Fueling agriculture from within: The biomethane and hydrogen potential of agricultural residual biomass

Residual biomass from agriculture can be used to produce renewable fuel to reduce emissions and promote energy independence within the sector. This study evaluated the potential of straw and manure to supply agricultural machinery with methane or hydrogen in Sweden. Conversion pathways based on gasification and anaerobic digestion (AD) showed energy yields of up to 6.7 TWh of methane or 3.8 TWh of hydrogen, exceeding the estimated national agricultural machinery fuel demand of 2.8 TWh or 1.4 TWh, respectively. Hydrogen gave a higher degree of regional self-sufficiency due to its higher tank-to-wheel efficiency while the energy potential of methane was higher. Gasification combined with methanation generated the highest energy yield but biomethane from AD showed the highest Energy Return On Investment. Regional analysis highlighted energy surpluses in the south and shortages in the north, mainly due to varying straw availability. Scenario evaluation showed that AD of manure and gasification of straw could exceed the national demand and cover most of the regional demands. Potential surplus energy could be used to further improve the self-sufficiency within the agricultural sector or provide renewable energy to other sectors. Sensitivity analyses showed that most technical pathways maintained positive net balances despite reduced straw volumes, while higher methane potentials improved AD competitiveness relative to gasification. However, cost trade-offs or changes to agricultural nutrient cycles were not assessed, despite their importance to understand system viability. Further work could include modelling heat integration and conducting life cycle and techno-economic assessments to evaluate their practical implementation potential.