Effects of pH and substrate: Inoculum ratio on batch methane fermentation

Batch digestion experiments were conducted to determine the effects of inoculum:substrate ratio and initial medium pH on methane production from glucose. A ratio between the chemical oxygen demands (GOD) of the substrate and inoculum solids (SISR) was used to quantify the food to microorganisms (FIM) ratio. Two periods of active methane production, separated by a period of inactivity, characterized the fermentation. The duration of inactivity was affected by both SISR and the initial medium pH. It decreased as SISR was decreased or when a higher initial pH was used. With a SISR of 4.8 and a pH of 7.2 or 7.0, the inactive period was eliminated, indicating satisfactory coupling of the acid- and methane-forming phases. Ultimate methane yield at a SISR of 4.8 was higher than at a SISR of 38.5. Copyright (C) 1996 Elsevier Science Ltd.