Environmental comparison of different technical possibilities for biogas use

In this study different possibilities of utilization of biogas were considered, modeled and evaluated from the environmental point of view, by applying a Life Cycle Assessment (LCA) approach. The considered possibilities of utilization are: direct use in internal combustion engines for combined heat and power production; direct use in molten carbonate fuel cell for combined heat and power production; upgrading of biogas to biomethane and injecting into the natural gas grid. Due to their high energy conversion efficiency, fuel cell use resulted the solution with the best environmental performances, followed by internal combustion engines and the by biomethane production. However, both fuel cell and internal combustion engine are able to provide such good scores when both electric and thermal energy are exploited, while when heat is not recovered, the differences with respect to the biomethane case are strongly reduced.