On Saturday, the New York Times published an impressive hand waving exercise by Joe Nocera touting the benefits of gasified coal and carbon sequestration. The article itself is here:
As is usual when it comes to energy discussions in the United States, there was negligible technical information in Mr. Nocera’s column. Rather, he asserts that “… because the gasification process doesn’t burn the coal, it makes for far cleaner energy than a traditional coal-fired plant.” He goes on to quote a representative of the Center for Climate Change and Energy Solutions who states that coal gasification plus carbon capture “is the only technology that can reduce CO2 emissions from existing, stationary sources by 90%.”
Well, that sounds pretty great, don’t you think?
Now, we can take issue with this in a number of ways, but let’s start with some plain horse sense. As we know from our posts on combustion, heat is liberated from fossil fuels when carbon and/or hydrogen combines with oxygen. While it is true that coal may contain a small amount of hydrogen, the vast, vast majority of the energy contained in coal is contained in carbon. The only way that coal gas makes sense is if there is plenty of carbon in it to burn. And burning carbon results in carbon dioxide as the predominant byproduct.
Mr. Nocera perhaps thinks that because the coal is “gasified” that it is turned into real natural gas (CH4) by this process. He is wrong. Coal gasification results in a carbon rich stew of chemicals (admittedly without many of the heavy elements contained in solid coal) that still must combine with oxygen to liberate heat. And create carbon dioxide as a combustion by product.
Secondly, while he attempts to conflate coal gasification and carbon-capture as reducing emissions and being a game-changing clean energy solution, he seems (at least to me) to skirt by the issue of “carbon capture” which I take it to be the end game after the carbon dioxide emissions are utilized for “enhanced oil recovery”. Basically, use the pressurized carbon dioxide gas to drive oil out of the ground, and then leave it underground where it will presumably stay forever.
Here too a little common sense is in order. First, if we are trying to reduce carbon emissions, in what way does facilitating “enhanced oil recovery” help the cause?
Beyond this, Mr. Nocera may not realize that septic systems do not last forever, and the plan to dump our power generation waste underground and to assume it will remain sequestered for all time is simply childishly naive. And to not openly admit that the carbon dioxide will physically be generated and stored in the earth seems an extreme oversight at best.
Then too there is the question of carbonic acid formation over time in moist areas where some of this gas might settle. Recall that carbonic acid is already damaging ocean corals. How might acidified soils affect the bacterial and animal life currently housed there? The question goes unasked. And the answer is probably not known.
But enough common sense, what about the numbers? Let’s go the Texas Clean Energy Project site located here:
You will note that this is a 400 MW plant. Let’s assume it’s going to run 97% of the time. Then each year it will generate:
400 MW x 8,500 hours = 3,400,000 MWh
Now they say, right there on the page, that 3 million tons of carbon dioxide will be used for “enhanced oil recovery”. They also say that this is roughly 90% of the plants carbon emissions, meaning the total emissions are about 3,300,000 tons.
Well look at that.
This plant emits about 1 ton of CO2 per megawatt-hour. Or about 2 pounds of CO2 per kWh.
This is higher, by the way, than the current average emissions in Boston, which has a supply mix that includes hydro, nuclear and solar. So this “Clean Energy” project is actually a step backwards from the status quo in Boston.
Thus, the Texas Clean Energy Project may be better than a conventional coal fired plant, but to call it a game changer is magical thinking.
Pretty magical that this got published in the New York Times, now that I think about it.
I think there are a few useful ideas we can take away from this column.
- Hiding waste products underground does not mean that they do not exist. Let’s stop the mendacious practice of calling carbon capture “clean”. If carbon dioxide is generated as a byproduct, it exists and should be counted. Where it is located is irrelevant.
- Ignoring the qualitative difference between natural gas and coal gas obscures the fact that the products of combustion are not the same, and that natural gas is a more energy-dense, clean burning fuel. To not state this up front is misleading. In discussing energy, words need to be specific and defined.
- Let us not conflate technologies in a confusing “bundle” (gasification, enhanced oil recovery and carbon capture) and then claim a result that is tenuously linked to the overall package of solutions. It is not necessary, and engineering doesn’t work that way. We deserve the details.
I think that Mr. Nocera sincerely believes that the Texas Clean Energy Project is a good thing that will deliver tangible results. But he owes it to his readers to explore the technical issues, including the chemistry of the combustion reactions, before promoting a “solution” that could be an environmental disaster.