This is the first installment in a series of posts on future energy sources. I make no claims on being an expert or knowing all the relevant issues. I’m just trying to get some information out there—enough to get people thinking and to help them weigh the options with some degree of informed opinion. I don’t know when future posts in the series will be put up, but I will try to get them done gradually over the summer.
The “Coal Conundrum” arises from the intersection of three simple facts:
1) Coal releases large amounts of CO2 into the atmosphere when burned
2) Climate change exists and is being accelerated by human-made CO2 emissions
3) There are still enormous reserves of coal in many parts of the world.
First, some quick information about coal and its usage:
Around 23% of our nation’s total energy consumption needs are met by coal. Most of it is used in power plants to generate electricity, supplying about 50% of our national grid’s power. Coal is not as easy to transport as oil and the lowest-grade coal (lignite) is almost not worth transporting.
There are, roughly, 4 main grades of coal:
Anthracite is the highest quality and releases the least carbon per unit mass burned. It’s Gross Heating Value (GHV, a measure of energy released per unit mass) is about 8.5 kcal/g.
Bituminous coal is next down on the list, with about 6.7 to 8.5 kcal/g burned. At best, it is pretty much equivalent to anthracite. At worst, you must burn 1.25 tons to equal the energy from 1 ton of anthracite.
Sub-bituminous coal’s GHV is about 5.5 kcal/g, so you must burn 1.5 tons for 1 ton of anthracite equivalent.
Lignite is the lowest quality coal, giving you about 3.9 to 5.4 kcal/g—or, between 1.5 and 2.1 tons of anthracite equivalent.
While the carbon emissions that result from burning 1 ton of each of the above types of coal are slightly different (due to different carbon concentrations within each), burning 2 tons of lignite will definitely give you more carbon than just 1 ton of anthracite. And the bad news here is that about half the proven coal reserves in the world are lignite.
For comparison, gasoline has a GHV of about 11 to 11.5 kcal/g and fuel oil is somewhere around 10 to 11 kcal/g. Another measure of the utility of an energy source is the ratio of input energy to output energy. Ratios for oil and coal vary greatly by source, but oil is generally at least 50% more efficient than coal.
Enough with the boring information! Let’s get to the meat of the problem:

Source: US EIA

Source: BP, 2006
Notice something interesting? The largest of the proven global coal reserves are in developed or developing nations. And global reserves are estimated to be enough to supply our coal needs for between 200 to 300 years, provided we keep our consumption constant and no new coal deposits are discovered. Both of those provisions will be broken, but it’s unclear exactly which direction they’ll go—new coal deposit discovery could, for a time, outpace consumption growth if enough money is put into the search.
But the point here is that this represents a huge temptation for the existing global energy order. It’s a step backwards, away from the higher-energy, oil-powered economies we currently have. But if oil gets too unstable and the tar sands of Alberta are to expensive, it might start looking good. After all, its an energy technology that we know and understand quite well. The only thing really stopping us from going full-steam ahead with it is our own willpower (ok, ok… and perhaps some economics too). Ramping up our coal usage will accelerate the pace of global climate change.
We see and hear coal’s newfound siren call on television, in the paper, and on the radio. It’s in ads for “clean coal,” “coal sequestration,” and various methods for extracting liquid fuels from coal. They put up pictures of children playing in green fields, of animals in the forest, of a clean, coal-powered future where carbon is sequestered under the ground.
Sequestration is not a well-proven technique. Given time, perhaps they’ll come up with some good solutions--though the best is to simply leave the carbon in the ground. I can’t speak with much authority on the subject, so I’ll give you two opposing views of sequestration:
Tree Hugger
Environmental Defense Fund
Coal is a great temptation for the developed and developing world. True, it represents a step backward in terms of energy concentration and utility. But it’s readily available right at home in large quantities, would last us more than a century, and uses known technology. More than that, when converted to liquid fuel, it could be used to maintain our current lifestyle at a reduced level.
I personally don’t think it’s sustainable in any form. It will be a transition technology, a step toward achieving a cleaner, better energy infrastructure. Coal would run out eventually, and its lower energy value and higher transportation costs make it much less appealing than oil. The real risk comes from short-sighted industry and government players who will see these massive reserves, sell their usefulness to the people using slick advertising that pretends to care about global warming, and then extort prodigious sums from us for the benefit of having “clean coal” (the death rent). They may try to drag out the transition as long as possible, exposing us to both financial hardship, delayed technological innovation, and increased risk of sequestered carbon escaping into the atmosphere. Plus, sequestration does not capture all the carbon, so the longer the transition the more we pump out.
We need a quick transition away from coal. The sooner the better. But given its huge reserves in accessible places, the enormous infrastructure built up around it, and its status as a known and proven energy source, I don’t know if that will happen.