Emissions of greenhouse gases from fossil fuels is one of the most prominent environmental perturbations caused by humans. Bioenergy sources can provide a carbon neutral or carbon negative fuel source, but emissions are usually positive after accounting for a full life-cycle of impacts. Life-cycle analysis quantifies the energy use and greenhouse gas emissions associated with a product throughout all stages of production. We quantified the life-cycle inventory differences that result from coproduction of anaerobic digestion and biomass crop production. The process of anaerobic digestion can be used to produce both biogas and fertilizers, which can in turn supplement nutrient requirements of biomass crops in place of environmentally costly fertilizers. Biomass crop residues can be added to anaerobic digestion to stabilize conditions and increase biogas quality.
Results/Conclusions
The benefits of coproduction for anaerobic digestion and bioenergy crops are primarily the result of improved resource use efficiency. The sharing of waste streams should reduce the cost of running a system and increase the return on investment. Baseline life cycle emissions were determined for sorghum, miscanthus, and anaerobic digestion. A new computational tool will be introduced to assess life cycle inventory savings from various coproduction systems. This work resolves how biomass crop coproduction with anaerobic digestion affects the life-cycle emissions of both bioenergy and bioproducts.