Feedstock fuel production, biomass

The market penetration of synthetic fuels from biomass and wastes in the United States depends on several basic factors, eg, demand, price, performance, competitive feedstock uses, government incentives, whether estabUshed fuel is replaced by a chemically identical fuel or a different product, and cost and availabiUty of other fuels such as oil and natural gas. Detailed analyses have been performed to predict the market penetration of biomass energy well into the twenty-first century. A range of from 3 to about 21 EJ seems to characterize the results of most of these studies. 

Biomass can be a renewable feedstock for methane. Biomass feedstocks for methane production include crop residues, municipal solid waste (MSW), and wood resources. Biomass resources for the production of alcohol fuels are estimated at about 5 million dry tons per day which could provide 500 million gallons of methanol per day. 

The primary product is fuel-grade, coal-derived gas which is similar to natural gas. The basic gasification process can also be applied to other carbon-based feedstocks such as biomass or municipal waste. 

Fischer-Tropsch synthesis requires a stochiometric H2 CO ratio of 2.1 1. If coal or biomass are used as feedstock, the raw syngas contains much less hydrogen than needed. Hence, CO is reacted with water to form C02 and hydrogen in the shift reactor. As the C02 cannot be used in the Fischer-Tropsch synthesis, part of the carbon for fuel production is lost in this process. If external hydrogen is added to increase the H2 CO ratio, the carbon of the coal or biomass is more effectively used and the hydrocarbon product yield is improved. 

The attractiveness of production of liquid fuels from biomass lies in the renewable characteristics of biomass. As a consequence, the costs of an industry based on biomass conversion would be more or less predictable by inflation forecasting, and essentially independent of external political factors. With the incorporation of municipal solid waste as a biomass feedstock, such an industry also presents the opportunity of developing improved methods of recycling and waste disposal. 

While this reaction is substantially exothermic (6), it provides an intriguing approach to the production of fuels from renewable resources, as the required acids (including acetic acid, butyric acid, and a variety of other simple aliphatic carboxylic acids) can be produced in abundant yields by the enzymatic fermentation of simple sugars which are, in turn, available from the microbiological hydrolysis of cellulosic biomass materials ( ] ) These considerations have led us to suggest the concept of a "tandem" photoelectrolysis system, in which a solar photoelectrolysis device for the production of fuels via the photo-Kolbe reaction might derive its acid-rich aqueous feedstock from a biomass conversion plant for the hydrolysis and fermentation of crop wastes or other cellulosic materials (4). 

The use of biomass as an alternative low-cost feedstock is still in its infancy, but could boost industrial biotech much further, and change the landscape of chemical and fuel production. To make biorefmeries work, however, industry players and governments will need to invest and collaborate to create an entirely new value chain. 

Recent studies have proven ethanol to be an ideal liquid fuel for transportation and renewable lignocellulosic biomass to be an attractive feedstock for ethanol fuel production by fermentation (1,2). The major fermentable sugars from hydrolysis of lignocellulosic biomass, such as rice and wheat straw, sugarcane bagasse, corn stover, corn fiber, softwood, hardwood, and grasses, are D-glucose and D-xylose except that softwood... 

Table I. Biomass Feedstocks Potentially Available for Ethanol Fuel Production...

An alternative to the utilization of food crops in biofuel production is lignocellu-lose, which can for instance be utilized in biomass-to-liquid (BTL) processes. That way, a direct competition between food and fuel production can be avoided. This feedstock is much more abundant than vegetable oils or sugar and starch crops. 

Lignocellulose, which comprises the main construction material of plant biomass, accounts for up to 90% of all biomass and is formed in amounts of approximately 1.5 trillion tons per year [12]. Consequently, lignocellulose is much more abundant than available amounts of vegetable oils, starch, and sugar crops. In addition to the high abundance of lignocellulose, it is inedible, and its utilization as feedstock for production of biofuels and chemicals could drastically reduce challenges of food versus fuel production. 

Navarro RM, Pena MA, Fierro JLG. Hydrogen production reactions from carbon feedstocks fossils fuels and biomass. Chem Rev. 2007 107(10) 3952-91. 

Many processes can be used to produce energy or gaseous, liquid, and solid fuels from virgin and waste biomass. In addition, chemicals can be produced from biomass by a wide range of processes. It is evident from the data and information presented in this chapter, however, that the characteristics of potential feedstocks, particularly their moisture and energy contents, can have profound effects on the utility of specific biomass species and waste biomass. Table 3.10 is a summary of the principal feedstock, process, and product types that are considered in developing a synfuel-from-biomass process. There are many interacting parameters and possible feedstock—process—product combinations, but not all are feasible from a practical standpoint. For example, the separation of small amounts of metals present in biomass and the direct... 

Other compounds that can be produced directly from biomass in good yields, but which do not retain the basic structural characteristics of biomass, are also classified as commodity chemicals. Examples are acetic acid, methane, and synthesis gas. They are not manufactured in large volumes from biomass because fossil fuels are the preferred feedstocks in commercial production systems. Technically, biomass can serve as a feedstock for production of the entire range of commodity organic chemicals presently manufactured from fossil fuels. The various routes to large-volume chemicals from biomass will be examined later. Consider first some of the existing biomass-based chemicals, most of which are specialty chemicals that are manufactured for commercial markets. 

Navarro, R.M., Pena, M.A., and Fierro, J.L.G. Hydrogen production reactions from carbon feedstocks Fossil fuels and biomass. Chemical Reviews, 2007, 107 (10), 3952. 

More than twenty years ago, it was recognized that cellulosic biomass, including agricultural residues (such as corn stover, rice and wheat straws, and sugarcane bagasse), municipal wastes (such as yard and paper wastes), and industrial wastes (such as wastes from paper mills), is an attractive feedstock for ethanol-fuel production by fermentation because cellulosic biomass is not only renewable and available domestically in most countries but also available at very low cost and in great abundance. 

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