Abstract
A highly promising energy crop for biogas production can be Miscanthus x giganteus. It has multiple advantages, which include low soil requirements and the existence of genotypes adapted to dry conditions in comparison to other energy crops. Miscanthus cannot be used in the biogas plant without a pretreatment due to the recalcitrant nature of lignocelluloses. One of the most efficient pretreatment methods for lignocellulosic biomass is steam explosion. This includes heating the biomass at high temperature values, followed by mechanical disruption of the biomass fibres by a rapid pressure drop. The objective of this study is to analyse the effect of the steam explosion pretreatment on the specific biogas and methane production of miscanthus. In addition methane hectare yields are calculated and compared to those of maize. Steam explosion pretreatment was carried out in a laboratory scale facility in Ås, Norway. The miscanthus was mixed with water and heated up to the desired temperature. After a defined pretreatment time the pressure in the reaction vessel was reduced rapidly, which caused the liquid water to vaporize immediately. The material was cooled down in a flushing tank and was then stored at 5°C until further analytical procedures. Pretreatment temperatures were 190°C and 210°C; holding times were 5, 10 and 15 minutes. Determination of the specific methane yield was done in triplicate using batch tests according to VDI 4630. The material was inoculated with the liquid fermentation residue of a biogas plant. The produced gas was collected in eudiometers and then analysed for the CH4 and CO2 content.