01 February 2006

Biofuels (2)

Part 1

The person who referred me to all the glowing articles "refuting" David Pimentel's essay is an anonymous enthusiast who got his articles at a website entitled "Journey to Forever." He says the site "presents both sides of the issue," although it is actually an unabashed supporter of biofuels. However, there is an article by Jürgen Krahl and Axel Munack, "Review: Utilization of Rapeseed Oil...," originally published by the Society of Automotive Engineers (SAE). The authors tested rapeseed oil methyl ester (RME), which is saffola converted to biodiesel; they also tested unmodified rapeseed oil, which requires a different type of engine.

Now, recall from Pimentel's paper that growing an acre of corn and rendering it into ethanol yields the energy equivalent of 190 gallons (720 L) of gasoline; the process requires 140 gallons (530 L) of gasoline, for a net yield of 50 gallons (190 L). So, consuming 1 gallon of "gasoline" would require a process in which 3.8 gallons of "gasoline" are produced and consumed, 1 of which is by the end user. That, I understand, is a component of the 10-fold increase in farmland requirement Pimentel mentions. So, if ethanol were to phase out gasoline entirely, proponents of biofuels can claim that growing all that maize will absorb the carbon released in combustion. But other byproducts of combustion would actually have to be 74% less than gasoline per gasoline-equivalent burned (or, 84% less per gallon burned). According to the chart here, that is not the case with rapeseed.

I am skeptical that ethanol can be so much better than rapeseed oil in energy emissions. But let us now turn to the favorable reports on energy outputs.

Here's "How Much Energy Does It Take to Make a Gallon of Ethanol?" (Lorenz & Morris, August 1995). They include a detailed breakdown of inputs using different processes. The main difference between them is that some require small amounts of fertilizer, which is the main energy input and "process steam." This is the process under which ethanol is transformed into a liquid fuel, and it is the principle variable. According to Lorenz and Morris, the steaming process has massively reduced energy per gallon; where once (in 1980) it required as much as 157% of the ethanol's energy yield, by '95 it averaged 33% of yield. Using "State of the art" technology meant for every gallon of gasoline (equivalent), 1.39 would be produced and consumed. That would mean, of course, that instead of requiring 10.7 times the land area currently used for US food consumption, 3.9 times as much land would be required. I reviewed the rest of the article and noticed little to arouse my suspicions, except that they tended to assume industrial efficiency that is rarely achieved in practice. Also, they "award" a lot of energy output to other products besides fuel, such as cogeneration. Should ethanol be embraced on a major scale, the opportunities to exploit cogeneration would decline sharply and we would most likely trend down to Pimentel's estimates of land use.

I skimmed through the "update" (PDF) by proponents (and USDA fellows) Shapouri, Duffield, and Wang. The article has a table on page 2. I should point out that SD&W show a surprisingly narrow range of estimates from different studies, with most of the difference being in expected BTU/gallon conversions (75K/gallon for Pimentel versus 50K for SD&W; Wang, et al. claimed the figure could be as low as 40K, which is an outlier). The other big variable was nitrogen fertilizer, which SD&W claimed used only 18K BTU/lb, an astonishingly low statistic. If one believes that energy employed in the production of nitrogen has fallen so much, or that use of such energy-intensive fertilizers can be sharply reduced, then you are still stuck with a political calamity when the US begins encroaching on the farmland of 3rd world countries as it scrambles to substitute gasoline or diesel with ethanol.

The bottom line is that, while the hardcore enthusiasts and techno-optimists look forward to higher net energy yields with ethanol and rapeseed, the grim fact is that their own incentivized statistics (I expect had they reported poorer results for ethanol they would have been sacked—and probably unemployable in their fields) still stick us with consuming 3-6 times as much oil-like fluid as we actually use. The extra would be used to make the net energy value that we use. And while massive improvements might conceivably made in the ecological impact of industrial farming, it would never be enough to offset the 4-10 times as much of it we would hereafter have to do.

BOTTOM LINE: Biofuels are a biohazard.

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3 Comments:

At 10:06 PM, February 10, 2006, Blogger Brice Timmons said...

Everyone is all chatty about ethanol these days, but there is little discussion of the impact of using huge amounts of agricultural land for fuel production, nor is the impact on water tables from incrased irrigation and fertilizer usage often considered. What do you know aboutthermal depolymerization?

 
At 10:07 PM, February 10, 2006, Blogger Brice Timmons said...

Oops, bad link. Try here.

 
At 2:33 PM, February 21, 2006, Blogger jrm said...

Sorry for taking so long to respond, Bruce. And yes, I really liked your blog. However, I don't know anything about thermal depolymerization.

 

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