Past, Present, and Future Production of Bio-oil
Bio-oil is a liquid product produced by fast pyrol-ysis of biomass. The fast pyrolysis is performed by heating the biomass rapidly (2 sec) at temperatures ranging from 350 to 650 oC. The vapors produced by this rapid heating are then condensed to produce a dark brown water-based emulsion composed of frag-ments of the original hemicellulose, cellulose and lignin molecules contained in the biomass. Yields range from 60 to 75% based on the feedstock type and the pyrolysis reactor employed. The bio-oil pro-duced by this process has a number of negative prop-erties that are produced mainly by the high oxygen content (40 to 50%) contributed by that contained in water (25 to 30% of total mass) and oxygenated compounds. Each bio-oil contains hundreds of chemi-cal compounds. The chemical composition of bio-oil renders it a very recalcitrant chemical compound. To date, the difficulties in utilizing bio-oil have limited its commercial development to the production of liq-uid smoke as food flavoring. Practitioners have at-tempted to utilize raw bio-oil as a fuel; they have also applied many techniques to upgrade bio-oil to a fuel. Attempts to utilize raw bio-oil as a combustion engine fuel have resulted in engine or turbine dam-age; however, Stirling engines have been shown to successfully combust raw bio-oil without damage. Utilization of raw bio-oil as a boiler fuel has met with more success and an ASTM standard has recently been released describing bio-oil characteristics in relation to assigned fuel grades. However, commercialization has been slow to follow and no reports of distribution of these bio-oil boiler fuels have been reported. Co-feeding raw bio-oil with coal has been successfully performed but no current power generation facilities are following this practice. Upgrading of bio-oils to hydrocarbons via hydroprocessing is being performed by several organizations. Currently, limited catalyst life is the obstacle to commercialization of this tech-nology. Researchers have developed means to increase the anhydrosugars content of bio-oil above the usual 3% produced during normal pyrolysis by mild acid pretreatment of the biomass feedstock. Mississippi State University has developed a proprietary method to produce an aqueous fraction containing more than 50% of anhydrosugars content. These anhydrosugars can be catalyzed to hydrogen or hydrocarbons; alter-nately, the aqueous fraction can be hydrolyzed to pro-duce a high-glucose content. The hydrolyzed product can then be filtered to remove microbial inhibitor compounds followed by production of alcohols by fer-mentation. Production of bio-oil is now considered a major candidate as a technology promising production of drop-in transportation and boiler fuels.
- Research Organization:
- Mississippi State Univ., Starkville, MS (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- FG36-06GO86025
- OSTI ID:
- 1079592
- Report Number(s):
- GO8602546
- Country of Publication:
- United States
- Language:
- English
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