Effect of Steam Explosion Pretreatment on the Specific Methane Yield of Miscanthus x giganteus

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 effi cient pretreatment methods for lignocellulosic biomass is steam explosion. Th is includes heating the biomass at high temperature values, followed by mechanical disruption of the biomass fi bres by a rapid pressure drop. Th e objective of this study is to analyse the eff ect of the steam explosion pretreatment on the specifi c 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. Th e miscanthus was mixed with water and heated up to the desired temperature. Aft er a defi ned pretreatment time the pressure in the reaction vessel was reduced rapidly, which caused the liquid water to vaporize immediately. Th e material was cooled down in a fl ushing 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 specifi c methane yield was done in triplicate using batch tests according to VDI 4630. Th e material was inoculated with the liquid fermentation residue of a biogas plant. Th e produced gas was collected in eudiometers and then analysed for the CH4 and CO2 content.