1 - Industrial Bioprocesses and the Biorefinery Concept

Abstract

Both economic and environmental drivers have been major considerations in the development of sustainable chemical production using renewable crop-based feedstocks. Biomass is characterized by a plentiful carbon-neutral renewable feedstock for the production of fuels and chemicals, replacing fossil fuels and petrochemicals. First-generation biorefineries use corn, soybeans, and sugarcane for bioethanol and biodiesel production, which can benefit from integrated biorefining that extracts high-value nutritional products while using the main feedstock component for biofuel and chemical production and further converting low-value by-products to additional marketable products such as animal feed and energy. Second-generation biorefineries use lignocellulosic biomass, including agricultural and forestry residues, and provide the opportunity to meet a significant portion of fuel and chemical needs. Third-generation biorefineries use aquacultures of either microalgae or macroalgae, which use sunlight and CO2 for growth, which could deliver all upcoming fuel needs without disturbing current land use for agricultural purposes. With continuing progress and improvements in new energy crops, aquaculture, synthetic biology for cell engineering, and conversion technologies, biorefining will have an increasingly important role in supplying energy, fuel, and chemicals to sustain economic growth without a substantial negative effect on the environment. Nevertheless, there are also numerous challenges facing the biorefinery industry. Lignocellulosic refining is not yet rationally cost-effective because of the complex nature of the feedstock as well as high costs of pretreatment and enzymatic hydrolysis of cellulose. Although a number of new bioprocesses of cellulosic biomass have been industrialized, it is clear that economic and technical barriers exist that must be addressed before the full potential of this area can be recognized. In addition, processes using microalgae with photosynthesis for cell growth and oil production are not only difficult to scale up but also far from cost-effective. To achieve the sustainable and economical production of biofuels and bio-based chemicals, new advances in process engineering and metabolic engineering for biomass conversion will be required. Moreover, a biorefinery should consume all components of a given biomass feedstock to produce fuels, chemicals, and energy, to take full advantage of product values, decrease waste generation, and recover process economics, which necessitates a combination of technologies from various areas, including new energy crops with higher biomass yields, improved and inexpensive enzymes for hydrolysis, innovative and upgraded cells and catalysts for biomass conversion to chemicals, fuels, and other marketable products, and more efficient processes for the production of these bio-based products on an industrial scale.