Comparative life cycle assessment of the integrated generation of solid fuel and biogas from biomass (IFBB) and whole crop digestion (WCD) in Germany

Today’s bioenergy systems are very different in cultivation, conservation, conversion of the biomass as well as in the form of the final energy. The assessment of bioenergy systems concerning environmental impacts is increasingly up for discussion. Future challenges will be the development of procedures which reconcile high-yielding and efficient approaches with environment friendly production. Against this background the system of Integrated Generation of Solid Fuel and Biogas from Biomass (IFBB) was suggested to increase net energy yields over a wide range of energy crops in order to obtain a higher biodiversity in energy crop cultivation. In the IFBB procedure the ensiled biomass is separated into a liquid phase for biogas production and into a solid fraction for combustion. ork is aimed at the assessment of the IFBB system in comparison to whole crop digestion (WCD). The assessment is based on crop production in a double-cropping system where winter rye and maize are grown subsequently within one growing season. The main parameters investigated are the efficiency of the whole process, primary energy and greenhouse gas savings as well as potentials of acidification and eutrophication according to principles of Life Cycle Assessment. The calculation of energy efficiency shows a superiority of the IFBB system due to a mainly thermal use of the biomass. Savings of fossil primary energy average at a similar level, whereas greenhouse gas savings are slightly higher for WCD. Investigations on acidification and eutrophication show that both bioenergy systems caused higher emissions compared to the fossil-based reference technique.