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By the Numbers: Ethanol

The propagation and increased use of ethanol has been a very contentious subject in green circles here in the US; on the one hand, it’s a domestically-produced alternative to oil, but on the other hand, you need engine modifications to use a high concentration of it, burning it results in lower gas mileage, and using corn is an inefficient has huge agro-political implications. Hmm…so what should we think about ethanol? Take a look at some of the numbers and decide for yourself.

90 percent — the amount of the world’s ethanol production that the US and Brazil combine to account for.
4.6 billion — US gallons of ethanol the US produced last year, making it the largest producer in the world.
35 liters — one bushel of corn.
10 liters — the fuel (2.8 gallons) netted from one bushel of corn.
330 – 420 — gallons of ethanol produced per acre of corn.
570 – 700 — gallons of ethanol produced per acre of sugar cane, Brazil’s feedstock of choice.
10 – 20 percent — the reduction in greenhouse gas emissions produced from burning corn-based ethanol, when compared to gasoline.
87 – 96 percent — the reduction in greenhouse gas emissions produced from burning sugar cane-based ethanol, when compared to gasoline.
34 percent — the amount of less energy per volume contained in ethanol, resulting in a similar reduction in gas mileage, if you’re burning 100% ethanol.
50 percent — the amount that the price of corn has risen in Mexico since last year, thanks in part to the increased demand for ethanol.

Proponents of the fuel argue that it’s an important step away from petroleum, and offers to help increase national security because it can be produced locally. Ethanol’s detractors point to blends above E10′s incompatibility with many gasoline engines, and some signs of increased wear and tear on some internal parts, especially rubber hoses and gaskets. Further, whether the energy balance of ethanol — whether the fuel contains more energy than was used to produce it — is positive or negative is debatable, as is whether or not the land used to grow the crop was obtained by, say, chopping down a rainforest, in which case the ethanol produced is just as unenvironmentally-friendly as fossil fuel due to the carbon released by the dead plants.

Moving forward, cellulosic ethanol has the potential to make ethanol a much more energy-efficient fuel, with yields that about double what the starch-based processes yield today. Because every plant contains cellulose, a huge variety of feedstocks — some that would otherwise be wasted, like corncobs, straw or sawdust — could be used. Switchgrass is one such feedstock, and was thrust into the energy spotlight when it was mentioned in President Bush’s 2006 State of the Union address. It grows eight or nine feet tall and is native to the US. Generally, it’s very hearty and will grow in nearly any climatic variation, from the Gulf Coast into Canada. As a crop, it has a very high yield per acre (five to tens tons) with little use of pesticides, and a low production cost, which are two keys for economical production of alternative fuels. However, until very recently, the cost for producing cellulosic ethanol has been prohibitive, and the process has yet to hit mainstream ethanol production.