BIOFUEL: PRESENT STATUS AND FUTURE PROSPECTS

The developments of sugar-derived ethanol as a major transportation fuel in Brazil and corn-derived ethanol as a niche (but rapidly growing) market in the United States were conditioned by different mixes of economic and environmental imperatives from the early 1970s to the present day. Together and separately, they have been criticized as unsuitable for sustainable alternatives to gasoline in the absence of tax incentives; highly integrated production processes, with maximum use of coproducts and high degrees of energy efficiency, are mandated to achieve full economic competitiveness. Although technically proven as a technology, the scope of ethanol production from food crops (primarily sugar and corn) is limited by agricultural and geographical factors, and only cellulosic sources offer the quantita­tive availability to significantly substitute for gasoline on a national or global basis. Even for that goal, however, bioethanol is only one player in a diverse repertoire of strategic and tactical ploys and mechanisms — from carbon capture and storage to hydrogen-utilizing fuel cells — with which to change the oil economy and reduce dependence on fossil fuels.103

Both corn — and sugarcane-derived ethanol have — unarguably but not irre­versibly — emerged as industrial realities.104 Even detailed questions about their NEBs and the implications of their use in mitigating greenhouse gas emissions have become unavoidable on Web site discussion forums. A major article in the October issue of National Geographic magazine accepted the marginal energy gain in corn ethanol production and the disappointingly small reduction of total CO2 emissions in the total production/use cycle but noted the much clearer benefits of sugarcane ethanol.105 Two quotes encapsulate the ambiguous reactions that are increasingly evident as the public debate over biofuels spreads away from scientific interest groups to embrace environmentalist and other “lobbies”:

It’s easy to lose faith in biofuels if corn ethanol is all you know, and

If alcohol is a “clean” fuel, the process of making it is very dirty… especially the

burning of cane and the exploitation of cane workers.

All forms of ethanol produced from plant substrates are, however, best viewed as “first-generation” biofuels, operating within parameters determined by (in varying allocated orders): the internal combustion engine, mass personal transport, and the global oil industry.105 Together with biodiesel (i. e., chemically esterified forms of the fatty acids present in vegetable oils — see chapter 6, section 6.1), they have proven potential for extending the availability of gasoline blends and are affordable within the budgets accepted by consumers in the late twentieth and early twenty — first centuries while helping to reduce greenhouse gas emissions and (with some technologies, at least) other atmospheric pollutants. It is, however, likely that different countries and supranational economic groupings (e. g., the European Union) will value differently energy security, economic price, and ecological factors in the face of fluctuating oil prices and uncertain mid — to long-term availabilities of fossil fuels.106 Fermentation products other than ethanol (e. g., glycerol, butanol) and their thermochemical conversion to synthesis gas mixtures to power electricity generation are second-generation technologies, whereas biohydrogen, fuel cells, and microbial fuel cells represent more radical options with longer lead times.107108

Sugar — and corn-derived ethanol production processes were simply extrapolated from preexisting technologies, and to varying extents, they reflect the limitations of “add-on” manufacturing strategies.109110 As one example of the National Geographic writer’s anticipated “breakthrough or two,” lignocellulosic ethanol only emerged as a commercial biofuel reality in 2004, and biotechnology is crucial to its establishment as a major industry.105111 For that reason, and because of the uniquely global potential of this nonfood sector of the bioethanol supply chain, the microbial biotechnology of cellulosic ethanol will now be considered at length, to provide not only a snapshot of commercially relevant contemporary science but also to extrapolate existing trends in the development of the scientific base.