How is life cycle assessment (LCA) applied to evaluate biofuel sustainability?

Life cycle assessment evaluates environmental impacts of biofuels across their entire lifecycle. Phases: Goal and scope definition - set system boundaries (cradle-to-gate, cradle-to-grave, well-to-wheels); define functional unit (MJ energy, km traveled). Life cycle inventory - quantify inputs (land, water, energy, fertilizers) and outputs (emissions, co-products) for all stages: feedstock cultivation, harvesting, transport, conversion, distribution, and combustion. Impact assessment - translate inventory to environmental impacts: global warming potential (GHG emissions), eutrophication, acidification, water use, land use change. Interpretation - identify hotspots, sensitivity analysis, comparison with fossil fuels. Key considerations for biofuels: Direct and indirect land use change - converting forests/grasslands releases stored carbon. Co-product allocation - credit for animal feed (DDGS), electricity from bagasse. Temporal dynamics - carbon payback time for perennial crops. Regional variability - different impacts by location. Results influence policy (RFS2 lifecycle GHG thresholds) and guide improvement efforts.