Opportunities of Co-Digesting Manure with Grass

摘要

Several researchers have reported higher biogas yields when co-digesting manure with other feedstocks compared to mono-digestion (De Moor et al., 2013 and Xie et al., 2011). The main reason behind this increase in biogas production is that in case ofco-digestion a more favorable carbon nitrogen ratio (C/N) can be found. Manure has in general - due to its high nitrogen content - a ratio around 10 whereas the optimal value is around 25. Therefore, products that increase the C-concentration should be added to the feedstock mix in order to increase this ratio and the biogas production.Besides that, co-digestion also has a positive effect of the macro- and micronutrient balance, the ammonium concentration, pH, and inhibitors/toxic compounds (Xie et al., 2011). When digesting cow or pig slurry with a dry matter (DM) content < 12 % it can be very useful to add more dry, fibrous products such as grass as it is necessary for the microbiological population to have some carrier material in the digester.