Biofuels gasification

The sources of biofuels and the methods for bioenergy production are too numerous for an exliaustive list to be described in detail here. Instead, electricity production using direct combustion, gasification, pyrolysis, and digester gas, and two transportation biofuels, ethanol and biodiesel, are discussed below. 

Solid biofuel conversion into syngas by pressurized circulating fluidized bed (PCFB) gasification using steam and oxygen. 

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. 

The same holds true for hydrogen however, biomass yields more kilometres when used via hydrogen in fuel-cell cars than liquid biofuels in ICE cars (see Fig. 7.5). Moreover, as hydrogen is produced via gasification, it is equivalent to second-generation biofuels, as it can use feedstock that does not interfere with the food chain. 

If renewable targets are set, biomass gasification is the cheapest renewable hydrogen supply option however biomass has restricted potential and competition of end-use, for instance, with other biofuels or stationary heat and power generation. Biomass gasification is applied in small decentral plants during the early phase of an infrastructure roll-out and in central plants in later periods. 

Thermochemical biomass-to-liquid (BtL) conversion, involving thermal gasification of the biomass and subsequent synthesis of biofuels by the Fischer-Tropsch process. Various aspects of the use of catalysis in this process are discussed in the several chapters. 

Biomass includes 60% wood and 40% non-wood materials. The conversion of wood into biofuels andbiochemicals is technically feasible. Wood valorization processes include fractionation, liquefaction, pyrolysis, hydrolysis, fermentation and gasification. 

This review defines the thermochemical conversion processes of solid fuels in general and biofuels in particular that is, what they are (drying, pyrolysis, char combustion and char gasification) and where they take place (in the conversion zone of the packed bed) in the context of the three-step model. 

Ethanol can also be produced from "non-food" materials, such as garbage or wastewater sludge, which are "negative-cost" feedstocks. If all American wastes (industrial and municipal) were converted to biofuels, not only would some 50 to 100 million gallons of fuel be obtained, but the emission of methane from landfills and other wastes would also be eliminated. Plasma gasification, a commercially available process, can also simultaneously increase the fuel supply and reduce greenhouse gas emissions. 

One can envisage the future production of liquid fuels and commodity chemicals in a biorefinery Biomass is first subjected to extraction to remove waxes and essential oils. Various options are possible for conversion of the remaining biofeedstock, which consists primarily of lignocellulose. It can be converted to synthesis gas (CO + H2) by gasification, for example, and subsequently to methanol. Alternatively, it can be subjected to hydrothermal upgrading (HTU), affording liquid biofuels from which known transport fuels and bulk chemicals can be produced. An appealing option is bioconversion to ethanol by fermentation. The ethanol can be used directly as a liquid fuel and/or converted to ethylene as a base chemical. Such a hiorefinery is depicted in Fig. 8.1. 

The guaranteed supply of biofuels is an important element for the promotion of bioenergy in general and gasification technologies in particular. This requires the... 

This demonstration plant has been installed at the Zeltweg power plant operated by DRAUKRAFT (15). The BIOCOMB process is designed for preparation of biofuels for co-combustion by partial gasification and attrition due to mechanical and thermal stress in a circulating fluidized bed reactor (CFB) (Fig. 2). 

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