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FIGURE 4-2 Gasification can be done in either a low-temperature fluidized bed system (left) or a high-temperature entrained-flow gasifier (right).

SOURCE: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science.

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FIGURE 4-3 Removing impurities from biomass-generated syngas is a major challenge.

SOURCE: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science.

From a technical standpoint, the advantages of fast pyrolysis are that it occurs rapidly and at atmospheric pressure. It is a pathway to drop-in fuels or hydrocarbons, and it can produce multiple products. Commercially, fast pyrolysis offers the lowest-cost option for drop-in biofuels today, and bio-oil can be economically produced on a scale as small as 200 tons per day, which offers opportunities for distributed processing. Small facilities, located near the source of biomass, could produce bio-oil that would then be transported to a centralized facility just as is done with petroleum today.

The primary technical challenges facing fast pyrolysis, according to Brown, are that bio-oil is unstable, corrosive, and contains high levels of oxygen and water. Also, as he already mentioned, the fundamentals of pyrolysis are poorly understood. Commercially, there have been no demonstrations of bio-oil production and upgrading. Also, the pathway to finished fuels is still uncertain, though he remarked that the fact that there are many possibilities that have not yet been explored is what excites him as a researcher.

Other Pyrolysis Routes

Brown then briefly discussed two other types of pyrolysis—catalytic pyrolysis and solvolysis. Catalytic pyrolysis employs catalysts in the pyrolysis reactor or immediately downstream before bio-oil recovery to produce



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