Assessing the carbon footprint of leaf protein concentrate and biomethane from organic multispecies grasslands

Advancing the circular bioeconomy requires climate-friendly valorization of locally available biomass. Organic multispecies grasslands provide multiple outputs, including leaf protein concentrate (LPC) for feed and biogas for energy, while supporting biodiversity, weed suppression, and carbon sequestration.

This study assessed the climate impacts of Protein, Pollinator, and Energy grassland mixtures under different cutting regimes using life cycle assessment (LCA) with the ReCiPe 2016 method, applying both economic allocation and system expansion approaches. The cradle-to-gate system boundary included grassland cultivation, transport, and processing in the biorefinery. Grassland carbon footprints were low, roughly 50–100 kg CO₂ eq per ton of dry matter. LPC from four-cut grass mixtures had a baseline carbon footprint around 1600 kg CO₂ eq per ton DM with no allocation, and reductions possible depending on co-product use. Biogas from energy grass mixtures had a climate impact of roughly 100–400 kg CO₂ eq per 1000 m³.

Climate performance of biorefinery products was strongly influenced by grass yields, protein content, allocation methods, and downstream valorization strategies. These findings highlight the potential of organic multispecies grasslands to provide LPC as a sustainable alternative to soy-based feed and biomethane as a renewable energy source while mitigating climate impacts.