Repeatability of a laboratory batch method to determine the specific biogas and methane yields

To evaluate the potential of a substrate to form biogas, it is essential to have a fast and accurate method to determine the specific biogas yield (SBY) and specific methane yield (SMY). The objectives of this study were to assess the repeatability of the Hohenheim Biogas Yield Test (HBT) and to assess the influence of sample withdrawal and preparation on the determined SBY and SMY. Samples of dried maize whole plant material, maize cob, and power fodder, with up to six different treatments for preparation, were analyzed for their SBY and SMY using a discontinuous fermentation assay. Further, chemical composition of the whole plant sample was examined and different calculation models were used to predict SMY. The HBT showed a strong repeatability and a high precision for SMY. Two of the tested chemical composition models showed a satisfactory performance compared to the mean of the measured methane values. Significant effects caused by different sample treatments could be observed.