Bio-oil is the major product of the fast pyrolysis of biomass. It is also sometimes called pyrolysis oil, or bio-crude. It is usually a dark, viscous liquid and is comprised of hundreds of oxygenated organic compounds (carboxylic acids, ketones, aldehydes, furans, sugars) and water. Because it is so highly oxygenated, its fuel value (energy content) is only 50 - 70% of petroleum fuels. The exact chemical composition of bio-oil is dependant on the pyrolysis feedstock and the conditions used. Because bio-oil is such a complex and variable mixture, characterization of its physical and chemical properties is challenging. At ERRC we have successfully produced bio-oil from numerous feedstocks including switchgrass, alfalfa stems, corn stover, corn cobs, barley straw, barley hulls, soybean straw, guayule, chicken litter, wood and several others. The composition and properties of some bio-oils produced at ERRC is shown in the table below. Generally, bio-oil is acidic (pH 2-3), unstable and corrosive which presents problems for its transportation, piping and storage. Producing stable and upgradable bio-oil with more favorable properties through measures such as addition of catalysts, changes in the processing conditions, and post production upgrading is the major research topic for CRIS-095.