Thursday, April 22, 2010 - 2:00 PM
12-03
Improving overall energy recovery and water reuse in cellulosic biorefineries via MFC/MEC technology
Abhijeet P. Borole and Jonathan Mielenz. Biosciences Division, Oak Ridge National Laboratory, 1-Bethel Valley Road, Bldg 1520, Rm 217, Oak Ridge, TN 37831
Improving biofuel yield and water reuse are two important issues in further development of biorefineries. The energy content of ethanol produced from cellulosic biomass via biochemical conversion route is about 49% of the biomass entering the biorefinery, on an energy basis. A significant portion of energy is lost in the form of heat via flue gases, water evaporation and ambient heat, when fermentation residues and evaporative solids are fed to the burner/boiler for generating heat and power. An alternate process to improve energy recovery from the residual organic streams after recovery of ethanol is described. Use of bioelectrochemical systems, such as microbial fuel/electrolysis cells (MFC/MECs) to convert residual sugars and process byproducts will be presented. Current process schemes remove water from residual organic streams to yield a syrup destined for use as fuel in boilers. Use of MECs for conversion of the residual organics to energy can result in multiple potential benefits to the biofuel production process. Major processes incurring heat losses such as evaporators and boilers can be eliminated and replaced by low temperature processes converting wastes to hydrogen or electricity. The need for 5-15 gallons of water per gallon of ethanol has been indicated for biomass conversion to ethanol. The possibility of water recycle in the proposed scheme will be discussed. Removal of inhibitory byproducts such as furans, phenolics and acetate in MFC/MECs will be demonstrated. Conversion of the sugar- and lignin- degradation products to electricity at power densities reaching 3700 mW/m2 using MFCs will be presented.