Photo: Wikipedia, CC
A Lesser Evil?
It's time for a round of "good news, bad news". The good news is that some U.S. utilities with aging coal plants are looking at the costs of installing anti-pollution equipment on them and at the future cost of carbon regulations (the details are uncertain right now, but at some point it's going to happen), and they're deciding it makes sense to them shut down instead of sinking more cash into this dirty source of power. The bad news is that they aren't exactly replacing them with wind, solar, geothermal, or hydro...
Photo: Wikipedia, GFDL
The replacement is natural gas, in good part because its market price has dropped significantly in the recent past. The New York Times gives the example of Progress Energy Carolinas:
Several of its coal-fired power plants were aging and needed scrubbers to reduce emissions and meet North Carolina pollution laws. Executives figured that even tougher regulations were coming from Washington, and overhauling 11 generators at four plants would have cost nearly $2 billion, which would have been passed on to the company's 1.5 million electric customers.
Plunging natural gas prices, however, offered Progress Energy an alternative that would save money and help it achieve pollution goals at the same time: scrapping the coal plants and replacing them with two gas plants over the next four years, at a cost of $1.5 billion.
So it's actually less expensive to build entirely new gas plants than to fix the old coal plants...
Of course, this is bad because natural gas is still a fossil fuel that produces greenhouse gases, and the new natural gas discoveries require fracking, which brings a whole other bunch of issues and uncertainties about the environmental impact. But I'm a pragmatist. I don't believe that all bad things are necessarily equally bad; if I'm given the choice between a kick to the stomach and a bullet to the gut, I'll take the kick. I know it's possible to die from both, but my chances are better with the kick. In this metaphor, coal is the bullet.
Natural gas produces about 50% to 70% less CO2 than coal for a given amount of energy produced (the higher figure is compared to the less efficient coal plants, which are probably those being closed right now), and while fracking and moving natural gas around isn't a free lunch by any mean, it compares favorably to mountaintop removal and all the energy that this requires (moving a whole mountain and grinding rock down to powder, can you imagine how energy intensive that is?). On top of that, natural gas produces less air pollution than coal, and you aren't left with millions of tons of coal fly ash (which contains mercury, among other things).
A Magical Red button
So it's kind of sad, but if I had a magical red button on my desk, and by pressing it all of the coal plants in the U.S. would be replaced by natural gas power plants, the rational thing would probably be to press it. It would instantly make the U.S. grid produce about 25-35% less CO2, reduce smog in many places, and make the grid a bit more flexible so that it can power up and down to keep up with the variability of wind and solar.
Obviously it would be even better to replace coal with wind (especially offshore), solar (especially concentrating thermal with molten salt heat storage), geothermal, hydro (including pumped storage), and even nuclear (thorium would fix most of the downsides), and that's happening slowly right now. But if natural gas can help this transition happen more smoothly and reduce the CO2 peak in the atmosphere, then we should recognize that. Pretty much anything is better than coal.
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