Conventional and Molecular Breeding for Improvement of Biofuel Crops

Past, Present, and Future

Authored by: Anjanabha Bhattacharya , Joseph E. Knoll

Handbook of Bioenergy Crop Plants

Print publication date:  March  2012
Online publication date:  April  2012

Print ISBN: 9781439816844
eBook ISBN: 9781315099255
Adobe ISBN:


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Initially when the potential of plants to produce liquid fuels was realized, the immediate focus was to use food and feed crops such as sugarcane (sugar), maize (starch), or soybean (oil) for biofuel production. Sugar can be directly fermented by yeast to produce ethanol, and starch can be easily converted into fermentable sugars. Many types of fats and oils can be chemically converted into biodiesel. Collectively, these fuels are known as first-generation biofuels. However, it was soon realized that these crops alone cannot meet the current demand for fuel because converting these crops into fuels is relatively inefficient with respect to the ratio energy output to input, mostly because only a fraction of the plant is utilized. Also, increased production of crops for fuel use has raised concerns about the environmental impacts of intensive agriculture and changing land usage. In addition, with the rapidly growing human population and increasing demand for animal products, the diversion of food and feed to fuel has become controversial. Biofuel production from food crops such as sugarcane, sunflower, soybean, sugarbeet, rapeseed, and maize has been blamed for triggering a food crisis in recent years. Whether or not increased biofuel production has really displaced a significant quantity of food is still highly debated. Nonetheless, this does raise a question: which should be given a priority when it comes to making a choice between energy and food resources? The answer to this paradox lies in utilization of crop residues and the many potential dedicated nonfood biofuel crops, including perennial grasses, such as switchgrass (Panicum virgatum L.) and Miscanthus spp.; fast-growing trees including poplar (Populus spp.) and willow (Salix spp.); fiber crops such as kenaf (Hibiscus cannabinus L.); and oil-rich nonedible crops such as Jatropha curcas L. and Millettia pinnata (L.) Panigrahi. Production of biofuels from food crop residues or from dedicated nonfood lignocellulosic crops utilizes the whole plant, thus capturing more energy per unit of land area.

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