Good Algae, Bad Algae
6:39 PM on Aug 11, 2011
Good news and bad news for biofuels. Researchers at the University of Virginia say algae will produce significantly more biofuel per hectare planted than canola or switchgrass, and can be grown on poor-quality marginal land that cannot easily be used for food crops.
But their study finds algae's environmental performance is mixed compared with other biomass sources. Producing biofuel from algae requires more energy (to dewater the algae and extract the oil) than other feedstocks, while cultivation requires substantial amounts of water.
Algae farm. (Photo: Sapphire Energy)
The study is looking at biodiesel and bioenergy, but apllies equally to jet fuel produced from algae - one the favored sustainable-fuel feedstocks of the aviation industry because it can produce a lot of oil from a small land area.
One of the report's authors, Lisa Colosi, says the value of algae depends on deciding what is important. If a lot of fuel is needed "we need to look at algae so we can produce as much fuel as possible. If we are concerned about energy use, climate changes and water supply, then we need to think more strongly about how we best use canola and switchgrass."
But cultivating oilseed crops for biofuels is not without its issues. A study by Michigan State University warns that farners and policymakers should wait before converting set-aside land to crop production because the "carbon debt" will take decades to pay off.
The study involves the US federal Conservation Reserve Progam (CRP), under which farmers are encouraged to grow natural vegetation rather than crops. Converting this "idle" land to biofuel crop production would release carbon dioxide from the soil and result in a carbon debt.
"It's called debt because until a new biofuel crop creates enough renewable fuel to offset the lost CO2, the new biofuel crop has no climate benefit," says researcher Ilya Gelfand, "In fact, it's the same as burning fossil fuel as far as the atmosphere is concerned."
Even with no-till cultivation - planting without plowing - it would still take 30-40 years to repay the carbon debt by growing corn or soybean for biofuel, the researchers say. In contrast, simply harvesting the natural grasses on CRP land for celullosic biofuel would incur no debt and provide immediate climate benefit, they say.
Biofuel au naturelle? (Photo: Michigan State University)
awt, environment, biofuels