Guest blogger Iain McClatchie here. Kirk asked me to cross-post my next energy related posting from Ambivalent Engineer.

I found some numbers for the oil cost of burning coal. As you know, coal moves primarily by train, and those trains are pulled by diesel-powered locomotives, and marginal diesel is of course imported. Coal is generally regarded as a domestic fuel, but it takes a fair bit of diesel to pull all that coal around. So the question is, are you paying mostly for coal, or mostly for diesel?

Here’s the first big clue: Freight trains in the United States burn 1 gallon of diesel to move a ton of frieght 436 miles.

Average distance coal travels in US: 628 miles from mine mouth to powerplant. At $4.03/gallon, that’s $5.80 for the diesel to move a ton of coal from the mine mouth to the powerplant, on average. Wyoming coal costs $9 at the mine mouth. So, electric producers pay almost as much for the diesel to move this coal as for the coal itself. Since marginal petroleum is imported, it’s fair to say that coal is not entirely a domestic fuel.

The average powerplant cost for coal in the U.S. in 2006 was $34.26/ton. That’s because coal mined outside of the Powder River basin in Wyoming costs a lot more to dig out — the average mine-mouth price across the U.S. in 2006 was $25.16/ton. The difference is $9.10/ton, which is the cost of transport. The cost of diesel was lower in 2006, but it looks like around half the transport cost is the diesel.

If the coal is 22 MJ/kg, and the plant is 35% efficient, then for each kWh at the powerplant you spend on average 1.8 cents for the coal. Just the fuel cost of the coal plant is more than the total operating cost of the Palo Verde nuclear powerplant, per kWh. This result is entirely independent of subsidies or clean coal requirements. The black stuff is apparently just really expensive.

A while back, I snarkily suggested that mine mouth coal powerplants were a way to keep the pollution away from rich people. Looks like I was wrong:

• Transporting a kWh of electricity 1000 miles increases the cost by 19%.
• Transporting the coal necessary to make that electricity 1000 miles costs $14.49/ton, assuming cost is linear with distance. That’s a 58% increase in the cost of the fuel. Assuming the fuel cost is 70% of the cost of producing electricity, that’s a 40% increase in the cost of the electricity.
• 4000 miles (across the continent) by electricity: increase cost by 107%.
• 4000 miles by coal train: 160% increase.

What about the extra carbon? Transporting 1000 miles as electricity means you must make an extra 8.7% more electricity which gets lost in the wires, which produces 8.7% more CO2. Transporting 1000 miles by coal train burns 6.3 kg of carbon in the diesel to deliver perhaps 800 kg of carbon, which increases the total carbon released by 0.8%. Clearly the diesel locomotive is the lower carbon, if much more expensive, alternative.

So what does all this mean? If I were crafting a national economic policy intended to stabilize the U.S. economy against changes in the price of oil, I would look into making those frieght trains electric. And, of course, I would build a bunch of standardized, mature nuclear powerplants.

P.S. Average distance coal travels in China: 230 miles. They’re burning a lot less diesel to take advantage of their domestic coal.