Switching to Switchgrass

Today the BBC ran a story entitled “Grass Biofuels cut CO2 by 94%.” This 94% is meant to be in comparison to fossil fuel, based on the fact that a recently grown biofuel, when burned, can only release as much CO2 as it absorbed when it was growing. Thus biofuels are considered “carbon neutral.” The BBC story referenced a study just released by the U.S. National Academy of Sciences entitled “Net Energy of Cellulosic Ethanol from Switchgrass.”

Switchgrass – an environmentally attractive
potential source for cellulosic ethanol.
(Photo: USDA)

One of the reasons many people are enthusiastic about switchgrass and other cellulosic crops is because they are believed to cause less collateral environmental damage. Switchgrass is presumably grown on cropland or open prairie, which means that switchgrass, unlike oil palms, sugar cane, cassava, and a host of lesser known biofuel crops, will not be grown on former rainforest.

The CO2 released during rainforest destruction is never recovered through subsequently using the land to grow biofuel. Possibly even worse tampering with the global climate, however, is the thermal impact of permanently losing the reflective clouds that form year-round over equatorial rainforests.

So here we go – let’s grow switchgrass and other cellulosic crops on prairies and savanna instead of oil palms and sugar cane on former tropical rainforests. But the ethanol in switchgrass needs to be extracted cellulosically – a process that is getting closer to being technologically and economically viable, but isn’t here yet. And what is the yield from switchgrass?

In our post “Biofuel’s Potential,” we make the case that today’s best biofuel yields – between 5,000 to 10,000 barrels per square mile per year – would make biofuel an interesting supplemental fuel, but there isn’t enough land for biofuel at that yield to begin to replace fossil fuels. If the best case predictions of biofuel experts come true however, and biofuel yields eventually top 50,000 barrels per square mile per year, then biofuel truly does have the potential to replace fossil fuel. How much potential ethanol was in the switchgrass referenced in the study?

According to the BBC report, “One acre (0.4 hectares) of the grassland could, on average, deliver 320 barrels of bioethanol.” That suggests (320 x 640) that 204,800 barrels per year per square mile would come from this switchgrass – an improbable amount. So we called one of the study’s authors, Dr. Ken Vogel at the University of Nebraska, to ask him to clarify this number. It turned out the BBC reporter had mixed up barrels and gallons. The researchers had actually estimated switchgrass can yield 4,896 barrels per square mile per year.

This yield is consistent with yields from crops currently being harvested for ethanol. It is somewhat more than corn yields, and it is somewhat less than sugar cane yields, but it is an order of magnitude removed from the best case numbers we have heard discussed.

There are two conclusions to draw from the BBC report. (1) The mainstream press is beginning to see – rather late in the game – that the subsidized market for biofuel has unleashed catastrophic rainforest destruction, and (2) Yet again it is apparent that the journalistic value of “fact checking” does not extend to quantitative data – and that value is needed now more than ever.

As far too many of our politicians and media pundits rather blithely (and opportunistically) advocate a radical socialist redesign of the political economy of the world in the name of protecting the environment, it is the duty of any activist, journalist, scientist, policymaker, or conscientious and opinionated person in any role – to personally question and attempt to verify everything they hear, and to embrace nuance and restraint. And this is imperative for environmental as well as economic reasons. We believe tropical deforestation has done more to hurt the earth’s climate than fossil fuel ever has or ever will – particularly if you consider not just the CO2 impact, but the thermal impact of turning millions of square miles of rainforests into biofuel plantations.

Categorized | Energy & Fuels, Other, People
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