Life Cycle Assessment of CO2, Rumen, and Biological Biomass Pretreatment Methods for Biomethane Production

This study evaluates the environmental impacts of different biomass pretreatment methods used for biomethane production using a life cycle assessment (LCA) approach. The three examined pretreatment technologies—CO2 injection, rumen fluid, and biological products—were applied to manure, alfalfa biomass, and winter wheat straw. The results indicate that cow manure pretreatment with CO2 increases fossil fuel depletion from 0.37 MJ/m3 to 17.31 MJ/m3 and increasing global warming potential by 1.08 kg CO2 eq/m3. Rumen fluid pretreatment moderately improves fossil fuel conservation but raises acidification (from 1.57 × 10−4 kg SO2 eq/m3 to 2.49 × 10−4 kg SO2 eq/m3) and eutrophication (from 2.67 × 10−5 kg PO4 eq/m3 to 5.3 × 10−5 kg PO4 eq/m3). Winter wheat straw CO2 pretreatment demonstrates the most favorable environmental profile, reducing human toxicity (from 0.1 kg 1,4-DB eq/m3 to 0.0058 kg 1,4-DB eq/m3) and minimizing fossil fuel depletion. The environmental trade-offs of biomethane production suggest that optimizing pretreatment strategies is essential to ensuring sustainable production.