Herbage from extensively managed grasslands for biogas production: methane yield of stands and individual species

The experiment aimed at identifying the capacity of herbage from species-rich, extensively managed meadows to serve as a substrate for biogas production. We determined methane yield of Arrhenatherum-dominated (approx. 26 species per 9 m2) and Lolium-dominated swards (approx. 15 species per 9 m2) using the Hohenheim biogas yield test. Both sward types received two levels of fertilizer application (0 and 80 kg N ha-1) and were cut at three harvest dates (mid-May, late May, and early June). In addition, we determined the substrate-specific methane yield of a range of individual grass species which are common in extensively managed grassland, but which have so far received little attention for their potential for biogas production: Arrhenatherum elatius, Trisetum flavescens, Holcus lanatus, Festuca rubra and Dactylis glomerata. We compared these with methane yields obtained from Lolium perenne. Our results revealed values of substrate-specific methane yield comparable to those of L. perenne for some species common in species-rich stands. Substrate-specific methane yield of the two sward types was similar; however, dry matter yield of the Arrhenatherum-dominated stands was significantly lower than that of Lolium-dominated stands, which resulted in comparatively lower methane yield per hectare of species-rich stands.