Feedstocks conversion from biomass

Methanol and ethanol are alcohol fuels that can be produced from various renewable sources. Alcohol fuels are converted from biomass or other feedstocks using one or several conversion techniques. Both government and private research programs are finding more effective, less costly methods of converting biomass to alcohol fuels. Methanol was originally a by-product of charcoal production, but today it is primarily produced from natural gas and can also be made from biomass and coal. 

A biorefinery is a facility that integrates biomass conversion processes and eqtrip-ment to produce fuels, power, and value-added chemicals from biomass. Biorefinery is the co-production of a spectram of bio-based products and energy from biomass. The biorefinery concept is analogous to today s crude oil refinery. Biorefinery is a relatively new term referring to the conversion of biomass feedstock into a host of valuable chemicals and energy with minimal waste and emissions. 

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. 

The fossil load factor is an important issue and its origin so evident and often unavoidable that we asked ourselves the question what the consequences are when this factor is reduced to zero. Whenever, in a biomass conversion process, a fossil fuel contribution was spotted, we replaced this contribution by one from biomass origin. For example, the process may require electricity, which is supplied by a nearby coal-fed power station. Then this amount of electricity was thought to be generated by a power station fed by biomass. Or the process may require heat or chemicals and again biomass is the raw material from which these requirements were met. Dr. Feng Wei made such an analysis for a process where a diesel-type product was obtained from wood chips as a feedstock. His work has been discussed as an example at the end of Chapter 13. 

A case study and forecast for the explicit production of bulk chemicals from biomass in the region of Rotterdam has recently been provided by Van Haveren et al. [46], As technologies for the conversion of, for example, ethanol, glycerol, and sugars to glycols, iso-propanol, and acetone are well known and readily available, and as the prices for feedstock are well below the selling prices for the named products, there is a clear short-term potential for these bulk chemicals (Table 2.2.2). 

Another important goal of green chemistry is the utilisation of renewable raw materials, i.e. derived from biomass, rather than crude oil. Here again, the processes used for the conversion of renewable feedstocks - mainly carbohydrates but also triglycerides and terpenes - should produce minimal waste, i.e. they should preferably be catalytic. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

Knowledge of the effects of various independent parameters such as biomass feedstock type and composition, reaction temperature and pressure, residence time, and catalysts on reaction rates, product selectivities, and product yields has led to development of advanced biomass pyrolysis processes. The accumulation of considerable experimental data on these parameters has resulted in advanced pyrolysis methods for the direct thermal conversion of biomass to liquid fuels and various chemicals in higher yields than those obtained by the traditional long-residence-time pyrolysis methods. Thermal conversion processes have also been developed for producing high yields of charcoals from biomass. 

As will become apparent in what follows, some oxygenates are manufactured by established, commercial, microbial processes using biomass feedstocks. Others can be manufactured by microbial conversion of biomass, but are currently produced using thermochemical conversion methods, usually with fossil feedstocks because of economic or technical factors. A few other oxygenates must be manufactured by thermochemical conversion of fossil feedstocks because suitable microbial processes do not yet exist to produce the oxygenate from biomass. Still others can be produced by a combination of thermochemical and microbial conversion. Microbial conversion systems with biomass feedstocks are emphasized here, but thermochemical methods are briefly reviewed to present a perspective on the options available and what advancements are necessary to perfect suitable processes. 

An approach to the production of ethylene from biomass that does not involve pyrolysis is ethanol dehydration. The catalytic conversion of syngas to ethanol from low-grade biomass (or fossil) feedstocks, and fermentation ethanol via advanced cellulose hydrolysis and fermentation methods, which make it possible to obtain high yields of ethanol from low-grade biomass feedstocks as well, are both expected to be commercialized in the United States (Chapter 11). Which technology becomes dominant in the market place has... 

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