Studies Deem Biofuels a Greenhouse Threat

[RedEarth]

Almost all biofuels used today cause more greenhouse gas emissions than conventional fuels if the full emissions costs of producing these “green” fuels are taken into account, two studies being published Thursday have concluded.

The benefits of biofuels have come under increasing attack in recent months, as scientists took a closer look at the global environmental cost of their production. These latest studies, published in the prestigious journal Science, are likely to add to the controversy.

These studies for the first time take a detailed, comprehensive look at the emissions effects of the huge amount of natural land that is being converted to cropland globally to support biofuels development.

The destruction of natural ecosystems — whether rain forest in the tropics or grasslands in South America — not only releases greenhouse gases into the atmosphere when they are burned and plowed, but also deprives the planet of natural sponges to absorb carbon emissions. Cropland also absorbs far less carbon than the rain forests or even scrubland that it replaces.

Together the two studies offer sweeping conclusions: It does not matter if it is rain forest or scrubland that is cleared, the greenhouse gas contribution is significant. More important, they discovered that, taken globally, the production of almost all biofuels resulted, directly or indirectly, intentionally or not, in new lands being cleared, either for food or fuel.

http://www.nytimes.com/2008/02/08/science/earth/08wbiofuels.html?ei=5065&en=76d0031108190f67&ex=1203138000&partner=MYWAY&pagewanted=print

[GliderGuider]

1. Have I used the phrase "Crime Against Humanity" recently?

I have seen nothing in the last year to alter my opinion that agrifuels are precisely that.

[wtmusic]

2. Cropland absorbs far less carbon than scrubland? I don't buy it.

Scrub dies. Scrub decays. Decay adds to CO2 in atmosphere (and resulting heat is wasted)

vs:

Low-producing scrubland is cleared (not burned). Switchgrass is planted, acts as a carbon sink, then is harvested and converted into ethanol. Ethanol powers vehicles and returns CO2 to atmosphere.

I would bet there are insidious petrodollars somewhere behind this study.

[NickB79]

3. Scrubland plants put down deep, deep taproots

Some prairie grasses, for example, can penetrate 20 feet with their roots. The vast majority of their biomass ends up below ground, where decay is slowed and carbon is sequestered.

On the other hand, plowing that scrubland allows air and water to penetrate further down to accelerate the decay of that root biomass, and the crops that are planted have nowhere near as deep of a root system as the native species.

"Switchgrass is planted, acts as a carbon sink, then is harvested and converted into ethanol."

You'll note that they stated that CORN-based biofuels are the culprits. They actually do advocated using switchgrass-ethanol where possible, so long as cropland isn't converted to biofuels. Switchgrass is one of the perennial prairie grasses that puts down deep taproots and doesn't require frequent plowing, so it would be an excellent biofuel crop.

[wtmusic]

4. Here's where it gets overly simplistic:

'"The clearance of grassland releases 93 times the amount of greenhouse gas that would be saved by the fuel made annually on that land, said Joseph Fargione, lead author of the second paper, and a scientist at the Nature Conservancy. “So for the next 93 years you’re making climate change worse, just at the time when we need to be bringing down carbon emissions.”'

Fargione is not considering any of the CO2 which makes it back into the atmosphere from normal plant respiration. It seems intuitive to me, although I don't know for sure, that this would constitute the bulk of CO2 production from cropland.

[speedbird]

5. there is a net carbon savings, or not?

there is a 1/93 of a carbon savings,
or an increase, as the O.P. would imply

[wtmusic]

6. I should know not to post when tired & hungry

What I meant to say is:

Fargione is not considering any of the CO2 which is sequestered in the ground as roots of the corn/switchgrass (ie, not used for fuel).

[NickB79]

7. I wouldn't think much CO2 would be sequestered by corn roots

From personal experience on the farm, corn puts down very shallow, widespreading roots in the upper foot or so of soil. Come fall, that land has to be plowed and the organic matter exposed to decomposition. I'd expect that between the shallow roots and constantly turned over soil, there is very little CO2 sequestration with conventional crops.

If you look at areas of the world that sequester the most carbon (grasslands, tundra, peat bogs), they all have soils that remain undisturbed, with the carbon either buried in anoxic, dry, or freezing conditions that prevent decomposition. Farming, on the other hand, relies on decomposition of organic material to release valuable nutrients back into the soil for future crops to feed upon.

[wtmusic]

8. OK that makes sense.

Thanks for your input. I'm looking forward to reading the studies myself. :thumbsup: