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Characterization and Utilization Overview
The U.S. renewable fuels standard (RFS2) requires increasing the domestic supply of alternative fuels to 36 billion gallons by 2022 (15 and 21 billion gallons from corn-based ethanol and advanced biofuels respectively). Either biochemical or thermochemical technologies (e.g., pyrolysis and gasification) can be used to convert lignocellulose resources to biofuels. This article focuses on the characteristics, utilization, and potential to produce transportation fuels and other products from pyrolysis liquids. Pyrolysis Overview. Biomass pyrolysis involves heating biomass in the absence of oxygen to produce pyrolysis oils (50-75 wt%), char (10-30 wt%) and syngas (5-15 wt%). The quantities produced depend on the heat rate (i.e., fast pyrolysis; slow pyrolysis) and the biomass resource (figure 1). Oil yield is maximized using fast pyrolysis which rapidly heats the biomass to temperatures of 450-550ºC (Diebold, 2002). Char is maximized using slow pyrolysis which heats the biomass to the same temperature range as fast pyrolysis, but at a much slower rate (Milosavljevic et al., 1996, Mok and Antal, 1983). This process has been used to make charcoal since ancient times. Torrefaction (a mild form of slow pyrolysis) heats the biomass to 200-320°C (Prins et al., 2006). It densifies the biomass (reducing transportation costs), increases its heat value (by removing the water), and improves the ability to grind the material (Bourgois and Guyonnet, 1988; Bridgeman et al., 2010; Repellin et al., 2010; Phanphanich and Mani, 2011). The current technologies for biomass pyrolysis, including the properties and uses of pyrolysis oil were recently reviewed (Mohan et al., 2006, Huber et al., 2006). Figure 1. Pyrolysis product distribution. Source: U.S. Department of Agriculture, Agricultural Research Service Biochar Initiative. Pyrolysis Liquid Production and Characteristics. Pyrolysis liquids are produced using modern reactor vessels capable of achieving high heat rates and vapor residence times of a few seconds. Fluidized bed reactors with either bubbling or circulating media are most commonly used for fast pyrolysis. Auger reactors are also used due to their simplicity and ease of control, but they do not achieve the rapid heat-rates obtained with fluidized bed reactors. Sadaka and Boateng (2009) provide a review of reactor types used for pyrolysis. During pyrolysis, the organic components of biomass (i.e., cellulose, hemicellulose, and lignin) are broken down and deconstructed (depolymerized) to form a mixture of vapors and numerous micron-sized droplets (aerosols) (Qiang Lu et al, 2009). Rapid cooling and condensing of the mixture form pyrolysis oil. Pyrolysis oil (approximately represented by C6H8O4) is a complex mixture of hundreds of oxygenated organic compounds (e.g., acids, alcohols, aldehydes, esters, furans, ketones, sugars, phenols and many multifunctional compounds) and water (~ 15-30 wt%). On an elemental basis, it is compositionally similar to the parent biomass, hence it is sometimes called "liquid plant matter" (Mullen et al, 2009). The high oxygen content of pyrolysis oil reduces its calorific value relative to most fossil fuels (e.g., about half of heavy fuel oil), but, it contains lower quantities of trace metals and sulfur making it attractive as a low-emission combustion fuel (table 1). Table 1. Pyrolysis oil characteristics, by feedstock type.   Oak Switchgrass Alfalfa Stems Corn Stover Barley Straw Barley Hulls Chicken Litter Total Water Wt % 22.3 15.8 28.6 9.2 26.7 13.8 20.1 PH 2.6 3.1 - 2.9 2.4 2.5 6.9 Elemental Analysis (db)               C (wt%) 58.13 47.47 56.84 53.97 50.78 54.37 55.64 H (wt%) 6.07 6.96 7.86 6.92 3.20 5.32 7.19 N (wt%) 1.50 .036 3.73 1.18 1.37 1.79 7.77 S (wt%) 0 - 0.07 <0.05 0.00 0.09 0.70 O (wt%) 34.30 45.19 31.30 37.94 44.42 38.49 29.27 HHV (MJ/kg, db) 18.1 18.4 20.6 24.3 17.7 20.8 23.3 HHV (MJ/kg, db) 23.3 21.9 28.9 26.7 24.2 24.1 29.2 Elemental analysis is on a dry weight basis (db). HHV is high heating value. Source: Mullen, C.A., G.D. Strahan, and A.A. Boateng, Energy & Fuels 23:2707-2718. 2009.

Pyrolysis Oil Stabilization and Upgrading
Despite its high yield and high concentration of oxygenated hydrocarbons (including aromatic compounds), conventional petroleum refining techniques (e.g., hydrotreating and hydrocracking) have not be used to convert pyrolysis oil into fungible (transportable) biomass-based hydrocarbon fuels such as gasoline and diesel. This is due, in part, to the lack of stability during long term storage. While pyrolysis oil physically resembles crude petroleum, it is not miscible with petroleum-derived fuels. Pyrolysis oils contain high concentrations of reactive components which cause condensation and polymerization reactions to continue during storage. Over time, these reactions increase the average molecular weight, viscosity, and water content of pyrolysis oil. Pyrolysis oil is also acidic (pH of 2 to 3) which makes the oil unstable and corrosive. Alkali metals sequestered in the fine char particles that remain in the oil catalyze reactions between the various organic compounds present in the oil, which accelerates ageing reactions and increases viscosity, further contributing to instability. Thus, for this technology to become commercially viable, long term storage stability must be addressed. Instability can be addressed by upgrading the pyrolysis oil which involves either conditioning the oil to a stable intermediate product (in-situ upgrade) or completely converting it to hydrocarbon fuels following the completion of pyrolysis (ex-situ upgrade). The purpose of upgrading is to reduce the rate of viscosity increase of the pyrolysis oil as it ages. The most effective method is to reduce the oxygen content of the numerous organic compounds that comprise pyrolysis oil. Other stabilization techniques involve preventing or removing suspended char particles in the oil. An in-situ upgrade removes oxygen during the initial pyrolysis step and produces a stable intermediate that can be shipped and stored. Either a non-catalytic or a catalytic upgrade can be used. Non-catalytic approaches include modifying process conditions (e.g., residence times, heating and quenching rates) or collection methodologies (e.g., char removal, condensation) (Oasmaa et al., 2005). Cyclones are most commonly used to remove particulates, but they are not 100% efficient. Alternative particle separation approaches, such as hot gas filtration, may improve the removal of trace elements that catalyze ageing reactions (Fahmi et al, 2007). Several in-situ catalytic approaches for thermochemical upgrading have been suggested to convert the pyrolysis oil into fungible fuels including catalytic cracking, hydrogenation, and aqueous reforming (Huber et al., 2006; NSF, 2008). Catalytic cracking modifies the decomposition pathways through the use of heterogenous acid catalysts to partially or fully deoxygenate the pyrolysis oil. Partial deoxygenation should improve the stability of pyrolysis oils by reducing the concentration of reactive oxygenated functional groups which improves downstream hydroprocessing. This also reduces coke formation and improves catalyst life. Several catalysts have been studied including ZnO, phosphoric acid and other salts, but zeolites (e.g., HZSM-5) and porous silicates have received the most attention (Carlson et al., 2008; Williams and Nugranad, 2000, Adam et al., 2005, Jackson et al., 2009, Zhang et al., 2009). The catalysts can be mixed directly with the dry-ground biomass, or first suspended with the biomass in water followed by drying prior to adding to the reactor. Both methods provide intimate contact and reduce mass transfer limitations, but result in the catalyst being mixed with the char which makes it more difficult to recover the catalyst and increases cost. Alternatively, the catalysts can be immobilized on a support within the reactor (the KIOR process) or made into pellets and substituted for sand as the heat transfer medium in fluidized or entrained bed reactors. A second stage process, where pre-condensed pyrolysis vapors are catalytically treated, is also possible. In the latter cases, any necessary reactivation of the catalysts can be achieved by intermittent combustion. Hydroprocessing (hydrogenation) is most effectively used for ex-situ upgrades, but in-situ hydrogenation has been suggested and tested (GTI). This approach catalytically converts the pyrolysis oil to hydrocarbons using a hydrodeoxygenation processes similar to that used in petroleum refineries (McCall, 2008). Cobalt-molybdenum (CoMo) and nickel-molybdenum (NiMo) sulfide catalysts have been successfully tested. The process can be expensive due to the need for high pressure systems and the high consumption of hydrogen. Also high levels of coke formation cause catalyst deactivation and reduce yield. The development of new catalysts and use of catalyst regeneration technologies may overcome these hurdles. Furimsky (2000) and Elliott (2007) have reviewed historical developments in pyrolysis oil hydrogenation. Aqueous reforming reforms the pyrolysis oil and char into syngas using nickel and related catalysts. The syngas can then be converted to hydrocarbon or alcoholic fuels using Fisher-Tropsch synthesis (Wang et al., 2007). Pyrolysis oil stabilization and upgrading have been the driving force behind current pyrolysis research and development in the United States. Catalyst development is an integral part of recent R&D efforts, and is the focus of several U.S. investigations (e.g., University of Massachusetts, USDA Agricultural Research Service, National Renewable Energy Laboratory (NREL), Iowa State University in collaboration with Conoco Phillips, Pacific Northwest National Laboratory (PNNL), University of Oklahoma, University of Colorado, Mississippi State University, etc.). The U.S. Department of Energy (DOE) is a principal source of funds for pyrolysis research and development. Funds have been made available through the Biomass Research & Development Initiative (BRDI) and the Advanced Research Projects Agency-Energy (ARPA-E), a new DOE agency established to promote and fund research and development of advanced energy technologies. A recent recipient of a large DOE grant is the National Advanced Biofuels Consortium of several entities with complementary expertise led by NREL and PNNL, formed to research and produce infrastructure compatible, fungible biomass-based hydrocarbon fuel intermediates (the so-called "drop-in" fuels). DOE-USDA collaboration on BRDI has also provided support for pyrolysis oil biorefinery research. Funding recipients for the past few years include Research Triangle International (RTI) in collaboration with Archer Daniel Midland (ADM), and a collaborative effort between W.R. Grace and Company of Maryland, PNNL-UOP, The Gas technology Institute (GTI) of Illinois, and Battelle Memorial Institute (Ohio). Other U.S. agencies that fund pyrolysis research include the U.S. Department of Defense Advanced Research Projects Agency (DARPA), the USDA National Institute for Food and Agriculture (NIFA—formerly CSREES), and the SunGrant Initiative. European Union (EU) efforts include the BIOCOUP project designed to allow biomass feedstocks to be co-fed into conventional oil refineries to produce energy and oxygenated chemicals. The Europeans have shown an interest in aqueous reforming, and plans are currently underway to build the first plant in Germany to use this technology (the Lurgi-Karlsruhe "bioliq" process) (Henrich et al., 2007). North America and Europe collaborate on pyrolysis oil development through the International Energy Agency (IEA) Bioenergy Task 34 - Pyrolysis (http://www.ieabioenergy.com/).

Commercial Production of Pyrolysis Oils
Commercial scale quantities of pyrolysis oils are available from two Canadian companies--Ensyn Technologies Inc. (http://www.ensyn.com/) and Dynamotive Inc. (http://www.dynamotive.com/). Since 1989, Ensyn has constructed 8 commercial facilities in the U.S. and Canada. The Renfrew, Canada plant built in 2007, is the largest (capacity of ~ 200 green ton per day; ~100 dried ton per day of biomass). Ensyn reports that since 1991, they have commercially produced specialty chemicals, binders, preservatives, road de-icers, and co-polymers via thermochemical liquification of biomass wastes, but have recently begun targeting its products as fossil fuel replacements. Its process is similar to that used in the petroleum industry and is well suited to produce fungible fuels via catalytic cracking. The technology could potentially be adapted for biomass resources if ash accumulation impacts on catalyst life can be resolved. In 2008, Ensyn and UOP formed a joint venture company, Envergent (http://www.envergenttech.com/) to convert biomass (i.e., forest and agricultural residues) to pyrolysis oil for power and heating applications. Envergent is also conducting research and development to commercialize upgrading technologies needed to refine pyrolysis oil into jet grade fuels (http://www.naylornetwork.com/ppi-biotech/articles/index.asp?aid=115582&issueID=21815). Dynamotive Inc., (Vancouver, Canada) produces fuel grade pyrolysis liquids at its facility in Guelph, Canada. The plant can reportedly process 66,000 dry tons of biomass per year (~200 ton per day capacity) with an energy output equivalent to 130,000 barrels of oil. Smaller quantities of pyrolysis oils have been produced, mainly in demonstration facilities including the Biomass Technology Group of the Netherlands (BTG) (http://www.btgworld.com/) facility in Malaysia (48 ton/day), the VTT Technical Research Center in Finland (5 ton per day), The Canada Center for Mineral and Energy Technology (CANMET), the National Renewable Energy Laboratory (NREL), and PYTEC Technologies (http://www.pytecsite.de/pytec_eng/index.htm). Uses of Pyrolysis Oils—Fuels. Instability is the major factor limiting refining of pyrolysis oil in existing petroleum refineries and to commercializing pyrolysis oil as a transportation fuel (Schwietzke et al., 2008). Successful development of upgrading technologies could overcome this limitation and allow for the use of the existing petroleum refinery infrastructure. Upgrading of pyrolysis liquids into fungible jet fuels has been successfully demonstrated. A hydroplane test run, conducted by UOP and Boeing in 2009, used 100% renewable jet fuel (98% Bio-synthetic paraffinic kerosene from natural oils and fats and 2% renewable aromatics from upgraded woody pyrolysis oil). It is believed that it will take about 3 years to complete R&D and within 5 years pyrolysis oil fuel substitutes could be certified for use as jet and other transportation fuels. Alternatively, pyrolysis oil can be used as a fuel in combustion applications. Pyrolysis oil is unsuitable for direct use in diesel engines, although trials in direct injection engines have been conducted (Solantausta et al., 1993; Shihadeh and Hochgreb, 2000). However, stabilized pyrolysis oil may address many challenges encountered in using pyrolysis oil as diesel fuel blends in combustion systems (e.g., IC engines, gas turbines, boilers, and kilns) used in the power and materials processing industries. Similar to the transportation fuel issues, combustion of the pyrolysis oil "as is" or as fuel oil substitute is challenged by stability problems. Acidity, high water content, high oxygen content, wide volatility distribution, and the presence of char all cause atomization problems (i.e., difficulty in breaking down the liquid into small droplets needed for spray combustion), ignition delay, propensity to coking, and particulate emissions. Droplet combustion rates of pyrolysis oils are about 2 or 3 factors lower than that of light diesel fuel (Shaddix and Hardesty, 1999; Shihadeh, and Hochgreb, 2000, 2002). Low combustion rates typically characterize flames that are long, lazy, of low intensity, and that produce more soot than diesel fuel fired under similar conditions. Field trials involving engine manufacturers, stationary gas turbine operators and boiler operators interested in co-firing pyrolysis oils with coal and/or natural gas have been conducted (Czernik and Bridgwater, 2004; Chiaramonti et al., 2007). Wartsila, a large engine manufacturer ( http://www.wartsila.com/ ), conducted extensive testing of pyrolysis oils as fuel substitutes in their VASA series of stationary engines. However, several technical problems occurred including acid attack on storage tanks, gaskets and seals in pumps; preheating problems (oligomerization); lacquering at pistons and nozzles, etc. Tests at MIT, CANMET, PYTEC, using various internal combustion (IC) engine types have yielded similar unfavorable results. To successfully operate IC engines solely on pyrolysis oils or admixtures thereof, a standard engine will have to be substantially modified (including changing the materials of construction)--a prospect engine manufactures feel is uneconomic. Co-firing pyrolysis oil in gas turbines and boilers has not performed well either, largely due to similar material construction issues (Lopez and Salva Monfort, 2000; Chiaramonti, et al., 2007). Greater success has been achieved with the use of pyrolysis oil in some industrial furnaces such as kilns and boilers (Li et al., 2004). An American Standard Test Method (ASTM) specification (D7544-09) has recently been released to guide the design and operation of industrial burners equipped to handle pyrolysis oils. The specification does not currently include pyrolysis oil use in residential heaters, small commercial boilers, engines or marine applications. For detailed studies of specific engine combustion tests, the reader is referred to Chiaramonti et al., 2007. Uses of Pyrolysis Oils—Chemicals. Although the major thrust of pyrolysis oil development is to provide advanced biofuels, research to identify pyrolysis oil components with unique applications and/or higher value than fuels is also underway. These potential chemical co-products could provide additional revenues to the pyrolysis operation and increase overall profitability. Pyrolysis oils include both a water-soluble fraction (WS, sometimes called Py-C because it consists mainly of carbohydrate degradation products) and a water insoluble fraction (WIS, sometimes called pyrolytic lignin, Py-L) (Dobele et al., 2009). Either fraction can be further fractionated to recover compounds of interest (Oasmaa and Kuoppola, 2008). Unfractionated pyrolytic lignin can be used as an adhesive (Chan et al., 2002). Other potential high-value components found in pyrolysis oils include food flavoring products ("liquid smoke,") (Simon et al., 2005), antioxidants (Dobele et　al., 2009), steroids (Pakdel and Roy, 1996) and lignans (Simonelt et al., 1993). Pyrolysis oil is known to contain a significant amount of monolignols (breakdown products of lignin) which can be precursors for industrial and pharmaceutical products (Garcia-Perez et al., 2007; Holbrook et al., 2005).

Pyrolysis Oil Cost and Logistics Issues and Concluding Remarks
The negative attributes of pyrolysis oil present transportation, pumping and storage challenges. To date, pyrolysis oil has found little practical use. Development of technologies to successfully stabilize pyrolysis oil and overcome storage and aging problems could substantially reduce barriers to use. The similarities between pyrolysis oil upgrading and fossil fuel refining could permit existing refinery infrastructure to accept stabilized pyrolysis oil as a blend stock or "drop-in" biocrude. The pyrolysis process has several potential advantages relative to other conversion technologies. Pyrolysis is feedstock neutral and uses the entire biomass. Although pyrolysis oil composition varies as a function of feedstock composition, this same issue occurs with biochemical conversion processes (Boateng et al., 2008). Pyrolysis can be conducted at small-scale (potentially farm level), permitting the establishment of regional distributed biorefinery systems utilizing a variety of biomass feedstocks (figure 2). Pyrolysis at the site of biomass production could reduce transportation costs due to the higher bulk density of pyrolysis oil relative to raw biomass. It has been shown that the reduced transport costs substantially improve the economics of a regional biorefinery system comprised of localized, distributed pyrolysis reactors and a centralized gasification plant that uses pyrolysis oil as a feedstock for Fischer-Tropsch (FT) synthesis (Wright et al., 2008). This is significant as existing commercial coal-to-liquid (CTL) FT facilities require large economies of scale for economic production of liquid fuels (Tijmensen et al., 2002, Jager, 1997). Other economic models also favor distributed, smaller scale pyrolysis systems (Jones, et al., 2009). Figure 2. Conceptual integrated distributed pyrolysis system.   Source: Adapted from Wright, M. M., R.C. Brown, A.A. Boateng. 2008. Biofuels Bioproducts, Biorefining 2:229-238. PNNL/NREL estimate the minimum selling price of biomass-derived gasoline and diesel produced via hydrotreating and hydrocracking of fast pyrolysis oil is less than $2 per gallon (2000 dry metric tons per day; delivered wood chip cost of $50.7/bone dry metric ton; 76 million gallons per year of gasoline and diesel). Estimated production costs are sensitive to assumptions regarding stability, scale, hydrogen use, and whether or not the hydrotreating step is integrated or co-located with an existing refinery infrastructure. Concluding Remarks. The use of pyrolysis oils as fuel substitutes face technical issues due to the instability of the oils, but research is underway to overcome the storage and aging problems, and to develop internal and external fuel combustion specifications. The similarities between pyrolysis oil upgrading and fossil fuel refining could permit the use of existing refinery infrastructure to accept stabilized pyrolysis oil as a blend stock or "drop-in" biocrude. Upgrading of pyrolysis liquids into fungible transportation fuels (including jet fuels) have been successfully demonstrated. It is believed that it will take about 3 years to complete the necessary R&D and that within 5 years, pyrolysis oil fuel substitutes could be certified for use as jet fuel and potentially other transportation fuels. Regional distributed production systems show economic promise and provide the potential for pyrolysis oil to be a near-term option to replace significant quantities of fossil fuels.

References
Adam, J., Blazsó, M., Mészáros, E., Stöcker, M., Nilsen, M. H., Bouzga, A., Hustad, J. E., Grønli, M., Øye. G. Pyrolysis of biomass in the presence of Al-MCM-41 type catalysts. Fuel 84:1494–1502. 2005. Boateng, A. A., Weimer, P. J., Jung, H. G. and Lamb, J. F. S. Response of Thermochemical and biochemical conversion processes to lignin concentration in alfalfa stems. Energy & Fuels, 22:2810-2815. 2008. Bridgeman, T.G., J.M. Jones, A. Williams, and D.J. Waldron. An investigation of the grindability of two torrefied energy crops. Fuel 89:3911-3918. 2010. Bourgois, J., and R. Guyonnet. Characterization and analysis of torrefied wood. Wood Sci. Tech. 22:143-155. 1988. Carlson, T. R., Vispute, T. P., Huber, G. W. Green gasoline by catalytic fast pyrolysis of solid biomass derived compounds. Chem. Sus. Chem. 1:397-400. 2008. Chan, F., Riedl, B., Wang, X-M., Lu, X., Amen-Chen, C., Roy, C. Performance of pyrolysis oil-based wood adhesives in OSB, Forest Products Journal 52:31-38. 2002. Chiaramonti, D., Oasmaa, A., and Solantausta, Y. Power generation using fast pyrolysis liquids from biomass. Renewable & Sustainable Energy Reviews, 11:1056-1086. 2007. Czernik, S., Bridgwater, A. V. Overview of applications of biomass fast pyrolysis oil. Energy & Fuels 18:590-598. 2004. Diebold, J. P. A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils, In Fast Pyrolysis of Biomass, A Handbook, AV Bridgwater ed., CPL Press, Liberty House, Newbury, UK, 2002. Dobele, G., Dizhbite, T., Urbanovich, I., Andersone, A., Ponomarenko, J., Telysheva, G., Pyrolytic oil on the basis of wood and the antioxidant properties of its water-soluble and -insoluble fraction, Journal of Analytical and Applied Pyrolysis 85:81-86. 2009. Elliott, D. C. Historical Developments in Hydroprocessing Bio-oils. Energy Fuels 21:17921815. 2007. Elliot, D. C., Hart, T.R., Neuenschwander, G. G., Rotness, L.J., Zacher, A. H. Catalytic hydroprocessing of biomass fast pyrolysis bio-oil to produce hydrocarbon products. Envirom. Progr. & Sustain. Energy 28:441–449. 2009. Fahmi, R., Bridgwater, A. V., Darvell, L. I., Jones, J. M; Yates, N., Thain, S., Donnison, I. S. The effect of alkali metals on combustion and pyrolysis of lolium and festuca grasses, switchgrass and willow. Fuel 86:1560–1569. 2007. Furimsky, E. Catalytic hydrodeoxygenation. Appl. Catal. A. 199:147–190. 2000. Garcia-Perez, M., Chaala, A., Pakdel, H., Kretschmer, D., Roy, C. Characterization of bio-oils in chemical families. Biomass and Bioenergy 31:222-242. 2007. Holbrook, A. M., Pereira, J. A., Labiris, R., McDonald, H., Douketis, J. D., Crowther, M., Wells, P. S. Systematic overview of warafin and its drug and food interactions. Arch. Intern. Med. 165:1095-1106. 2005. Henrich, E., Dahmen, N., Raffelt, K., Stahl, R., Weirich, F. The Karlsruhe "Bioliq" process for biomass gasification, Summer School, University of Warsaw, 2007. http://www.baumgroup.de/Renew/download/5%20-%20Henrich%20-%20paper.pdf Huber, G. W., Iborra, S., Corma, A. Synthesis of transportation fuels from biomass: chemistry, catalyst and engineering. Chem. Rev. 106:4044–4098. 2006. Jackson, M. A., Compton, D. L., Boateng, A. A. Screening of heterogeneous catalysts for the pyrolysis of lignin. J. Anal. Appl. Pyrolysis 85:226-230. 2009. Jager, B. Developments in Fischer-Tropsch Technology. Studies in Surface Science and Catalysis 107:219-224. 1997. Jones, S.B., Holladay, J.E., Valkenburg, C., Stevens, D.J., Walton, C.W., Kinchin, C., Elliott, D.C., and Czernik, S. Production of Gasoline and Diesel from Biomass via Fast Pyrolysis, Hydrotreating and Hydrocracking: A Design Case. U.S. Department of Energy - Contract DE-AC05-76RL01830 Report, 2009 http://www.pnl.gov/main/publications/external/technical_reports/PNNL-18284.pdf. Li, Y., Barr, P.V., Watkinson, A.P. Bio-oil Firing for Industrial Kiln Operations. Proc. 6’th Int. Symposium on Waste Processing and Recycling, COM 2004, Hamilton Lopez, G., Salva Monfort, J.J. Preliminary test on combustion of wood derived fast pyrolysis oils in a gas turbine combustor. Biomass & Bioenergy, 19:119-128. 2000. Milosavljevic, I., Oja, V., Suuberg, E. M. Thermal effects in cellulose pyrolysis: relationship to char formation processes. Ind. Eng. Chem. Res. 35:653-662. 1996. Mohan, D., Pittman Jr., C. U., Steele, P. H. Pyrolysis of wood/biomass for bio-oil: a critical review. Energy Fuels, 20:848–889. 2006. Mok, W.S.L., Antal, M.J. Effects of pressure on biomass pyrolysis II, heats of reaction of cellulose pyrolysis. Thermochim. Acta 68:165-186. 1983. McCall, M.J. Production of Chemicals from Pyrolysis Oil. US Patent Application 20080312476. 2008. Mullen, C.A., Strahan, G.D., and Boateng, A.A. Characterization of various fast-pyrolysis bio-oils by NMR spectroscopy. Energy & Fuels 23:2707-2718. 2009. NSF. 2008. Breaking the chemical and engineering barriers to lignocellulosic biofuels: Next generation hydrocarbon biorefineries, Huber, G. W. Ed. University of Massachusetts, National Science Foundation, Chemical, Bioengineering, Environmental, and Transport Systems Division, Washington DC. June 25-26. Oasmaa, A., Sipila, K, Solantausta, Y., Kuoppala, E. Quality Improvement of Pyrolysis Liquid: Effect of light volatiles on the stability of pyrolysis liquids. Energy & Fuels 19:2556-2561. 2005. Oasmaa, A., Kuoppala, E. Solvent fractionation method with brix for rapid characterization of wood fast pyrolysis liquids, Energy Fuels 22:4245-4248. 2008. Pakdel, H., Roy, C. Separation and characterization of steroids in biomass vacuum pyrolysis oils. Bioresource Technol. 58: 83–88. 1996. Phanphanich, M., and S. Mani. Impact of torrefaction on the grindability and fuel characteristics of forest biomass. Bioresour. Technol. 102:1246-1253. 2011. Prins, M.J., K.J. Ptasinski, and F.J.J.G. Janssen. Torrefaction of wood: Part 1. Weight loss kinetics. J. Anal. Appl. Pyrolysis 77:28-34. 2006. Qiang, Lu, Wen-Zhi, L., Xi-Feng, Z. Overview of fuel properties of biomass fast pyrolysis oils. Energy Conservation & Management, 50:1376-1383. 2009. Sadaka, S. and Boateng, A.A. Pyrolysis and Bio-oil, University of Arkansas publication - FSA1052, 2009. http://www.uaex.edu/Other_Areas/publications/PDF/FSA-1052.pdf Schwietzke, S., Ladisch, M., Russo, L., Kwant, K., Makinen, T., Kavalov, B., Maniatia, K., Zwart, R., Shananan, G., Sipila, K., Grabowwski, P., Telenius, B., White, M., Brown, A. Analysis and identification of gaps in research for the production of second-generation liquid transportation biofuels. Report of the IEA Bioenergy Task 41, Project 2 (2008). Shaddix, C.R., and Hardesty, D.R. Combustion properties of biomass flash pyrolysis oils: Final project report. Sandia National Laboratories, Albuguerque, New Mexico, 1999. Shihadeh, A. and Hochgreb, S. Diesel engine combustion of biomass pyrolysis oils. Energy & Fuels 14:260-274. 2000. Shihadeh, A. and Hochgreb, S. Impact of biomass pyrolysis oil process conditions on ignition delay in compression ignition engines. Energy & Fuels 16:552-561. Simon, R., de la Calle B., Palme, S., Meier, D., Anklam, E. Composition and analysis of liquid smoke flavouring primary products, J. Sep. Sci. 28:871-882. 2005. Simonelt, B.R., Rogge, W.F., Mazurek, M.A. Standley, J.L. Hildemann, L.M. Cass, G.R. Lignin pyrolysis products, lignans, and resin acids as specific tracers of plant classes of emissions from biomass combustion, Environ. Sci. Technol. 27:2533-2541. 1993. Solantausta, Y., Nylund, N-O., Westerholm, M., Koljonen, T., Oasmaa, A. Wood-pyrolysis oil as fuel in a diesel-power plant. Bioresource Technol. 46:177-188. 1993. Tijmensen, M.J.A., Faaij, A.P.C., Hamelinck, C.N., van Hardeveld, M.R.M. Exploration of the possibilities for production of Fischer Tropsch liquids and power via biomass gasification. Biomass Bioenergy 23:129-152. 2002. Williams, P. T. and Nugranad, N. Comparison of products from the pyrolysis and catalytic pyrolysis of rice husks, Energy 25:493–513. 2000. Wang, Z. X., Dong, T., Yuan, L. X., Kan, T., Zhu, X. F., Torimoto, Y., Sadakata, M. Li, Q. X. Characteristics of bio-oil-syngas and its utilization in Fischer-Tropsch synthesis. Energy & Fuels 21:2421–2432. 2007. Wright, M. M. Brown, R. C., Boateng, A. A. Distributed processing of biomass to bio-oil for subsequent production of Fischer-Tropsch liquids. Biofuels Bioproducts, Biorefining 2:229-238. 2008. Zhang, H., Xaio, R., Huang, H., Xiao, G. Comparison of non-catalytic and catalytic fast pyrolysis of corn cob in a fluidized bed reactor. Bioresource Technol. 100:1428–1434. 2009.