An Economic Worthiness Assessment of Bio-filter Microbial Fuel Cell for Leachate Wastewater Treatment

Abstract

This research aims to assess an economic worthiness of a microbial fuel cell (MFC) for wastewater treatment in order to provide information for investment guidance in new renewable fuel. Parameters of concern were incomes of electricity production from microbial activity and carbon credit earned from burning released biogas, which reduce greenhouse gas emission. Researchers operated a laboratory-scale reactor of MFC models (7.8 liters in volume) for landfill leachate wastewater treatment, filled with Bioballs as bio-filter, void ratio of 10%, and varying hydraulic retention time (HRT) in ranges of 24 – 96 hours. The result showed that the reactor with HRT of 96 hour, operated with filtration rate of 16 liters/day, had the highest efficiency of COD removal and electricity potential difference, which were 76% and 41.67 millivolt, respectively. Therefore, the reactor with HRT of 96 hours was selected to assess incomes of electricity sale and carbon credit from MFC. The analysis pointed out that revenue from the MFC was caused from only carbon credit, 1,079 baht/reactor/year earned, derived from greenhouse gas emission reduction of 2.2 ton-carbon dioxide equivalent/reactor/year, while electricity sale did not cause revenue significantly by producing electricity of 0.03 watt-hour/reactor/year. From the results of worthiness analysis for the above MFC system, to meet criteria of net present value (NPV) and internal rate of return (IRR) for 10-year operating period with an constant discounted rate of 7.73%, it expressed that the MFC reactor was not worthy for an investment with NPV and IRR of -27,106 baht and -22%, respectively, from all equipment and operation costs of 35,000 baht. Nevertheless, when considering the analysis of an investment, it would be more worthy by increasing the number and improving treatment efficiency of reactors. Increasing a number of reactors to 10 reactors (equivalent to filtration rate of 160 liters/day) effected a change of NPV and IRR to 37,537 baht and 16%, respectively, from all investment costs of 41,404 upon 10-year operating period. If increasing a number of reactors comprised with improving COD treatment efficiency from 76% to 86%, IRR would increase to 22%. From the abovementioned results, the researchers suggested that who is interested in MFC investment for now should consider factors, such as treatment capacity and efficiency of the system for purpose of wastewater treatment together with a biogas collecting system for utilization, as information for an investment decision making.