Feedstock availability biomass feedstocks

Many available biomass feedstocks have a high moisture content, which lowers their heat value. Preprocessing can help, but adds to the cost. There are also some biomass conversion technologies that are only marginally beneficial and this keeps them from being cost-competitive. 

The means by which synthetic gaseous fuels could be produced from a variety of biomass sources are variable and many of the known gasification technologies can be appHed to the problem (70,71,76—82). For example, the Lurgi circulatory fluidized-bed gasifier is available for the production of gaseous products from biomass feedstocks as well as from coal (83,84). 

Second-generation biofuel technologies make use of a much wider range of biomass feedstock (e.g., forest residues, biomass waste, wood, woodchips, grasses and short rotation crops, etc.) for the production of ethanol biofuels based on the fermentation of lignocellulosic material, while other routes include thermo-chemical processes such as biomass gasification followed by a transformation from gas to liquid (e.g., synthesis) to obtain synthetic fuels similar to diesel. The conversion processes for these routes have been available for decades, but none of them have yet reached a high scale commercial level. 

All coal and central natural-gas hydrogen plants are assumed to have carbon-capture and sequestration (CCS). Biomass hydrogen plants are assumed to be smaller (30-200 tonnes/day), compared with 50-400 tonnes/day for natural gas central SMRs, and 250-1200 tonnes/day for coal plants. We use a regional biomass supply curve (which specifies the amount of biomass available at a certain /tonne) (Walsh et al., 1999), to reflect biomass feedstock cost increases as demand grows. 

Commercial gasifiers are available in a range of sizes and types, and run on a variety of fuels, including wood, charcoal, coconut shells and rice husks. Power output is determined by the economic supply of biomass, which is limited to 80 MW in most regions. The producer gas is affected by various gasification processes from various biomass feedstocks. Table 6.7 shows composition of gaseous products from various biomass fuels by different gasification methods. 

A core aspect of the model is the determination of the chemical conversion of gasifier SG to hydrogen by the RP. For conditions where steam availability is not limiting, the chemical conversion relates to the difference between the initial and final combustion/fuel ratio of the fuel gas. The initial CP/SG ratio is determined by the gasifier and the biomass feedstock. The final CP/SG ratio is determined by the thermochemical properties of the metal oxide material. Ideally the difference between the initial (CP/SG),and final (CP/SG)j , ratios should be as large as possible. In reality the availability of steam for the re-oxidation of the metal oxide is limiting for conditions where the difference in the CP/SG ratios are large. 

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

BIOMASS FEEDSTOCK MATERIAL POTENTIALLY AVAILABLE FOR ETHANOL PRODUCTION PRODUCTION POTENTIAL, MILLION GALLONS PER YEAR ETHANOL... 

As illustrated in Fig. 33.14, biomass feedstocks can vary widely in the number of constituents and the concentration of each constituent. In biomass conversion processes, up to 20 constituents may need to be monitored to characterize the conversion of feedstock into a desired product or products. Standard wet chemical methods for the chemical characterization of biomass feedstocks and biomass-derived materials have been validated through the International Energy Agency and are available from the American Society for Testing and... 

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