Methane yield of different energy crops grown in Estonian conditions

To investigate the suitability of different alternative crops in Estonian conditions for methane production, a plant field collection was established in 2008 at the Institute of Agricultural and Environmental Sciences of Estonian University of Life Sciences on Haplic Luvisol (Hypereutric) soil near Tartu (58°23 N, 26°44 E) in Estonia. The species grown in this collection field were: Jerusalem artichoke (Helianthus tuberosus L.), fibre hemp (Cannabis sativa L.) cv USO–31, energy sunflower (Helianthus annuus L.) cv Wielkopolski, Amur silver– grass (Miscanthus sacchariflorus), energy grass cv Szarvasi–1, and foxtail millet (Setaria italic L.). The correlation between methane yield and lignin content was significantly negative. The expected average decrease in methane yield is 7.49 LCH4 kgTS with an increase of 1% lignin content in biomass. The highest methane yield was obtained from Miscanthus sacchariflorus, Helianthus tuberosus L., and Setaria italica L. samples. The alternative non–food crops from southern areas gave higher methane yield in Estonian conditions, because their development rate was slower, lignin content smaller and development stage more suitable for methane production. The variety of plant biomass improves the operational management of biogas plants and favours agro–ecosystem biodiversity.