Non-food sources of liquid fuels
Non-food sources of liquid fuels
Jesse Capecelatro, Dr. Peter van Walsum
University of Maine Department of Chemical Engineering, 5737 Jenness Hall, Orono, ME 04469
Abstract
In a joint collaboration to reduce our dependence on petroleum and harvest valuable byproducts in the pulp and paper industry, there is an interest to produce fuels or chemicals from non-food sources. Replacing crude oil with biomass feedstocks has the potential to lower fossil-fuel CO2 emissions that cause a great threat to our planet, as renewable forest material is carbon neutral. The US pulp and paper industry currently processes approximately 108 million tons of wood per year. During paper production only about 70% of the wood is utilized. The solid cellulose fraction of wood is saved while the lignin and a fraction of the hemicellulose components are discarded. This waste material can potentially be converted and sold into valuable products such as ethanol and acetic acid without disturbing the amount of paper being produced.
A pre-extraction process can be implemented to remove the hemicellulose by a green liquor treatment. A secondary hydrolysis step is required to hydrolyze oligomeric sugars into monomeric sugars before fermentation. If this fermentation occurs in an anaerobic environment, ethanol, acetic acid, butanol and acetone are some of the possible metabolic products.
In the case of hardwoods, the most abundant fermentable wood component in the hemicellulose is xylan. Xylan is a polymer of the sugar xylose, and is broken down into xylose through acid or enzyme-catalyzed hydrolysis. Xylose is a relatively difficult sugar to ferment, but some xylose utilizing organisms can be found in nature and several have also been genetically engineered.
Four organisms will be used in this study; Clostridium phytofermentans, which produces primarily ethanol and some acetic acid; Moorella thermoacetica, which produces acetic acid; Thermoanaerobacterium thermosaccharolyticum, which produces ethanol and acetic acid; Clostridium acetobutylicum, which produces acetone, butanol and ethanol.
These microorganisms may have the ability to produce an abundant amount of ethanol and acetic acid from the hemicellulose extract, and some may also do so with little or no need for secondary hydrolysis. If successful, introducing this form of integrated forest bio-refinery (IFBR) to existing mills would help them remain competitive while simultaneously improving today’s fuel crisis.
Interview with Jesse Capecelatro on July 10 2008 (5:23 minutes)
