Co-fermentation of waste steamed bun and municipal wastewater towards energy recovery for wastewater treatment plant

Co-fermentation of waste steamed bun (WSB) and municipal wastewater (MWW) for biohydrogen generation was investigated to support the energy demand of municipal wastewater treatment plant. WSB was ultra-fast hydrolyzed by solid enzymes which were produced by fungi through solid state fermentation (scenario 1), and commercial enzymes (scenario 2), respectively. The separated WSB hydrolysate with MWW was fed into a digester for biohydrogen generation. Compared to the traditional anaerobic fermentation (scenario 3), the yield of hydrogen with scenarios 1 and 2 were 3.17 and 2.43 times higher. The techno-economic assessment of the plant with capacity of 100 t/d WSB and 700 m3/d MWW was also conducted. The minimum selling price (MSP) of hydrogen with scenarios 1-3 were US$ 0.072/kWh, US$ 1.046/kWh and US$ 0.347/kWh, respectively. Scenario 1 was the most competitive alternatives because of the lowest annualized total cost (US$/y 1,070,920), the highest revenue (US$/y 1,016,400) and the lowest net cost (US$/y 54,520). This was the first study to examine the biohydrogen generation from co-fermentation of WSB and MWW and provide the economic analysis for practical application.