May 10, 2006

Debunking Switchgrass "Rural Legends"

Ever since President Bush said the word "switchgrass" in the State of the Union address, people have been curious about the role this particular feedstock will play in solving the energy crisis. The theory goes that corn is almost a net energy loser because we put as much petroleum energy into plowing, seeding, fertilizing, harvesting, and distilling corn into ethanol as we get out of it. Switchgrass, which grows like a weed natively in parts of the country that are otherwise considered unarable, does not need nearly as much energy input to grow or cultivate with irrigation.

In an article posted on The Oil Drum blog, contributor named "Kyle" wrote a piece about what he considers the "rural legends" about switchgrass, to set the record straight. His main point is that it is NOT substantially cheaper as a feedstock than corn for producing ethanol.

That may be true but it doesn't mean that it shouldn't be considered a feedstock option for ethanol. Read the article to see his response to each "rural legend" - here are a few excerpts:


Life in a Grass House
by Kyle, contributor to The Oil Drum blog

Switchgrass is a perennial grass native to the great plains, suitable for marginal lands because it grows well with relatively moderate inputs and can effectively protect soil against erosion. So far so good - one of the major attractions to switchgrass is that it is more environmentally friendly than corn....

This is why so many folks are beating their drums over switchgrass - in theory, it can be grown on marginal lands with ethanol yields 3 times that of corn with "minimal inputs." From this description, one gets the sense of legends in the making. Let's take a critical look at some of them.

Legend 1: Switchgrass does not require fertilizer or irrigation (America's strategic imperative: a "Manhattan Project" for energy by Lt. Col. John Amidon).


Legend 2: It is estimated that 15 percent of the North American continent consists of land that is unsuitable for food farming but workable for switchgrass cultivation. If all that land was planted with switchgrass, we could replace every single gallon of gas consumed in the United States with ethanol. (Sam Jaffe, "Independence Way," The Washington Monthly (July/August 2004)).


Legend 3: Switchgrass yields a certain amount now, but in the future, with selective breeding, etc., it will yield much more.


Legend 4: Switchgrass is substantially cheaper as a feedstock than corn for producing ethanol.


What's the moral in all of this? If corn ethanol is marginal on an energy returned on energy invested (EROEI) basis, it is very difficult to argue that biomass grown to make ethanol will be any better. To be blunt, if there are concentrated stocks of waste biomass in place, such as at lumber mills, then biomass ethanol probably makes sense. Otherwise, it appears to be more or less equivalent to corn based ethanol - in other words, a wash.

technorati , , , ,

No comments: