Agro-ecosystem modeling can aid in the optimization of biomass feedstock supply

The use of life cycle assessment (LCA) as a comprehensive tool to assess environmental impacts of bioenergies is recommended. Nevertheless, several methodological points remain under debate, particularly regarding the feedstock production step, which is a key stage of bioenergy chains. The present work focuses on field emissions during feedstock production, improving assessment methods by the use of process‐based models. To do so, a real bioenergy chain, the local feedstock supply for a boiler located in northern France, was studied. The LCA compares flax shives, (the reference) with four other biomass sources: Miscanthus, cereal straw, linseed straw, and triticale as a whole plant. Six feedstock supply scenarios were also compared. The study aimed to test a new LCA methodology for agricultural chains by integrating local characteristics (such as climate, soil, and crop management data) and using models to estimate field dynamics of pesticide emissions and soil organic carbon (SOC). Results showed that flax shives and linseed straw had the lowest impacts, except for global warming: as a consequence, supply scenarios with the largest share of flax shives had the lowest impacts. For all selected impact categories, transportation and fertilization were the main contributors. SOC dynamics led to high C sequestration level (e.g. with Miscanthus) or to high CO 2 emissions level (e.g. with flax shives), thus significantly influencing the global warming impact. Sensitivity analysis showed a large influence of allocation method (economic or mass‐based). This study demonstrated the relevance of integrating simulation models using local data in agricultural LCAs, especially for dynamics of SOC and pesticide from fields. Moreover, this work brought scientific elements to support the choice of flax shives as the main biomass feedstock, and the ranking of the other sources as alternative biomass supplies for the boiler.

Impact of feedstock, land use change, and soil organic carbon on energy and greenhouse gas performance of biomass cogeneration technologies

The Biomass Research and Development Technical Advisory Committee established a goal that biomass will supply 5% of the nation’s power, 20% of its transportation fuels, and 25% of its chemicals by 2030. These combined goals are approximately equivalent to 30% of the country’s current petroleum consumption. The benefits of a robust biorefinery industry supplying this amount of domestically produced power, fuels, and products are considerable, including decreased demand for imported oil, revenue to the depressed agricultural industry, and revitalized rural economies. A consistent supply of highquality, low-cost feedstock is vital to achieving this goal. This biomass roadmap defines the research and development (R&D) path to supplying the feedstock needs of the biorefinery and to achieving the important national goals set for biomass. To meet these goals, the biorefinery industry must be more sustainable than the systems it will replace. Sustainability hinges on the economic profitability of all participants, on environmental impact of every step in the process, and on social impact of the product and its production. In early 2003, a series of colloquies were held to define and prioritize the R&D needs for supplying feedstock to the biorefinery in a sustainable manner. These colloquies involved participants and stakeholders inmore » the feedstock supply chain, including growers, transporters, equipment manufacturers, and processors as well as environmental groups and others with a vested interest in ensuring the sustainability of the biorefinery. From this series of colloquies, four high-level strategic goals were set for the feedstock area: • Biomass Availability – By 2030, 1 billion dry tons of lignocellulosic feedstock is needed annually to achieve the power, fuel, and chemical production goals set by the Biomass Research and Development Technology Advisory Production Committee • Sustainability – Production and use of the 1 billion dry tons annually must be accomplished in a sustainable manner • Feedstock Infrastructure – An integrated feedstock supply system must be developed and implemented that can serve the feedstock needs of the biorefinery at the cost, quality, and consistency of the set targets • System Profitability – Economic profitability and sustainability need to be ensured for all required participants in the feedstock supply system. For each step in the biomass supply process—production, harvesting and collection, storage, preprocessing, system integration, and transportation—this roadmap addresses the current technical situations, performance targets, technical barriers, R&D needs, and R&D priorities to overcome technical barriers and achieve performance targets. Crop residue biomass is an attractive starting feedstock, which shows the best near-term promise as a biorefinery feedstock. Because crop residue is a by-product of grain production, it is an abundant, underutilized, and low cost biomass resource. Corn stover and cereal straw are the two most abundant crop residues available in the United States. Therefore, this roadmap focuses primarily on the R&D needed for using these biomass sources as viable biorefinery feedstocks. However, achieving the goal of 1 billion dry tons of lignocellulosic feedstock will require the use of other biomass sources such as dedicated energy crops. In the long term, the R&D needs identified in this roadmap will need to accommodate these other sources of biomass as well.« less

A comparison of methods to quantify greenhouse gas emissions of cropping systems in LCA

Climate change mitigation is the most important driving force for bioenergy development. Consequently, the environmental design of bioenergy value chains should address the actual savings of both primary energy demand and greenhouse gases (GHG) emissions. According to the EU Renewable Energy Directive (2009/28/EC), no direct impacts and no GHG emissions should be attributed to crop residues (like cereal straws) when they are removed from agricultural land for the purpose of bioenergy utilisation. The carbon neutral assumption applied to crop residues is, however, a rough simplification. Crop residues, indeed, should not be viewed simply as a waste to be disposed, because they play a critical role in sustaining soil organic matter and therefore have an inherent C-capturing value. Moreover, considering straws as an energy feedstock, its status of co-product is clearly recognised and its availability could be obtained according to different cropping systems, corresponding to different primary energy costs and GHG emissions. This paper highlights some hidden features in the assessment of agricultural energy and carbon balance, still very difficult to be detected and accounted for. Although they are frequently disregarded, these features (such as long term dynamic trend of soil organic carbon and annual nitrous oxide emissions from the soil) should be carefully considered in assembling the energy and emission balance. By using a crop simulation model, the long-term soil organic matter and annual N2O soil emissions were estimated. Consequently, a comprehensive energy and GHG balance was determined in accordance with the life cycle assessment methodology. Contrasting methods of straw management and wheat cultivation were compared: straw retention vs removal from the soil; conventional vs conservation tillage; wheat cropping system as a single-crop or in rotation. The resulting carbon footprint of straws has different magnitudes with respect to the several experimental conditions. By selecting the best agricultural practices, energy from straw can be optimally coupled with grain productions, without detrimental effects on soil fertility. An improved and specifically tailored cropping system is designed to obtain an optimal trade-off.

Life cycle assessment of greenhouse gas emissions for various feedstocks-based biochars as soil amendment

Biochemical production of bioenergy from agricultural crops and residue in Iran

Bioenergy from perennial grasses mitigates climate change via displacing fossil fuels and storing atmospheric CO2 belowground as soil carbon. Here, we conduct a critical review to examine whether increasing plant diversity in bioenergy grassland systems can further increase their climate change mitigation potential. We find that compared with highly productive monocultures, diverse mixtures tend to produce as great or greater yields. In particular, there is strong evidence that legume addition improves yield, in some cases equivalent to mineral nitrogen fertilization at 33–150 kg per ha. Plant diversity can also promote soil carbon storage in the long term, reduce soil N2O emissions by 30%–40%, and suppress weed invasion, hence reducing herbicide use. These potential benefits of plant diversity translate to 50%–65% greater life-cycle greenhouse gas savings for biofuels from more diverse grassland biomass grown on degraded soils. In addition, there is growing evidence that plant diversity can accelerate land restoration. Bioenergy from perennial grasses mitigates climate change via displacing fossil fuels and storing atmospheric CO2 belowground as soil carbon. Here, we conduct a critical review to examine whether increasing plant diversity in bioenergy grassland systems can further increase their climate change mitigation potential. We find that compared with highly productive monocultures, diverse mixtures tend to produce as great or greater yields. In particular, there is strong evidence that legume addition improves yield, in some cases equivalent to mineral nitrogen fertilization at 33–150 kg per ha. Plant diversity can also promote soil carbon storage in the long term, reduce soil N2O emissions by 30%–40%, and suppress weed invasion, hence reducing herbicide use. These potential benefits of plant diversity translate to 50%–65% greater life-cycle greenhouse gas savings for biofuels from more diverse grassland biomass grown on degraded soils. In addition, there is growing evidence that plant diversity can accelerate land restoration.

Organic matter content increases in soil with no-tilled permanent raised beds (PBs) compared with soil with conventionally tilled beds (CBs), and this might affect greenhouse gas (GHG) emissions. Greenhouse gas (CO2, N2O, and CH4) emissions were measured from PBs, from which crop residue was either removed or retained and from CBs where crop residue was retained. The CO2 emission was not affected by tillage, but CH4 and N2O emissions were lower in PBs when residue was retained than in CBs. Removing crop residue from PBs reduced CO2 emissions compared with when it was retained, but it had no effect on N2O and CH4 emissions. The global warming potential (GWP) of GHG emissions was higher in CBs (801 kg CO2/ha/year) than in PBs (517 kg CO2/ha/year) with crop-residue retention, but more C was sequestered in the 0–60 cm soil layer in PBs (83.4 Mg C/ha) than in CBs (79.2 Mg C/ha). Crop-residue removal in PBs had little effect on the GWP of GHG compared with PBs with crop residue retained, but less C was sequestered in the latter (63.1 Mg C/ha). Net GWP (considering soil C sequestration, GHG emissions, fuel used, glyphosate application, fertilizer and seed production) was lower in CBs with crop-residue retention (1062 kg CO2/ha/year) than in PBs with crop-residue removal (6,120 kg CO2/ha/year), but it was larger than in PBs with crop-residue retention (−681 kg CO2/ha/year). We found that reduced tillage when beds were made permanent and crop-residue retention greatly reduced net GWP compared with when beds were tilled and remade each year.We found that retention of crop residue in PBs increased the emission of CO2 compared with where it was removed, but tillage did not affect fluxes of CO2. Emission of CH4 and N2O was larger from CBs than from PBs, but crop-residue management in PBs had no significant effect on fluxes of CH4 and N2O. Concentrations of mineral N were larger in CBs than in PBs, whereas the removal of crop residue from PBs increased mineral N concentration. Soil temperature was higher in CBs than in PBs and in PBs with crop residue retained compared with where it was removed. Soil water was better preserved in PBs than in CBs and in PBs where residue was retained than where it was removed. The higher water content in the PB compared with the CB will favor plant growth during dry spells. However, retaining crop residues in PBs will require sufficient application of inorganic N, as mineral N in soil is lower in PBs than in CBs or PBs with crop residue removed. Limited N availability in PBs with crop residue retained might reduce yields as poor farmers in the central highlands of Mexico apply little or no N fertilizer. Reduced tillage on PBs and crop-residue retention strongly reduced the net GWP of the system compared with the case when beds were remade each year. PBs with residue retention reduced net GWP by 50% compared with CBs with residue retention, but the removal of residues from the PBs more than doubled it.

Feedstocks from lignocellulosic biomass (LCB) include crop residues and dedicated perennial biomass crops. The latter are often considered superior in terms of climate change mitigation potential. Uncertainty remains over their availability as feedstocks for biomass provision and the net greenhouse gas emissions (GHG) during crop production. Our objective was to assess the optimal land allocation to wheat and Miscanthus in a specific case study located in England, to increase biomass availability, improve the carbon balance (and reduce the consequent GHG emissions), and minimally constrain grain production losses from wheat. Using soil and climate variables for a catchment in east England, biomass yields and direct nitrogen emissions were simulated with validated process‐based models. A ‘Field to up‐stream factory gate’ life‐cycle assessment was conducted to estimate indirect management‐related GHG emissions. Results show that feedstock supply from wheat straw can be supplemented beneficially with LCB from Miscanthus grown on selected low‐quality soils. In our study, 8% of the less productive arable land area was dedicated to Miscanthus, increasing total LCB provision by about 150%, with a 52% reduction in GHG emission per ton LCB delivered and only a minor effect on wheat grain production (−3%). In conclusion, even without considering the likely carbon sequestration in impoverished soils, agriculture should embrace the opportunities to provide the bioeconomy with LCB from dedicated, perennial crops. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Climate change and energy security concerns have driven the development of policies that encourage bioenergy production. Meeting EU targets for the consumption of transport fuels from bioenergy by 2020 will require a large increase in the production of bioenergy feedstock. Initially an increase in ‘first generation’ biofuels was observed, however ‘food competition’ concerns have generated interest in second generation biofuels (SGBs). These SGBs can be produced from co-products (e.g. cereal straw) or energy crops (e.g. miscanthus), with the former largely negating food competition concerns. In order to assess the sustainability of feedstock supply for SGBs, the financial, environmental and energy costs and benefits of the farm system must be quantified. Previous research has captured financial costs and benefits through linear programming (LP) approaches, whilst environmental and energy metrics have been largely been undertaken within life cycle analysis (LCA) frameworks. Assessing aspects of the financial, environmental and energy sustainability of supplying co-product second generation biofuel (CPSGB) feedstocks at the farm level requires a framework that permits the trade-offs between these objectives to be quantified and understood. The development of a modelling framework for Managing Energy and Emissions Trade-Offs in Agriculture (MEETA Model) that combines bio-economic process modelling and LCA is presented together with input data parameters obtained from literature and industry sources. The MEETA model quantifies arable farm inputs and outputs in terms of financial, energy and emissions results. The model explicitly captures fertiliser: crop-yield relationships, plus the incorporation of straw or removal for sale, with associated nutrient impacts of incorporation/removal on the following crop in the rotation. Key results of crop-mix, machinery use, greenhouse gas (GHG) emissions per kg of crop product and energy use per hectare are in line with previous research and industry survey findings. Results show that the gross margin – energy trade-off is £36GJ−1, representing the gross margin forgone by maximising net farm energy cf. maximising farm gross margin. The gross margin–GHG emission trade-off is £0.15kg−1 CO2 eq, representing the gross margin forgone per kg of CO2 eq reduced when GHG emissions are minimised cf. maximising farm gross margin. The energy–GHG emission trade-off is 0.03GJkg−1CO2 eq quantifying the reduction in net energy from the farm system per kg of CO2 eq reduced when minimising GHG emissions cf. maximising net farm energy. When both farm gross margin and net farm energy are maximised all the cereal straw is baled for sale. Sensitivity analysis of the model in relation to different prices of cereal straw shows that it becomes financially optimal to incorporate wheat straw at price of £11t−1 for this co-product. Local market conditions for straw and farmer attitudes towards incorporation or sale of straw will impact on the straw price at which farmers will supply this potential bioenergy feedstock and represent important areas for future research.

We examined life cycle environmental and economic implications of two near-term scenarios for converting cellulosic biomass to energy, generating electricity from cofiring biomass in existing coal power plants, and producing ethanol from biomass in stand-alone facilities in Ontario, Canada. The study inventories near-term bio-mass supply in the province, quantifies environmental metrics associated with the use of agricultural residues for producing electricity and ethanol, determines the incremental costs of switching from fossil fuels to biomass, and compares the cost-effectiveness of greenhouse gas (GHG) and air pollutant emissions abatement achieved through the use of the bioenergy. Implementing a biomass cofiring rate of 10% in existing coal-fired power plants would reduce annual GHG emissions by 2.3 million metric tons (t) of CO2 equivalent (7% of the province’s coal power plant emissions). The substitution of gasoline with ethanol/gasoline blends would reduce annual provincial light-duty vehicle fleet emissions between 1.3 and 2.5 million t of CO2 equivalent (3.5–7% of fleet emissions). If biomass sources other than agricultural residues were used, additional emissions reductions could be realized. At current crude oil prices ($70/barrel) and levels of technology development of the bioenergy alternatives, the biomass electricity cofiring scenario analyzed is more cost-effective for mitigating GHG emissions ($22/t of CO2 equivalent for a 10% cofiring rate) than the stand-alone ethanol production scenario ($92/t of CO2 equivalent). The economics of biomass cofiring benefits from existing capital, whereas the cellulosic ethanol scenario does not. Notwithstanding this result, there are several factors that increase the attractiveness of ethanol. These include uncertainty in crude oil prices, potential for marked improvements in cellulosic ethanol technology and economics, the province’s commitment to 5% ethanol content in gasoline, the possibility of ethanol production benefiting from existing capital, and there being few alternatives for moderate-to-large-scale GHG emissions reductions in the transportation sector.

Commercial‐scale liquid‐biofuel production utilizing forest‐based biomass would require feedstock supply from a large geographical area. Feedstock composition, supply chains' arrangements, and the resulting greenhouse gas (GHG) emissions are location dependent, and case‐specific assessments are needed if one is to guarantee the fulfillment of GHG reduction requirements by a specific biofuel product. This work assessed GHG emissions derived from the feedstock supply and transportation chain to three possible commercial‐scale biodiesel plant locations in Finland (Rauma, Porvoo, and Kemi) at site‐specific level. The supply of 7.2 PJ yr−1 (approximately 1 million m3solid) of forest biomass (harvesting residues, stumps, and small‐diameter energy wood) was assessed for each location, including four distinct scenarios for truck and railway transportation and two scenarios for biomass availability. Biomass availability and transportation‐network assessments were conducted through utilization of geographical information system methods, and the GHG emissions were assessed by means of life‐cycle assessment. The results showed that the GHG emissions of the supply chains can be effectively reduced through use of railway transportation from distant supply areas. Furthermore, even though the supply‐chain GHG emissions differed by up to 30% between the case‐study locations, the GHG emissions of the feedstock supply chain, from roadside stores of uncomminuted biomass to comminuted biomass delivered to the plants, were relatively low (2–4%) when compared with the GHG emissions of fossil diesel.

The possibility to produce biofuels from different agricultural feedstocks has raised huge interest during the last decade. This interest can be related to the parallel increase in fossil oil prices and the growing awareness about the need to reduce greenhouse gas (GHG) emissions worldwide. Biofuels are also seen by many governments as a means to contribute to the diversification of energy supply and sustain agricultural incomes by creating new outlets for several agricultural products, notably cereals, vegetable oils and sugar plants. Ambitious public policies aiming at developing biofuel production and consumption in replacement of fossil fuels used in road transport have thus been set up all around the world. Policy instrumentation varies depending on the country. Altogether, policies aim at encouraging the supply of agricultural feedstocks used as raw materials for biofuels, the industrial production of biofuels and/or their domestic consumption by setting blending mandates and/or subsidizing biofuel use. A period of keen interest was witnessed in the first years of the current decade which has led many countries such as the United States (US), the European Union (EU), Brazil and also several countries in Asia to set very ambitious policy targets for biofuels. But the boom in agricultural prices and the following food crisis in 2007-2008 have severely depreciated the public image of biofuels because of their potential negative impact on world food security in a context of land scarcity. Simultaneously, the issue of the impact of biofuel crops on GHG emissions due to induced land use changes has progressively emerged; it is today a matter of considerable controversy. In addition, concerns have risen about the relatively low energy yield of current biofuels and the budget cost of public policies aiming at encouraging their development. Initially, the debate about these interrelated issues has been confined to a narrow audience, mainly in the academic sphere. However, over the past three years, many stakeholders including environmental organizations, farmers’ unions, the media, etc., have shown a considerable interest in the matter leading to a very lively debate worldwide, and more particularly in the EU. First-generation (1G) biofuels produced from traditional food and feed crops are increasingly criticized for their adverse impacts on world food security and GHG emissions, essentially because they can divert land from food and feed, as well as land forest uses. As a result, hopes turn to a quick development of second-generation (2G) biofuels produced from various sources of biomass that do not directly compete with food and feed crops and,

This review paper synthesizes the current understanding of greenhouse gas (GHG) emissions from field cropping systems. It examines the key factors influencing GHG emissions, including crop type, management practices, and soil conditions. The review highlights the variability in GHG emissions across different cropping systems. Conventional tillage systems generally emit higher levels of carbon dioxide (CO2) and nitrous oxide (N2O) than no-till or reduced tillage systems. Crop rotation, cover cropping, and residue management can significantly reduce GHG emissions by improving soil carbon sequestration and reducing nitrogen fertilizer requirements. The paper also discusses the challenges and opportunities for mitigating GHG emissions in field cropping systems. Precision agriculture techniques, such as variable rate application of fertilizers and water, can optimize crop production while minimizing environmental impacts. Agroforestry systems, which integrate trees and crops, offer the potential for carbon sequestration and reducing N2O emissions. This review provides insights into the latest research on GHG emissions from field cropping systems and identifies areas for further study. It emphasizes the importance of adopting sustainable management practices to reduce GHG emissions and enhance the environmental sustainability of agricultural systems.