Biohydrogen production from solar and wind assisted AF-MEC coupled with MFC, PEM electrolysis of H2O and H2 fuel cell for small-scale applications

Small-scale biohydrogen production is a promising option to reduce GHG emissions for a sustainable H2 economy. Thus, solar and wind aided AF-MEC and MFC coupled with the electrolysis of H2O and a H2 fuel cell were developed. The integrated system uses a microwave oven for digestate pretreatment, and solar or wind energy sources to operate the electrical units. The results show that thermal pretreatment of AF digestate facilitated enzymes’ activities, while the highest energy efficiency recorded in MFC was attributed to the use of AF-MEC by-products as feedstock. The generated electricity by MFC in addition to solar or wind energy systems reduced the overall cost by eliminating AF-MEC separation and purification units for biohydrogen recovery. Renewable energy-powered PEMEC produced H2 and O2 and PEMFC generated electricity for the developed system in the absence of wind and sunlight. Energy efficiency >68.6% and H2 selling price <$5/kg which is cheaper than single electrolysis of H2O unit were recorded with a minimal CO2 by-product. By-product CO2 capture is recommended for an increase in electricity production from the MFC unit. In terms of service life and energy required for manufacturing, this developed system for energy conversation and storage outperforms lithium batteries by >10% efficiency.