Life cycle assessment of osmotic microbial fuel cells for simultaneous wastewater treatment and resource recovery

Abstract

Purpose An osmotic microbial fuel cell (OsMFC) is derived from the integration of a forward osmosis (FO) membrane into a conventional microbial fuel cell (MFC), with enhanced performance in bioelectricity generation from organic matter and recovery of high-quality water. The environmental impacts of this newly developed technology, however, have not been studied. To understand and potentially reduce the environmental impacts of the OsMFC technology, the environmental impacts have been assessed.

Methods An attributional life cycle assessment (LCA) model has been developed to evaluate the cradle-to-grave environmental impacts of the OsMFC based on a lab-scale prototype. The International Life Cycle Data System (ILCD) method has been applied to calculate and characterize the environmental impacts of treating 1 L of water by using the OsMFC technology in GaBi 8.7. Sensitivity and scenario analyses have been employed to assess the environmental impact variations based on changing power densities and different disposal methods, respectively.

Results and discussion The results indicate that several factors including raw material extraction, system operation, and end-of-life (EoL) stages have relatively large impacts in certain categories. The raw material extraction and system operation take up 50.04% and 32.06% of global warming potential (GWP), respectively. The EoL expends 98.02% of ecotoxicity potential (ETP), 54.31% of eutrophication potential (EP), and 52.24% of human toxicity potential (HTP). A comparison of the OsMFC with other bioelectrochemical systems (BESs) reveals that it has higher GWP due to the polymethylmethacrylate (PMMA) sheeting used to construct the cell and the stainless steel used to build the cathode electrode, but comparable acidification potential (AP), eutrophication potential (EP), ozone depletion potential (ODP), and respiratory inorganics (RI). The greenhouse gas (GHG) emissions of the OsMFC are also benchmarked with those of the conventional wastewater treatment methods, and it shows that the OsMFC has higher GHG emissions than the conventional wastewater treatment methods at the current power density. However, the results may change dramatically with the change of materials and cell configurations.

Conclusions According to the analysis, cell materials, cell configuration, electricity usage during the operation stage, and disposal methods are major problems to solve in the development of the OsMFC technology. Enhancement of power density and alternation of cell materials and configuration may turn out to be effective methods to alleviate the environmental impacts and increase market competitiveness of the OsMFC technology in the future.