Integration of Green Biorefineries and Pyrolysis: Climate Footprint Assessment of Co-Management of Grass Pulp and Cattle Manure in Denmark

Abstract Grass production with subsequent green biorefining into value-added products is developing fast in Denmark. Environmental assessments indicate promising performance, two full-scale plants are in operation, and R&D-focus is substantial. Currently, the fibrous pulp fraction from grass refining is used to boost manure digestion in biogas plants. Recently, it has been investigated experimentally if the grass pulp is suitable for pyrolysis, and previous work has shown its usefulness as cattle feed. In this study, the climate footprint of grass pulp management in both single-use and cascade use systems encompassing anaerobic digestion, cattle feed, and thermal pyrolysis is investigated. A total of seven approaches for grass pulp and manure co-management are modelled, and differences in GHG emissions are compared. Results show that all investigated management options offer substantial climate benefits ranging from around 700 to almost 1300 kg CO 2 e pr ton grass pulp solids co-managed with cattle manure in a GWP100 perspective. Integrating biomass pyrolysis in grass pulp and cattle manure co-management systems encompassing fodder use and/or anaerobic digestion is found to have substantial climate benefits in all cases, averaging at a 30% higher climate benefit from co-management of these resources.