“I say we should ban cows and human farting.” So says friend and former colleague Simon M. in his sarcastic reaction to the news about the EPA proposing to regulate methane, carbon dioxide, and other “climate change inducing” chemicals from commercial airliners.
His comment relates to the fact that cow farts and human farts are also sources of methane, and therefore potentially subject to EPA regulation as well. Mandated Beano, anyone? I suspect my wife would approve :)
Aircraft engines produce (primarily) nitrogen, water vapor, and carbon dioxide as exhaust gas components. There isn't much room to make the engines more efficient, as commercial pressure from high fuel prices has done wonders there already. Nitrogen isn't a concern with respect to climate change. Carbon dioxide is the main thing the EPA is proposing to regulate. The EPA does not propose regulating water vapor emissions, despite the fact that water vapor is dozens of times more potent a greenhouse gas than carbon dioxide is.
So lets think about this for a moment. The EPA tells commercial aircraft manufacturers that they must reduce the carbon dioxide emissions. What mechanisms do the manufacturers have available to them? The most obvious one is to switch to fuels that have more of their energy in hydrogen, rather than carbon – which will have the effect of increasing water vapor emissions. Which, remember, are far worse for climate change than carbon dioxide is.
Now does this make sense in any universe? Sure it does! In the universe of the loony politicians!
The only other choices are to switch to exotic fuels that don't have carbon in them (very, very expensive), or to slow down the aircraft (because overall fuel consumption goes down non-linearly with speed, thus reducing emissions).
Shakespeare wrote (in Henry the Sixth) “The first thing we do, let's kill all the lawyers.” I think his priorities were slightly off – first should have been the environmentalist wackos, then the lawyers (which has the knock-on effect of getting most politicians as well)...