The generation of energy from semi-natural, high diversity grasslands can be an alternative to the abandonment of such sites, which is a noticeable trend in many developed countries. One possible path of converting grassland biomass to energy is through anaerobic digestion of silages. Little is known about the linkages between increasing plant diversity and the effects on energy production. In this study, changes in energy content (substrate-specific methane yield) as well as the respective energy yields (methane yield per hectare), along a well defined diversity gradient (1-60 species) and across different combinations of functional groups (legumes, small herbs, tall herbs and grasses), were investigated. The substrate-specific methane yields were estimated through the concentrations of the Weende constituents and their documented digestibility values. It was found that increasing diversity had a negative effect on energy content, while the energy yield increased due to a strong increase in biomass with increasing diversity. Energy content and yield varied between functional group monocultures and all functional group mixtures.
