The carbon balance of green biorefineries is significantly impacted by the processing of fibrous side streams

Green biorefineries that produce protein feed from grasses or legumes generate fibrous side streams which can be used to produce biobased products. An analysis was conducted on the net greenhouse gas emissions of five products: (1) transportation fuel (biomethane); (2–3) bioplastics with either a short or long service life; (4) biochar used as a soil amendment; and (5) cellulose products intended for single-use purposes. Analyses consider three land-use scenarios for Sweden, representing different ley (temporary perennial grass-clover crops) cultivation strategies, and include supply-chain emissions, carbon storage in soils and biobased products, and substitution effects from the use of biobased products and N recycling to soils. Biochar consistently provided the largest emission savings, reaching −39 to −200 t CO₂-eq ha −1 over 100 years depending on scenario. The transportation fuel option matched biochar in the short term, reaching −39 to −133 t CO₂-eq ha −1 by year 100. Long-lived bioplastics reached −97 t CO₂-eq ha −1 , whereas cellulose products and short-lived plastics reached −97 and −45 t CO₂-eq ha −1 by year 100 in the most favorable scenario. Carbon storage and fossil fuel substitution were the most important mitigation levers. In a scenario with expansion of ley cultivation constrained by farmers' preferences, the analyzed options could contribute 10% of the emissions reduction needed for Sweden to meet its 2045 climate target. For the agriculture and LULUCF sectors, some options have an emissions reduction potential exceeding the sectoral target, highlighting that the treatment of residues in green biorefineries can have a significant impact on climate outcomes. • Climate benefits of products made from fibrous residues in green biorefineries • Feedstock derived from perennial grass-clover crops • Biochar scores best, followed by transportation fuel and long-life bioplastics • Main factors: size and longevity of carbon storage, and fossil fuel substitution • Deployment scenario indicates significant contribution to Sweden's climate targets.