Renewable feedstocks, components

The pyrolysis-based technology, in particular, because of the co-products opportunity, has the most favorable economics. An added advantage of biomass as a renewable feedstock is that it is not intermittent, but can be used to produce hydrogen as and when required. With scientific and engineering advancements, biomass can be viewed as a key and economically viable component to a renewable-based hydrogen economy. Economic viability of different types of energy generation processes is summarized in Table 8.1 (Bockris, 1981 Tanisho, 1996 Benemann, 1997). 

Advanced genetic engineering techniques are being used to improve existing renewable feedstocks for the production of industrial bioproducts. In some cases, the feedstock composition is modified to increase the content of a desired component and/or decrease the content of an undesired component, whereas in others, a new metabolic pathway is inserted into the plant genes so that the modified plant produces an entirely new component. These research efforts are recent, and very little, if any, published information is currently available. However, we provide brief descriptions of the research activities to give perspective on the opportunities for new industrial bioproducts that may emerge from feedstock modification. 

The need for novel catalytic processes is clear and, as discussed in Chapter 9, combining catalytic steps into cascade processes, thus obviating the need for isolation of intermediate products, results in a further optimization of both the economics and the environmental footprint of the process. In vivo this amounts to metabolic pathway engineering [20] of the host microorganism (see Chapter 8) and in vitro it constitutes a combination of chemo- and/or biocatalytic steps in series and is referred to as cascade catalysis (see Chapter 9). Metabolic engineering involves, by necessity, renewable raw materials and is a vital component of the future development of renewable feedstocks for fuels and chemicals. 

A methodology was described to assess the feasibihty of success in making commodity chemicals from renewable resources. The methodology uses a five-step process in the assessment. The first step is portfolio selection, and some of the key selection criteria are high theoretical yields from substrate, high market interest, and volume. The second phase involves initial economic screening and uses an economic criterion called the Fraction of Revenue for Feedstock (FRF). In this calculation, the cost of the feedstock is divided by the value of all the products, and the products that show the most promise are those where the fraction is smallest. This value takes into account the yields of the products derived from the various feedstock components. The third phase is a comparative analysis of bioprocessing routes that uses a raw material cost ratio, which... 

NMR spectroscopy is a well-established analytical technique in biofuel research. Over the past few decades, lignocellulosic biomass and its conversion to supplement or displace non-renewable feedstocks has attracted increasing interest. The application of solid-state NMR spectroscopy has long been seen as an important tool in the study of cellulose and lignocellulose structure, biosynthesis, and deconstruction, especially considering the limited number of effective solvent systems and the significance of plant cell wall three-dimensional microstructure and component interaction to conversion yield and rate profiles. The article by Foston reviews common and recent applications of solid-state NMR spectroscopy methods that provide insight into the structural and dynamic processes of cellulose that control bulk properties and biofuel conversion. 

Chapter 3 provides a brief review of recent developments in areas of amorphous polymer blends. Differential mixing, chain dynamics, and glass transition properties for individual polymer components in miscible binary blends, as well as new methods to experimentally acquire such information, are considered. Miscible blend dynamics and length scales of mixing of amorphous polymer blends are discussed. Amorphous biopolymer blends involving polymers obtained from renewable feedstocks is also briefly reviewed. 

The castor plant is widely considered to be a nuisance plant, because it proliferates rapidly in poor, depleted soils that cannot sustain other more important commercial crops. It spreads quickly as a weed, and in some places has been listed as an intrusive species to be eliminated [51, 52]. Nevertheless, in recent years the industrial volume of castor oil has increased dramatically, driven primarily by the global interest in renewable resources for fuel and feedstocks as an alternative to petrochemicals. The majority of the volume growth has come from the Asian continent, primarily from India, where the castor plant is harvested commercially [53]. In addition to its direct use in pol3mrethane products, the oil and its components have been the focus of innovative new derivatization strategies to improve their properties for use in plastics, while retaining high levels of renewable content in the final products. These developments will be described in Section 4.5. 

The production of multiple products is generally seen as necessary to increase the economic viability of biomass conversion. This is encapsulated in the concept of a biorefmery , which according to the National Renewable Energy Laboratory (NREL) is a facility that integrates conversion processes and equipment to produce fuels, power and chemicals from biomass [23], Examples of chemicals that can be produced from biomass include ethanol, methanol, furfural, paper, lignin, vanillin, lactic acid, dimethylsulfoxide and xylitol. In many cases, using biomass as a feedstock for chemical production requires an initial step to separate or fractionate the three main components into usable fractions [20, 22], This also maximises the usage of the different biomass components. 

Ethanol is the only renewable liquid fuel made in commercial quantities and supplies about 1% of the gasoline type transport fuels used in the USA. Approximately 95% of the commercial production of ethanol in the USA is currently by direct fermentation of com-sourced carbohydrates. However, fermentation of synthesis gas has the advantage over direct fermentation of sugars from cellulose and the hemicelluloses in that all wood components, including lignin and bark, are suitable feedstocks. 

One must also examine possible barriers in the overall production of chemicals. However, there are some interesting similarities between the renewables and petrochemical industries. Both face the same three general issues for producing chemicals. First is an issue of supply. Both industries need to know the source of their feedstock, its lifetime, and methods for its removal from the structures in which it is found. Second, both industries must face issues of separation by determining what components are present in the feedstock and how these components are separated from one another. Finally, both industries face the issue of conversion. Once the building blocks are removed from the feedstock, they must be converted to products. Of these three... 

Bozell, J. J. Landucci, R. eds.. Alternative Feedstocks Program Technical and Economic Assessment Thermal/Chemical and Bioprocessing Components, available from the author at the National Renewable Energy Laboratory, 1993. 

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