Dark fermentation, anaerobic digestion and microbial fuel cells: An integrated system to valorize swine manure and rice bran

•Integrated systems treating agricultural wastes need to diversified products.•We propose dark fermentation, anaerobic digestion and microbial fuel cells as integrated system.•These processes produce methane, hydrogen, electricity and fertilizers.•Waste produces 27.3 ± 7.2 LH2 kg−1COD, 154 ± 14 LCH4 kg−1COD and 39.8 W h kg−1COD to 54.2 W h kg−1COD.•Waste gave 0.3 kg of bio-fertilizers kgwaste1.

This work describes how dark fermentation (DF), anaerobic digestion (AD) and microbial fuel cells (MFC) and solid-liquid separation can be integrated to co-produce valuable biochemicals (hydrogen and methane), bioelectricity and biofertilizers. Two integrated systems (System 1: AD + MFC, and System 2: DF + AD + MFC) are described and compared to a traditional one-stage AD system in converting a mixture (COD = 124 ± 8.1 gO2 kg−1Fresh Matter) of swine manure and rice bran. System 1 gave a biomethane yield of 182 LCH4 kg−1COD-added, while System 2 gave L yields of bio-hydrogen and bio-methane of 27.3 ± 7.2 LH2 kg−1COD-added and 154 ± 14 LCH4 kg−1COD-added, respectively. A solid-liquid separation (SLS) step was applied to the digested slurry, giving solid and liquid fractions. The liquid fraction was treated via the MFC-steps, showing power densities of 12–13 W m−3 (500 Ω) and average bioelectricity yields of 39.8 W h kg−1COD to 54.2 W h kg−1COD.

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