SIMULATING MICROBIAL ELECTROLYSIS FOR RENEWABLE HYDROGEN PRODUCTION INTEGRATED WITH SEPARATION IN BIOREFINERY

Biomass conversion to hydrocarbon fuels requires significant amounts of hydrogen. Fossil resources typically supply hydrogen via steam reforming. A new technology called microbial electrolysis cells (MECs) has emerged which can generate hydrogen from organic sources and biomass. The thermochemical route to fuels via pyrolysis generates bio-oil aqueous phase (BOAP) which can be used to make hydrogen. A process engineering and economic analysis of this technology was conducted for application in biorefineries of the future. Steam methane reforming, bio-oil separation and microbial electrolysis unit operations were simulated in Aspen Plus to derive the mass and energy balance for conversion of biomass. A process scheme using MEC to generate hydrogen, while minimizing use of natural gas was developed. A process design developed by Pacific Northwest National Laboratory was used as baseline biorefinery flowsheet. The results show that hydrogen production at a rate of 1,723 lb/hr can be derived using 19.5 % of the bio-oil as the substrate BOAP, while eliminating the need for natural gas. A two-step quench system allows separation of an aqueous stream containing about 23,000 lb/hr of organic substrate, sufficient for hydrogen generation, besides that generated from off-gas, so as to meet the total biorefinery hydrogen needs. The techno-economic analysis (TEA) showed that hydrogen can be generated for a minimum hydrogen selling price of $ 3.35/kg-H₂. The results of this study show that hydrogen can be practically derived from an aqueous soluble bio-oil stream, while majority of the bio-oil is used for hydrocarbon production, using a wholly biomass-sourced hydrogen. This alternative has potential to reduce greenhouse gas emissions from the biorefinery.