Abstract
Improving biofuel yield and water reuse are two important issues in further development of biorefineries. The total energy content of liquid fuels (including ethanol and hydrocarbon) produced from cellulosic biomass via biochemical or hybrid bio-thermochemical routes can vary from 49% to 70% of the biomass entering the biorefinery, on an energy basis. Use of boiler for combustion of residual organics and lignin results in significant energy and water losses. An alternate process to improve energy recovery from the residual organic streams is via use of bioelectrochemical systems such as microbial fuel cells (MFCs) microbial electrolysis cells (MECs). The potential advantages of this alternative scheme in a biorefinery include minimization of heat loss and generation of a higher value product, hydrogen. The need for 5-15 gallons of water per gallon of ethanol can be reduced significantly via recycle of water after MEC treatment. Removal of inhibitory byproducts such as furans, phenolics and acetate in MFC/MECs to generate energy, thus, has dual advantages including improvements in energy efficiency and ability to recycle water. Conversion of the sugar- and lignin- degradation products to hydrogen is synergistic with biorefinery hydrogen requirements for upgrading F-T liquids and other byproducts to high-octane fuels and/or high value products. Some of these products include sorbitol, succinic acid, furan and levulinate derivatives, glycols, polyols, 1,4-butenadiol, phenolics polymers, etc. Potential process alternatives utilizing MECs in biorefineries capable of improving energy efficiency by up to 30% are discussed.