Today's Washington Post cast some serious doubts on the environmental sustainability of producing ethanol from Brazilian sugar cane, demonstrating yet again that when it comes to energy, the temporary resemblance of any option to a silver bullet usually only reflects our poor understanding of its consequences. The cost in this case is the potential deforestation of the Cerrado, Brazil's non-rainforest plateau. While Brazilian cane ethanol clearly has a role to play in the world's future energy balance, this prospect should remind us that meeting the world's daily energy demand entails breaking eggs on a vast scale. Despite the growing sophistication of the public and our leaders on energy matters, the discussion is still not being framed in terms of the hard trade-offs involved.
Since ethanol has become the cornerstone of US energy policy, let's look at the size of the problem relative to the ethanol volumes we hear bandied about in the news and on the floor of Congress. The US currently produces about 6 billion gallons of ethanol, mostly from corn. The administration and Senate want to expand this volume six-fold. It's not clear that we can do that without a large contribution from cellulosic ethanol technology that is not yet commercial, but let's assume it could all come from corn. At a yield of about 2.7 gallons per bushel, this would consume 13 billion bushels annually, roughly equal to at least one estimate for the entire 2007 corn crop, planted on 90 million acres, or about 20% of total US cropland. So if it were all planted in corn for ethanol, our current agricultural land would yield something less than 200 billion gallons per year. That's a big number, but put it in perspective. The US uses 100 quadrillion BTUs per year of energy. That equates to 1.25 trillion gallons of ethanol on volume alone. Replacing the actual net BTUs from fossil fuels would require roughly 3.5 trillion gallons of ethanol, based on its current energy yield of 1.3:1 (energy return on energy invested.)
Of course, this is an absurd comparison, because we're not going to grow corn to make ethanol to feed power plants, home furnaces, or factories. The point here is to emphasize just how large the implied equivalent agricultural footprint of our energy consumption is. If we want an appreciable fraction of those needs to be met with biofuels, even if the actual crops involved are not corn, but Brazilian cane or US switchgrass--both of which are much more efficient net energy producers than corn--it's still a big footprint. And make no mistake, as long as oil prices remain high and federal incentives are in place, the market will deliver it, even if it has to overcome an import tariff to do it.
For all of our new-found environmental concern relating to climate change, I have yet to hear any politician debate how the total environmental impact of greatly increased biofuels output--including all land, water, and air impacts--compares to the environmental footprint of getting the same quantity of energy from natural gas drilling in protected areas, from large offshore wind farms, or new nuclear power plants, among our other choices. None of those options are silver bullets, either, but they could all be part of the mix, along with biofuels. Unless we talk about it in these terms, how can we be sure that the mix of broken eggs we're implicitly choosing is really the one we want? We ought to discuss this now, rather than after the Cerrado has all been planted in cane to power our cars.