Last week in “The Secret Life of Vegetable Oil” I reviewed biodiesel both from a technical and a food-versus-fuel perspective. This week I tackle the other major biofuel, ethanol.
Ethanol production is quite simple. Find some sugar, feed it to some yeast, and they make the ethanol. The most straightforward way to make ethanol from crops is to use either sugar cane or sugar beets. The other common way to make ethanol is from starches. Starches are just long chain sugars which are relatively easy to break down into the individual sugars which can then be fed to the yeast. Starch sources for ethanol production include corn, potatoes, and cassava. We will touch on cassava again later. Corn and sugar cane are, far and away, the most common feed stocks for ethanol production.
Ethanol is used as a fuel for both cooking and cars. Prior to 1908, the Ford Model T was designed to run on 100% ethanol. Today’s “flex fuel” cars and trucks are limited to 10% ethanol because the gaskets in the engines are designed for gasoline and would fall apart if a higher concentration of ethanol were used.
Similar to biodiesel, ethanol is a renewable fuel which does not contribute to global warming. However, like most things in life it also has drawbacks, significant ones. The first issue relates to the amount of energy you get from the ethanol compared to the energy you expend in producing it. Fuels are often compared by this ratio, which is known as “energy returned over energy invested” or EROEI for short.
The debate over the EROEI for ethanol from corn has been raging for years, with published estimates ranging from 0.8 to 1.5. An EROEI of 0.8 means that you have to expend one BTU of energy to get 0.8 BTU out, a rather sad outcome. An EROEI of 1.5 is at least somewhat positive, but is significantly lower than any other fuel on the market. If you look at the sources for the EROEI calculations, the outcomes are clearly influenced by the perspective of the author – environmentalists tend to come up with values of less than 1 and those receiving government subsidies to make ethanol tend to come up with higher numbers. No matter who is correct, ethanol is not a very impressive fuel from an energy balance perspective.
Not that the low EROEI for ethanol is dissuading anyone from moving forward. In the year 2000 the world produced 4.5 billion gallons of ethanol. By 2010 production had risen to 23 billion gallons. Combined, the United States, from corn, and Brazil, from sugar cane, produce 88% of the world’s ethanol.
You will have noticed that the sources for ethanol are also foods. It’s hard to find a way to tackle the food-versus-fuel issues for ethanol in a single blog, so I’ll try using the story of ethanol production in China as a proxy. China has lots of people, money, and coal. Since coal makes a lousy transportation fuel, they are using their money to buy petroleum and to build ethanol production facilities so they can power their cars and trucks. The Chinese started out making ethanol with corn but quickly ran into shortages and price spikes, which is a big problem when you have 1.3 billion mouths to feed. In 2007, China outlawed the use of grains to make biofuels. For comparison, 40% of the US corn harvest is converted to ethanol.
But the Chinese still need fuel, so they turned to Thailand which grows cassava. Cassava is a high-starch tuber which looks like a yam. In 2010 the Chinese demand for cassava resulted in the doubling of its price. This is particularly bad news if you are a poor person in Thailand and were planning on having cassava for dinner. In addition, since the Chinese are so keen to pay cold hard cash for cassava, farmers in Thailand, who formerly grew food for the domestic market, are planting cassava for export. Thailand did build some of its own ethanol production capacity, but at present the Chinese are outbidding them for the cassava, so the Thai factories sit idle or underutilized.
Allow me a brief tangent on the dangers of mono-cropping. Planting large swaths of the same crop is very efficient for the farmer. Unfortunately it is also allows pests that feed on that plant to thrive. In the case of cassava in Thailand, production is currently way down due to an explosion in the aphid population. It’s hard for me to contain my frustration when reading about these sorts of very predictable problems not being avoided. To me, these situations are proof positive that relying solely on the free market will not produce the optimal outcome for our societies. OK, back to the ethanol blog.
Last week, I reviewed how the purported savior for biodiesel’s shortcomings was algae. The equivalent for ethanol is cellulose. Cellulose is a class of stiffer hydrocarbons which give grass and tess their strength. With the proper conditions and some special enzymes, cellulose can be broken down into sugars. As yet, no one has determined an economically viable way to do this on a large scale. If they could, things like grasses and corn stover (the cob, stalk, and husks) could be used to make ethanol.
Corn stover gets most of the press. The idea sounds almost perfect at first. You grow corn then use the kernels for food and the rest of the plant for fuel. We will probably see this process commercialized at some point in the future. It’s important to remember though, that currently the stover is tilled back into the soil which recycles nutrients and organic matter. If you remove the stover to make ethanol corn fields are going to need a lot more fertilizer to remain productive.
Taken together, the last two blogs on biodiesel and ethanol start to bring into focus a theme I have been addressing since I started this blog in the spring of 2011. Since fossil fuels represent hundreds of millions of years of stored solar energy, using them allows us to live in an unsustainable way. The switch to biofuels, which is inevitable, will require adjusting the energy consumption of our societies to live in balance with what is provided by the sun. This is going to be a tremendous change, a change for which we have not even begun to prepare. I’ll pick up on that theme next week.
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