Performance and recent development in sewage sludge-to-bioenergy using microbial fuel cells: A comprehensive review

Sewage sludge as a byproduct of industrial and municipal wastewaters treatment is produced worldwide at large quantities. This organic waste contains nutrients, pathogens, heavy metals, organic pollutants and other toxic substances. In recent years, the significant increase in the amount of sludge as an important environmental issue, which is considered both a threat and an opportunity, has highlighted the issue of its proper management. In recent decades, various methods have been used to manage and energy recovery from sewage sludge, including pyrolysis, incineration, gasification, anaerobic digestion, aerobic digestion, landfill, composting, lime and microbial fuel cell. Nowadays bioenergy production from sewage sludge attracted the attention of environmentalists due to environmental and economic considerations. In this regard, microbial fuel cells (MFCs) have gained a great importance as an alternative energy conversion method for bioenergy production. This system converts the chemical energy in the organic substance directly into valuable electrical energy by the catalytic reaction of microorganisms. The effectiveness of the system depends on the reactor configuration, operational and environmental parameters. Identifying and optimizing these parameters are important to increase the system efficiency. In this paper, we reviewed and discussed the effects of different parameters on the treatment and electricity generation from waste activated sludge (WAS) using MFC system such as nature of electrode materials, oxygen flow rate, reactor design, substrates and pH. Furthermore, a better understanding of the MFCs performance for bio-fuel generation from WAS, as well as solving concerns associated to the abilities of this technology in real application is aims of this review.