For bioethanol to become more sustainable to replace petrol the production process has to be more efficient i.e. the cost of conversion to be reduced, to increase yields and to increase the diversity of crop used.
With the current methods we convert 50% to 72% ethanol per 1 gram glucose.
Microbiology and biotechnology will be helpful in the genetic engineering so to come to microbes which convert glucose into sugar so the latter to ferment in bioethanol.
Feedstocks
Crops used in bioethanol production | |
Brazil | sugar cane |
USA | corn |
Europe | wheat and barley |
Sugar is required to produce ethanol by fermentation. Plant materials (grain, stems and leaves) are composed mainly of sugars, so in principle almost any plants can serve as feedstock for ethanol manufacture. In practice, the choice of raw material depends on what grows best under the prevailing conditions of climate, landscape and soil composition, as well as on the sugar content and ease of processing of the various plants available. The result is a wide variety of ethanol feedstocks, and hence production processes.
Worldwide, most bioethanol is produced from sugar cane (Brazil), molasses and corn (USA), but other starchy materials such as wheat, barley and rye are also suitable. Crops that contain starch have to be converted to sugars first.
R&D activities on using lignocellulosic or woody materials as feedstock. These include short rotation energy crops (for example willow, popular, miscanthus and eucalyptus), agricultural residues (e.g. straw and sugar cane bagasse), forest residues, waste woods, and municipal solid wastes.
Reasons for shifting to ethanol production from lignocellulosic biomass:
Lignocellulosic biomass is more abundant and less expensive than food crops, especially when it concerns a waste stream with very little or even negative economic value. Furthermore, it has a higher net energy balance, which makes it more attractive from an environmental point of view. Indeed, ligno-cellusolic bioethanol has the potential to accrue up to 90% in greenhouse gas savings, well ahead of first generation biofuels. However, these kinds of biomass are more difficult to convert to sugars due to their relatively inaccessible molecular structure.
