Methane yield of perennial grasses as affected by the chemical composition of their biomass

The aim of the research work was to study the chemical properties of most cultivated perennial Fabaceae and Poaceae plants: common cocksfoot (Dactylis glomerata L.), reed canary grass (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), common lucerne (Medicago sativa L.), common sainfoin (Onobrychis viciifolia Scop.) and switchgrass (Panicum virgatum L.), and to link them to methane (CH4) and biogas yields under laboratory conditions. The results of chemical analyses showed that the biomass of legumes was most suitable for biogas production: high digestibility: 78.4-73.5% dry matter (DM) and low cellulose concentration 20.8-24.4% DM, were determined to be most suitable for anaerobic digestion. The biomass of L. perenne and F. arundinacea was best-suited for anaerobic digestion due to the highest content of water-soluble carbohydrates (WSC) 16.4-20.3% DM, and the lowest content of cellulose 27.3-28.9 % DM and acid detergent fibre (ADF) 31.3-32.8% DM. The best yields of methane were obtained from O. viciifolia -277.7 L CH4 kg(-1), D. glomerata -213.9 L CH4 kg(-1) and L. perenne -205.7 L CH4 kg(-1). The correlations corroborated that the methane yield depended on the chemical composition of the biomass. Methane yield positively and significantly correlated with WSC -0.761** and digestibility -0.744** (P <= 0.01), and negatively correlated with cellulose -0.793** and ADF -0.762**. The best results of specific methane yields were demonstrated by O. viciifolia (1453 m(3) CH4 ha(-1) DM), M. sativa (1326 m(3) CH4 ha(-1) DM) and L. perenne (1060 m(3) CH4 ha(-1) DM). This study with seven species of perennial grasses could serve as a basis for more advanced experiments on how to choose grass species for the best methane yield.