Comparative Life Cycle Assessment of Agro-Industrial Residues: Environmental Impacts of Grape Marc and Brewer’s Spent Grain Combustion

Abstract Agro-industrial residues such as grape marc (GM) and brewer’s spent grain (BSG) represent a waste management challenge and an opportunity for renewable energy production. This study presents a Life Cycle Assessment (LCA) of GM and BSG combustion for thermal energy generation, applying the ReCiPe 2016 method at midpoint and endpoint levels in openLCA. The functional unit was 1 GJ of thermal energy, with harmonized system boundaries enabling direct comparison. Results show GM outperforms BSG. At the midpoint level, GM exhibited 76.3% lower global warming potential (21.70 vs. 98.51 kg CO₂-eq/GJ), 74.6% lower terrestrial ecotoxicity, and 62.2% lower fossil resource use, alongside reduced NOₓ, SO₂, and PM emissions. Endpoint analysis confirmed GM’s advantages, with 81.4% lower ecosystem quality damage, 64.9% lower human health impacts, and 77.9% lower natural resource depletion. Key drivers of environmental burden included moisture content, electricity demand for drying, and transport distance. Recommended optimization strategies involve reducing feedstock moisture, integrating renewable electricity into pre-treatment, and applying Best Available Techniques for emission control. GM emerges as a more sustainable local biofuel, supporting circular economy objectives and contributing to EU decarbonization and waste valorization goals.