GHG emissions and other environmental impacts of indirect land use change mitigation

The implementation of measures to increase productivity and resource efficiency in food and bioenergy chains as well as to more sustainably manage land use can significantly increase the biofuel production potential while limiting the risk of causing indirect land use change (ILUC). However, the application of these measures may influence the greenhouse gas (GHG) balance and other environmental impacts of agricultural and biofuel production. This study applies a novel, integrated approach to assess the environmental impacts of agricultural and biofuel production for three ILUC mitigation scenarios, representing a low, medium and high miscanthus‐based ethanol production potential, and for three agricultural intensification pathways in terms of sustainability in Lublin province in 2020. Generally, the ILUC mitigation scenarios attain lower net annual emissions compared to a baseline scenario that excludes ILUC mitigation and bioethanol production. However, the reduction potential significantly depends on the intensification pathway considered. For example, in the moderate ILUC mitigation scenario, the net annual GHG emissions in the case study are 2.3 MtCO₂‐eq yr^?1 (1.8 tCO₂‐eq ha^?1 yr^?1) for conventional intensification and ?0.8 MtCO₂‐eq yr^?1 (?0.6 tCO₂‐eq ha^?1 yr^?1) for sustainable intensification, compared to 3.0 MtCO₂‐eq yr^?1 (2.3 tCO₂‐eq ha^?1 yr^?1) in the baseline scenario. In addition, the intensification pathway is found to be more influential for the GHG balance than the ILUC mitigation scenario, indicating the importance of how agricultural intensification is implemented in practice. Furthermore, when the net emissions are included in the assessment of GHG emissions from bioenergy, the ILUC mitigation scenarios often abate GHG emissions compared to gasoline. But sustainable intensification is required to attain GHG abatement potentials of 90% or higher. A qualitative assessment of the impacts on biodiversity, water quantity and quality, soil quality and air quality also emphasizes the importance of sustainable intensification.     

Spatial distribution of usable biomass feedstock and technical bioenergy potential in China

Bioenergy will play an intimate and critical role in energy supply and carbon mitigation in the future. In recent years, “customizing the development of bioenergy to local conditions” and “prioritizing distributed utilization” have been the two key principles that have been released by the Chinese government to promote the national‐ and provincial‐level development of bioenergy. While many recognize the importance of bioenergy in achieving low‐carbon transition, little is known about the high‐resolution distribution of usable biomass feedstock and technical bioenergy potential in China, which brings about uncertainties and additional challenges for creating localized utilization plans. We propose a new assessment framework that integrates crop growth models, a land suitability assessment, and the geographic information systems to address these knowledge gaps. Distributions of 11 types of usable biomass feedstock and three kinds of technical bioenergy potential are mapped out through specific transformation technologies at 1 km resolution. At the national level, the final technical biogas potential is 1.91 EJ. The technical bioethanol potential (0.04–0.96 EJ) from the energy crop can supply 0.13–3.12 times the bioethanol demand for the consumption of E10 gasoline in 2015. The technical heat potential (1.06 EJ) can meet 20% of the demand for heating in all provinces (5.38 EJ). Most of the 2020 bioenergy goals can be achieved, excluding that for bioethanol, which will need to require more cellulosic ethanol from residues. At the provincial level, Henan and Inner Mongolia have the potential to develop clean heating alternatives via the substitution of agroforestry residues for coal. The results can provide a systematic analysis of the distribution of biomass feedstocks and technical bioenergy potential in China. With economic factors taken into consideration in further research, it can also support national and provincial governments in making bioenergy development plans in an effective and timely manner.     

Modeling biogeochemical impacts of bioenergy buffers with perennial grasses for a row‐crop field in Illinois

Current research on the environmental sustainability of bioenergy has largely focused on the potential of bioenergy crops to sequester carbon and mitigate greenhouse gas emissions and possible impacts on water quality and quantity. A key assumption in these studies is that bioenergy crops will be grown in a manner similar to current agricultural crops such as corn and hence would affect the environment similarly. In this study, we investigate an alternative cropping system where bioenergy crops are grown in buffer strips adjacent to current agricultural crops such that nutrients present in runoff and leachate from the traditional row‐crops are reused by the bioenergy crops (switchgrass, miscanthus and native prairie grasses) in the buffer strips, thus providing environmental services and meeting economic needs of farmers. The process‐based biogeochemical model Denitrification‐Decomposition (DNDC) was used to simulate crop yield, nitrous oxide production and nitrate concentrations in leachate for a typical agricultural field in Illinois. Model parameters have been developed for the first time for miscanthus and switchgrass in DNDC. Results from model simulations indicated that growing bioenergy crops in buffer strips mitigated nutrient runoff, reduced nitrate concentrations in leachate by 60–70% and resulted in a reduction of 50–90% in nitrous oxide emissions compared with traditional cropping systems. While all the bioenergy crop buffers had significant positive environmental benefits, switchgrass performed the best with respect to minimizing nutrient runoff and nitrous oxide emissions, while miscanthus had the highest yield. Overall, our model results indicated that the bioenergy crops grown in these buffer strips achieved yields that are comparable to those obtained for traditional agricultural systems while simultaneously providing environmental services and could be used to design sustainable agricultural landscapes.     

Meeting Europe's climate change commitments: quantitative estimates of the potential for carbon mitigation by agriculture

Under the Kyoto Protocol, the European Union is committed to a reduction in CO₂ emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). The Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere. Thus, land‐use/land‐management change and forestry activities that are shown to reduce atmospheric CO₂ levels can be included in the Kyoto targets. These activities include afforestation, reforestation and deforestation (article 3.3 of the Kyoto Protocol) and the improved management of agricultural soils (article 3.4). In this paper, we estimate the carbon mitigation potential of various agricultural land‐management strategies and examine the consequences of European policy options on carbon mitigation potential, by examining combinations of changes in agricultural land‐use/land‐management. We show that no single land‐management change in isolation can mitigate all of the carbon needed to meet Europe's climate change commitments, but integrated combinations of land‐management strategies show considerable potential for carbon mitigation. Three of the combined scenarios, one of which is an optimal realistic scenario, are by themselves able to meet Europe's emission limitation or reduction commitments. Through combined land‐management scenarios, we show that the most important resource for carbon mitigation in agriculture is the surplus arable land. We conclude that in order to fully exploit the potential of arable land for carbon mitigation, policies will need to be implemented to allow surplus arable land to be put into alternative long‐term land‐use. Of all options examined, bioenergy crops show the greatest potential for carbon mitigation. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the mitigation potential is finite. We suggest that in order to exploit fully the bioenergy option, the infrastructure for bioenergy production needs to be significantly enhanced before the beginning of the first Kyoto commitment period in 2008. It is not expected that Europe will attempt to meet its climate change commitments solely through changes in agricultural land‐use. A reduction in CO₂‐carbon emissions will be key to meeting Europe's Kyoto targets, and forestry activities (Kyoto Article 3.3) will play a major role. In this study, however, we demonstrate the considerable potential of changes in agricultural land‐use and ‐management (Kyoto Article 3.4) for carbon mitigation and highlight the policies needed to promote these agricultural activities. As all sources of carbon mitigation will be important in meeting Europe's climate change commitments, agricultural carbon mitigation options should be taken very seriously.     

Economic and environmental performance of miscanthus cultivated on marginal land for biogas production

Environmental issues surrounding conventional annual biogas crops have led to growing interest in alternative crops, such as miscanthus. In addition to the better environmental performance, miscanthus can be grown on marginal land where no competition with feed and food crops is anticipated. On marginal land however, biomass yields are significantly lower than on good agricultural land. This raises the question of the economic and environmental sustainability of miscanthus cultivated on marginal land for biogas production. This study assessed the environmental and economic performance of miscanthus cultivated on marginal land for biogas production by conducting a Life‐Cycle Assessment and complementary Life‐Cycle Cost analysis. The functional unit chosen was 1 GJ of electricity (GJ_el.). The substitution of a fossil reference was included using a system expansion approach. Electricity generated by the combustion of miscanthus‐based biogas in a combined heat and power has considerably lower impacts on the environment than the fossil reference in most of the categories assessed. In the impact category “climate change”, the substitution of the marginal German electricity mix leads to a carbon mitigation potential of 256 kg CO₂e/GJ_el.. At 45.12 €/GJ_el., the costs of miscanthus‐based biogas generation and utilization are considerably lower than those of maize (61.30 €/GJ_el.). The results of this study clearly show that it can make economic and environmental sense to cultivate miscanthus on marginal land as a substrate for biogas production. The economic sustainability is however limited by the biomass yield. By contrast, there are no clear thresholds limiting the environmental performance. The decision needs to be made on a case‐by‐case basis depending on site‐specific conditions such as local biodiversity.     

Mitigation of unwanted direct and indirect land‐use change – an integrated approach illustrated for palm oil,pulpwood, rubber and rice production in North and East Kalimantan,Indonesia

The widespread production of cash crops can result in the decline of forests, peatlands, rice fields and local community land. Such unwanted land‐use and land‐cover (LULC) change can lead to decreased carbon stocks, diminished biodiversity, displaced communities and reduced local food production. In this study, we analysed to what extent four main commodities, namely, palm oil, pulpwood, rice and rubber, can be produced in North and East Kalimantan in Indonesia without such unwanted LULC change. We investigated the technical potential of four measures to mitigate unwanted LULC change between 2008 and 2020 under low, medium and high scenarios, referring to the intensities of the mitigation measures compared with those implemented in 2008. These measures are related to land sparing through (i) the improvements of yields, (ii) chain efficiencies, (iii) chain integration and (iv) the steering of any expansion of these commodities to suitable and available underutilised (potentially degraded) lands. Our analyses resulted in a land‐sparing potential of 0.4–1.2 Mha (i.e. 24–62% of the total land demand of the commodities) between 2008 and 2020, depending on the land‐use projection of the four commodities and the scenario for implementing the mitigation measures. Additional expansion on underutilised land is the most important mitigation measure (45–62% of the total potential), followed by yield improvements as the second most important mitigation measure (32–46% of the total potential). Our study shows that reconciling the production of palm oil, pulpwood, rice and rubber with the maintenance of existing agricultural lands, forests and peatlands is technically possible only (i) under a scenario of limited agricultural expansion, (ii) if responsible land zoning is applied and enforced and (iii) if the yields and chain efficiencies are strongly improved.     

Potential impacts on ecosystem services of land use transitions to second‐generation bioenergy crops in GB

We present the first assessment of the impact of land use change (LUC) to second‐generation (2G) bioenergy crops on ecosystem services (ES) resolved spatially for Great Britain (GB). A systematic approach was used to assess available evidence on the impacts of LUC from arable, semi‐improved grassland or woodland/forest, to 2G bioenergy crops, for which a quantitative ‘threat matrix’ was developed. The threat matrix was used to estimate potential impacts of transitions to either Miscanthus, short‐rotation coppice (SRC, willow and poplar) or short‐rotation forestry (SRF). The ES effects were found to be largely dependent on previous land uses rather than the choice of 2G crop when assessing the technical potential of available biomass with a transition from arable crops resulting in the most positive effect on ES. Combining these data with constraint masks and available land for SRC and Miscanthus (SRF omitted from this stage due to lack of data), south‐west and north‐west England were identified as areas where Miscanthus and SRC could be grown, respectively, with favourable combinations of economic viability, carbon sequestration, high yield and positive ES benefits. This study also suggests that not all prospective planting of Miscanthus and SRC can be allocated to agricultural land class (ALC) ALC 3 and ALC 4 and suitable areas of ALC 5 are only minimally available. Beneficial impacts were found on 146 583 and 71 890 ha when planting Miscanthus or SRC, respectively, under baseline planting conditions rising to 293 247 and 91 318 ha, respectively, under 2020 planting scenarios. The results provide an insight into the interplay between land availability, original land uses, bioenergy crop type and yield in determining overall positive or negative impacts of bioenergy cropping on ecosystems services and go some way towards developing a framework for quantifying wider ES impacts of this important LUC.     

Contribution of above‐ and belowground bioenergy crop residues to soil carbon

GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above‐ vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above‐ and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1‐m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25–100%) resulted in C stock reduction in areas of corn–corn–soybean rotation under conventional tillage, while no‐till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C‐residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate.     

Miscanthus biomass productivity within US croplands and its potential impact on soil organic carbon

Interest in bioenergy crops is increasing due to their potential to reduce greenhouse gas emissions and dependence on fossil fuels. We combined process‐based and geospatial models to estimate the potential biomass productivity of miscanthus and its potential impact on soil carbon stocks in the croplands of the continental United States. The optimum (climatic potential) rainfed productivity for field‐dried miscanthus biomass ranged from 1 to 23 Mg biomass ha^?1 yr^?1, with a spatial average of 13 Mg ha^?1 yr^?1 and a coefficient of variation of 30%. This variation resulted primarily from the spatial heterogeneity of effective rainfall, growing degree days, temperature, and solar radiation interception. Cultivating miscanthus would result in a soil organic carbon (SOC) sequestration at the rate of 0.16–0.82 Mg C ha^?1 yr^?1 across the croplands due to cessation of tillage and increased biomass carbon input into the soil system. We identified about 81 million ha of cropland, primarily in the eastern United States, that could sustain economically viable (>10 Mg ha^?1 yr^?1) production without supplemental irrigation, of which about 14 million ha would reach optimal miscanthus growth. To meet targets of the US Energy Independence and Security Act of 2007 using miscanthus as feedstock, 19 million ha of cropland would be needed (spatial average 13 Mg ha^?1 yr^?1) or about 16% less than is currently dedicated to US corn‐based ethanol production.     

Initial soil C and land‐use history determine soil C sequestration under perennial bioenergy crops

In the UK and other temperate regions, short rotation coppice (SRC) and Miscanthus x giganteus (Miscanthus) are two of the leading ‘second‐generation’ bioenergy crops. Grown specifically as a low‐carbon (C) fossil fuel replacement, calculations of the climate mitigation provided by these bioenergy crops rely on accurate data. There are concerns that uncertainty about impacts on soil C stocks of transitions from current agricultural land use to these bioenergy crops could lead to either an under‐ or overestimate of their climate mitigation potential. Here, for locations across mainland Great Britain (GB), a paired‐site approach and a combination of 30‐cm‐ and 1‐m‐deep soil sampling were used to quantify impacts of bioenergy land‐use transitions on soil C stocks in 41 commercial land‐use transitions; 12 arable to SRC, 9 grasslands to SRC, 11 arable to Miscanthus and 9 grasslands to Miscanthus. Mean soil C stocks were lower under both bioenergy crops than under the grassland controls but only significant at 0–30 cm. Mean soil C stocks at 0–30 cm were 33.55 ± 7.52 Mg C ha^?1 and 26.83 ± 8.08 Mg C ha^?1 lower under SRC (P = 0.004) and Miscanthus plantations (P = 0.001), respectively. Differences between bioenergy crops and arable controls were not significant in either the 30‐cm or 1‐m soil cores and smaller than for transitions from grassland. No correlation was detected between change in soil C stock and bioenergy crop age (time since establishment) or soil texture. Change in soil C stock was, however, negatively correlated with the soil C stock in the original land use. We suggest, therefore, that selection of sites for bioenergy crop establishment with lower soil C stocks, most often under arable land use, is the most likely to result in increased soil C stocks.     

Land management and climate change determine second‐generation bioenergy potential of the US Northern Great Plains

Bioenergy with carbon capture and storage (BECCS) has been proposed as a potential climate mitigation strategy raising concerns over trade‐offs with existing ecosystem services. We evaluate the feasibility of BECCS in the Upper Missouri River Basin (UMRB), a landscape with diverse land use, ownership, and bioenergy potential. We develop land‐use change scenarios and a switchgrass (Panicum virgatum L.) crop functional type to use in a land‐surface model to simulate second‐generation bioenergy production. By the end of this century, average annual switchgrass production over the UMRB ranges from 60 to 210 Tg dry mass/year and is dependent on the Representative Concentration Pathway for greenhouse gas emissions and on land‐use change assumptions. Under our simple phase‐in assumptions this results in a cumulative total production of 2,000–6,000 Tg C over the study period with the upper estimates only possible in the absence of climate change. Switchgrass yields decreased as average CO₂ concentrations and temperatures increased, suggesting the effect of elevated atmospheric CO₂ was small because of its C4 photosynthetic pathway. By the end of the 21st century, the potential energy stored annually in harvested switchgrass averaged between 1 and 4 EJ/year assuming perfect conversion efficiency, or an annual electrical generation capacity of 7,000–28,000 MW assuming current bioenergy efficiency rates. Trade‐offs between bioenergy and ecosystem services were identified, including cumulative direct losses of 1,000–2,600 Tg C stored in natural ecosystems from land‐use change by 2090. Total cumulative losses of ecosystem carbon stocks were higher than the potential ~300 Tg C in fossil fuel emissions from the single largest power plant in the region over the same time period, and equivalent to potential carbon removal from the atmosphere from using biofuels grown in the same region. Numerous trade‐offs from BECCS expansion in the UMRB must be balanced against the potential benefits of a carbon‐negative energy system.     

Environmental implications of the use of agro‐industrial residues for biorefineries: application of a deterministic model for indirect land‐use changes

Biorefining agro‐industrial biomass residues for bioenergy production represents an opportunity for both sustainable energy supply and greenhouse gas (GHG) emissions mitigation. Yet, is bioenergy the most sustainable use for these residues? To assess the importance of the alternative use of these residues, a consequential life cycle assessment (LCA) of 32 energy‐focused biorefinery scenarios was performed based on eight selected agro‐industrial residues and four conversion pathways (two involving bioethanol and two biogas). To specifically address indirect land‐use changes (iLUC) induced by the competing feed/food sector, a deterministic iLUC model, addressing global impacts, was developed. A dedicated biochemical model was developed to establish detailed mass, energy, and substance balances for each biomass conversion pathway, as input to the LCA. The results demonstrated that, even for residual biomass, environmental savings from fossil fuel displacement can be completely outbalanced by iLUC, depending on the feed value of the biomass residue. This was the case of industrial residues (e.g. whey and beet molasses) in most of the scenarios assessed. Overall, the GHGs from iLUC impacts were quantified to 4.1 t CO₂‐eq.ha^?1_demanded yr^?1 corresponding to 1.2–1.4 t CO₂‐eq. t^?1 dry biomass diverted from feed to energy market. Only, bioenergy from straw and wild grass was shown to perform better than the alternative use, as no competition with the feed sector was involved. Biogas for heat and power production was the best performing pathway, in a short‐term context. Focusing on transport fuels, bioethanol was generally preferable to biomethane considering conventional biogas upgrading technologies. Based on the results, agro‐industrial residues cannot be considered burden‐free simply because they are a residual biomass and careful accounting of alternative utilization is a prerequisite to assess the sustainability of a given use. In this endeavor, the iLUC factors and biochemical model proposed herein can be used as templates and directly applied to any bioenergy consequential study involving demand for arable land.     

Water and energy footprints of bioenergy crop production on marginal lands

Water and energy demands associated with bioenergy crop production on marginal lands are inextricably linked with land quality and land use history. To illustrate the effect of land marginality on bioenergy crop yield and associated water and energy footprints, we analyzed seven large‐scale sites (9–21 ha) converted from either Conservation Reserve Program (CRP) or conventional agricultural land use to no‐till soybean for biofuel production. Unmanaged CRP grassland at the same location was used as a reference site. Sites were rated using a land marginality index (LMI) based on land capability classes, slope, soil erodibility, soil hydraulic conductivity, and soil tolerance factors extracted from a soil survey (SSURGO) database. Principal components analysis was used to develop a soil quality index (SQI) for the study sites based on 12 soil physical and chemical properties. The water and energy footprints on these sites were estimated using eddy‐covariance flux techniques. Aboveground net primary productivity was inversely related to LMI and positively related to SQI. Water and energy footprints increased with LMI and decreased with SQI. The water footprints for grain, biomass and energy production were higher on lands converted from agricultural land use compared with those converted from the CRP land. The sites which were previously in the CRP had higher SQI than those under agricultural land use, showing that land management affects water footprints through soil quality effects. The analysis of biophysical characteristics of the sites in relation to water and energy use suggests that crops and management systems similar to CRP grasslands may provide a potential strategy to grow biofuels that would minimize environmental degradation while improving the productivity of marginal lands.     

Biomass production potential from Populus short rotation systems in Romania

The aim of this study was to assess the potential of biomass production by short rotation poplar in Romania without constraining agricultural food production. Located in the eastern part of Europe, Romania provides substantial land resources suitable for bioenergy production. The process‐oriented biogeochemical model Landscape DNDC was used in conjunction with the forest‐growth model PSIM to simulate the yield of poplar grown in short‐rotation coppice at different sites in Romania. The model was validated on five sites with different climatic conditions in Central Europe. Using regional site conditions, with climatic parameters and organic carbon content in soil being the most important, the biomass production potential of poplar plantations was simulated for agricultural areas across Romania. Results indicated a mean productivity of 12.2 ± 0.5 t ha^?1 year^?1 of poplar coppices on arable land in Romania. The highest yields were simulated for lowland areas in the south‐east and west and for the Mures valley, whereas the lowest yields – due to either temperature or water limitations – were found for the mountainous regions, the Danube valley, and the region west of Bucharest. The amount of abandoned arable land in the past 10 years indicates that around 10% of cropping land in production in 1999 (approximately 1 million ha) is available for bioenergy production systems today. Production of poplar grown in short‐rotation coppices on these areas would result in a yield of approximately 10 million tons of wood per year. The energy that can be generated by conversion of poplar short rotation coppice biomass may contribute up to approximately 8% of the national energy demand if these set‐aside areas are used for lignocellulosic bioenergy.     

Bioenergy crops,biodiversity and ecosystem services in temperate agricultural landscapes—A review of synergies and trade-offs

The Paris agreement on climate change requires rapid reductions in greenhouse gas emissions. One important mitigation strategy, at least in the intermediate future, is the substitution of fossil fuels with bioenergy. However, using agriculture- and forest-derived biomass for energy has sparked controversy regarding both the climate mitigation potential and conflicts with biodiversity conservation. The urgency of the climate crisis calls for using forests for carbon sequestration and storage rather than for bioenergy, making agricultural biomass an attractive alternative for fossil energy substitution. However, this calls for comprehensive assessments of its sustainability in terms of consequences for biodiversity and ecosystem services. In this review, we provide a first holistic overview of the impacts on ecosystems of land-use changes from bioenergy crop production in temperate climates, by synthesizing results on both biodiversity and ecosystem service impacts. We found that bioenergy-related land-use changes can have both positive and negative effects on ecosystems, with original land use, bioenergy crop type and scale of bioenergy production being important moderators of impacts. Despite the risk of opportunity cost for food production, perennial crop cultivation on arable land had the lowest occurrence of negative impacts on biodiversity and ecosystem services. Growing biomass for bioenergy on surplus land has been suggested as a way to alleviate competition with food production and biodiversity conservation, but our results demonstrate that utilizing marginal or abandoned land for bioenergy crop production cannot fully resolve these trade-offs. Furthermore, there is a lack of empirical studies of the biodiversity value of marginal and abandoned land, limiting our understanding of the sustainability implications of biomass cultivation on surplus land. We argue that future research and policies for bioenergy production must explicitly consider biodiversity and ecosystem services in combination to avoid potential trade-offs between the two and to ensure sustainable bioenergy production.     

Life cycle assessment of ethanol production from miscanthus: A comparison of production pathways at two European sites

Lignocellulosic ethanol represents a renewable alternative to petrol. Miscanthus, a perennial plant that grows on marginal land, is characterized by efficient use of resources and is considered a promising source of lignocellulosic biomass. A life cycle assessment (LCA) was performed to determine the environmental impacts of ethanol production from miscanthus grown on marginal land in Great Britain (Aberystwyth) and an average‐yield site in Germany (Stuttgart; functional unit: 1 GJ). As the conversion process has substantial influence on the overall environmental performance, the comparison examined three pretreatment options for miscanthus. Overall, results indicate lower impacts for the production in Stuttgart in comparison with the corresponding pathways in Aberystwyth across the analysed categories. Disparities between the sites were mainly attributed to differences in biomass yield. When comparing the conversion options, liquid hot water treatment resulted in the lowest impacts, followed by dilute sulphuric acid. Dilute sodium hydroxide pretreatment represented the least favourable option. Site‐dependent variation in biomass composition and degradability did not have substantial influence on the environmental performance of the analysed pathways. Additionally, implications of replacing petrol with miscanthus ethanol were examined. Ethanol derived from miscanthus resulted in lower impacts with respect to greenhouse gas emissions, fossil resource depletion, natural land transformation and ozone depletion. However, for other categories, including toxicity, eutrophication and agricultural land occupation, net scores were substantially higher than for the fossil reference. Nevertheless, the results indicate that miscanthus ethanol produced via dilute acid and liquid hot water treatment at the site in Stuttgart has the potential to comply with the requirements of the European Renewable energy directive for greenhouse gas emission reduction. For ethanol production at the marginal site, carbon sequestration needs to be considered in order to meet the requirements for greenhouse gas mitigation.     

Opportunities for avoidance of land‐use change through substitution of soya bean meal and cereals in European livestock diets with bioethanol coproducts

An analysis is presented which quantifies the potential for distillers dried grains with solubles (DDGS, a coproduct of wheat bioethanol production) to replace soya bean meal (SBM) and cereals in livestock rations. A major proportion of the SBM imported into Europe as a protein‐rich feedstuff for livestock comes from South America, where land‐use change (LUC) is associated with high carbon emissions. Production of DDGS can therefore reduce LUC in South America by substitution of SBM in animal feed. The analysis indicates that a single bioethanol distillery processing 1 million tonnes of wheat, and producing ca. 330 000 tonnes of DDGS per annum, would substitute at least 136 493 tonnes of whole soya beans grown on 47 725 ha of land, and save greenhouse gas emissions equivalent to 0.63 million tonnes CO₂ per annum. By growing sugar beet and wheat in an average ratio of 0.06 : 0.94 on 1 ha of land in Europe, the net area of agricultural land required to produce feed ingredients equivalent to 6.08 t of sugar beet pulp (SBP) and 1.72 t of DDGS associated with 2363 L of bioethanol, is reduced to 0.40 ha. This accounts for 0.42 ha of soya that is not required when DDGS displaces SBM, and 0.18 ha of wheat that is not required when DDGS and SBP displace wheat in livestock rations.     

Trade‐offs between land and water requirements for large‐scale bioenergy production

Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large‐scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade‐offs between land and water requirements of large‐scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land‐ and water‐use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr^?1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr^?1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large‐scale bioenergy production will require policies that balance associated water and land requirements.     

Baseline time accounting: Considering global land use dynamics when estimating the climate impact of indirect land use change caused by biofuels

Purpose

Current estimations of the climate impact from indirect land use change (ILUC) caused by biofuels are heavily influenced by assumptions regarding the biofuel production period. The purpose of this paper is to propose a new method (baseline time accounting) that takes global land use dynamics into account that is consistent with the global warming potential, that is applicable to any phenomenon causing land use change, and that is independent of production period assumptions.

Methods

We consider ILUC in two forms. The first is called “accelerated expansion” and concerns ILUC in regions with an expanding agricultural area. The second is called “delayed reversion” and concerns ILUC in regions with a decreasing agricultural area. We use recent trends in international land use and projections of future land use change to assess how ILUC from biofuels will alter the development in global agricultural land use dynamics compared to the existing trend (i.e., the baseline development). We then use the definition of the global warming potential to determine the CO₂ equivalence of the change in land use dynamics.

Results and discussion

We apply baseline time accounting to two existing ILUC studies in the literature. With current trends in global agricultural land use, the method significantly reduces the estimated climate impact in the previous ILUC studies (by more than half). Sensitivity analyses show that results are somewhat sensitive to assumptions regarding carbon sequestration and assumptions regarding postreversion ecosystems.

Conclusions

The global dynamic development in land use has important implications for the time accounting step when estimating the climate impact of ILUC caused by biofuel production or other issues affecting land use. Ignoring this may lead to erroneous conclusions about the actual climate impact of ILUC. Several land use projections indicate that the global agricultural area will keep expanding up to and beyond 2050. We therefore recommend to apply the baseline time accounting concept as an integrated part of future ILUC studies and to update the results on a regular basis.     

An integrated biogeochemical and economic analysis of bioenergy crops in the Midwestern United States

This study integrates a biophysical model with a county‐specific economic analysis of breakeven prices of bioenergy crop production to assess the biophysical and economic potential of biofuel production in the Midwestern United States. The bioenergy crops considered in this study include a genotype of Miscanthus, Miscanthus×giganteus, and the Cave‐in‐Rock breed of switchgrass (Panicum virgatum). The estimated average peak biomass yield for miscanthus in the Midwestern states ranges between 7 and 48 metric tons dry matter per hectare per year ( t DM ha^?1 yr^?1), while that for switchgrass is between 10 and 16 t DM ha^?1 yr^?1. With the exception of Minnesota and Wisconsin, where miscanthus yields are likely to be low due to cold soil temperatures, the yield of miscanthus is on average more than two times higher than yield of switchgrass. We find that the breakeven price, which includes the cost of producing the crop and the opportunity cost of land, of producing miscanthus ranges from $53 t^?1 DM in Missouri to $153 t^?1 DM in Minnesota in the low‐cost scenario. Corresponding costs for switchgrass are $88 t^?1 DM in Missouri to $144 t^?1 DM in Minnesota. In the high‐cost scenario, the lowest cost for miscanthus is $85 t^?1 DM and for switchgrass is $118 t^?1 DM, both in Missouri. These two scenarios differ in their assumptions about ease of establishing the perennial crops, nutrient requirements and harvesting costs and losses. The differences in the breakeven prices across states and across crops are mainly driven by bioenergy and row crop yields per hectare. Our results suggest that while high yields per unit of land of bioenergy crops are critical for the competitiveness of bioenergy feedstocks, the yields of the row crops they seek to displace are also an important consideration. Even high yielding crops, such as miscanthus, are likely to be economically attractive only in some locations in the Midwest given the high yields of corn and soybean in the region.