viernes, febrero 08, 2008

¿Es el etanol la solución del problema energético?

Ni mucho menos. The Oil Drum nos dice por qué:

a. Not scalable. A very large amount of land is required to produce a small amount of fuel. In 2007, over 20% of America’s corn was devoted to ethanol, but this provided only the energy equivalent of 3% of our gasoline use (or 1.1% of our petroleum use). More than doubling this will be very difficult.

b. Causes food prices increases. Competition of corn for land raises food prices. We end up paying a second time for corn ethanol through higher food prices.

c. Causes fertilizer shortages. Corn uses a lot of fertilizer. Fertilizer is made from natural gas and mostly imported. Fertilizer prices are now double what they were a year ago. The situation may get worse in future years and lead to shortages of fertilizer for food crops.

d. Environmental impacts as bad as gasoline (or worse). There are problems in several areas. Ethanol produces more global warming gasses than gasoline, according to recent studies. Older studies say that ethanol might produce slightly less global warming gasses than gasoline, but even this is not much help. A Stanford study says that air pollution is also worse than with gasoline. Ozone, which causes smog, is likely to be worse with ethanol than gasoline. Ethanol decreases some carcinogens, but increases others. The planting of corn also has negative environmental impacts, including aquifer depletion, topsoil erosion, and fertilizer runoff. These are especially problems if expansion of corn acreage means that corn is planted in hilly or arid locations where it would not usually be planted.

e. Energy intensive. Nearly as much energy must be used to make ethanol as is gotten back in return, so we are mostly recycling scarce fuels. Ethanol is not like petroleum, which has a positive energy balance to benefit our standard of living. If corn ethanol replaces petroleum, the impact on standard of living is likely to be negative. (See Item 3e)

f. Poor fit with petroleum system. At most 10% ethanol can be used in gasoline, without causing corrosion, unless autos are especially modified. Ethanol cannot be transported by pipeline, so costly and complex special arrangements must be made.

g. Less energy per gallon than oil. Ethanol has only about two-thirds the energy (calories) of gasoline.

h. Summer gasoline price run-up. Adding ethanol to gasoline makes gasoline evaporate at lower temperatures. To counter this, the fraction of gasoline that evaporates most easily (molecules with 4 or 5 carbon atoms, rather than 6 to 10 carbon molecules) must be removed from the gasoline mixture. Removing this portion of the gasoline reduces supply in the summer, and increases prices.

i. Drought sensitive. Supply depends on good weather in growing regions.

j. Expensive. Requires subsidies to be cost-competitive. Subsidies raise tax levels. Even with subsidies, ethanol's cost is often higher than that of gasoline.

Si sus resultados como sustitutivo de los carburantes son tan poco satisfactorios y los problemas derivados de su producción son tan importantes, ¿por qué se subsidia su producción y se impulsa entonces como una alternativa viable al petróleo? ¿Por qué Estados Unidos y China son dos de los tres países que más fuertemente han apostado por el etanol? ¿Es que acaso no hay otra alternativa a los combustibles?

Creo que no soy el único que no lo tiene muy claro:

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