New Avenues of Bioenergy Production from Plants: Green Alternatives to Petroleum

Abstract

Depleting fossil fuel reserves and growing demand for energy have necessitated the renewed search for alternative energy resources such as plants and algae. The first generation biofuels were produced from starch and sugars (bioethanol) and from seed oils (biodiesel). These, however, soon became negatively associated with issues such as competition with food supply, significant land-use changes and many other ethical issues. The production of second generation biofuels from lignocellulosic materials from grasses and trees requires high-input technologies involving extensive pre-treatments and expensive cellulolytic enzymes, adding to the high costs of second generation bioethanol. Recently, third generation biofuels derived from microalgae have attracted the attention of plant biologists and industrialists due to fast growth rate, high CO2 fixation ability and high production capacity of microalgae. Now, there also exists a promising fourth generation of biofuels on the horizon which involves metabolically-engineering of plants and algae possessing traits such as high biomass yield, improved feedstock quality and high CO2 fixation. Various novel processes such as gasification, pyrolysis and torrefaction are also being pursued for improving the total energy yield from plant biomass. Recent investigations in biofuels area are aimed at developing plants with improved feedstock quality, developing recombinant enzymes for rapid cell wall degradation, improving capacity of microorganisms for efficient fermentation, and discovering novel methods for efficient utilization of plants and algae for producing biofuels.