Solar and wind assisted biohydrogen production from integrated anaerobic digestion and microbial electrolysis cell coupled with catalytic reforming

To promote and improve the efficiency of biohydrogen production systems, an integrated AD and MEC (anaerobic digestion and microbial electrolysis cell) with catalytic syngas steam reforming (CSSR) was developed and simulated. This innovative integrated model predicts syngas formation from AD and MEC units, uses recovered heat for substrates pretreatment and solar parabolic dish (SPD) for heat source to decompose reformers’ feeds. A combined 46 degradation reactions were used for acidogenesis, acetogenesis, and methanogenesis decomposition to predict syngas formation at different hydraulic retention time (HRT) and organic-loading rate (OLR). Biogas consisted of CH_4 and CO_2 from both AD and MEC were the CSSR feeds. The electric units of the hybrid system were powered by solar cells and wind turbine systems. The by-product CO_2 was captured and collected for underground storage. Controlled pH value, thermal pretreatment of AD and MEC digestates, and equilibrium feed rate improve overall efficiency by >5% with minimal volatile fatty acids (VFAs) and H_2 S production. The results show that the developed system can accommodate both waste and biomass feeds with 64% system efficiency. The stated efficiency excluded power generation units (solar and wind). The H_2 sales price of this developed system is between $2/kg and $6/kg. However, by installing this proposed system in areas with more sunlight during the day, a further reduction in H_2 price is possible. Adopting this new proposed technology means that for every 1kg of produced H_2 using biomass plants as feedstock and replanting used feedstocks, 10.92kg of CO_2 can be removed from the atmosphere because plants fix and store CO_2 in their roots. Meanwhile, the proposed work encouraged the use of organic waste feedstock instead of agricultural products without replanting.