Biomass-based feedstocks

Crude-Oil-Based Feedstock Biomass-Based Feedstock... 

Bioconversion of renewable feedstocks to industrial chemicals has been described. In this chapter, we have illustrated technology that Genencor International has developed to harness biomass as carbon feedstocks for conversion to industrial products and to make available its bioengineered enzymes to convert biomass into fermentable sugars. This research effort provides a means for the production of desired bioproducts by enzymatic conversion of biomass-based feedstock substrates. This concept of using cellulosic biomass for manufacturing industrial chemicals has several incentives that can be explored and implemented. 

In the future, biorefineries will process a variety of biomass-based feedstocks in order to produce new base chemicals for the production of many new and already existing bulk chemicals and polymers. White biotechnology will play an important role in this development, as it does already in the production of pharmaceuticals, fine chemicals and speciality chemicals. 

However, the different chemical composition of fossil feedstocks versus biomass-based feedstocks poses a new set of challenges in the development of active, selective, and stable zeolite catalysts. In contrast to petroleum resources, biomass feedstocks generally consist of highly oxygenated compounds with bulky and high molecular weight components such... 

Alternative feedstocks for petrochemicals have been the subject of much research and study over the past several decades, but have not yet become economically attractive. Chemical producers are expected to continue to use fossil fuels for energy and feedstock needs for the next 75 years. The most promising sources which have received the most attention include coal, tar sands, oil shale, and biomass. Near-term advances ia coal-gasification technology offer the greatest potential to replace oil- and gas-based feedstocks ia selected appHcations (10) (see Feedstocks, coal chemicals). 

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. 

Gasification technologies offer the potential of clean and efficient energy. The technologies enable the production of synthetic gas from low or negative-value carbon-based feedstocks such as coal, petroleum coke, high sulfur fuel oil, materials that would otherwise be disposed as waste, and biomass. The gas can be used in place of natural gas to generate electricity, or as a basic raw material to produce chemicals and liquid fuels. 

The primary product is fuel-grade, coal-derived gas which is similar to natural gas. The basic gasification process can also be applied to other carbon-based feedstocks such as biomass or municipal waste. 

Both in the USA and the EU, the introduction of renewable fuels standards is likely to increase considerably the consumption of bioethanol. Lignocelluloses from agricultural and forest industry residues and/or the carbohydrate fraction of municipal solid waste (MSW) will be the future source of biomass, but starch-rich sources such as corn grain (the major raw material for ethanol in USA) and sugar cane (in Brazil) are currently used. Although land devoted to fuel could reduce land available for food production, this is at present not a serious problem, but could become progressively more important with increasing use of bioethanol. For this reason, it is important to utilize other crops that could be cultivated in unused land (an important social factor to preserve rural populations) and, especially, start to use cellulose-based feedstocks and waste materials as raw material. 

As discussed in this book (Chapter 2, for example) a main difference between fossil fuels and biomass as feedstocks is that in the former case the functionalization of base chemicals obtained from the oil (ethylene, propylene, aromatics, etc.) occurs essentially by introduction of heteroatoms, while in the case of biomass-derived based chemicals (glycerol, for example) it is necessary to eliminate heteroatoms (oxygen, in particular). Consequently, the catalysts required to develop a petrochemistry based on bio-derived raw materials need to be discovered and cannot simply be translated from existing ones, even if the knowledge accumulated over many years will make this discovery process much faster than that involved in developing the petrochemical catalytic routes. 

A general conclusion is that incentives to convert conventional fossil fuel based technology into biomass based technologies are large, but implementation will be slowed down for several reasons. Firstly, there is the availability of biomass itself. The preferred feedstock should not compete with food production. Processes to convert such biomass practically into secondary energy carriers are not yet commercially available. In the mean time, technologies converting food related biomass will be implemented. But this will only occur for a limited period in the near future. 

Although technologies have been developed over past 50 years to process petroleum-based feedstock efficiently to generate hydrogen, its production from rene v-able biomass-derived resources remains a major challenge, because conversion processes often suffer from low hydrogen production rates and/or complex processing requirements [24, 25]. 

The use of organometallic rhenium complexes has found a very broad scope as oxidation catalysts as described in the previous section, making MTO the catalyst of choice for many oxidation reactions of olefins. Interestingly, MTO and related rhenium compounds have also found application in the reverse reaction, the deoxygenation of alcohols and diols. Especially in recent years, this reaction has attracted much attention due to the increased interest in the use of biomass as feedstock for the chemical industry. This section provides an overview of the use of rhenium-based catalysts in the deoxygenation reaction of renewables. 

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 ... 

It is important to emphasize that all conventional motor fuels—petroleum gasolines and diesel—are produced by complex refining processes. These fuels are mixtures and contain hundreds of organic compounds. None is a single, pure substance. Similarly, almost all biomass-based liquid motor fuels contain numerous organic compounds, but in some cases can consist of relatively few compounds, as in the case of the methyl esters of fatty acids in biodiesel. The exceptions are the lower molecular weight alcohols and a few derivatives that can be used directly as neat motor fuels. They can easily be manufactured from biomass feedstocks as individual compounds. 

Other compounds that can be produced directly from biomass in good yields, but which do not retain the basic structural characteristics of biomass, are also classified as commodity chemicals. Examples are acetic acid, methane, and synthesis gas. They are not manufactured in large volumes from biomass because fossil fuels are the preferred feedstocks in commercial production systems. Technically, biomass can serve as a feedstock for production of the entire range of commodity organic chemicals presently manufactured from fossil fuels. The various routes to large-volume chemicals from biomass will be examined later. Consider first some of the existing biomass-based chemicals, most of which are specialty chemicals that are manufactured for commercial markets. 

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