(374b) Developing Sustainable Water Use Technologies for Biorefineries

Improving water reuse in biorefineries is an important issue in further development of biofuel production technologies. Typical process schemes for cellulosic ethanol production treat the wastewater and the organic carbon either via aerobic/anaerobic digestion or concentrate the organics via evaporators to use it as fuel for combustion in a boiler. A significant portion of the biomass energy and water are lost in the form of heat via flue gases, water evaporation and ambient heat, particularly when using the latter option. An alternate process to improve energy recovery from the residual organic streams is the use of bioelectrochemical systems, such as microbial fuel/electrolysis cells (MFC/MECs). The potential advantages of this alternative scheme in a biorefinery include minimization of heat and water loss. Conversion of the energy in the organic streams to hydrogen via MECs is a low temperature process. 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. The hydrogen can be used for upgrading low quality biofuel products or other byproducts. The paper will discuss process options and estimates of reductionin in water and energy usage.