Evaluation of environmental performance and selection of the most suitable system for MFCs with different electron acceptors by life cycle assessment and PROMETHEE approach

Abstract

The aim of this study is to evaluate the environmental performance with life cycle assessment (LCA) for MFCs with different electron acceptors and to select the most suitable system with the PROMETHEE approach. For this, MFC studies using different electron acceptors have been taken into account. In this study, four systems as MFC 1 (raw sludge at anode, azo dye at cathode), MFC 2 (thermochemically pre-treated sludge at anode, azo dye at cathode), MFC 3 (synthetic wastewater at anode, algal growth at cathode), and MFC 4 (synthetic wastewater at anode, nitrate at cathode) were examined. The functional unit of this LCA has been selected as the generation of 1 kW h of electrical energy. According to the LCA results, MFC 3 was the most advantageous option in terms of environmental performance, followed by MFC 2. Using the microalgaes in cathode chamber have ensured 10.3% additional environmental gains on the land use impact category owing to producing algal biomass, which is a valuable energy source. The most dominant sub-process on the environmental performance of MFCs was determined as the reactor material. In the second stage of the study, MFCs were ranked by the PROMETHEE approach. The criteria for ranking were determined as climate change, mineral fossil and renewable resource depletion, water resource depletion, quality of recovered water and maximum power density. The order of the MFC's is determined as MFC 3 > MFC 2 > MFC 4 > MFC 1. The MFC 3 has been the most preferred option in terms of electricity generation and environmental impacts in alignment with LCA results.