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EarthFix Conversations: Counting Up Coal’s CO2

April 10, 2012 | KUOW
CONTRIBUTED BY:
Ashley Ahearn

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  • Climate expert Steve Davis tallies the amount of greenhouse gas emitted as coal makes its way from Wyoming to China. Step 1: The fuel burned in mining operations amounts to 30-40 kg of CO2 emissions per ton of coal mined. credit: Flickr/KimonBerlin
  • Step 2: train transport. Trains are fairly efficient, so the 1,100 mile trip from Wyoming to a Pacific port will emit 50-60 kilograms of CO2 per ton of coal transported. credit: Flickr/gibbseynz
  • Step 3: shipping the coal. As with trains, shipping coal across the ocean doesn't account for a big share of the fuel's greenhouse emissions. Davis pegs it at eight kilograms of CO2 per ton of coal shipped across the Pacific. credit: Flickr/Ben Eriksen
  • Step 4: Burning the coal. Davis figures 86 percent of the coal's carbon footprint results from its burning at plants like this in China; the other 14 percent is the result of its journey from Wyoming overland to the U.S. coast and across the Pacific. credit: WikiCommons/Rodrigo
Climate expert Steve Davis tallies the amount of greenhouse gas emitted as coal makes its way from Wyoming to China. Step 1: The fuel burned in mining operations amounts to 30-40 kg of CO2 emissions per ton of coal mined. | credit: Flickr/KimonBerlin | rollover image for more

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A half-dozen Northwest ports are considering building export terminals. The main export: coal. Where’s it going? Asia.

So, we wanted to take a look at what mining, transporting and burning American coal looks like in terms of CO2 emissions. Hypothetically speaking, if all the terminals are built, that could mean about 100 million tons of coal passing through Washington and Oregon ports en route to be burned in power plants on the other side of the Pacific. EarthFix’s Ashley Ahearn turns to Steve Davis, a research associate at the Carnegie Institution for Science and a visiting scholar at UW’s Climate Impacts Group, to do the numbers. The figures he cites below are based on previous research and studies.

EarthFix: Ok Steve, let’s start at the top, you start in Wyoming. They’re mining this stuff. What are the CO2 emissions from mining this coal?

Steve Davis: As you might expect mining coal entails machinery to dig in the earth and haul the coal out of the mine and the mining that’s going on in Wyoming is primarily surface mining so you don’t have to do the kind of tunneling and things you may be familiar with that happen in the East, places like West Virginia and Kentucky. And so the machinery that they use there is burning primarily diesel fuel, it’s an oil product and per ton of coal that is dug up and transported out of the mine there, just locally we’re talking about the transport, hauling it out of the hole basically, when you factor in the carbon emissions factor of that diesel that’s being burned, it’s roughly 30-40 kg of CO2 emissions per ton of coal that gets mined.

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Steve Davis

EarthFix: I’m having a hard time visualizing that. In my mind, what does that look like? One ton, to get it mined, to get it out of the ground is equal to…?

Steve Davis: That’s roughly a couple gallons of diesel fuel so it’s a fairly efficient process. Associated with the mining there’s the equipment that we talked about but there’s also something called coal bed methane. As the coal is originally laid down as plant material basically and compacted over millions of years, methane is often generated and trapped in between these coal beds and so when you mine coal often that methane is released and while some mines are set up to capture that methane and use it as a fuel, most of them just it out into the atmosphere where it actually contributes to climate change. Methane is a stronger greenhouse gas than CO2.

So the mines in Wyoming per ton of coal that’s produced are releasing something that effectively is equal to 20 kg of CO2 as methane.

EarthFix: Ok, and then we put it on a train. So from Wyoming, from Montana that train moves across the Northwest. That’s a lot of distance to cover. What are the emissions there?

Steve Davis: As it happens train transport is pretty darn efficient. It’s actually consistently more efficient than over the road trucking assuming the tracks are going where you want them to but assuming an 1100-mile trip from the Powder River Basin in Wyoming to Bellingham say, a train will burn in the neighborhood of 2-4 gallons of diesel fuel for every ton of coal on board. So even counting the fuel burned on the return trip, because mostly these trains return to Wyoming empty, we’re talking only about 50-60 kilograms of CO2 per ton of coal transported.

EarthFix: So let’s follow it to the next step now. The train arrives in say Bellingham where there is a proposed export terminal that’s in the beginnings of the EIS process, the environmental impact assessment process. It goes on a ship. It has to go all the way across the Pacific Ocean. What are the CO2 emissions there?

Steve Davis: Believe it or not ocean shipping is even more efficient than the trains that we just talked about. Fully-loaded one of the big bulk cargo transport ships can carry upwards of 300,000 tons of coal, and it does burn somewhere in the neighborhood of 50 gallons of bunker fuel for every nautical mile it travels. And so here if we’re assuming a trip of 4,000 nautical miles to get from the Washington state coast over to China, somewhere near Beijing, we’d be talking about 10 kilograms of CO2 or less, I actually calculated eight per ton of coal that’s being shipped across the ocean.

EarthFix: Alright, so lets tally it up now. That one ton of coal coming from Wyoming, Montana, going all the way to the power plant say in China, how much extra CO2 emissions have been attached at this point or are coming out of this ton of coal?

Steve Davis: So we’re talking about 100 million tons of coal being burned and that releases in the neighborhood of 175 million tons of CO2 and of that 175 million tons about 150 million tons of it are from the burning of the coal itself and 25 million tons from all these other processes of extracting and transporting.

EarthFix: I’m not going to lie, I’m kind of surprised at what a small percentage the transport and the mining of this commodity to its overall carbon footprint. Do you think we should look at coal differently? I mean, is it just another commodity that’s being transported by rail and ship around the world like other things we buy every day?

Steve Davis: I think with respect to the Powder River coal and the climate impacts of extracting that and exporting it to China really I think we have to ask ourselves: what would happen to the coal in the case where it wasn’t sent to China? Would it still ultimately be extracted from the ground and burned somewhere because …

…The negative impacts in terms of climate are going to come from the burning of the coal… and not the transportation of the coal, so it really doesn’t matter to the atmosphere and the climate where that coal is burned but whether it’s burned.

EarthFix: So should it be burned?

Steve Davis: I think it’s a pretty clear case that it should not be burned and that we should try to eliminate carbon based sources of energy to the greatest extent possible and coal is the most carbon intensive of the fossil fuels so it should go first.

Steve Davis is a research associate at the Carnegie Institution for Science and a visiting scholar at the University of Washington’s Climate Impacts Group.

© 2012 KUOW
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