Membrane-less microbial fuel cell: effect of pH on the electricity generation powered by municipal food waste

Fossil fuels have supported the industrialization and economic growth of countries during the past centuries and it is clear that they cannot indefinitely sustain in a longer time. In this study, membrane-less microbial fuel cell (ML-MFC) with mediators-less and air cathode had potential solution to generate electricity power and at the same time could reduce the abundant of food waste (1.64 kg/daily, around 8 tonnes/year) which dumped in the landfill and it’s cost effective device. The ML-MFC operated electrochemically incorporate electrogenic bacteria (EB) acted as a biocatalyst in order to produce electricity. The performance and optimization performance of food waste was evaluated using one-factor-at-a-time (OFAT) method and it was focused to pH for power generation. To determine the generated electricity the polarization curve was used to evaluate the performance of ML-MFC. The chemical oxygen demand (COD) of food waste was studied. The optimization of pH condition in ML-MFC was ranging from 7 to 9. Results showed that pH 8 was the optimum pH for EB strain, Bacillus Subtilis, with the high voltage (807 mV), EB biomass (15.46 mg/L), and power density (373.3 mW/m2) generated. Clearly the pH environment condition affected the efficiency of ML-MFC performance. The increase in EB biomass also increased the voltage in the ML-MFC, proving that EB biomass and voltage were associated with growth.

Evaluation of Biogas Production from the Co-Digestion of Municipal Food Waste and Wastewater Sludge at Refugee Camps Using an Automated Methane Potential Test System

The potential benefits of the application of a circular economy—converting biomass at Za'atari Syrian refugee camps into energy—was investigated in this study. Representative organic waste and sludge samples were collected from the camp, mixed in different ratios, and analyzed in triplicate for potential biogas yield. Numerous calorific tests were also carried out. The tangential benefit of the co-digestion that was noticed was that it lowered the value of the total solid content in the mixture to the recommended values for wet digestion without the need for freshwater. To test the potential methane production, the automated methane potential test system (AMPTS) and the graduated tubes in the temperature-controlled climate room GB21 were utilized. Also, calorific values were determined for the organic waste and sludge on both a dry and a wet basis. The maximum biogas production from 100% organic waste and 100% sludge using AMPTS was 153 m3 ton-1 and 5.6 m3 ton-1, respectively. Methane yield reached its maximum at a Vs sub/ Vs inoculum range of 0.25–0.3. In contrast, the methane yield decreased when the Vs sub/ Vs inoculum exceeded 0.46. The optimum ratio of mixing of municipal food waste to sludge must be carefully selected to satisfy the demands of an energy production pilot plant and avoid the environmental issues associated with the sludge amount at wastewater treatment plants (WWTPs). A possible ratio to start with is 60–80% organic waste, which can produce 21–65 m3· biogas ton-1 fresh matter (FM). The co-digestion of organic waste and sludge can generate 38 Nm3/day of methane, which, in theory, can generate about 4 MW in remote refugee camps.