Bioelectricity and Biohydrogen Production Using High Solid Content of Oily-Kitchen Wastes in Air Cathode Microbial Fuel Cells

For the first time, the ability of a Microbial Fuel Cell (MFC) to produce value-added products from the high content of oily kitchen waste was evaluated. A Single-chamber, air-cathode MFC containing 30% solids was designed for evaluation of the rate of biohydrogen and bioelectricity production. Food wastes were studied in four states: oil-free (0%), containing 3% oil, 6%, and 9% oil during 30 days of operation. Experiments showed with increasing the amount of oil, the amount of biohydrogen produced increased from 0 to 6% of the oil, and with the addition of 9% of oil, no significant change was observed in the biohydrogen production rate. The average daily production of biohydrogen for 0, 3, 6 and 9% of the oil was estimated at 42.5, 58.7, 69.6 and 70.1 mL per day, respectively, which showed that adding oil up to 6% could increase the efficiency of the system for biohydrogen production. On the other hand, with the increase in the amount of oil, the production of bioelectricity decreased, so that the maximum output voltage was recorded for the fourth day of zero state: 472 mV, and the lowest voltage on most of the days recorded for 9% of oil. The results of Chemical Oxygen Demand (COD) removal showed with increasing the amount of oil, although the amount of initial COD increased, the amount of COD removal decreased, which is consistent with the process of electricity production. Volatile fatty acids including acetate, butyrate, and propionate were other valuable products of the system, although the accumulation of VFA was indicated as an inhibitor for biohydrogen production The results showed kitchen waste without oil separation can be used as a useful substrate in MFC systems to produce value-added products, in this way, sewage pollution by oil resulted from food waste could be prevented.