Influence of Composition of Food Waste to Methane Recovery by Two-Stage Low Solid Anaerobic Digestion.

Abstract

The study was carried out to assess influences of composition of household food waste and retention time to methane gas recovery by two-stage low solid anaerobic digestion process without adjustment of pH, alkalinity, and temperature. It is found that except for food waste containing only starch or only fruit peels with essential oil, it is possible to recover about 445-775 L CHR4R/gVS of household food waste mixture at the methanogenesis retention time of 60 days. However, the mixture of 30% fruit peels + 50% wasted vegetables + 10% starch food remnants + 10% other food remnants give the best methane gas recovery with 775 L CHR4R/gVS. Food waste containing only fruit peels without essential oil allows achieving higher amount of methane gas at shorter the retention time compared to that of food waste containing only fruit peels with essential oil. It is possible to get 747 L CHR4R/gVS of fruit peels without essential oil at the retention time of 60 days compared to only 493 CHR4R/gVS of essential oil-fruit peels at the retention time of 120 days. If the food waste containing only starch food remnant or only fruit peels with essential oil, it is necessary to control retention time of the methanogenesis reactor of 120 days. It is possible to achieve 493 L CHR4R/gVS of fruit peels with essential oil and 300 L CHR4R.gVS of starch food waste at the retention time of 120 days and organic loading rate of 1.1 gVS/L.day and 2.6 gVS/L.day, respectively. With shorter the retention time, lower amount of methane gas can be recovered. In the case of starch food waste, it is impossible to recover biogas at the retention time of 30 days.