Anaerobic Digestion of Cuttings from Grassland in Protected Landscape Areas

Abstract

Orchard meadows are biodiversity hotspots, as the understory often consists of species-rich lowland hay meadows. Due to the low energy density of the grass, it is not suitable as feed, but the energetic utilisation of cuttings from orchard meadows for biogas production could facilitate the protection of these semi-natural grasslands. Here, lowland hay meadows and extensively used orchards were investigated to assess their potential for anaerobic digestion in biogas plants. Aboveground biomass was harvested weekly from three lowland hay meadows differing in conservation statuses and analysed for cell wall components (aNDF, ADF, and ADL), nutritional values (XF, XL, XP), and methane formation potential by anaerobic digestion. Further, orchard meadows were harvested twice during summer and analysed in the same way. Specific methane yield decreased linearly with cutting dates from 0.325 m3 kg−1(oDM) to 0.237 m3 kg−1(oDM). The cumulated area-related methane yields of the orchards ranged from 818 m3 ha−1 to 1036 m3 ha−1. Specific methane yields were linearly correlated with XL, aNDF, ADF, and ADL.