Treethanol vs Ethanol

“Why use trees, rather than maize or sugar cane, as a feedstock for ethanol? Because “treethanol” has the potential to be much more energy efficient. The ratio of the energy yielded by a given amount of ethanol to the energy needed to produce it is called the “energy balance”. The energy balance for ethanol made from maize is the subject of much controversy, but America's energy department puts it at 1.3; in other words, the ethanol yields 30% more energy than was needed to produce it. For ethanol made from sugar cane in Brazil, the energy balance is 8.3, according to the International Energy Agency.

But for ethanol made from trees, grasses and other types of biomass which contain a lot of cellulose, the energy balance can be as high as 16, at least in theory. In practice the problem is that producing such “cellulosic” ethanol is much more difficult and expensive than producing it from other crops. But the science, technology and economics of treethanol are changing fast. Researchers are racing to develop ways to chip, ferment, distil and refine wood quickly and cheaply.

Interest in cellulosic ethanol is growing as the drawbacks of making ethanol from maize and sugar become apparent. Both are important food crops, and as ethanol production is stepped up around the world, greater demand is driving up the prices of everything from animal feed to cola and biscuits. The price of a bushel of corn rose by 70% between September 2006 and January 2007 to reach its highest level in a decade. Mexico's president, Felipe Calderón, even capped the price of corn tortillas in January as America's fast-growing ethanol industry caused prices to rocket. There are clear signs of a backlash against ethanol made from food crops. Supply is struggling to keep up, and as more governments introduce schemes to promote biofuels and cut greenhouse-gas emissions, the tension between food and fuel will only intensify.

Growing maize requires a lot of land, water and agrichemicals, so environmental groups such as America's Natural Resources Defence Council argue that it is merely a short-term, first-generation approach to making ethanol. Most energy experts reckon that using maize-based ethanol as a substitute for petrol can reduce America's demand for petrol by 10-15% at best. As for sugar, its growing value as a biofuel feedstock means that in Brazil, which is now one of the world's largest producers and exporters of ethanol, there is pressure to flatten rainforests to make more room for sugar production. One green objective (reducing dependency on fossil fuels) thus conflicts with another (preserving the environment)."

- Woodstock revisited