Biofuels, for the most part, are a nonsense hustle. There are a few proposals that make some sense in that they produce more than they cost when all factors, including system degradation, are considered. Here's another one.

A new study led by David Tilman, Regents Professor of Ecology in the University of Minnesota's College of Biological Sciences, shows that mixtures of native perennial grasses and other flowering plants provide more usable energy per acre than corn grain ethanol or soybean biodiesel and are far better for the environment.

"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," Tilman said. . .

Based on 10 years of research at Cedar Creek Natural History Area, the study shows that degraded agricultural land planted with highly diverse mixtures of prairie grasses and other flowering plants produces 238 percent more bioenergy on average, than the same land planted with various single prairie plant species, including monocultures of switchgrass.

This is what we should expect. Polycultures out produce monocultures. Period.

Fuels made from prairie biomass are "carbon negative," which means that producing and using them actually reduces the amount of carbon dioxide (a greenhouse gas) in the atmosphere. This is because prairie plants store more carbon in their roots and soil than is released by the fossil fuels needed to grow and convert them into biofuels. Using prairie biomass to make fuel would lead to the long-term removal and storage of from 1.2 to 1.8 U.S. tons of carbon dioxide per acre per year. This net removal of atmospheric carbon dioxide could continue for about 100 years, the researchers estimate.

In contrast, corn ethanol and soybean biodiesel are "carbon positive," meaning they add carbon dioxide to the atmosphere, although less than fossil fuels.

Again, as expected. It isn't only that carbon accumulates in such biomes, soil builds. The deep roots store carbon and also mine the subsoil for nutrients, shuffling them closer to the surface, enriching the soil from below.

Switchgrass, which is being developed as a perennial bioenergy crop, was one of 16 species in the study. When grown by itself in poor soil, it did not perform better than other single species and gave less than a third of the bioenergy of high-diversity plots.

"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 Hill.

To date, all biofuels, including cutting-edge nonfood energy crops such as switchgrass, elephant grass, hybrid poplar and hybrid willow, have been produced as monocultures grown primarily in fertile soils.

The researchers estimate that growing mixed prairie grasses on all of the world's degraded land could produce enough bioenergy to replace 13 percent of global petroleum consumption and 19 percent of global electricity consumption.

More good sense. Those with knowledge and experience of swards have been saying this all along, and now we have specific scientific support.

A small portion of fuels can be produced from biomass without degrading the environment or competing directly with food and fiber production. If they go a step further and consider not just wildlife habitat but something more like restoration of the pre-settlement ecology - meaning large grazers and their predators as well as rodents and birds etc. - you'd have something durable and resilient as well as productive. To do good while doing well it is necessary to do good accounting, to consider all of the factors and seek an accommodation among them that yields a greater net benefit, rather than focusing on a single factor and seeking to optimize it at the expense of other factors.

Their estimate of "13 percent of global petroleum consumption and 19 percent of global electricity consumption" is unrealistically high, especially when whole systems are considered, but some lesser amount is feasible, and they are moving in that direction by making the first baby step away from monoculture.

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Tracked: December 7, 2006 01:10 PM