Bioethanol appears to have been firmly established as an important form of alternate fuel. With the second and later generation of bioethanol production focusing on the use of cellulosic biomass, the need for improvement of biomass plants is evident from the above discussion. Despite the occasional controversies raised, bioethanol is an environmentally friendly renewable energy source, and its large-scale use will lead to significant reduction in net emission of GHG. Alternate forms of biofuels such as oils to be used as biodiesel either from plants or from algae are also being explored. The emerging field of synthetic biology strives to convert microalgae into an efficient fuel oil production system. Although it is in its infancy, based on the underlying biological facts, synthetic biology for biofuel production by microalgae is expected to be successful in the coming decades.

It is important to phase out the use of food grains for fuel production in the coming decades. Because of the significant increase in demand for food grain expected, the conflicting demands on agricultural land will lead to serious social conflicts. Therefore, improving the efficiency and scaling up production of cellulosic ethanol is imperative. In order to achieve this, it is important to generate sufficient amounts of cellulosic biomass. Well over a trillion liters of ethanol (theoretical yield per year) can be obtained if all the available corn stover, rice straw and wheat straw (estimated 3 billion tons per year, [6]) are utilized for biofuel production. This represents one year’s oil demand of USA or approxi­mately 25% of the annual world usage of petroleum. Currently, a significant amount of straw is either burnt and disposed off or used for animal feed. Therefore, use of non-food crop biomass plants becomes essential to broaden the availability of raw material for bioethanol production. Unlike with food crops, objections will be minimal if genetic modification strategies are applied to the biofuel plants to enhance yield, be tolerant to stresses and adverse growth conditions.

We have identified manipulation of the intermediates of phytohormone sig­naling pathways as an important strategy for enhancing plant biomass. The key developmental processes affecting biomass, which include reduced apical domi­nance and increased branching, plant height, leaf area and root to shoot ratio etc., are strongly influenced by phytohormones. The fact that phytohormones have pleiotropic effects on growth and development combined with the recent findings of the multiple signaling intermediates presents tremendous untapped opportuni­ties for modifying specific traits listed above for improvement of the biofuel plants. The various signaling intermediates and downstream target genes can serve as candidates for biotechnological improvement or future marker-assisted breeding efforts.

The foregoing discussion has highlighted the need for and feasibility of using genetic and biotechnological approaches to enhance biomass production from a unit land area. Knowledge gained from model plants can be adapted to the biofuel crops in order to achieve this and to ensure sustainable biofuel production as a valuable alternative fuel in the decades to come.

Acknowledgments We thank Ms. Petra Stamm for helping to prepare Fig. 8.1. Research in the author’s laboratory is funded by the Science and Engineering Research Council (SERC Grant No.: 0921390036) of the Agency for Science Technology and Research, Singapore; and the National University of Singapore.