Thermochemical Processing of Biomass
Thermochemical Processing of Biomass: Conversion into Fuels, Chemicals and Power, 2nd Edition will appeal to all academic researchers, process chemists, and engineers working in the field of biomass conversion to fuels and chemicals. It is also an excellent book for graduate and advanced undergraduate students studying biomass, biofuels, renewable resources, and energy and power generation.
Thermochemical Processing of Biomass
Introduction to Thermochemical Processing of Biomass into Fuels, Chemicals, and Power
Xiaolei Zhang1 and Robert C. Brown2
1School of Mechanical and Aerospace Engineering, Queen's University Belfast, Belfast, BT9 5AH, UK
2Department of Mechanical Engineering, Iowa State University, Ames, IA, USA
Thermochemical processing of biomass uses heat and catalysts to transform plant polymers into fuels, chemicals, or electric power. This contrasts with biochemical processing of biomass, which uses enzymes and microorganisms for the same purpose. In fact, both thermochemical and biochemical methods have been employed by humankind for millennia. Fire for warmth, cooking, and production of charcoal were the first thermal transformations of biomass controlled by humans, while fermentation of fruits, honey, grains, and vegetables was practiced before recorded time. Despite their long records of development, neither has realized full industrialization in processing lignocellulosic biomass. While petroleum and petrochemical industries have transformed modern civilization through thermochemical processing of hydrocarbons, the more complicated chemistries of plant molecules have not been fully developed.
Ironically, the dominance of thermochemical processing of fossil resources into fuels, chemicals, and power for well over a century may explain why thermochemical processing of biomass is sometimes overlooked as a viable approach to bio-based products. Smokestacks belching pollutants from thermochemical processing of fossil fuels is an indelible icon from the twentieth century that no one wishes to replicate with biomass. However, as described in a report released by the US Department of Energy in 2008  , thermal and catalytic sciences also offer opportunities for dramatic advances in biomass processing. Actually, thermochemical processing has several advantages relative to biochemical processing, as detailed in Table 1.1 . These include the ability to produce a diversity of oxygenated and hydrocarbon fuels, reaction times that are several orders of magnitude shorter than biological processing, lower cost of catalysts, the ability to recycle catalysts, and the fact that thermal systems do not require the sterilization procedures demanded for biological processing. The data in Table 1.1 also suggest that thermochemical processing can be done with much smaller plants than is possible for biological processing of cellulosic biomass. Although this may be true for some thermochemical options (such as fast pyrolysis), other thermochemical options (such as gasification-to-fuels) are likely to be built at larger scales than biologically based cellulosic ethanol plants when the plants are optimized for minimum fuel production cost  .
Table 1.1 Comparison of biochemical and thermochemical processing.
Biochemical processing Thermochemical processing Products Primarily alcohols Range of fuels and chemicals Reaction conditions Less than 70°C, 1atm 100-1200°C, 1-250atm Residence time 2-5d 0.2s-1h Selectivity Can be made very selective Depends upon reaction Catalyst/biocatalyst cost $0.50/gal ethanol $0.01/gal gasoline Sterilization Sterilize all feeds No sterilization needed Recyclability Difficult Possible with solid catalysts Size of plant (biomass input) 2000-8000 tons/d 5-200 tons/d (fast p