New research in Biomass and Bioenergy finds that turning common cover crops into biofuels could slash greenhouse gas emissions by up to 70 %, offering Washington farmers a dual benefit: healthier soils and a path toward cleaner transportation fuels.
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The researchers assessed the environmental impacts, economic viability, and technical performance of converting crops into transportation fuels, with an emphasis on life-cycle analysis (LCA) and techno-economic factors. They aim to determine whether cover crops can serve as a sustainable biomass source that aligns with broader efforts to develop renewable fuels, reducing reliance on fossil fuels and minimizing ecological footprints.
Biomass Sources for Renewable Energy Production
Agricultural landscapes in Washington State and similar regions are increasingly exploring underutilized biomass sources for renewable energy production. Cover crops such as soybean hay, sudangrass, hairy vetch, and triticale are common in these areas due to their soil-improving properties, but their biomass also offers a promising avenue for biofuel feedstock.
Prior research highlights the feasibility of hydrothermal liquefaction, a process that converts wet biomass into biocrude oil under high pressure and temperature without the need for drying, thereby reducing energy inputs. This process produces biocrude that can be upgraded into drop-in transportation fuels with comparable properties to fossil fuels. The environmental benefits of using non-food biomass are well recognized, including the avoidance of food versus fuel conflicts and the promotion of carbon sequestration.
The Current Study
The authors adopted a comprehensive approach combining laboratory data, process modeling, and life-cycle assessment techniques to evaluate the potential of cover crop-derived biofuels. They first characterized the biomass composition of various cover crops - soybean hay, sudangrass, hairy vetch, and triticale - by analyzing their carbohydrate, lipid, protein, lignin, and ash content.
Empirical models established from decades of experimental data were used to predict the yields of biocrude during HTL based on the biomass composition, with lipids identified as the most influential component in determining biocrude yield. These models, validated by prior research, provided estimates of process output based on the biomass's chemical makeup.
The techno-economic analysis (TEA) framework was then constructed to simulate costs and revenues associated with the production process, accounting for farming practices, crop yields, transportation logistics, and processing costs. They evaluated different scenarios varying in crop type, planting, harvesting, and feedstock transportation distances, typically set at 100 miles but explored between 50 and 200 miles to gauge the influence of logistics on environmental impacts. The life-cycle analysis encompassed greenhouse gas emissions (carbon intensity), fossil energy consumption, water footprint, and other environmental indicators, offering a quantitative assessment of the entire biofuel pathway from crop cultivation to fuel deployment.
Results and Discussion
The modeling and analysis revealed that converting cover crops into biofuels via HTL offers substantial environmental benefits over conventional fossil fuels. Specifically, the life-cycle greenhouse gas emissions, measured as carbon intensity, showed reductions ranging from approximately 65 % to over 70 % across various scenarios in Washington State, including different planting conditions and crop types. The most significant contributors to the overall emissions profile were related to crop cultivation - particularly fertilizer application, which accounts for a large share of soil N2O emissions - and transportation. For instance, transportation distances of 100 miles notably impacted emissions, with doubling that distance increasing the carbon footprint by nearly 50 %, underscoring the importance of efficient logistics.
The analysis also highlighted the dominant role of the biomass conversion process, where more than 60 % reduction in fossil energy consumption was observed compared to traditional fuel pathways, with significant savings in water footprint, reducing impacts by approximately 58 % to 66 %. Though the contribution of cover crop production to environmental impacts varied depending on crop type, fertilizer use, and transportation, the study found that the utilization of hairy vetch and other legumes minimized fertilizer-driven emissions, thereby improving sustainability metrics.
Incorporating blended feedstocks, such as mixing cover crops with wastewater sludge, enhanced the conversion efficiency and environmental performance, achieving reduction levels exceeding 70 % in greenhouse gas emissions relative to fossil fuels. The variability in impact reduction across different compositions was primarily linked to the biomass's chemical makeup - higher lipid content led to more biocrude and thus greater environmental benefits.
Turning Cover Crops into Biofuels Offers Promising Future
This comprehensive study demonstrates that converting cover crops into biofuels through hydrothermal liquefaction offers a promising pathway for sustainable energy production in Washington State.
While operational and logistical challenges remain, including optimizing supply chain logistics and ensuring economic competitiveness, the findings bolster the case for harnessing biomass from cover crops to support renewable transportation fuels.
The results advocate for policy measures, technological innovations, and agricultural management strategies that promote localized feedstock collection and efficient processing. The potential to contribute significantly to greenhouse gas mitigation and resource conservation positions this pathway as a vital component of a broader transition toward sustainable energy systems. Overall, the research underscores the feasibility and environmental merits of using cover crops as a renewable biomass source for biofuel production, aligning with global efforts to reduce carbon emissions and foster sustainable development within agricultural landscapes.
Journal Reference
Santosa D. M., Potter T., et al. (2025). Unlocking the biofuel power of cover crop in Washington State: Enhancing potential through hydrothermal liquefaction. Biomass and Bioenergy, 203, 108311. DOI: 10.1016/j.biombioe.2025.108311, https://www.sciencedirect.com/science/article/pii/S0961953425007226