Kinetics of Methane Production from Co-digestion of Agricultural Wastes

Anaerobic digestion (AD) is widely used for treatment of organic waste for biogas production. Codigestion
of agricultural wastes with various substrate combinations is one of the ways to increase
and stabilize biogas yield. The influence of co-substrates on kinetics of methane production in
anaerobic fermentation of pig and manure slurry was studied by performing a series of laboratory
experiments using food waste, biowaste and winemaking waste as co-substrates. Experiments were
performed in the laboratory reactors of «Hohenheim» biogas testing system in batch mode at the
temperature of 37ºC. Methane production rate was used to evaluate co-digestion of agricultural 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 about 10-15 days. Maximal methane production rate was reduced 2-3 times in codigestion
than in mono-digestion of pig and cattle manure during anaerobic digestion for 35 days.