Top 7 alternative energies listed

The US could replace all its cars and trucks with electric cars powered by wind turbines taking up less than 3 square kilometres - in theory, at least. That's the conclusion of a detailed study ranking 11 types of non-fossil fuels according to their total ecological footprint and their benefit to human health.

The study, carried out by Mark Jacobson at Stanford University, found wind power to be by far the most desirable source of energy. Biofuels from corn and plant waste came right at the bottom of the list, along with nuclear power and "clean" coal.

The energy sources that Jacobson found most promising were, in descending order:

• Wind

• Concentrated solar power (mirrors heating a tower of water)

• Geothermal energy

• Tidal energy

• Solar panels

• Wave energy

• Hydroelectric dams

To compare the fuels, Jacobson calculated the impacts each would have if it alone powered the entire US fleet of cars and trucks.

He considered not just the quantities of greenhouse gases that would be emitted, but also the impact the fuels would have on the ecosystem - taking up land and polluting water, for instance. Also considered were the fuel's impact on pollution and therefore human health, the availability of necessary resources, and the energy form's reliability.

"Some options that have been proposed are just downright awful," he says. "Ethanol-based biofuels will actually cause more harm to human health, wildlife, water supply, and land use than current fossil fuels." Jacobson says it would take 30 times more space to grow enough corn to power the US fleet than would be needed to erect enough wind turbines, while bioethanol would produce more greenhouse gases than wind power.

Nuclear is another energy source whose merits have been debated by European and US leaders alike in the past 12 months. "It results in 25 times more carbon and air pollution than wind," says Jacobson.

"Clean" coal - the process of burning coal then capturing the emitted carbon dioxide and storing it underground - is another political favourite. Jacobson's calculations show that building and using enough clean coal power plants would emit up to 110 times more carbon than building and using wind turbines only.

"The philosophy that we should try a little bit of everything is wrong," says Jacobson. "We need to focus on the technologies that provide the best benefit. We know which these are."

Jacobson acknowledges that politicians are calling for a massive jobs programme to pull the economy out of recession, but says investment in renewable energy is one way to do that. "Putting people to work building wind turbines, solar plants, geothermal plants, electric vehicles, and transmission lines would not only create jobs but also reduce costs due to healthcare, crop damage, and climate damage - as well as provide the world with a truly unlimited supply of clean power," he says.

http://www.newscientist.com/article/dn16419-top-7-alternative-energies-listed.html