-eq for HT obtained by some authors [41], but much lower than those obtained by other authors [e.g., 30] 0.08 kg CO 2 eq. Table 2 show the results of sensitivity analysis carried out for briquetting with blends of rice husks and corn cobs. ...
Purpose
Previous Life Cycle Assessment (LCA) studies of biomass briquetting have shown wide variations in the LCA outcomes as a result of variations in LCA methodological parameters and briquetting technological parameters. An LCA model of biomass briquetting was therefore developed to enable transparent comparison of life cycle environmental impacts of briquetting with individual or blends of biomass feeds with a variety of technological options.
Methods
The model was developed according to the standard LCA procedure of ISO14044. A comparative approach was utilised, and a set of integrated excel worksheets that describe process flows of material, energy and emissions across different units of the briquetting process was used in developing the model components.
Results
The main model components include materials and process inventory databases derived from standard sources, main process calculations, user inputs and results sections. The model is open-access in a user accessible format (Microsoft Excel). A representative case study with mixed rice husks and corn cobs was used in validating the model. Results showed that the briquetting unit made the largest contribution, 42%, to the total life cycle operational energy of the briquetting system. For all the blends of rice husks and corn cobs explored in this study, the total life cycle energy of briquetting was in the range 0.2 to 0.3 MJ/MJ. For the same blend ratios, a total life cycle energy of briquetting in the range 0.2 to 1.7 MJ/MJ was also obtained with change in other LCA input parameters, in a sensitivity test. An increase in rice husk content of the blend increased the environmental impact of briquetting in terms of global warming potential (kg CO2-eq), acidification potential (kg SO2-eq), human toxicity (kg 1,4-DB-eq), ozone layer depletion (kg CFC-11-eq), and terrestrial ecotoxicity (kg 1,4-DB-eq) per MJ briquette energy content, as it was associated with a lower briquette density, which increased the energy required for handling.
Graphic Abstract
... Several LCA studies of wood pellet production have indicated that the environmental impacts of wood pellet production are related to energy use from electricity and fossil fuels [20,21]. In a review of 19 sources with 48 case scenarios, Muazu et al. (2017) emphasized that fuel use during transport was a large contributor to the environmental burdens of the wood pellet production [22]. The LCA studies, which included cultivation of wood, showed that chemical fertilizers and pesticides contributed significantly to the environmental impacts [23,24]. ...
... Several LCA studies of wood pellet production have indicated that the environmental impacts of wood pellet production are related to energy use from electricity and fossil fuels [20,21]. In a review of 19 sources with 48 case scenarios, Muazu et al. (2017) emphasized that fuel use during transport was a large contributor to the environmental burdens of the wood pellet production [22]. The LCA studies, which included cultivation of wood, showed that chemical fertilizers and pesticides contributed significantly to the environmental impacts [23,24]. ...
... Stratospheric ozone depletion, marine eutrophication, and mineral resource scarcity are associated with use of chemical fertilizers (N, K2O, and P2O5). This result is in accordance with the other LCA studies which also show that chemical fertilizers and pesticides contributed substantially to the life cycle environmental impacts [22,23]. ...
Thailand has increased wood pellet production for export and domestic use. The variations in production processes, raw materials, and transportation related to wood pellet production make it necessary to evaluate the environmental impacts assessment. The objective of this study was to compare via Life Cycle Assessment (LCA), eight different cases of wood pellet production varying in terms of raw materials, production processes, energy use, and the format of transportation and to compare LCA of electricity production from wood pellets and fossil fuels. The comparison results show that leucaena is better as a feedstock for wood pellet production than acacia due to shorter harvest cycle and lesser use of resources. Pellet production consumes the most energy contributing significantly to the environmental impacts. The use of fossil fuels in wood pellet production and transportation also has a major contribution to the environmental impacts. Using wood pellets for electricity production is better than lignite in terms of human health, ecosystem quality and resource scarcity. Recommendations from this study include increasing yield of feedstock plants, shortening harvest cycle, reducing overuse of fertilizers and herbicides, pollution control, reducing fossil fuel use in the supply chain, good logistics, feedstock access, and offering incentives considering the externality cost.
... Sustainability assessments are required to guide stakeholders as to the best methods to adopt in tackling the current challenges related to the biomass densification process. Several research studies have been carried out to evaluate the sustainability of biomass densification using the life cycle assessment (LCA) and other sustainability assessment tools [13][14][15][16]. Often missing in most of the research on the LCA of biomass densification is an understanding of the relevance of process variables to the environmental effects of the life cycle. ...
... kg CO 2 -eq per MJ of output energy (heat and electricity) in this study and 0.05 kg CO 2 -eq per MJ of output energy (heat and electricity) in [46], is due to the different unit operations or system boundaries considered in the densified biomass fuel production system. Other methodological choices may also be responsible for the small difference, which is not uncommon among LCA studies [16]. ...
This work presents new data on the life cycle impact assessment of various lignocellulosic biomass types in Mexico. A comparative life cycle assessment model of biomass densification systems was conducted. An integrated approach that incorporated various process variables, such as technology and variations in feed properties, within the analysis was employed to evaluate the environmental impact of producing 1 MJ of energy-containing densified fuel. The results show that the densification unit and curing (fuel drying) have the highest impact on the life cycle’s operational energy and the total life cycle energy, respectively. Of all the 33 biomass types from the 17 species sources considered in this study, sweet sorghum and sandbur grass have the highest global warming potential, 0.26 and 0.24 (kg CO2-eq), and human toxicity 0.58 and 0.53 (kg 1,4-dichlorobenzene-eq), respectively, while coffee pulp and cooperi pine wood have the least impact in both categories, with values of 0.08 and 0.09 (kg CO2-eq), and 0.17 and 0.16 (kg 1,4-dichlorobenzene-eq), respectively. Chichicaxtla sawmill slabs also have a low environmental impact, and cooperi pine and Ceiba wood have the lowest ozone depletion and ecotoxicity potential. A sensitivity analysis indicated the effects of the transportation system and energy source on the life cycle’s environmental impact. Adequate feed preparation, the blending of multiple feeds in the optimum ratio, and the careful selection of densification technology could improve the environmental performance of densifying some of the low-bulk-density feed biomass types.
... The energy requirement for the densification of biomass primarily depends upon the pressure applied and the moisture content of the material to be compressed, as well as the physical properties of the material, including particle size and initial bulk density [8]. The sustainability of biomass densification depends on the energy consumption, emissions, and cost integrated with densification itself and the application of the densified biomass in the combustion or gasification process [6,27]. The machinery for biomass densification is experiencing greatly increasing interest as a result of the concern for its easier mechanical handling of biomass residues, lower storage, and transport space. ...
... One of the major limitations of using biomass as a feedstock is its low bulk density, which ranges from 80 to 100 kg/m 3 for agricultural straws and grasses and from 150 to 200 kg/m 3 for woody resources such as wood chips and sawdust [4] Inefficient transportation and large volume requirements for storage are some of the challenges associated with biomass energy usage [5]. Biomass densification for both bioenergy and animal feed utilization has been the approach to mitigate the cost of transportation, handling, and storage [6,7]. Additionally, densified biomass improves fuel feeding in co-firing operations and provides an increased regulation of combustion, thus reducing particulate emissions [8][9][10]. ...
Using the uniaxial compression process, the mechanical behaviour of densified briquettes from ground sunflower stalks and hazelnut husks was studied under different forces (100, 200, 300, and 400 kN), particle sizes (0, 3, 6, and 10 mm), and moisture contents (sunflower; 11.23%, 14.44%, and 16.89% w.b.) and (hazelnut; 12.64%, 14.83%, and 17.34% w.b.) at a constant speed of 5 mm min −1. For each test, the biomass material was compacted at a constant volume of 28.27 × 10 −5 m 3 using a 60 mm-diameter vessel. Determined parameters included densification energy (J), hardness (kN·mm −1), analytical densification energy (J), briquette volume (m 3), bulk density of materials (kg·m −3), briquette bulk density (kg·m −3), and briquette volume energy (J·m −3). The ANOVA multivariate tests of significance results showed that for ground sunflower stalk briquettes, the force and particle size interactions had no significant effect (p > 0.05) on the above-mentioned parameters compared to the categorical factors, which had a significant effect (p < 0.05) similar to the effects of forces, moisture contents, and their interactions. For ground hazelnut husk briquettes, all the factors and their interactions had a significant effect on the determined parameters. These biomass materials could be attractive for the briquette market.
... Certain LCA studies on biomass densification have been caried out. Muazu et al. (2017) reviewed data from 19 sources with 48 case scenarios to assess the current status of LCA of biomass densification. As a result of different decisions regarding system boundary, functional unit, allocation procedure, densification technology, and biomass residues, it was discovered that existing LCA studies of biomass densification did not provide enough and inconsistent information for full transparency and comparability. ...
Up to now, the people of Mantewe (South Kalimantan, Indonesia) have utilized ironwood waste by turning it into commercial charcoal. However, most charcoal production processes still use traditional combustion methods which have negative impacts on the environment and society, such as air pollution due to incomplete combustion. Therefore, this study aims to analyze the environmental impact of the charcoal production process using the Life Cycle Assessment (LCA) method and to design improvement strategies to reduce environmental impacts using the Analytical Network Process (ANP). This study selected a wood charcoal industry in South Kalimantan as the case study with a "gate-to-gate" scope. The CML2001 method with nine impact categories selected in the LCA. Furthermore, the ANP method is used to design environmental impact reduction strategies based on the LCA results. The result of the analysis shows that the main critical point in the wood charcoal industry is the burning of ironwood waste, while the second critical point is the use of heat energy from peat soil. Based on the weight, the environmental impact reduction strategies obtained from the ANP method are product diversification (0.4031), formulating the right materials (0.2765), replacing raw materials (0.26027), and using the furnace method (0.0618). This research is expected to be useful for the owners of the wood charcoal industry and can be a reference for how LCA and ANP can produce strategies for reducing environmental impacts in the wood charcoal industry.
... Another review concluded that biomass densification is a worthwhile addition to the biomass energy conversion system obtaining a net energy and greenhouse gas emissions savings of 200-1000 kJ MJ − 1 and 9-50 g CO 2 -eq. MJ − 1 (Muazu et al., 2017). Similarly, a research conducted in China suggested that climate change impacts of biomass briquettes, equal to 11 g CO 2 -eq. ...
Developing countries suffer from both lack of resources and appropriate solid waste management systems. Therefore, the introduction of alternative options for waste valorisation is imperative. The current research introduces an environmental Life Cycle Assessment (LCA) of waste-based briquettes produced with 80 % of non-recyclable cardboard waste from separate collections and 20 % sawdust from sawmills in Bolivia. The aim is to compare the environmental impacts generated within the briquette's life cycle with conventional fuels. Primary data from a development project implemented in La Paz in 2021 were collected for building the inventory. SimaPro9.0 was employed to conduct the analysis, with IMPACT2002+ as the impact assessment method. Re-sults' normalization, contribution evaluation, interval assessment, and sensitivity analysis were carried out, and the results were compared with conventional fossil fuels, namely: coal, methane, and LPG. Results suggest that briquettes' life cycle contributes to seven of fifteen impact indicators, with global warming, use of non-renewable energy, and respiratory inorganics, the most important. The global warming potential ranges from 23.9 to 26.7 gCO 2-eq. MJ − 1 , lower than about 485 % compared to coal and 185 % to methane. Considering the avoided impacts from wood and methane substitution, global warming potential can decrease to about 20.0 and 18.9 gCO 2-eq. MJ − 1 respectively. On balance, compared to other fuels for heating and cooking, waste-based briquettes always have better environmental performance transporting the briquettes to about 100-130 km from the production plant. These results suggest that waste-based briquettes can contribute to mitigating environmental impacts and carbon footprint at a global level.
... Densification of biomass is a promising method to enhance the biomass properties by applying mechanical force to compact the waste material into a uniform shape of pellet, briquettes, and logs. The main purpose of densification is to upsurge the bulk density of biomass to several magnitudes as uniformly sized fuel pellets or briquettes and to minimize the storage space and costs involved in transportation and handling [112]. Fuel pellets produced from torrefied and carbonized biomass are more attractive due to their higher heating value, high-energy content, and hydrophobic nature. ...
The utilization of lignocellulosic biomass is closely related to one of the renewable sources of energy. However, a few inherent properties of lignocellulosic biomass such as high moisture content, low density, high volume, and heterogeneous composition make it unfavorable for bulk transportation, storage, handling, and conversion. The pretreatment of biomass is found to resolve a few of the aforementioned limitations while increasing the conversion efficiency of lignocellulosic biomass into biofuels. This article reviews the opportunities, challenges, and state-of-art research on torrefaction as a widely used biomass upgrading technique for solid fuel production and thermochemical biomass conversion. Some notable applications of such pretreatments in high-value solid biofuel production, densification, combustion, co-firing, gasification, and metallurgy have been reviewed. The broad changes in physicochemical characteristics and structural chemistry of lignocellulosic biomass because of torrefaction have been thoroughly described. This review also comprehends the effects of different process parameters and operating conditions of torrefaction of lignocellulosic biomass to produce high-value solid fuel. This article attempts to highlight some recent advancements in biomass torrefaction technology concerning the fundamental characteristics of biomass and process operation and optimization as well as the evolution of physicochemical features of torrefied biomass. Lastly, the value-added industrial applications of torrefaction technology and torrefied biomass are also elucidated.
... A biorefinery has long been considered as a sustainable way to produce gaseous, liquid, or solid bio-fuels to partially replace fossil fuels [1]. Densification is one of the biorefinery techniques that aims to modify biomass by mechanical pressing, thus producing solid fuels with high volumetric density and volumetric heating values [2,3]. The densified lignocellulosic biomass can then be used as feedstocks for traditional coal burners for process heat generation [4,5]. ...
Thermoplastics, linear low-density polyethylene (LLDPE) and polypropylene (PP), were used as binders for the briquetting of sawdust. A novel hot-extrusion method (at 200 °C for 3 min) was developed to achieve the mixing of plastics and sawdust. The durability of briquettes containing 0–10% w/w plastic and produced under different pressures (150–300 kN) was investigated by laboratory and outdoor tests. Results from drop and tumble tests suggested that the use of plastics significantly enhances the strength of briquettes and the stability improves with the increase of plastic content. An outdoor weather test was conducted for two weeks with cumulative rainfall of > 50 mm to test the weather-resistance of briquettes. The briquettes prepared at 300 kN with 10% of PP showed superior durability to weather exposure with 100% survival rate to mechanical damage and an increase of moisture content at ~ 8% in post-exposure testing. The binding mechanisms and effect of plastics on briquettes are discussed. Moreover, the addition of plastics at 10% and densifying at 300 kN could produce solid fuels with heating values > 18 GJ/m³ which is comparable to coal and suitable to be used for co-firing existing coal-fired boilers. Collectively, results of this study recommend co-briquetting of waste plastics and lignocellulosic biomass to produce solid fuels with high durability, hydrophobicity, and moderate to high heating values; and as a solution to waste plastic management.
... The densification of wood has resulted in higher bio-oil yields [43]. Furthermore, it could be considered to be a valuable method that reduces the moisture content of biomass, and therefore improves the composition of the bio-oil [44]. The most common techniques for biomass densification include pelleting, briquetting, and the use of a screw extruder [45]. ...
Pyrolysis process has been considered to be an efficient approach for valorization of lignocellulosic biomass into bio-oil and value-added chemicals. Bio-oil refers to biomass pyrolysis liquid, which contains alkanes, aromatic compounds, phenol derivatives, and small amounts of ketone, ester, ether, amine, and alcohol. Lignocellulosic biomass is a renewable and sustainable energy resource for carbon that is readily available in the environment. This review article provides an outline of the pyrolysis process including pretreatment of biomass, pyrolysis mechanism, and process products upgrading. The pretreatment processes for biomass are reviewed including physical and chemical processes. In addition, the gaps in research and recommendations for improving the pretreatment processes are highlighted. Furthermore, the effect of feedstock characterization, operating parameters, and types of biomass on the performance of the pyrolysis process are explained. Recent progress in the identification of the mechanism of the pyrolysis process is addressed with some recommendations for future work. In addition, the article critically provides insight into process upgrading via several approaches specifically using catalytic upgrading. In spite of the current catalytic achievements of catalytic pyrolysis for providing high-quality bio-oil, the production yield has simultaneously dropped. This article explains the current drawbacks of catalytic approaches while suggesting alternative methodologies that could possibly improve the deoxygenation of bio-oil while maintaining high production yield.
... LCA methodology has been applied in many sectors, particularly in the forest sector, as a direct consequence of recognition of its importance as a decision-making support tool. Among areas where LCA has been applied are forestry and forest production (González-García et al., 2009;Karjalainen et al., 2001;Michelsen et al., 2008), buildings or building materials and component combinations (Yuan & Guo, 2017), wood and wood products (J Ferreira et al., 2016(J Ferreira et al., , 2018bHöglmeier et al., 2014;Mahalle et al., 2014;Silva et al., 2014;Suter et al., 2017), the timber industry (Eshun et al., 2010) and wood for energy production (J Ferreira et al., 2018a(J Ferreira et al., , 2014Muazu Rukayya et al., 2017;Pergola et al., 2018). LCA was applied to quantify the environmental profiles of maritime pine round wood production in Portugal and France by González-García et al. (2014), though this was undertaken using the ReCiPe impact assessment method. ...
Life Cycle Assessment has become one of the most recognized and
internationally accepted method for examining the environmental
performance of forest products and processes. The main aim of this
study was to evaluate the potential environmental impact associated
with different commercial outputs of maritime pine wood (round,
industrial, and residual) produced in the Portuguese forest under
natural regeneration. Identifying the hotspots in the life cycle (cradleto-gate) of each sort of maritime pine was another objective of the
study. SimaPro software was used for this study, whilst the CML-IA
(baseline) method was chosen to assess the environmental impacts.
The study showed that round wood presented the highest values in
all impact categories and industrial wood presented the lowest
values except in photochemical oxidation where residual wood was
the best co-product when economic allocation is chosen. The major
hot spots appeared to be the felling and hauling processes due to
fossil fuel combustion in the chainsaw and forwarder, respectively.
The co-product that should be more environmentally friendly considerably depends on the allocation procedure chosen.
... It is reflected in terms of CO 2 equivalent, which counts the emission of CO 2 , CH 4 , and N 2 O. Generally, pretreatment process and production process for bioenergy C, cost of the equipment; S, size/capacity of equipment; x, power-sizing component Lang Factor C plant = F lang ∑ C i C plant , capital cost of the plant; C i , purchased cost for the major equipment units; F lang , Lang Factor Learning curve T N = T initial • N b T N , time required for the Nth unit of production; T initial , time required for first unit of production; b, learning curve exponent products are the "hot spot" in terms of global warming potential. The moisture content and particle size distribution are key factors affecting the energy consumption in the pretreatment process [89]. During the production process, for example, pyrolysis for biofuel production has higher GWP impact than combustion or co-firing for biopower production [14•]. ...
Purpose of Review
Forest and biomass utilization is of great significance in the context of global change toward renewable energy and products. Supply chain management has been proven as an effective path to improve economic and environmental performance of forest and biomass products. However, the existing studies are fragmented and task-oriented. In this paper, we aim to systematically form a data-oriented modeling and analytics summary including the framework and toolbox for enhancement of forest and biomass supply chain management.
Recent Findings
With the coming of the big data era, data analytics methods and tools for forest and biomass supply chain management are progressively updated. Conventional analytical methods are facing challenges, though most of them are still currently dominant in practice. The big data era provides promising opportunities for data-driven methods and tools, based on which the data-oriented modeling framework is gradually emerging.
Summary
Generally, rapid development of computing capability and algorithms greatly facilitates the application and accuracy of the simulations and optimization, while built-in databases play an important role in the data analytics. Macro-enabled spreadsheet-based models and tools are still popularly used in practices due to their ease-of-use. Specifically, development of advanced techniques improves upon the efficiency and accuracy of conventional time-motion study approaches. A statistically appropriate experimental design and the underlying assumption verification are essential to obtaining reliable results. Traditionally, suitability modeling has been the trusted approach for optimal facility siting, but the emerging probability modeling is a promising data-driven approach in the context of the big data era. Linear programming modeling is still dominating in the supply chain optimization, while non-linear programming modeling is emerging due to the rapid development of algorithm and computational capacity. Techno-economic analysis (TEA) and life cycle assessment (LCA) provide important results regarding the economic and environmental efficiency of various forest and biomass supply chain systems. However, TEA and LCA results can vary due to modeling approach, data availability, and differences among underlying methods and databases. Monte Carlo simulation could be a fundamental approach to examining the uncertainty issues in both TEA and LCA.
... Hence, it is important to sensitize people regarding the advantages of biomass over conventional fossil fuels and develop a proper supply chain mechanism to encourage the usage. Furthermore, agricultural residue which has low energy density, high moisture content (more than 20%), and random particle size poses the problem of supply (high transportation and storage cost) and feed (bridging and channelling problem) in gasification process [38,39]. In this regard, biomass gasification needs the support from certain energy intensive processes such as drying, chopping and pelletization. ...
... Considering that renewable energy play the main role in seeking the reduction of GHG emission, a number of studies were devoted on analysing how bioenergy contributes to the GHG pollution. Most of authors analysing biomass impact on GHG emissions applied the life cycle assessment and almost all of them confirmed that bioenergy as alternative renewable source mitigates a climate change (Weldu, 2017;Thornley et al., 2015;Muench, 2015;Uusitalo et al., 2014;Muazu et al., 2017;Liu et al., 2017;Petersen et al., 2014;Zhang, 2016 and etc.). However the main question remains whether the development of bioenergy contributes to sustainable economic growth particularly in the case of GHG emissions. ...
Bioeconomy is an important element of European Union (EU) political agenda. Promotion of bioenergy is one of the main aspects of bioeconomy strategy. The aim of this paper is to show how the development of bioenergy can contribute to climate change (and the associated policy). Specifically, we look into the possible reduction of GHG emissions within the framework of Environmental Kuznets Curve (EKC). The panel models are estimated for the EU countries by modifying the classical EKC by including in the EKC model biomass and other renewables. The results showed that the coefficient associated with GDP decreases when renewables are included in the model. More specifically, the more types of renewables are included, the lower values of the coefficient associated with the linear term are observed. Furthermore, the effect of biomass on the reduction of GHG emission is higher if opposed to that caused by the other renewable resources. If we hold other factors fixed, increase in biomass use of 1% would reduce GHG emission by 0.089%, whereas the effect of the other renewable energy sources is 0.025%. Therefore, the development of bioeconomy and the promotion of bioenergy are one of the main tools for climate change mitigation.
... One of the bioenergy technologies promoted in the EU is wood pellet and wood chip heating using advanced and environmentally friendly installations [10]. Biomass heating systems already operating in Europe are evidence of the viability of the biomass fuel market. ...
Self-sustaining systems are considered by researchers, policy makers and investors to be one of the most interesting technologies in the world. The proportion of energy being derived from biological sources is increasing due to processes for converting wood biomass. In rural areas in Europe, bioenergy can effectively alleviate energy dependence on external energy resources for green energy development. An applied bioenergy study was conducted in Ezcaray, Spain, a forested village representative of rural areas in cold climate zones in southern Europe. The present study aims to evaluate and use existing forest resources and assess their thermal potentiality and replicability in remote areas via self-sustaining systems for distributed thermal production. Knowledge gaps and technology options for assessing and meeting sustainability criteria are analyzed. The implemented methodology considers a combination of mass, energy and costs from the source to the bioenergy heating system, and it assesses the techno-economic feasibility of such systems against boilers using different fuels. Two proposals were studied, namely, starting a pellet mill for the thermal system market and replacing existing boilers with biomass in self-sustaining systems. The first proposal is profitable, with a selling price equal to or higher than 146.04 €/t. In the second proposal, the non-renewable primary energy consumption in the studied households was between 13- and 15-times higher with fossil fuel boilers than with biomass boilers. In both cases, thermal systems in rural areas may effectively alleviate dependence on non-renewable energy to increase green energy use in Europe by 2020.
... But, according to Mikulandrić et al. (2016), the wide availability of agricultural biomass does not necessarily translate to availability of biomass for energy applications because intermediate processes are necessary in order to increase the bulk density. In principle, thermochemical processing of biofuels can have three main possible upsides; production of an energy dense fuel (Pahla et al., 2017), reduction of the transportation cost (Muazu et al., 2017) and carbon sequestration since according to Gupta et al. (2018) this is considered as an opportunity for carbon dioxide sequestration. ...
This work introduces the process of Frictional Torrefaction and comes as a continuation to the previous work done on Frictional Pyrolysis, which is a novel method of pyrolysis that does not utilize heat but only friction and pressure. Both processes (i.e. Frictional Torrefaction and Frictional Pyrolysis) take place in a Rotary Compression Unit without and with a reflux condenser respectively. Rotating augers are used for the development of friction and the simultaneous increase of pressure. The following types of analysis were performed: TGA, BET, CHNS and HHV. Both products have similar heating values, around 21 MJ/kg. The elemental compositions are comparable but lower hydrogen content (3.5%) was measured for Frictional Torrefaction. BET analysis showed differences on the surface areas and porous sizes of the materials. Frictional Torrefaction has higher fixed carbon (31.23% vs 28.31%), higher surface area (58.16 m2/g vs 36.88 m2/g) and higher absorbance (35 cm3/g vs 26 cm3/g).
... LCA methodology has been applied in many sectors, particularly in the forest sector, as a direct consequence of recognition of its importance as a decision-making support tool. Among areas where LCA has been applied are forestry and forest production (González-García et al., 2009;Karjalainen et al., 2001;Michelsen et al., 2008), buildings or building materials and component combinations (Yuan & Guo, 2017), wood and wood products (J Ferreira et al., 2016(J Ferreira et al., , 2018bHöglmeier et al., 2014;Mahalle et al., 2014;Silva et al., 2014;Suter et al., 2017), the timber industry (Eshun et al., 2010) and wood for energy production (J Ferreira et al., 2018a(J Ferreira et al., , 2014Muazu Rukayya et al., 2017;Pergola et al., 2018). LCA was applied to quantify the environmental profiles of maritime pine round wood production in Portugal and France by González-García et al. (2014), though this was undertaken using the ReCiPe impact assessment method. ...
Abstract
The aim of this work is to generate generic life cycle inventory data for Portuguese softwood as material and as fuel.
The ecoinvent database was used where the principal assumptions were changed to include the Portuguese situation. New economic allocation and correction factors to include mass, energy, and carbon dioxide uptake from nature were calculated forming the new inventory tables for round, industrial, and residual wood (Portuguese softwood). The Ecoindicator99 method was chosen to assess the environmental impact and to check the influence of the data adaptation on the life cycle impact assessment (LCIA) final results.
The study shows that differences exist between ecoinvent and Portuguese data for the softwood production in relation to tree species, yield of forest and time from planting trees to final harvesting, length and width of forest roads or total area and land use. The life cycle impact assessment results are completely different for all sorts of softwood: Portuguese round wood is better than ecoinvent round wood; and Portuguese industrial and residual wood are worse than ecoinvent industrial and residual wood.
Keywords: Portuguese softwood; wooden products; ecoinvent database; life cycle impact assessment (LCIA).
The typical forest and biomass supply chain is comprised of several discrete processes, including harvesting, transporting, storage, preprocessing, and manufacturing. Analysis of the entire supply chain system can be employed toward optimizing the supply chain as a whole and assessing and enhancing its economic and environmental performance. Mathematical programming is the foundation of forest and biomass supply chain optimization. Techno-Economic Analysis (TEA) is a popular methodological framework for analyzing the economic performance of forest and biomass supply chains with consideration given to technical issues, while Life Cycle Assessment (LCA) has been popularly used to assess the potential environmental impacts associated either with specific processes of the supply chain system or with the supply chain as a whole.
Due to its richness and carbon neutrality, biomass is emerging as a useful resource in the hunt for renewable energy sources. The process of pyrolysis is widely used to transform biomass into useful hydrocarbons or alternative energy sources. Lignocellulosic biomass is a renewable energy source that is high in carbon. This review article describes the pyrolysis process, which includes biomass pre-treatment, pyrolysis mechanism, and process product upgrading. The pre-treatments of bio material using chemical and physical methods are investigated. One of the ineffective methods for transforming lignocellulosic biomass—which contains components of hemicellulose, cellulose, and lignin—into solids, liquids, and gases is pyrolysis. The pyrolysis conversion mechanism includes the production of char, depolymerization, fragmentation, and several secondary reactions. Research gaps are also identified, along with suggestions for improving pre-treatment methods. It is also described how the performance of the pyrolysis process is affected by the properties of the feedstock, operating parameters, and biomass kinds. Using a few research concepts, rapid progress in pyrolysis instrument identification is discussed. This study starts with a review of the chemistry of contemporary lignocellulose pyrolysis and moves on to the production of various products like oil, gas, and char.
The agricultural sector and its related production chains are good sources of residual biomass. Olive and vineyard pruning residues are present in high quantities in Italy. The limited bulk and energy densities of these biomass materials affect the harvesting and logistic costs, limiting energy and environmental sustainability. Pelletisation is the most efficient process for increasing bulk and energy densities. This study evaluates the pelletisation process of olive and vineyard prunings, pure, or blended with variable quantities of spruce sawdust. A 15 kW pelletisation system was chosen, in line with production at the farm level. The most important quality parameters of the produced agripellets were analyzed. The results of this investigation suggest that blending could valorize other biomass materials less suitable for pelletisation and reach the pellet quality required by Italian technical standards. The addition of pruning residues to spruce sawdust leads to an improvement in durability. Spruce sawdust pellets have a durability value of 78.4%. Adding 20% of olive prunings (S80O20) increases this value to 92.2, while adding 20% vineyard prunings (S80V20) increases this value up to 90.3. The addition of 20% of pruning residues significantly increased the length and decreased fines
The world market for solid biofuels has increased in the last few years, with special attention to the production of pellets and briquettes in emerging bioeconomies. This study presents a systematic review and exploratory Life Cycle Assessment (LCA) of biomass briquettes and pellets produced in Latin America, and suggests short-term opportunities and political implications. The review was organized following the scoping methodology en bloc with the Standardized Technique for Assessing and Reporting Reviews of Life Cycle Assessment Data - STARR-LCA, in Scopus, Web of Science and Scielo databases. A final list of 150 publications was selected. The review results showed that most of the publications were from Brazil, Colombia, Chile, Mexico and Costa Rica, and are mainly focused on exploring the thermo-mechanics properties of pellets and briquettes instead of the environmental impacts. Thus, an exploratory LCA was performed based on the data gathered from literature with a focus on global warming potential, terrestrial acidification potential, freshwater eutrophication potential, cumulative energy demand, land use and water consumption. Global warming results ranged from −68.7 (Chilean pellets) to 103 g CO2-eq (Brazilian charcoal briquettes), and pellet productions showed lower values of impacts (−68.7 to 1.33 g CO2-eq) per functional unit. The best scenario, however, was found for the Brazilian briquettes production contributing with less than 10% of the overall relative impacts for cumulative energy demand (0.340 MJ-eq), terrestrial acidification potential (8.59 mg SO2-eq), freshwater eutrophication potential (0.969 mg PO4-eq), land use (136 cm²a crop-eq) and water consumption (108 cm³), where urban forest residues were used as biomass. The worst-case scenario was found for the charcoal briquettes in Brazil and pellet productions from palm fruit branches in Colombia. Dedicated systems to the pellets/briquettes production seem to be more environmentally benign options than the multifunctional systems investigated. In terms of political implications, it was verified the great potential from these different types of densified biomass in improving and expanding emission trading systems both inside and outside Latin America.
Briquetting is an effective way to ensure the comprehensive utilisation of straw. However, in the production of straw briquettes there can be problems of low productivity and high-power consumption caused by ring die wear. The working principle of briquetting machines and wear of the ring die wear studied to determine the relationship between different forming factors of straw briquette and ring die wear. The wear mechanism of the ring die was analysed by scanning electron microscope, and the pattern of wear on the inner wall of the ring die in the extrusion direction was studied. The friction and wear test of rice straw briquette was used to analyse the influence of different moulding factors on the friction coefficient. Results showed that the wear depth of the ring die module decreased slowly in the direction of extrusion. Deep scoring was found in the entrance section. Wear in the tail section was weak and mainly appeared in the form of spalling pits. The main wear mechanisms of the ring die were abrasion and fatigue. The main forming factors affecting friction coefficient were briquette density, moisture content and extrusion velocity. According to the comparison between the wear prediction model and the actual production, the maximum deviation between the calculated value and the simulated value was 12%, and the minimum deviation was 5%. The wear of circular ring die module was low, which could improve service life.
In light of legislative requirements and circular economy principles, valorization of wastes is the best strategy for its management. The biodegradable fraction of industrial wastes is a sustainable source of biomass, thereby optimizing its management by energy valorization, decreasing the quantity of waste that needs to be managed (and its economic costs), minimizing the environmental impact and health risks, and reducing the high dependence of industries on primary sources and fossil energy. Although traditional biomass sources, such as wood, crops, agricultural and forestry residues, and food and municipal wastes, are renewable, sustainable and cost-efficient, they compete with food and their energy processes release waste into the environment. Waste to Energy (WtE) is a recent, efficient and sustainable method of waste management based on the idea that energy sustainability involves both sustainable energy sources and sustainable energy systems. This paper reviews studies that propose industrial waste and by-products as sustainable, renewable and unlimited sources of biomass for use in sustainable energy systems to generate electricity, heat and cold, bioliquids and biofuels. The advantages and disadvantages of various types of resources are presented, and their limitations and the challenges that must be overcome are analyzed and compared.
Although declining in Europe and Canada, cofiring biomass with coal is a subject of growing interest in Asia so work continues on developing the technology. This review facilitates the technology transfer ‘from West to East’. Biomass characteristics and the options for cofiring are described, of which direct cofiring is the most widely used method. Biomass pretreatment methods include washing and leaching, torrefaction, steam explosion, densification and pelletisation. Generally, pretreatment methods are combined such as the pelletisation of torrefied material. Agricultural residues are of interest for cofiring in Asia, partly to improve local air quality. However, compared to woody biomass, they have a higher concentration of chlorine, phosphorus, and alkali and alkaline earth elements, which result in slagging and fouling. The report discusses the latest developments in combustion related issues such as cofiring in CFB boilers, cogasification cofiring, oxyfuel cofiring and cofiring ratios. Oxyfuel cofiring of biomass, if combined with carbon capture and storage has the potential to result in negative emissions of CO2. Attention should be paid to biomass handling, storage and fire protection as it has a lower ignition temperature and is more explosive than coal. Computational fluid dynamics (CFD) is a powerful tool in the development of coal and biomass cofiring technologies for increased understanding, exploration of unfamiliar conditions, design, troubleshooting, and optimisation of combustion processes.
The impacts on emission controls and ash utilisation from cofiring are analysed. Cofiring biomass can help meet various Sustainable Development Goals including Goal 7 affordable and clean energy, Goal 9 industry innovation and infrastructure, Goal 12 ensure sustainable consumption and production, and Goal 13 climate action. However, government support, and favourable regulatory and environmental policies are still required for the widespread deployment of cofiring.
Strew pellet production not only contribute to regional sustainable development and localized energy transition, but also help to mitigate global greenhouse gas emissions. With the development strew pellet products in China, it is critical to uncover the embodied emissions, land use and economic cost effectiveness from producing strew pellet. In order to reach such a target, two main categories of biomass pellet production including a large-scale centralized factory and a small-scale distributed workshop are investigated. Compared with raw coal production, the unit co-benefits in terms of per gigajoule of straw pellets from centralized factory are 1687 kg CO2, 8.65 g SO2, 3.21g NOx, and 3.897 g PM10, and 0.33 m² land use, and those for straw pellets from centralized factory are 1352 kg CO2, 8.46 g SO2, 3.12 g NOx, and 4.22 g PM10, and 0.33 m² land use. Cost-effectiveness for the two straw pellets production system were also uncovered so that the relevant interested agents such as decision makers, business investors or environmental researchers can see the potential economic performance from developing such kind biomass plants. We conclude that environmental performance of the straw pellets whether from centralized factor or decentralized workshop have attractive alternatives to coal production.
Este livro reúne algumas tendências teórico-acadêmicas e descobertas no campo da Engenharia de Processos em Sistemas de Energia no contexto brasileiro e internacional, em nível de graduação e pós-graduação stricto sensu. Como exemplo de tendências, cito a visão sistêmica de processos e uso da técnica da árvore de estados para um estudo prospectivo de otimização de processos. O livro é dividido em duas partes sendo que a primeira parte aborda uma visão histórico-tecnológica a produção de petróleo, gás e energias renováveis, discutindo a síntese de gás natural, teste de água de processo de floculação, produção de bio-óleo por pirólise, estudos de aproveitamento energético pela queima de casca de café e de cacau. A segunda parte revela aspectos teóricos da qualificação e estimativa da eficiência energética de processos, abordando a pirólise de resíduos de embalagens de cartonagem, a combustão de licor negro em caldeiras de recuperação química, processo de secagem de solução, síntese de estrutura de processamento, um estudo sobre a secagem de amêndoas de cacau e sobre a filtração de ar usando sistemas particulados. Portanto, este livro será adequado para estudos sobre a engenharia de processos realizados na graduação e na pós-graduação stricto sensu.
The aim of this research was to optimize technological applications of biomass waste to obtain energy using both the heuristic and the evolutionary methods. Six steps for the generation of energy were studied with the option of energy integration in the drying and chemical reaction sub-systems. The waste used was the husks of Robusta coffee beans resulting from two distinct treatments, the wet and dry ones. The structural synthesis characterized by branch-and-bound trees resulted in 3780 plausible flowsheets to be analyzed for the four waste-to-energy technologies approached. Experimental studies allowed identification of fundamental characteristics to define the embryonic flowsheet to the process. The heuristic rules made it possible to point out pyrolysis as a promising technology regarding the energy conversion of coffee husks. The finding primary flowsheet, nº89, become an economic alternative for generation of electric power from coffee husks. Moreover, impacts of neighbor flowsheets on energy conversion were also analyzed and discussed.
Developing renewable energy sources with low environmental impacts is becoming increas- ingly important as concerns about consuming fossil fuel sources grow. Cultivating, harvesting, drying, and densifying raw biomass feedstocks into pellets for easy handling and transport is one step forward in this endeavor. However, the corresponding environmental performances must be quantified. This study presents cradle-to-gate life cycle inventory and impact assessment data for switchgrass fuel pellets potentially manufactured in the US Southeast. Because there are no current manufacturers of switchgrass pellets, inventory data were based on field trials of cultivation and harvest of switchgrass combined with a separate study of wood pelletization. Energy inputs for cultivation and harvest of switchgrass were collected by survey from farmers in Tennessee and represent the years 2008, 2009, and 2010. Data for pelletization were taken from a report on wood pellet manufacturing in the US Southeast. To produce 1.0 Mg of pellets
To meet Energy Independence and Security Act (EISA) cellulosic biofuel mandates, the United States will require an annual domestic supply of about 242 million Mg of biomass by 2022. To improve the feedstock logistics of lignocellulosic biofuels in order to access available biomass resources from areas with varying yields, commodity systems have been proposed and designed to deliver quality-controlled biomass feedstocks at preprocessing “depots”. Preprocessing depots densify and stabilize the biomass prior to long-distance transport and delivery to centralized biorefineries. The logistics of biomass commodity supply chains could introduce spatially variable environmental impacts into the biofuel life cycle due to needing to harvest, move, and preprocess biomass from multiple distances that have variable spatial density. This study examines the uncertainty in greenhouse gas (GHG) emissions of corn stover logistics within a bio-ethanol supply chain in the state of Kansas, where sustainable biomass supply varies spatially. Two scenarios were evaluated each having a different number of depots of varying capacity and location within Kansas relative to a central commodity-receiving biorefinery to test GHG emissions uncertainty. The first scenario sited four preprocessing depots evenly across the state of Kansas but within the vicinity of counties having high biomass supply density. The second scenario located five depots based on the shortest depot-to-biorefinery rail distance and biomass availability. The logistics supply chain consists of corn stover harvest, collection and storage, feedstock transport from field to biomass preprocessing depot, preprocessing depot operations, and commodity transport from the biomass preprocessing depot to the biorefinery. Monte Carlo simulation was used to estimate the spatial uncertainty in the feedstock logistics gate-to-gate sequence. Within the logistics supply chain GHG emissions are most sensitive to the transport of the densified biomass, which introduces the highest variability (0.2–13 g CO2e/MJ) to life cycle GHG emissions. Moreover, depending upon the biomass availability and its spatial density and surrounding transportation infrastructure (road and rail), logistics can increase the variability in life cycle environmental impacts for lignocellulosic biofuels. Within Kansas, life cycle GHG emissions could range from 24 g CO2e/MJ to 41 g CO2e/MJ depending upon the location, size and number of preprocessing depots constructed. However, this range can be minimized through optimizing the siting of preprocessing depots where ample rail infrastructure exists to supply biomass commodity to a regional biorefinery supply system.
Rising demand for energy is one of the major challenges facing the world today and charcoal is a principal fuel in Kenya. Faced with energy poverty many poor households turn to briquette making. This study assessed the additional cooking fuel obtained from recycling charcoal dust into charcoal briquettes. It applied Life Cycle Assessment (LCA) to assess the global warming potential (GWP) from use of charcoal and production of briquettes from charcoal dust and cooking a traditional meal for a standard household of five people. Native vegetation of Acacia drepanolobium and a low efficiency kiln were considered the common practice, while an Acacia mearnsii plantation and a high efficiency kiln was used as an alternative scenario. Charcoal and kerosene were considered as reference fuels. Recovering charcoal dust for charcoal briquettes supplied an additional 16% cooking fuel. Wood carbonization and cooking caused the highest GWP, so there is a need for technologies to improve the efficiency at these two stages of charcoal briquettes and charcoal supply chain. Supplying energy and cooking a traditional meal in a combined system using charcoal and recovering charcoal dust for charcoal briquettes and charcoal alone accounted for 5.3–4.12 and 6.4–4.94 kg CO2 eq. per meal, respectively, assuming trees were not replanted. These amounts declined three times when the carbon dioxide from the carbonization and cooking stages was assumed to be taken up by growing biomass. This requires replanting of trees cut down for charcoal if the neutral impact of biomass energy on GWP is to be maintained.
In this article, we present cradle-to-gate life-cycle inventory (LCI) data for wood fuel pellets manufactured in the Southeast United States. We surveyed commercial pellet manufacturers in 2010, collecting annual production data for 2009. Weighted-average inputs to, and emissions from, the pelletization process were determined. The pellet making unit process was combined with existing LCI data from hardwood flooring residues production, and a life-cycle impact assessment was conducted using the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) model. The potential bioenergy and embodied nonrenewable energy in 907 kg (1 ton, the functional unit of this study) of wood fuel pellets was also calculated. The pelletization of wood requires significant amounts of electrical energy (145 kWh/Mg), but the net bioenergy balance is positive. Wood pellets require 5.8 GJ of fossil energy to produce 17.3 GJ of bioenergy (a net balance of 10.4 GJ/Mg). However, if environmental burdens are allocated to the pellet raw material (flooring residues) by value, then the embodied fossil energy is reduced to 2.3 GJ. The pelletization unit process data collected here could be used in an assessment of the environmental impacts of pellet fuel, or when pellets are a pretreatment step in wood-based biorefinery processes.
The present paper reports on experiments of fluidized bed combustion of dry and wet olive husks. The olive husks are a biogenic residue of the olive oil industry, accounting for around 80 % of olive mass on wet basis. They have residual water content up to 70 % and rather high heating value (i.e. 22.3 MJ/kg on dry basis). Huge production of olive husks occurs seasonally in the Mediterranean area, posing problems for proper disposal and valorisation because of the difficulty to store this material for long times. The research demonstrated that the olive husks can be smoothly and effectively burnt in fluidized bed with high combustion efficiency and very low emissions of pollutants and solid particulate in a bed temperature range between 800 and 850 °C. The energy balance on the combustor shows that a fraction of 10-15 % of the heat input can be directly extracted from the fluidized bed, the remaining being available in the hot flue gases. The focus was also on the emissions of nitrogen oxide. The research can have practical application for small scale and local installation, e.g. at olive oil factory, as demonstrated by the experimental campaign at pilot scale.
An engineering economic analysis of a biomass pelleting process was performed for conditions in North America. The pelletization of biomass consists of a series of unit operations: drying, size reduction, densifying, cooling, screening, and warehousing. Capital and operating cost of the pelleting plant was estimated at several plant capacities. Pellet production cost for a base case plant capacity of 6 t/h was about $51/t of pellets. Raw material cost was the largest cost element of the total pellet production cost followed by personnel cost, drying cost, and pelleting mill cost. An increase in raw material cost substantially increased the pellet production cost. Pellet plants with a capacity of more than 10 t/h decreased the costs to roughly $40/t of pellets. Five different burner fuels - wet sawdust, dry sawdust, biomass pellets, natural gas, and coal were tested for their effect on the cost of pellet production. Wet sawdust and coal, the cheapest burner fuels, produced the lowest pellet production cost. The environmental impacts due to the potential emissions of these fuels during the combustion process require further investigation.
Purpose
Densification, a process used to manufacture pellets in order to increase biomass bulk density, plays a crucial role in the economics of biomass utilization. The Canadian Prairies produce large quantities of agricultural residues each year, in particular wheat straw. This study performs life cycle assessment of wheat straw pellets by evaluating environmental effects of the entire pellet production system comprising feedstock production (on-farm wheat straw production), harvesting, baling, transportation, and the industrial processing involving drying, grinding, pelletizing, and packing in the densification plant. The effects of each process on the environmental performance of wheat straw pellets were investigated.
Methods
This study was conducted using LCA software and incorporating the Ecoinvent database supplemented with literature data for the Canadian Prairies. Wheat straw pellets manufactured from the densification plant are evaluated with respect to their use of resources and energy consumption. Environmental emissions associated with the agricultural processing and manufacturing systems are quantified. Sensitivity analysis is conducted to compare allocation methods and investigate the environmental impact of pelletizing and drying processes. The functional unit is defined as 1 kg wheat straw pellet.
Results and discussion
The study quantified the environmental impact of producing wheat straw pellets in terms of global warming potential, acidification, eutrophication, ozone layer depletion, abiotic depletion, human toxicity, photochemical oxidation, fresh water aquatic ecotoxicity, and terrestrial ecotoxicity. Drying, pelletizing, and fertilizer are the main contributors to global warming, acidification, abiotic depletion, human toxicity, terrestrial ecotoxicity, photochemical oxidation, and most of the other environmental impacts. Wheat seed has more impact on eutrophication. Transportation has an impact on ozone layer depletion, while grinding has an effect on freshwater aquatic ecotoxicity.
Conclusions
The environmental impact of materials and energy fluxes on producing wheat straw pellet in the Canadian Prairies is assessed. The effect of each processing step on the entire manufacturing process is described. Overall, drying and pelletizing processes contribute the most environmental burdens except eutrophication and terrestrial ecotoxicity which are dominated by agricultural fertilizer/seed utilization and harvesting. In order to mitigate the environmental impact of wheat straw pellet production, minimizing energy consumption and machinery burdens from the drying and pelletizing processes are the main intervention points for wheat straw densification. Fertilizer production and utilization are key variables in strategies to lower eutrophication and terrestrial ecotoxicity.
Developing uniformly formatted, densified feedstock from lignocellulosic biomass is of interest to achieve consistent physical properties such as size and shape, bulk and unit density, and durability, which significantly influence storage, transportation and handling characteristics, and, by extension, feedstock cost and quality. A variety of densification systems are considered for producing a uniform format feedstock commodity for bioenergy applications, including (i) pellet mill, (ii) cuber, (iii) screw extruder, (iv) briquette press, (v) roller press, (vi) tablet press, and (vii) agglomerator. Each of these systems has varying impacts on feedstock chemical and physical properties, and energy consumption. This review discusses the suitability of these densification systems for biomass feedstocks and the impact these systems have on specific energy consumption and end-product quality. For example, a briquette press is more flexible in terms of feedstock variables where higher moisture content and larger particles are acceptable for making good quality briquettes; or among different densification systems, a screw press consumes the most energy because it not only compresses but also shears and mixes the material. Pre-treatment options like pre-heating, grinding, steam explosion, torrefaction, and ammonia fiber explosion (AFEX) can also help to reduce specific energy consumption during densification and improve binding characteristics. Binding behavior can also be improved by adding natural binders, such as proteins, or commercial binders, such as lignosulfonates. The quality of the densified biomass for both domestic and international markets is evaluated using PFI (United States standard) or CEN (European standard). Published in 2011 by John Wiley & Sons, Ltd
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This paper contributes to the discussion of how different kinds of industrial scale dryers for biomass influence the quality properties of wood pellets. It also discusses how the drying technique can affect the environment. The most common biomass drying processes in use, i.e., convection dryers are discussed. The discussion of drying techniques is based on advantages and disadvantages with a focus on the drying medium, temperature and residence time. The choice of drying technique is particularly important if the end-user’s choice of pellets is made due to the specific requirements for the heating system used. Some specific parameters were tested in order to investigate how the choice of drying technique affects the pellet quality. The parameters tested were moisture content and the emissions of volatile hydrocarbons. Pellets available on the market were chosen for the tests. The amount of volatile hydrocarbons left in sawdust after drying vary with drying technique, as emissions of terpenes are larger in dryers with long residence times. Low emissions of volatile hydrocarbons would improve the energy content of the sawdust, and by decreasing air pollution improve the work environment and the environment in the surroundings of the dryers.
The exploitation of biomass for energy production purposes can significantly reduce the environmental burdens associated with the highly criticized fossil fuelled energy production. Life cycle assessment (LCA) methodology has proven to be one of the most effective tools for carrying out environmental impact analysis of any process or system. The interpretation of the findings of LCA can be used as a basis for recommendations and decision making in accordance to the goal and scope definition. The aim of this paper is to conduct a comprehensive LCA for the environmental evaluation of the biomass pelleting process with the focus being on the transportation and manufacturing stages. To achieve this aim, four scenarios are presented, investigating the pelleting process of olive husk, an abundant waste biomass found in Cyprus. Two alternative scenarios are developed in an effort to compare the centralised and the decentralised management of olive husk. Regarding those two scenarios, a novel mathematical parametric model was developed and Non-Linear Programming was applied for the computation of the optimal locations for a set of management facilities which achieve the lowest energy needs for transportation purposes. Additionally, a third and fourth scenario aimed to the comparison of the potential improvement of the environmental footprint of the olive husk pellets with regard to their reference cases (Scenario 1 and 2 respectively), when Renewable Energy Sources (RES) are incorporated in the pelleting process system. The authors concluded that the selection of location for the biomass management centres, as well as the employment of renewable energy technologies (RET) for energy generation can significantly affect the environmental impact of biomass utilisation. The environmental impact of olive husk pellet production was improved by more than 85% in selected impact categories when RES were incorporated in the manufacturing stage. The comparison of centralised and decentralised scenarios for olive husk management has indicated the latter to be the most environment-friendly solution.
As yet, the application of an uncertainty and variability analysis is not common practice in LCAs. A proper analysis will
be facilitated when it is clear which types of uncertainties and variabilities exist in LCAs and which tools are available
to deal with them. Therefore, a framework is developed to classify types of uncertainty and variability in LCAs. Uncertainty
is divided in (1) parameter uncertainty, (2) model uncertainty, and (3) uncertainty due to choices, while variability covers
(4) spatial variability, (5) temporal variability, and (6) variability between objects and sources. A tool to deal with parameter
uncertainty and variability between objects and sources in both the inventory and the impact assessment is probabilistic simulation.
Uncertainty due to choices can be dealt with in a scenario analysis or reduced by standardisation and peer review. The feasibility
of dealing with temporal and spatial variability is limited, implying model uncertainty in LCAs. Other model uncertainties
can be reduced partly by more sophisticated modelling, such as the use of non-linear inventory models in the inventory and
multi media models in the characterisation phase.
Developing renewable energy sources with low environmental impacts is becoming increasingly important as concerns about consuming fossil fuel sources grow. Cultivating, harvesting, drying, and densifying raw biomass feedstocks into pellets for easy handling and transport is one step forward in this endeavor. However, the corresponding environmental performances must be quantified. This study presents cradle-to-gate life cycle inventory and impact assessment data for switchgrass fuel pellets potentially manufactured in the US Southeast. Because there are no current manufacturers of switchgrass pellets, inventory data were based on field trials of cultivation and harvest of switchgrass combined with a separate study of wood pelletization. Energy inputs for cultivation and harvest of switchgrass were collected by survey from farmers in Tennessee and represent the years 2008, 2009, and 2010. Data for pelletization were taken from a report on wood pellet manufacturing in the US Southeast. To produce 1.0 Mg of pellets
On a global scale, bioenergy is highly relevant to renewable energy options. Unlike fossil fuels, bioenergy can be carbon neutral and plays an important role in the reduction of greenhouse gas emissions. Biomass electricity and heat contribute 90% of total final biomass energy consumption, and many reviews of biofuel Life Cycle Assessments (LCAs) have been published. However, only a small number of these reviews are concerned with electricity and heat generation from biomass, and these reviews focus on only a few impact categories. No review of biomass electricity and heat LCAs included a detailed quantitative assessment. The failure to consider heat generation, the insufficient consideration of impact categories, and the missing quantitative overview in bioenergy LCA reviews constitute research gaps. The primary goal of the present review was to give an overview of the environmental impact of biomass electricity and heat. A systematic review was chosen as the research method to achieve a comprehensive and minimally biased overview of biomass electricity and heat LCAs. We conducted a quantitative analysis of the environmental impact of biomass electricity and heat. There is a significant variability in results of biomass electricity and heat LCAs. Assumptions regarding the bioenergy system and methodological choices are likely reasons for extreme values. The secondary goal of this review is to discuss influencing methodological choices. No general consensus has been reached regarding the optimal functional unit, the ideal allocation of environmental impact between co-products, the definition of the system boundary, or how to model the carbon cycle of biomass. We concluded that a higher level of transparency and a harmonisation of the preparation of biomass electricity and heat LCAs are needed to improve the comparability of such evaluations.
The efficient utilization of the enormous crop-residue resources in China is crucial for providing biofuel, reducing the risk of environmental pollution, and increasing farmers income. Examining the case of a crop-residue densification plant in the city of Jinzhou, China, this study examines the economic feasibility of this plant by analyzing raw material supply, product market, energy policy, and financial reports. The results indicate that these factors, such as the raw material supply, market, and energy policy, favor the development of densified biofuel from crop residues. The typical financial indicators were estimated as being notably positive over a 10-year timeframe, and a sensitivity analysis indicated no threats to project profit stability. These aforementioned analyses suggest that the utilization of crop residues as densified biofuel in China possesses good economic viability. If the numerous historical, industrial, geographical, and energy-related similarities are taken into account, this study can also be used to provide a feasibility evaluation methodology for crop-residue densification plants in other similar regions.
Biomass densification processes increase fuel energy density for more efficient transport. This study presents new data to show that blending different types of biomass improves the properties of densified biomass briquettes. The specific objectives were to investigate the effects of sample batch (biomass source), material ratio (rice husks to corn cobs), addition of binder (starch and water mixture) and compaction pressure, on briquette properties, using a factorial experiment.
Briquettes had a unit density of up to 1.9 times the loose biomass bulk density, and were stronger than briquettes from the individual materials. Considering average values from two biomass sources, an unconfined compressive strength of 176 kPa was achieved at a compaction pressure of 31 MPa for a 3:7 blend of rice husks to corn cobs with 10% binder. These briquettes were durable, with only 4% mass loss during abrasion and 10% mass loss during shattering tests. They absorbed 36% less water than loose corn cobs. Statistical analysis of the results showed that starch and water addition was required for adequate briquette strength, but significantly reduced green and relaxed densities. The source of the biomass had a significant effect on densification, which emphasises the need to understand factors underlying biomass variability.
Torrefaction is a thermal pre-treatment process for upgrading raw biomass into a more energy dense fuel. Torrefied biomass is combined with a densification process to increase its bulk density similar to conventional wood-pelleting production. This paper identifies the significant environmental impacts associated with production and delivery of these two fuels, using cradle-to-gate life cycle assessment. A feedstock of Scots Pine is modelled for a localised torrefaction/wood pellet plant located in Norway, with the products from each facility delivered to a power station in the UK.Results show that the relative benefits of torrefaction over wood-pellets are higher on per MJ delivered basis due to the higher calorific value of the fuel. The climate change and fossil depletion impacts for torrefied pellets modelled were lower than wood pellets, using an assumption that the drying requirement of the reactor was 3.0 MJ/kg water removed for both cases. Sensitivity analysis of the model indicated that the relative impact improvement of the torrefied pellet case compared to wood pellets is strongly dependent on the biomass drying requirement and the proportion of total process heat supplied by the re-circulated torrefaction gas. Land requirements for torrefied pellets are higher due to the mass losses in production.
In this paper the Life Cycle Assessment (LCA) is used to evaluate the environmental benefits on global warming, acidification and photochemical oxidation potentials, of biomass direct co-firing with coal on a 20% energy input basis, when compared with coal-fired power generation in The Netherlands. The solid biofuel is produced from Dutch or Canadian forestry biomass via pelletisation, torrefaction or torrefaction and pelletisation. The results show that torrefied biomass co-firing chain can be considered the best option when Dutch biomass is utilised. The reduction is approximately 12% for global warming, 7% for acidification and 5% concerning photochemical oxidation potentials. Even when biomass is imported from Canada, this also results in substantial reduction regarding global warming potential, when compared to the reference case. Alternatively, co-firing of domestic biomass results in a better performance than Canadian biomass for all three impact categories. Therefore, concerning global warming all the suggested resources for co-firing result in environmental benefits compared to coal-fired power generation.
The development of economic growth, population, and rapid urbanization is increasing the pace of energy consumption and waste production. These trends, if left unchecked, will lead to massive environmental degradation. Waste-to-energy (WtE) conversion is one way of alleviating the twin problems of fossil fuel use and solid waste disposal, and their related problems (climate change, pollution etc). Life Cycle Assessment (LCA) is a useful tool for assessing the environmental performances of WtE systems. Over fifty LCA studies on various WtE systems are reviewed, comprising different waste sources, energy products, and including countries from six continents. A variety of waste types, such as agricultural residues, used cooking oil, manure, municipal solid waste, and waste wood were studied. The review found that a large majority of WtE has lower greenhouse gas emissions when compared to fossil fuels. However, some WtE studies showed an increase in environmental impacts such as acidification and eutrophication, compared to fossil fuel extraction and use. This is due to the use of chemicals (fertilizers, pesticides) in agriculture and the allocation of these impacts to the use of the agricultural waste for energy conversion. Other problems with LCA are also highlighted, including allocation issues, definition of reference systems and functional units.
Life cycle assessment (LCA) has been used extensively within the recent decade to evaluate the environmental performance of thermal Waste-to-Energy (WtE) technologies: incineration, co-combustion, pyrolysis and gasification. A critical review was carried out involving 250 individual case-studies published in 136 peer-reviewed journal articles within 1995 and 2013. The studies were evaluated with respect to critical aspects such as: (i) goal and scope definitions (e.g. functional units, system boundaries, temporal and geographic scopes), (ii) detailed technology parameters (e.g. related to waste composition, technology, gas cleaning, energy recovery, residue management, and inventory data), and (iii) modeling principles (e.g. energy/mass calculation principles, energy substitution, inclusion of capital goods and uncertainty evaluation). Very few of the published studies provided full and transparent descriptions of all these aspects, in many cases preventing an evaluation of the validity of results, and limiting applicability of data and results in other contexts. The review clearly suggests that the quality of LCA studies of WtE technologies and systems including energy recovery can be significantly improved. Based on the review, a detailed overview of assumptions and modeling choices in existing literature is provided in conjunction with practical recommendations for state-of-the-art LCA of Waste-to-Energy.
The challenges in reducing the world's dependence on crude oil and the greenhouse gas accumulation in the atmosphere, while simultaneously improving engine performance through better fuel efficiency and reduced exhaust emissions, have led to the emergence of new fuels, with formulations blending petrodiesel, biodiesel, bioethanol and water in various proportions. In parallel, the sustainability of the new biofuel industries also requires to maintain a high level of biodiversity while playing on techno-diversity, using a variety of resources that do not compete with edible crops (nor by using arable land for energy crops or food crops for energy production) and flexible conversion technologies satisfying the eco-design, eco-energy and eco-materials criteria. In addition, it would be relevant to consider blending ethyl biodiesel, instead of methyl biodiesel, with petrodiesel, particularly if the fuel formulation is completed with bioethanol (or even water). The supercritical ethanolysis of lipid resources to produce ethyl biodiesel is a simple but efficient route that should have the potential to satisfy the sustainability criteria if analyzed holistically. Therefore, this review focuses specifically on the production of ethyl biodiesel via triglyceride supercritical ethanolysis within a global analysis “feedstocks-conversion-engine”. The scientific and technical bottlenecks requiring further development are highlighted by emphasizing (i) the kinetic and thermodynamic aspects (experiments and modeling) required for the process simulation, the results of which aim at securing the life cycle assessment, first at the process level and then at the fuel level; (ii) the proposals to improve the supercritical process performance in terms of eco-material and eco-energy; (iii) the impacts of ethyl vs. methyl biodiesel fuels and of biodiesel–ethanol–petrodiesel blends (with or without water) on the diesel engine emissions and performance; (iv) the technological flexibility of the supercritical process allowing its conversion toward production of other key products. Finally, built on the state-of-the art review, a new R&D direction combining supercritical ethanolysis of lipids with the addition of CO2, glycerol recovery, and cogeneration, according to the biorefinery concept, is proposed and discussed.
A life cycle assessment (LCA) study was conducted to understand and assess potential greenhouse gas (GHG) emissions reduction benefits of a biomass torrefaction business integrated with other industrial businesses for the use of the excess heat from the torrefaction off-gas volatiles and biocoal. A torrefaction plant processing 30.3 Mg h−1 of corn stover at 17% wet basis (w.b.) moisture content was modeled. The torrefaction plant produced 136,078 Mg y−1 of biocoal at 1.1% w.b. moisture content and 28.1 MW of excess heat energy in the torrefaction off-gas volatiles. At the torrefaction plant gate, the life-cycle GHG emission for the production of biocoal (including corn stover logistics emissions) is 11.35 g MJ−1 carbon dioxide equivalent (dry basis) (i.e., 229.5 kg Mg−1 carbon dioxide equivalent of biocoal at 1.1% w.b. moisture content). The excess heat from the torrefaction plant met 42.8% of the process steam needs of a U.S. Midwest dry-grind corn ethanol plant producing 0.38 hm3 y−1 of denatured ethanol, which results in about 40% reduction in life-cycle GHG emissions for corn ethanol compared to gasoline. Co-firing 10%, 20%, and 30% (energy basis) of biocoal at a coal-fired power plant reduced the life-cycle GHG emissions of electricity generated by 8.5%, 17.0%, and 25.6%, respectively, compared to 100% coal-fired electricity. A sensitivity analysis showed that adding a combined heat and power (CHP) system at the torrefaction plant to meet 100% electricity demand of the torrefaction plant (2.5 MW) could further reduce the GHG emissions for biocoal, corn ethanol, and co-fired electricity.
This paper aims at reviewing the life cycle assessment (LCA) literature on second generation bioethanol based on lignocellulosic biomass and at identifying issues to be resolved for good LCA practice. Reviews are carried out on respective LCA studies published over the last six years. We use the classification of lignocellulosic biomass to define system boundaries, so that the comparison among LCA results can be thoroughly assessed based on identified system components. A basis for attributing environmental burden for different biomass feedstocks is also suggested. Despite the non-homogeneous systems, we conclude that second generation bioethanol performs better than fossil fuel at least for the two most studied impact categories, net energy output and global warming. For the latter category, carbon sequestration at the biomass generation stage can even consistently offset the GHG emissions from all parts of the life cycle chains at high ethanol percentage (≥85%). The aspect of biogenic carbon and agrochemical input for energy crops and biomass residues, and the effect of removal of the latter from soil have not been treated consistently. In contrast, the exclusion of upstream chain of biomass waste feedstocks is observed in practice. The bioethanol conversion process is mostly based on simultaneous saccharification and co-fermentation, characterized by high yield and low energy input. In this regard, the LCA results tend to under estimate the real impacts of the current technology. The choice of allocation methods strongly influences the final results, particularly when economic value is used as a reference. Substitution of avoided burden seems to be the most popular allocation method in practice, followed by partition based on mass, energy, and economic values.
Bioenergy from lignocellulosic biomass offers the potential to provide a significant source of clean, low carbon and secure energy. In recent years, a number of studies have been carried out to assess the environmental performance of lignocellulosic ethanol fuel. However, the complexity of biofuel systems generates significantly different results due to the differences in input data, methodologies applied, and local geographical conditions. Moreover, much attention has been placed on assessing climate change potential and energy consumption. This study draws on 53 published life cycle assessment of the lignocellulosic ethanol. More than half of the articles reviewed focus on assessing greenhouse gas (GHG) emission or fossil energy consumption or combination of both. All studies but two reviewed conclude that there is a reduction of GHG emission when using lignocellulosic ethanol in comparison to fossil fuel reference system. However, different studies have reported different sources contributing to GHG emission: some reports majority of GHG emissions come from biomass cultivation stage; others argue significant GHG emissions from ethanol conversion process. All articles suggest a reduction of fossil consumption in all cases of ethanol fuel. Contrary results for the impact of acidification and eutrophication potential from lignocellulosic ethanol are also observed—some reports less impact in comparison to conventional gasoline whiles others report significant increase of acidification and eutrophication potential by ethanol production. Studies also show water consumption varies significantly depending on biomass types, irrigation requirement, and regional irrigation practices; with different findings on whether agricultural practices or ethanol conversion being the main sources for water consumption. Contrary findings on emissions contributing to ecotocixity and human health have also been reported with some being favourable while others not. Results from the literature also suggest strong dependency of LCA results on system boundary, functional unit, data quality and allocation methods chosen.
This paper describes the trend of utilizing oil palm residue, i.e. the empty fruit bunches (EFB) left after extraction of the palm oil, using a case study of Malaysia, which is one of the world's major palm oil producers, and discusses the environmental performance of recycling technologies being developed in Malaysia for fuel, fiber, and fertilizer. Seven technologies are analyzed: ethanol production, methane recovery, briquette production, biofuel for combined heat and power (CHP) plants, composting, medium density fiberboard (MDF) production, and pulp and paper production. The life cycle assessment (LCA) method is used to discuss the environmental impacts of these technologies for adding value to this biomass. Sensitivity analyses are conducted to determine the land use effects for the various technologies utilizing EFB and to estimate the energy generation potential of raw EFB in CHP plants and methane production. Among the technologies for energy production, CHP plants have the best performance if the electricity generated is connected to the national grid, with superior benefits in the majority of impact categories compared to briquette, methane, and ethanol production. Overall, we find that methane recovery and composting are more environmentally friendly than other technologies, as measured by reduction of greenhouse gas emissions. Pulp and paper, and MDF production are favorable technologies for land use impacts; however, they have intense primary energy requirements, chemical use in the processes, and emissions from their waste treatment systems. Our results provide information for decision makers when planning for sustainable use of oil palm biomass.
Life cycle energy and environmental performances of nine different biomass/coal co-firing pathways to power generation were compared. Agricultural residue (AR), forest residue (FR), and whole trees (WT) as feedstock were analyzed for direct (DC) and parallel co-firing (PC) in various forms (e.g., chip, bale and pellet). Biomass co-firing rate lies in the range of 7.53–20.45% (energy basis; rest of the energy comes from coal) for the co-firing pathways, depending on type of feedstock and densification. Net energy ratios (NER) for FR-, WT-, and AR-based co-firing pathways were 0.39–0.42, 0.39–0.41, and 0.37–0.38, greenhouse gas (GHG) emissions were 957–1004, 967–1014, and 1065–1083 kg CO2eq/MWh, acid rain precursor (ARP) emissions were 5.16–5.39, 5.18–5.41, and 5.77–5.93 kg SO2eq/MWh, and ground level ozone precursor (GOP) emissions were 1.79–1.89, 1.82–1.93, and 1.88–1.91 kg (NOx + VOC)/MWh, respectively. Biomass/coal co-firing life cycle results evaluated in this study are relevant for any jurisdiction around the world.
The environmental performance of production and distribution of densified form of lignocellulosic biomass (i.e., agri-residue based pellets) in Western Canada in terms of energy and greenhouse gas (GHG) emission was assessed. The results show that energy usage and resulted emissions are highest in field activities especially if emission and energy are attributed to straw in farming stage where nitrogen fertilizer is the highest contributor. Significant reduction of energy use (64%) and emission (65%) are possible if the organic fertilizer is used in farming. Adopting the zero tillage option instead of conventional practice results in energy saving (10%) and emission reduction (8%). From the scenario analyses it is also evident that using biomass as an energy source during drying or no drying in pellet production stage or using alternate mode (i.e., truck and train) of transport for pellet delivery result in less than 5% reduction of the energy use and emissions compared to the base case. Agri-pellet has the potential to offset substantial amount of GHG emission compared to other fuel sources including wood pellets. The energy and emission of production chain of agri-pellets may vary between countries but overall trend compared to other fuel sources would be similar.
The pre-treatment step has a significant influence on the performance of bioenergy chains, especially on logistics. Torrefaction, pelletisation and pyrolysis technologies can convert biomass at modest scales into dense energy carriers that ease transportation and handling.Torrefaction is a very promising technology due to its high process efficiency (94%) compared to pelletisation (84%) and pyrolysis (64%).11Process efficiency includes sizing and drying of biomass. When torrefaction is combined with pelletisation, the product (TOP22TOP: torrefied and pelletised biomass.) energy content is as high as 20.4–22.7GJ/ton. The primary energy requirement for TOP delivery from Latin America to Rotterdam harbour can be as low as 0.05GJ/GJ, in contrast to 0.12GJ/GJ for pellets and 0.08GJ/GJHHV for pyrolysis oil. TOP can be delivered to Europe at over 74€/ton (3.3€/GJ) and electricity could be produced as cheap as 4.4€cent/kWhe from an existing co-firing plant. Fisher Tropisch fuel costs 6€/GJHHV for TOP, 7€/GJ for conventional pellets and 9.5€/GJHHV for pyrolysis oil. Consequently, fuel production from TOP and conventional pellets is comparable to the current gasoline production cost ranging from 3 to 7€/GJHHV and diesel from 2 to 7€/GJHHV, depending on the oil market.3 Thus, well designed supply chains make international trade of biomass feasible from energy efficiency and economic perspective.
This paper presents a LCA study about household heat from Short Rotation Coppice wood pellets combustion. The overall process, from field growth to ash disposal, was considered; environmental analysis was carried out using a LCA software programme (Simapro 7.0) and adopting the EcoIndicator 99 model for the evaluation of the global burden; analysis with EPS 2000 and EDIP methodologies were also carried out, in order to compare the different approaches. For the pellet production process, mass and energy flows were measured on an existing Italian plant, while other data were obtained from the Literature; a comparison between results obtained using only data from Literature and using data from the existing plant was made, showing for the pelleting phase a value of about 23% lower if measured data are used. The LCA study showed that agricultural operations account for most of the environmental impact if evaluated both with EcoIndicator 99 and EPS 2000; EDIP gave results that were not very reliable for this chain, due to the high weight given to the infra-structures and machinery construction. The comparison between data obtained consid-ering and not considering the infra-structures contribution in the LCA analysis with EcoIndicator 99 showed a modest contribution of infra-structures on the final score (about 2%). The overall impact evaluated with EcoIndicator 99 is considerably less than the one caused by natural gas heating. The Energy Return Ratio was finally calculated; a value of 3.25 was found, good if compared to the one for the methane combustion, equal to 6.
Before further investments are made in utilizing biomass as a source of renewable energy, both policy makers and the energy industry need estimates of the net greenhouse gas (GHG) reductions expected from substituting biobased fuels for fossil fuels. Such GHG reductions depend greatly on how the biomass is cultivated, transported, processed, and converted into fuel or electricity. Any policy aiming to reduce GHGs with biomass-based energy must account for uncertainties in emissions at each stage of production, or else it risks yielding marginal reductions, if any, while potentially imposing great costs.This paper provides a framework for incorporating uncertainty analysis specifically into estimates of the life cycle GHG emissions from the production of biomass. We outline the sources of uncertainty, discuss the implications of uncertainty and variability on the limits of life cycle assessment (LCA) models, and provide a guide for practitioners to best practices in modeling these uncertainties. The suite of techniques described herein can be used to improve the understanding and the representation of the uncertainties associated with emissions estimates, thus enabling improved decision making with respect to the use of biomass for energy and fuel production.Highlights► We describe key model, scenario and data uncertainties in LCAs of biobased fuels. ► System boundaries and allocation choices should be consistent with study goals. ► Scenarios should be designed around policy levers that can be controlled. ► We describe a new way to analyze the importance of covariance between inputs.
Life-cycle assessment (LCA) practitioners build models to quantify resource consumption, environmental releases, and potential environmental and human health impacts of product systems. Most often, practitioners define a model structure, assign a single value to each parameter, and build deterministic models to approximate environmental outcomes. This approach fails to capture the variability and uncertainty inherent in LCA. To make good decisions, decision makers need to understand the uncertainty in and divergence between LCA outcomes for different product systems. Several approaches for conducting LCA under uncertainty have been proposed and implemented. For example, Monte Carlo simulation and fuzzy set theory have been applied in a limited number of LCA studies. These approaches are well understood and are generally accepted in quantitative decision analysis. But they do not guarantee reliable outcomes. A survey of approaches used to incorporate quantitative uncertainty analysis into LCA is presented. The suitability of each approach for providing reliable outcomes and enabling better decisions is discussed. Approaches that may lead to overconfident or unreliable results are discussed and guidance for improving uncertainty analysis in LCA is provided.
To evaluate the cost effectiveness of rice husk utilization, a life cycle cost analysis was
conducted for 18 scenarios developed in a previous study. The allocation of fuels other
than rice husks was decided on the basis of current demand for and supply of rice husks.
The production of rice husk briquettes is also discussed as a means of circumventing
problems arising from the bulk of the material. In the power generation scenarios,
differences between two generating capacities (5 and 30 MW) were analyzed. Costs savings
are possible by using rice husk to replace fossil fuels for cooking. With regard to power
generation, operation on a 30-MW scale by combustion of all available rice husk was
identified as the most economically efficient scenario, followed by small-scale gasification
scenarios (5 MW). The combustion of rice husk briquettes for power generation appeared to
be less cost-efficient than direct combustion, whereas large-scale gasification scenarios
and pyrolysis scenarios give rise to increases in cost compared with the baseline. When
both GHG abatement and costs are taken into consideration, suitable scenarios that are
practicable involve the use of rice husk for cooking, for large-scale combustion power
generation, and for small-scale gasification.
The adequacy and feasibility of methods recommended for allocation by the current international standard on life cycle inventory analysis (LCI) are reviewed. The review is based on the view that an LCI should provide information on the environmental consequences of manipulating technological systems. On this basis, subdivision and allocation based on physical, causal relationships are adequate methods to deal with allocation problems for certain multifunction processes where the production volume of exported functions are unaffected. Further research is needed to develop methods that can deal with a broader range of processes. System expansion is an adequate method when exported functions are affected if data can be obtained for the competing production of the exported function, and if the data uncertainties are not too large. In LCI practice, system expansion is often based on inaccurate data on the effects on the exported functions as well as on the indirect effects of changes in the exported functions. Further research is needed to establish what data should be used at system expansion. Other approaches to the allocation problems are adequate only where the effects on the LCI results are small. The ISO procedure should be revised to take into account the type of information provided by the different methods.
The substitution of conventional fossil fuels with biomass for energy production results both in a net reduction of greenhouse gases emissions and in the replacement of non-renewable energy sources. However, at present, generating energy from biomass is rather expensive due to both technological limits related to lower conversion efficiencies, and logistic constraints. In particular, the logistics of biomass fuel supply is likely to be complex owing to the intrinsic feedstock characteristics, such as the limited period of availability and the scattered geographical distribution over the territory. In this paper, the economical feasibility of biomass utilization for direct production of electric energy by means of combustion and gasification-conversion processes, has been investigated and evaluated over a capacity range from 5 to 50 MW, taking into account total capital investments, revenues from energy sale and total operating costs, also including a detailed evaluation of logistic costs. Moreover, in order to evaluate the impact of logistics on the bio-energy plants profitability, the effects of main logistic variables such as specific vehicle transport costs, vehicles capacity, specific purchased biomass costs and distribution density, have been examined. Finally, a mapping of logistic constraints on plant profitability in the specified capacity range has been carried out.
There have been increased interests on exporting wood pellets from Canada to Europe to meet the increased demand on biofuels in European countries. The wood pellet industry in Canada, especially in the west coastal region, has grown at an annual rate of more than 20% averaged over last 5 years due to the steady supply of wood residues. This paper attempted to analyze the fuel consumption and air emissions associated with the wood pellet production in British Columbia and export to Sweden based on a streamlined life cycle analysis, starting from tree harvesting for wood residue production to the shipping of wood pellets from Vancouver to Stockholm in Sweden. The results showed that about 7.2 GJ of energy is consumed for each tonne of wood pellets produced and shipped to Europe, representing about 39% of the total energy content of the wood pellets. Among those energies consumed over the life cycle, about 2.6 GJ is associated with long-distance ocean transportation. The ocean transportation is also the major contributor to environmental and health impacts, followed by the pellet production processes. The fossil fuel content, which quantifies the amount of fossil fuel consumed over the life cycle, for exported wood pellets ranged from 19% to 35%, depending on whether natural gas or wood residue is used in the drying operation during the wood pellet production stage. To reduce the fossil fuel content and the environmental impacts, wood residues should be used in the drying operation and, if possible, local market should be explored to reduce the energy consumption associated with wood pellet transportation over long distances.
Properties of biomass relevant to combustion are briefly reviewed. The compositions of biomass among fuel types are variable, especially with respect to inorganic constituents important to the critical problems of fouling and slagging. Alkali and alkaline earth metals, in combination with other fuel elements such as silica and sulfur, and facilitated by the presence of chlorine, are responsible for many undesirable reactions in combustion furnaces and power boilers. Reductions in the concentrations of alkali metals and chlorine, created by leaching the elements from the fuel with water, yield remarkable improvements in ash fusion temperatures and confirm much of what is suggested regarding the nature of fouling by biomass fuels. Other influences of biomass composition are observed for the rates of combustion and pollutant emissions. Standardized engineering practices setting out protocols of analysis and interpretation may prove useful in reducing unfavorable impacts and industry costs, and further development is encouraged.
Environmental life cycle assessment (LCA) developed rapidly during the 1990s and has reached a certain level of harmonisation and standardisation. LCA has mainly been developed for analysing material products, but can also be applied to services, e.g. treatment of a particular amount of solid waste. This paper discusses some methodological issues which come into focus when LCAs are applied to solid waste management systems. The following five issues are discussed. (1) Upstream and downstream system boundaries: where is the ‘cradle’ and where is the ‘grave’ in the analysed system? (2) Open-loop recycling allocation: besides taking care of a certain amount of solid waste, many treatment processes also provide additional functions, e.g. energy or materials which are recycled into other products. Two important questions which arise are if an allocation between the different functions should be made (and if so how), or if system boundaries should be expanded to include several functions. (3) Multi-input allocation: in waste treatment processes, different materials and products are usually mixed. In many applications there is a need to allocate environmental interventions from the treatment processes to the different input materials. The question is how this should be done. (4) Time: emissions from landfills will continue for a long time. An important issue to resolve is the length of time emissions from the landfill should be considered. (5) Life cycle impact assessment: are there any aspects of solid waste systems (e.g. the time horizon) that may require specific attention for the impact assessment element of an LCA? Although the discussion centres around LCA it is expected that many of these issues are also relevant for other types of systems analyses.
Biomass is a key renewable energy source expected to play an important role in US electricity production under stricter emission regulations and renewable portfolio standards. Willow energy crops are being developed in the northeast US as a fuel source for increasing biomass energy and bioproduct demands. A life cycle inventory is presented that characterizes the full cradle-to-grave energy and environmental performance of willow biomass-to-electricity. A willow biomass production model is developed using demonstration-scale field experience from New York. Scenarios are presented that mimic anticipated cofiring operations, including supplemental use of wood residues, at an existing coal-fired generating facility. At a cofiring rate of 10% biomass, the system net energy ratio (electricity delivered divided by total fossil fuel consumed) increases by 8.9% and net global warming potential decreases by 7–10%. Net SO2 emissions are reduced by 9.5% and a significant reduction in NOx emissions is expected. In addition, we estimate system performance of using willow biomass in dedicated biomass gasification and direct-fired generating facilities and demonstrate that the pollution avoided (relative to the current electricity grid) is comparable to other renewables such as PV and wind.
Effectiveness of a densification process to create strong and durable bonding in densified products such as pellets, briquettes, and cubes can be determined by testing the strength (i.e., compressive resistance, impact resistance, and water resistance), and durability (i.e., abrasion resistance) of the densified products. These tests can indicate the maximum force/stress that the densified products can withstand, and the amount of fines produced during handling, transportation, and storage. In this article, the procedures used for measuring the strength and durability of the densified products are discussed. The effects of constituents of the feed such as starch, protein, fiber, fat, lignin and extractives; feed moisture content; feed particle size and its distribution; feed conditioning temperature/preheating of feed; added binders; and densification equipment variables (forming pressure, and pellet mill and roll press variables) on the strength and durability of the densified products are reviewed. This article will help select process parameters to produce strong and durable densified products from new biomass feedstocks or animal feed formulations. Guidelines for developing standards on criteria for the acceptance levels of strength and durability of the densified products are presented.
To be a viable alternative, a biofuel should provide a net energy gain and be capable of being produced in large quantities without reducing food supplies. Amounts of agricultural waste are produced and require treatment, with rice straw contributing the greatest source of such potential bio-fuel in Taiwan. Through life-cycle accounting, several energy indicators and four potential gasification technologies (PGT) were evaluated. The input energy steps for the energy life cycle assessment (ELCA) include collection, generator, torrefaction, crushing, briquetting, transportation, energy production, condensation, air pollution control and distribution of biofuels to the point of end use. Every PGT has a positive energy benefit. The input of energy required for the transportation and pre-treatment are major steps in the ELCA. On-site briquetting of refused-derived fuel (RDF) provides an alternative means of reducing transportation energy requirements. Bio-energy sources, such as waste rice straw, provide an ideal material for the bio-fuel plant.
The use of different input data, functional units, allocation methods, reference systems and other assumptions complicates comparisons of LCA bioenergy studies. In addition, uncertainties and use of specific local factors for indirect effects (like land-use change and N-based soil emissions) may give rise to wide ranges of final results. In order to investigate how these key issues have been addressed so far, this work performs a review of the recent bioenergy LCA literature. The abundance of studies dealing with the different biomass resources, conversion technologies, products and environmental impact categories is summarized and discussed. Afterwards, a qualitative interpretation of the LCA results is depicted, focusing on energy balance, GHG balance and other impact categories. With the exception of a few studies, most LCAs found a significant net reduction in GHG emissions and fossil energy consumption when bioenergy replaces fossil energy.
Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing system boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input-output analysis have shown that, in practice, excluded processes can contribute as much to the product system under study as included processes; thus, the subjective determination of the system boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the boundary selection problem in LCA. An input-output model can be used to describe at least a part of a product system, and an ISO-compatible system boundary selection procedure can be designed by applying hybrid input-output-assisted approaches. There are several hybrid input-output analysis-based LCA methods that can be implemented in practice for broadening system boundary and also for ISO compliance.