London, January 8 : US scientists are figuring out whether prairie grasses hold the future of biofuels, after finding that switchgrass yields 540 per cent more energy than is used to grow it.
Kenneth Vogel, an expert at the US Department of Agriculture and the University of Nebraska, led a large-scale field test of the grass by studying its growth on the borders of 10 farms in Dakota.
The farmers in those areas were asked to take account of the amount of seeds, fertilizer and fuel used for growing the grass, the frequency of rains, and the quantity of grass harvested over five years.
Vogel said that farms in different areas produced different amounts of switchgrass mostly because of different amounts of rainfall, an information that he used to estimate how much bioethanol could be produced from the grass.
He reckoned that, on average, 60 gigajoules of energy per hectare could be produced every year if the grass were turned into bioethanol.
As compared to corn grain ethanol that currently returns 25 per cent more energy than is used to produce it, Vogel calculated that the net energy gain from the switchgrass would be 540 per cent higher.
He also said that greenhouse-gas emissions from the switchgrass would be 94 per cent lower than emissions from petrol.
The renewable fuel should be seriously considered as a low-greenhouse-gas, high-energy biofuel source, the researchers say.
While use of prairie grasses as a renewable fuel has been highly debatable because of the competition for land that could otherwise be used to grow food, Vogel clarified that he was not proposing to replace corn or other crops with switchgrass.
"We are developing switchgrass for use on marginal cropland in the US. We do not expect it to replace corn or other grain or oilseed crops on the best land," Nature magazine quoted him as saying.
Vogel also admitted that even conducting field trials on arable land for a large period was difficult.
He, however, strongly feels that land-management, breeding improvements and advances in cellulosic-ethanol production techniques may enable further increase the 540 per cent energy figure in future.
He has also hinted that the fiscal economics of growing switchgrass as a biomass energy crop are positive too.
Vogel's findings have been published in the Proceedings of the National Academy of Sciences.