Biochemical biorefinery

Main type of conversion processes applied thermochemical biorefineries, biochemical biorefineries, two platform concept biorefineries. 

Besides production of biochar as an intended or unintended coproduct during conversion of biomass to biofuels and chemicals in thermochemical biorefineries, biochemical biorefineries also provide opportunities for production of biochar as a standalone process, valorizing residues resulting from biological treatments. Various residues can be left behind after enzymatic, microbial, and other treatments in biorefineries, mainly constituting recalcitrant fractions high in lignin and mineral matter. Both of these streams can be used in biochar production, as discussed below. 

Figure 1.12 Afuture biorefinery model based on a biochemical production plant.

The alternative pathway is the biochemical route. It processes starches/sugars into ethanol, a standard technology with installations world-wide, but in a biorefinery the start is the whole-plant material or biomass residues containing hemicel-lulose, which is broken into sugars that then can be fermented to ethanol and/or other alcohols such as butanol. As mentioned before, there is the need to develop novel and/or improved biocatalysts for alternative organic fuels, such as biobutanol, by fermentation processes. 

Wright, M. and R.C. Brown, Comparative Economics of Biorefineries Based on the Biochemical and Thermochemical Platforms, Biofuels, Bioprod. Bioref, 1, 49-56 (2007a). 

On the other hand, the six-carbon unit of glucose is one of the most prominent components in biomasses, is easy to produce, and represents one of the most attractive building blocks for the preparation of a variety of chemical intermediates. Thus, glucose will play a central role in feeding the so-called biorefinery, a future plant where chemical and biochemical processes are advantageously employed for the synthesis of intermediates and fine chemicals as an alternative to fossil-derived chemicals (Figure 21.1). 

Wright, M.M. and Brown, R.C. (2007) Comparative economics of biorefineries based on the biochemical and thermochemical platforms. BioJUels Biorfineries Bioproducts, 1,49-56. 

Despite some successes in PHA production by plants, Drs. Yves Poirier and Stevens Brumbley believe production of PHA in crops and plants remains a challenging project. The challenges for the future are to succeed in the synthesis of PHA co-polymer with a narrow range of monomer composition, at levels that do not compromise plant productivity, and to find methods for efficient and economical extraction of polymers from plants. These goals will undonbtedly require a deeper understanding of plant biochemical pathways and advances in biorefinery. 

Processes employed in biorefinery concepts to convert biomass feedstock into marketable products include biochemical (e.g., anaerobic digestion, microbial fermentation, enzymatic conversion), chemical (e.g., hydrolysis, transesterification, hydrogenation, oxidation), and thermochemical (e.g., pyrolysis, gasification) processes. 

To evaluate the sustainability concerning economic, environmental, and social aspects the Department of Energy (DOE) is funding integrated biorefinery projects in pilot, demonstration, and commercial scale. The importance of biochemical conversion is underlined by the fact that four out of five commercial scale plants funded by the DOE are based on biochemical conversion (Department of Energy, 2012). 

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