This article is reproduced with the permission of New Scientist for exclusive use by Nova users.

Can biofuels rescue American prairies?
18 August 2007
NewScientist.com news service
Jim Giles, San Jose

It is boom time in the agricultural states of the American Midwest. On bumper stickers and billboards, locals are celebrating the arrival of a profitable industry. Golden corn cobs are being turned into ethanol, an alternative to gasoline. If you believe the posters, corn ethanol will enrich the environment as well as the region, while reducing dependence on foreign oil.

But one group definitely does not buy the sales talk. Last week in San Jose, California, ecologists lined up to criticise corn ethanol. At a special session of the annual meeting of the Ecological Society of America (ESA), they argued that the expansion of corn ethanol is damaging soils and threatening wildlife, while doing little to cut US greenhouse gas emissions.

Ecologists also fear that the corn boom will suck resources away from the development of cellulosic ethanol, extracted from fast-growing wild grasses. They claim that this technology could deliver cleaner energy while simultaneously helping to restore one of the country's disappearing ecosystems: the mixed grasslands of the American prairie.

Spurred on by rising oil prices and the 2005 Energy Policy Act, which demanded that at least 28 billion litres of ethanol be produced annually by 2012, the number of US corn ethanol plants has doubled to around 120 in the past five years. Indeed, the industry is already close to the 2012 target, according to figures from the Renewable Fuels Association, an ethanol industry body based in Washington DC.

This rapid development has come at a cost. David Sample of the Wisconsin Department of Natural Resources in Madison told the ESA meeting that corn production jumped 10 per cent last year in his state alone. As the cornfields expand, government grants aimed at encouraging farmers to set aside marginal land to protect soils and biodiversity are going unused.

This trend is especially damaging for birds that nest in the grass that grows on set-aside land. Sample estimates that 16 per cent of land protected under the set-aside scheme will be lost this year. In Wisconsin, the figure could exceed one-third. "Marginal land is being developed for corn, but corn is pretty much useless as a habitat for the birds we care about," says Sample.

Such sacrifices might be considered justified if corn ethanol were having a big impact on greenhouse gas emissions. However, corn requires large amounts of fertiliser, which is energy-intensive to produce. As a result, corn ethanol releases at most only 25 per cent more energy than is required to grow and process the crop, according to calculations published last year by a team led by Alex Farrell of the University of California at Berkeley (Science, DOI: 10.1126/science.1121416). His team calculated that the total greenhouse gas emissions associated with running a car on corn ethanol are just 13 per cent lower than gasoline. The fertilisers used on corn also pollute streams and create dead zones - water so low in oxygen it kills marine life - at the mouths of rivers.

Yet studies presented at the ESA meeting suggest that cellulosic ethanol from native grasses could fix many of these problems. Ethanol is fermented from sugars, which can be produced easily from corn starch or extracted directly from sugar cane (see "All aboard the Brazilian bandwagon"). But sugars can also be produced from cellulose, which makes up most of the biomass of fast-growing prairie grasses. Although the process of extracting sugar is more complex than for corn starch, cellulosic ethanol from wild grasses has big potential energetic and environmental advantages.

Robert Mitchell of the University of Nebraska in Lincoln has been monitoring 10 farm-scale plots of switchgrass since 2000. Based on yields from these plots, and models describing the production of cellulosic ethanol, he told the ESA meeting that ethanol produced from such grasses would yield up to 15 times more energy than it uses during production, a huge improvement on corn.

Jason Hill of the University of Minnesota in St Paul has come up with similarly impressive projections. Hill did not add the fertiliser that Mitchell's group used, so the energy yield from his grasses was 2 to 6 times less.Significantly, though, the grasses took in more carbon dioxide from the atmosphere than was released from the fuel used to grow and process them. The carbon dioxide removed - around a third of a tonne per hectare per year - was taken up by the roots and so remained in the soil after the harvest. This means that the greenhouse gas savings from wild-grass ethanol could be up to 16 times as great as those from corn (Science, DOI: 10.1126/science.1133306).

Hill's work also suggests that wild grass could be farmed more efficiently in mixed species plots, mimicking the make-up of natural prairie. When his group combined eight species of grass in a single plot, yields were more than 150 per cent higher than from grass monocultures. In 16-species plots, the improvement was 238 per cent.

Such diverse mixes provide better havens for wildlife. In Wisconsin, Sample has studied field-sized plots of mixed grasses of the type that would be suitable for biofuel farming. He found that a typical plot hosted three threatened bird species, while the average for corn was less than one species per plot. Harvesting the grass should not wipe out these gains in biodiversity, because it would have a similar effect to the fires that sweep through natural prairies most years. It all suggests that America's prairies, which now cover just 1 per cent of their original area, could be partially restored by biofuel farming, Hill says.

However, the ecologists who presented their results at the ESA meeting face some hurdles in bursting the corn ethanol bubble. For instance, David Pimentel, an agricultural scientist at Cornell University in Ithaca, New York, questions the assumptions of the models wild-grass researchers use to calculate energy yields. He claims the resulting estimates are much too high and also argues that much of the land suitable for grasses is already used to produce fodder for livestock, limiting how much could be switched over.

The biggest obstacles may be political, however. For grass cultivation to really take off, government incentives will be needed to build new facilities for large-scale processing of cellulose and to rival the generous subsidies currently paid to corn growers. Yet the powerful agricultural lobby is doing all it can to get politicians to focus on corn ethanol, which promises more immediate gains for farmers.

Roger Samson, a specialist in biofuels policy at Resource Efficient Agricultural Production Canada, a not-for-profit organisation based in St Anne de Bellevue, believes corn ethanol is the wrong approach. "If this is a horse race, the US government has bet on a donkey," he says.

From issue 2617 of New Scientist magazine, 18 August 2007, page 8-9

All aboard the Brazilian Bandwagon Last week, two Latin American presidents embarked on separate tours of neighbouring countries to sell their conflicting visions of the future of energy. While firebrand Hugo Chavez of Venezuela went to Argentina, Ecuador, Bolivia and Uruguay to talk about oil and gas, Brazil's Luiz Inàcio Lula da Silva headed to Mexico, Honduras, Nicaragua, Jamaica and Panama to try and export his nation's experience in making ethanol from sugar cane. But can Brazil's biofuel boom, which has seen the nation switch 30 per cent of its demand for automobile fuel over to ethanol from sugar cane, really be reproduced elsewhere? Brazil's expertise in growing and processing sugar cane is certainly transferable. The Brazilian Agricultural Research Corporation, or Embrapa, has developed hundreds of varieties of sugar cane, each adapted to a certain climate and soil. Plantations mix and match varieties to obtain maximum yields. Factories use the crop to produce sugar or ethanol, and can switch back and forth depending on which commodity is trading at a higher price on any given day. However, Brazil's bioethanol success is also tightly linked to its particular environmental and economic circumstances. In south-east Brazil, where most of the sugar cane is produced, land is still relatively cheap. It is also flat, making it easy to mechanise sugar cane production, and the crops are entirely rain-fed. With no need for irrigation, sugar can be extracted with little expenditure of energy. "The cane is simply squeezed and the sugar runs out," says Alex Farrell of the University of California at Berkeley. Unfortunately for Lula, this happy combination of factors cannot easily be exported. Brazil has created a guaranteed market by demanding that fuel pumps supply either ethanol or a gasoline mix containing 25 per cent ethanol. As countries elsewhere adopt targets for mixing ethanol with gasoline, Lula sees an important export opportunity. Still, the US and other developed countries would be nervous about depending on a single nation for the majority of their ethanol imports. Hence Lula's determined efforts to get other Latin American nations on the biofuel bandwagon. "The Brazilian government has the sophisticated view that it will do well if there are multiple producers in the world," says John Briscoe, director of the World Bank in Brazil. "A market five times bigger that they have 50 per cent of is a lot better than a market the current size which they have 90 per cent of." Catherine Brahic

For the latest from New Scientiist visit www.newscientist.com