A time-lag model for biogas production by anaerobic digestion

This work presents a simple time-lag model for biogas production from anaerobic digestion of organic wastes (biomass) in a batch digester. The model has the ability of predicting the S-shaped nature of the cumulative biogas yield with retention time that is commonly observed experimentally. The model is calibrated against biogas production data from anaerobic digestion of three types of organic waste: OFMSW (organic fraction of municipal solid waste), FVW (fruit and vegetable waste) and RH (rice husk). For these three wastes, the fit of the model to the experimental data has an average root-mean-square deviation of 9%. The time-lag model leads to the formulation of two measures or indexes of biodegradability of a particular waste. The values of these indexes are much higher for FVW compared to those for OFMSW and RH showing that the susceptibility of FVW to anaerobic digestion far exceeds that of the other two wastes.