Two-stage conversion of crude glycerol to energy using dark fermentation linked with microbial fuel cell or microbial electrolysis cell

Crude glycerol is a main byproduct of the biodiesel industry, and the beneficial use of waste glycerol has been a major challenge. This study characterises the conversion of crude glycerol into bioenergy such as H₂ and electricity using a two-stage process linking dark fermentation with a microbial fuel cell (MFC) or microbial electrolysis cell (MEC). The results showed that fermentation achieved a maximum H₂ rate of 332mL/L and a yield of 0.55mol H₂/mol glycerol, accompanied by 20% of organic removal. Fed with the raw fermentation products with an initial COD of 7610mg/L, a two-chamber MFC produced 92mW/m² in power density and removed 50% of COD. The Columbic efficiency was 14%. When fed with 50% diluted fermentation product, a similar power output (90mW/m²) and COD removal (49%) were obtained, but the CE doubled to 27%. Similar substrates were used to produce H₂ in two-chamber MECs, and the diluted influent had a higher performance, with the highest yield at 106mL H₂/g COD and a CE of 24%. These results demonstrate that dark fermentation linked with MFC/MEC can be a feasible option for conversion of waste glycerol into bioenergy.