Influence of Co-substrates for the Methane Production Rate Kinetics in Anaerobic Fermentation of Pig Slurry

The influence of co-substrates on kinetics of methane production in anaerobic fermentation of pig slurry was studied by performing a series of laboratory experiments using food waste and biowaste as co-substrates. Experiments were performed in the laboratory reactors of «Hohenheim» biogas testing system in batch mode at the temperature of 37ºC. Given 40 g of fresh pig slurry was fed to each digester and mixed with co-substrates in the ration of 55-45% by organic dry matter content. Methane production rate was used to evaluate co-digestion of pig slurry. Research results showed that co-substrates gave significant effect to methane production kinetics. The kinetic parameters of methane production i.e. potential yield of methane (P), maximum methane yield rate (Rm) and duration of lag-phase (λ) were analyzed using modified Gompertz equation. Technical time to produce 95% of potential methane yield was investigated and efficient period of anaerobic digestion was calculated. The potential production of methane was reached in lag-phase duration (λ) of 10-13 days. Maximal methane production rate was reduced 2-3 times in co-digestion than in mono-digestion of pig slurry. The potential yield of methane (P) was 0.420 Nm3(kg оDM)-1, 0.246 Nm3(kg оDM)-1 and 0.198 Nm3(kg оDM)-1 in mono-digestion and co-digestion of pig slurry with food waste and biowaste, respectively.