Study: Biofuels More Efficient As Electricity Source

BiomassGlobal biofuel production would use limited farmland more efficiently if the biomass were converted into electricity to power electric cars rather than refined into ethanol, a new analysis finds.

The findings, published last week in the journal Science, suggest that transportation policies in the United States and Europe that seek to address climate change may allow vehicles to travel farther and offset more greenhouse gas emissions if biomass resources were used to charge electric vehicles. Instead, current biofuel production mandates support the conversion of biomass feedstocks into ethanol or biodiesel.

"If you [have the choice to] burn biomass to make electricity or to convert it to ethanol and make power in an internal combustion vehicle, you make more efficient use of the land and more efficient use of the plant biomass by making electricity rather than ethanol," said Elliott Campbell, an environmental scientist at the University of California, Merced, who led the study. "It's another reason that, rather than race to liquid biofuels, we should consider other uses of bio-resources such as for electricity."

To measure the efficiency of liquid biofuel, the study used a lifecycle assessment to calculate the energy required to run ethanol refineries (often natural gas-powered), produce internal combustion engines, and transport the fuel to filling stations. For comparison, the researchers then examined the efficiencies of biomass-fired power plants, electric vehicle production, and electricity transmission.

The study, which was co-authored by Stanford University's David Lobell and Chris Field, also compared the transportation and greenhouse gas emission savings of advanced biofuels - more energy-efficient fuels derived from sources such as waste material, algae, and switchgrass. Regardless of the fuel source, the researchers found that bioelectricity was the most efficient option.

For switchgrass, a promising "energy crop" for use in both cellulosic ethanol and biomass fuel, the analysis found that a hectare of switchgrass would allow vehicles to travel 81 percent farther on average if it were pressed into pellets and burned to generate electricity than if it were converted to liquid fuel for vehicles.

Converting switchgrass to electricity would also reduce greenhouse gases by 108 percent more than if the feedstock were converted to ethanol, according to the study. The analysis noted that biofuel-powered power plants could even become "carbon-negative" energy sources if they used carbon capture and sequestration (CCS) technologies that remove carbon from smokestacks and store the gas underground.

For either pathway to become a widespread climate solution, technological breakthroughs are necessary, analysts say. Researchers continue to search for more cost-effective methods to develop cellulosic ethanol and advanced vehicle batteries.

The efficiency of farm land and biofuels production can play a role in climate change mitigation as well, according to studies. Environmentalists worry that if biofuel policies reduce feedstock supplies and increase crop prices, farmers may have an incentive to expand cropland. When tropical forests, peatlands, and other lands that are rich in carbon are converted to cropland, large quantities of greenhouse gases are potentially released.

In the United States, the world's biofuel leader, producing 1 billion gallons of ethanol requires an estimated 100,000-122,000 hectares of land. Estimates for land usage overseas, however, are less precise. Iowa State University economist Bruce Babcock estimates that between 162,000 and 283,000 hectares will be converted for every billion gallon of biofuel produced.

If farmers grow their crops in abandoned fields or degraded areas, however, converting land to grow biofuels could help to mitigate climate change and lessen the chance of raising food prices as well. But in most countries in North America, Europe, and Asia, abandoned lands would provide less than 10 percent of primary energy demand, Campbell estimated in a 2008 study.

"If you're dealing with a limited, constrained resource, you really have to ask the question of what is the most efficient use of biomass with respect to how much land you will need," Campbell said. "With a limited amount of biomass or a limited amount of land, you can use more for transportation and more of a greenhouse gas offset by making electricity."

Global biofuels production continues to rise, reaching an estimated 54 billion liters in 2007. U.S. corn and Brazilian sugar cane are the leading feedstocks, generating as much as 95 percent of the world's ethanol.

By comparison, biomass supplies about 52 gigawatts of power generation capacity worldwide, equivalent to less than 5 percent of U.S. electric power capacity, according to the Renewable Energy Policy Network (REN21). Biomass plants most commonly burn wood products, municipal garbage, and agricultural waste.

Ben Block is a staff writer with the Worldwatch Institute. He can be reached at bblock@worldwatch.org.

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