The biorefining story: Progress in the commercialization of biomass-to-ethanol

Abstract

Continued insecurity around oil supplies has helped to keep oil prices high, and the combination of these factors have driven a rapid expansion in global bioethanol and biodiesel production. While foods such as sugar and corn are still the dominant feedstock for biofuel production, interest in utilizing lignocellulose for the production of a 2nd generation of biofuels has grown significantly. The agricultural sector has made significant progress in developing bio-based fuels and chemicals. Technologies from the agricultural sector may be combined with recent technical improvements that have made wood-based bioconversion more feasible. The biorefinery concept has been proposed as a means to extract maximum value from lignocellulosics, of which only a portion of the chemical structure is suitable for biofuel production. Within the biorefinery, some components of the lignocellulosic feedstock may be converted into a range of material, chemical and energy, as the basis products, such as wood chips. The continued development of new conversion technologies will allow these biorefineries to utilize lignocellulosic feedstocks, enabling the production of additional value-added bioproducts and more efficient recovery of bioenergy. There are a number of complementary platforms for processing lignocellulosic feedstocks, including traditional platforms (i.e. existing pulping technologies) as well as emerging technologies that are biological-based or thermochemical-based. Each of these platforms can be organized to produce bioenergy, biofuel, and/or bioproducts (including both material and chemical products). The emerging biological platform uses biological agents, including enzymes and microbes, to hydrolyze and ferment components of lignocellulose to ethanol and other value-added products. The thermochemical platform utilizes pyrolysis and gasification stages to convert lignocellulosic biomass into synthesis gas, which can then be catalyzed into a variety of products. It is apparent that technical barriers remain for 2nd generation biofuel production. Production costs are uncertain but currently thought to be around USD 0.80-1.00/l of gasoline equivalent. There is no clear candidate for best technology pathway between the competing biochemical and thermo-chemical routes and monitoring of large-scale demonstration projects is essential to provide accurate comparative data. Even at higher oil prices, 2nd-generation biofuels will probably not become fully commercial nor enter the market for several years to come without significant government support. Considerably more investment in research, development, demonstration and deployment (RDD&D) is needed to ensure that future production of the various biomass feedstocks can be undertaken sustainably and that the preferred conversion technologies are identified and proven to be viable. Once proven, there will be a steady transition from 1st to 2nd generation biofuels (with the exception of sugarcane ethanol that will continue to be produced sustainably in several countries).