... native vegetation!

Dec 8, 2006 13:49 GMT  ·  By

Would you like to see out of view the horrific pollution triggered by accidents involving oil tanks or oil rigs? Well, the best solution is the biofuel, obtained from biomass.

A team from the University of Minnesota has found that the best biomass source to produce biofuel is the mixture of native prairie perennial grasses and other flowering plants. This biomass would produce per acre more biofuel than corn grain ethanol or soybean biodiesel and is far more environment-friendly.

"Biofuels made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere. Even when grown on infertile soils, they can provide a substantial portion of global energy needs, and leave fertile land for food production," said David Tilman, an ecologist at UM.

The is study based on 10 years of research at Minnesota's Cedar Creek Natural History Area, one of 26 NSF long-term ecological research (LTER) sites. 10 years of research revealed that degraded agricultural land planted with diverse mixtures of prairie plants produces 238 % more biofuel on average than the same land planted with various single prairie plant species, including switchgrass. "This study highlights very clearly the additional benefits of taking a less-intensive management approach and maintaining higher biodiversity in the process," said Henry Gholz, lead researcher. "It establishes a new baseline for evaluating the use of land for biofuel production".

Biofuel made from this prairie biomass yielded 51 % more energy per acre than ethanol from corn grown on fertilized land. Prairie plants require little costs to grow and all parts of the plant above ground are usable. Fuels made from prairie plants biomass are "carbon negative": producing and using them actually reduces the amount of carbon dioxide, the main greenhouse gas, in the atmosphere.

Prairie plants deposit more carbon in their subterranean organs and soil than in their aerial parts converted into biofuels. Prairie vegetation stores on long term 1.2 to 1.8 tons of carbon dioxide per acre per year, during about 100 years. In contrast, corn ethanol and soybean biodiesel are "carbon positive": they add carbon dioxide to the atmosphere, although less than fossil fuels.

Switchgrass was one of the 16 species in the study. "Switchgrass is very productive when it's grown like corn in fertile soil with lots of fertilizer, pesticide and energy inputs, but this approach doesn't yield as much energy gain as mixed species in poor soil nor does it have the same environmental benefits," said Jason Hill, also of the University of Minnesota.

At present, all biofuels - including nonfood energy crops such as switchgrass, elephant grass, hybrid poplar and hybrid willow - are produced as monocultures grown primarily in fertile soils.

Growing mixed prairie grasses on degraded land could produce a stable bioenergy production that could replace 13 % of global petroleum consumption and 19 % of global electricity consumption, not to mention environmental benefits, like renewed soil fertility, cleaner ground and surface waters, preservation of wildlife habitats, and ecotourism.