Biomass feedstocks chemical conversion

When implementing a biomass-based thermochemical conversion system, it is important to critically evaluate the feedstock characteristics such as cost, distribution, mass, and physical and chemical properties. The feedstock qualities must be considered when matching feedstocks with a proper conversion technology. 

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. 

Conversion of such biomass into chemicals may be expected to have a much longer future perspective. Most chapters in this book are committed to the catalysis of biomass feedstock to bulk or fine chemicals. Here one notes the need to define platform molecules and their conversion technologies as well as the need for more insights in the fundamental catalysis of these processes. 

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. 

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. 

Industrialbiobased products have enormous potential in the chemical and material industries. The diversity of biomass feedstocks (sugars, oils, protein, lignocellulosics), combined with the numerous biochemical and thermochemical conversion technologies, can provide a wealth of products that can be used in many applications. Targeted markets include the polymer, lubricant, solvent, adhesive, herbicide, and pharmaceutical markets. Industrial bioproducts have already penetrated some of these markets, but improved technologies promise new products that can compete with fossil-based products in both cost and performance. 

For organic chemicals, transmaterialisation must mean a shift from fossil (mainly petroleum) feedstocks (which have a cycle time of > 107 years) to plant-based feedstocks (with cycle times of < 103 years). This immediately raises several fundamentally important questions Can we produce and use enough plants to satisfy the carbon needs of chemical and related manufacturing, while not compromising other (essentially food and feed) needs Do we have the technologies necessary to carry out the conversions (biomass to chemicals) and in a way that does not completely compromise the environmental and transmaterialisation characteristics of the new process ... 

Yadvika S., Seekrishnan, T.R., Kohli, S. and Rana, V. (2004). Enhancement of Biogas Production From Solid Substrates Using Different Techniques - A Review. Bioresour. Technol., 95, 1-10. Yaman, S. (2004). Pyrolysis of Biomass to Produce Fuels and Chemicals Feedstocks. Energy Conversion Manag., 45, 651-671. 

Yaman S, (2004). Pyrolysis of biomass to produce fuels and chemical feedstocks. Energy Conversion and Management 45(5) 651-671... 

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... 

Fitzpatrick, S. W., The Biofine technology A bio-refinery concept based on thermochemical conversion of cel-lulosic biomass. Feedstocks for the Future Renewables for the Production of Chemicals and Materials, 2006, 921,271-287. 

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. 

If biomass is subjected to the ASTM D 3172 procedure for determination of fixed carbon, chemical transformation of a portion of the organic carbon in biomass into carbonaceous material occurs as described here. All of the fixed carbon determined by the ASTM procedure is therefore generated by the analytical method. Furthermore, the amount of fixed carbon generated depends on the heating rate used to reach biomass pyrolysis temperatures and the time the sample is subjected to these temperatures. Nevertheless, such analyses are valuable for the development of thermal conversion processes for biomass feedstocks. But application of the ASTM procedures to biomass might more properly be called a method for determination of pyrolytic carbon or coking yields. In the petroleum industry, the Conradson carbon (ASTM D 189, differ-... 

Many research studies have been carried out to examine the possibilities for conversion of biomass feedstocks to liquid products by direct thermochemical treatment. These studies include the treatment of aqueous and nonaqueous slurries of wood particles with different reactants and catalysts at elevated temperatures and pressures, and the pyrolysis of wood under conditions that maximize liquid yields (Chapter 8). The prime objective was to develop processes for production of liquid fuels and not chemicals. The resulting products are generally acidic and contain high concentrations of carboxylic acids, phenolic compounds, and heterocyclic oxygen and alicyclic oxygenated compounds. With only a few exceptions, the products contain low concentrations of BTX. 

Thus, the building blocks for synthesis of commodity organic chemicals— synthesis gas, the light olefins ethylene, propylene, and butadiene, and BTX— can be obtained from biomass feedstocks by thermochemical conversion. 

The questions of how and when the microbial synthesis of commodity oiganic chemicals will play a larger role in the world s chemical markets remain to be answered. The subject has appeared, disappeared, and then reappeared many times since the mid-1970s when petroleum and natural gas prices increased to unacceptable levels in the United States. It is highly probable, however, that most of the specialty chemicals that are manufactured today by microbial conversion of biomass feedstocks will continue to be manufactured the same way. 

Biomass feedstocks usually contain a wide variety of chemical functional pes within the biopolymer structure. Since thetmocbemical conversion has typically focused on the use of the "whole" biomass, separating the chemical function types has been of less interest. Using the "whole" has been viewed as the most cost-effective approach while the thermocliemical processes were considered robust enough to handle the range of chemical functional types. As a result, the products were a complex mixture of chemical entities useful primarily for fuel applications. The costs of collecting individual chemical products could not be justified in most cases. 

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