Kinetic study of the mesophilic anaerobic digestion of organic waste components

Batch mesophilic anaerobic digestion to produce methane were conducted using potato, lettuce, meat and peanut oil as the typical components of organic fraction of municipal solid wastes (amylaceous, cellulosic, proteinic and lipidic materials). Modified Gompertz equation were used to fit the cumulative methane production and the anaerobic degradation processes were analyzed with first-order kinetics equation. The results showed that the methane yields of potato, lettuce, meat and peanut oil were 260.1, 145.7, 258.4 and 757.2 mL·gVS-1, respectively. Lag phase were 0, 1.3, 1.6 and 13.1 day. The periods which cumulative methane production achieved 80% of methane yield were 7.2, 9.6, 8.1 and 59.7 per day. Biodegradability were 74%, 31%, 51% and 85%, respectively. The determining results of total volatile fatty acids concentrations and pH in liquid phase and hydrogen concentrations in gas phase showed that there is no accumulation of intermediary products during the anaerobic digestion processes. First-order methane production kinetics could be used describing anaerobic degradation rate of organic substrates. The degradation rate constants of potato, lettuce, meat and peanut oil were 0.183, 0.147, 0.190 and 0.020 d-1.