Effect of Total Solid Content of Lignocellulose Pulp and Paper Mill Sludge on Methane Production and Modeling

This work studied the effect of total solids content on methane production potential from pulp and paper mill sludge and its kinetic modeling. The modified Gompertz, logistic function, and transference function models were used for the model prediction. The results showed that food:microorganisms (F/M) ratios of 0.5-2.0 produced significant increments in methane production and biodegradability. Conversely, a F/M ratio of 2.5 was observed with reduced methane production. This decrement was because of the presence of higher solids content that makes the hydrolysis stage difficult and mass transfer problems for the degraded organic matter. A F/M ratio of 2.0 produced higher biodegradability and cellulose removal of about 66% and 47% respectively. Three models fitted the experimental data with R2>0.98. A significant difference was observed for the maximum methane production rate among the three models. The modified Gompertz and logistic models had the best fit and mimicked the experimental data, whereas the transfer function model was in slight accord with the experimental data.