Updated on 7 September 2012
There will be a progressive scarcity of fossil fuel products if immediate and innovative measures are not taken for its sustainable use. There is also a need to develop sustainable and renewable alternatives. In fact, bioenergy derived from sources such as starch from corns, sugar from cane, and oils from plants, will play an essential role in reaching targets and replace petroleum-based transportation fuels as a cost-effective and environmentally sustainable alternative and in reducing long-term CO2 emissions.
Although plant-derived biofuels are renewable resources and often carbon-neutral, they have been criticized because of concomitant land use change, detrimental effects to biological diversity and increases in the food prices. These drawbacks have led to tremendous amount of recent research taking place in second-generation biofuel development that primarily focus on mining energy from lignocellulosic biomass sources, where stems, leaves and husks (dedicated feedstocks and agricultural wastes) are used for the production of biofuels.
Unlike the easily processed sugars and oils in first-generation biofuels, lignocellulosic, biomass consists of matter composed of difficult-to-digest material found in cell walls of plants such as grasses, crop residue, and woody forest waste. These second generation biofuels have advantage as they are not restricted to current agricultural land, thus removing competition between the uses of land for food or fuel production.
Of special interest is the role of dedicated bioenergy feedstocks to the production of the second generation biofuels. It is envisaged that new crops, such as switchgrass, could reliably be produced to offset petroleum. Switchgrass is a C4 perennial warm season species of the North American tallgrass prairie. Its widespread environmental adaptation, ability to grow from seed on marginal lands, low nutrient requirements and production costs, high water-use efficiency, capacity to protect soil from erosion, ease of harvesting, potential for carbon storage, and winter hardiness among others, makes it a promising dedicated bioenergy feedstock for biofuel production. If the aboveground biomass is harvested once, at the end of the growing season, typical ethanol yield has been calculated to be 4353 liters per acre.
Unlike the maize grain, which must be replanted every year, switchgrass is planted once every 10-to-12 years. It is a perennial grass that re-sprouts each spring and summer from the underground parts of the plant. A detailed study involving multi-location field trails examined the net energy output, greenhouse gas emissions, biomass yields, agricultural inputs and estimated cellulosic ethanol production from switchgrass grown and managed for biomass fuel.