Relationship of Substrate and Inoculum on Biochemical Methane Potential for Grass and Pig Manure Co-digestion

The effects of substrate mix ratio and inoculum/substrate ratio (ISR) on biochemical methane potential of para-grass (PG) and pig manure (PM) were investigated in batch test that maintained temperature at 35 +/- 1 degrees C and continuously shaked at 120 rpm. Cumulative methane production data at different mix ratios and ISRs were evaluated and fitted with Gompertz equation to derive methane production potential (mL) and maximum methane production rate (mL/d). The maximum and average methane yields at each respective ISR of 1, 2, 3, and 4 were [413.0, 315.5], [539.7, 455.6], [590.3, 472.5], and [593.1, 473.5] mL/gVS(added). Relationship of ISR and PG mix ratio to specific methane yield were expressed in quadratic regression model. The generated response surface showed that methane yield was elevated at higher ISR and higher PG mix ratio. This suggests a careful investigation at different ISR and substrate mix ratios should be performed in order to develop a realistic biochemical methane potential of anaerobic co-digestion.