Biogas Production From Switchgrass: Issues of Energy Efficiency

Abstract

Installation and generation of renewable energy sources is a very fast growing area in the world during the past decade due to the resources depletion and climate change. Growing interest in the use of biomass for energy purpose has created demand for high biomass yielding crops. Therefore, C4 grass species, such as switchgrass (Panicum virgatum), should become strategic agricultural crops. Switchgrass cultivation in Europe for bioenergy is new. Biogas production of switchgrass provides an outstanding opportunity to convert biomass into energy. The objective of this study is to examine possibilities of the biogas production from switchgrass silage and evaluate energy efficiency. The experiments were performed under mesophilic conditions (38±1oC) using AMPTS laboratory digesters. Grass was chopped to 3-5 mm just after harvesting and ensiled in a 3 l jars for 120 days. After the evaluation of the biogas yield and energy conversion efficiency performance it was found that switchgrass biomass is suitable as raw material for the production of biogas. The biomethane yield of selected plants ranged from 189 to 243 l CH4/kg dry organic matter.The energy potential from switchgrass legume can reach 31,2 - 36,7 GJ/ha. Direct and indirect energy input for switchgrass biomass production was 5,53 - 5,71 GJ/ha and for biogas production – 6,1 GJ/ha. The energy efficiency factor for biogas production from switchgrass silage was in the range of 2.39 - 3.15.