Doing the Math

With the release of the latest IPCC Report, it is obvious that something must be done to curb global GHG emissions. But what?

As the majority of global emissions is the result of the (very) large-scale burning of fossil fuels to produce electricity, the electrical sector is a logical place to start. However, much of the debate around how to decarbonize the electrical sector is buried in generalization and rhetoric. As a result, the scale of this problem is lost in the noise.

Let’s fix that.

Large-scale energy usage is measured in quads, or quadrillion British Thermal Units (BTUs), a common measure of the energy content of a given fuel.

One quad is roughly:

  • 36 million tons of coal, or
  • About 970 million cubic feet of natural gas, or
  • About 170m barrels of oil

The world used 524 quads of energy in 2010. That’s one quad every 17 hours or so.

The US uses roughly 100 quads per year, or about 20% of global consumption. That’s one quad every 87.6 hours.

To put that number in perspective, think about this: Large-scale coal deliveries are measured in “unit trains”, a 100-130 boxcar long train full of coal. They’re typically 1 to 1.5 miles long. Each train carries roughly 10,000 tons of coal. One quad is the equivalent of 3,600 of these trains. The entire annual energy budget of the United States would require 360,000 of them — or about 986 unit trains per day.

The largest active coal basin in the US is the Powder River Basin, in Wyoming. The ten largest coal mines in the US all sit on this basin. The entire basin produces about 60 unit trains per day.

To make a meaningful dent in US emissions, we need a combination of two things: a reduction in overall energy demand, and a cleaner fuel mix. Demand has declined for the last couple of years, but as this site has already discussed, energy efficiency alone won’t get us where we need to be. We need to dramatically retool our energy mix.

In 2011, the US used roughly 4 trillion kilowatt hours of electricity — or about four million gigawatt hours (GwH). Roughly 42% of this, or 1.68M GwH, came from coal. Just to replace this coal generation (while leaving older natural gas, oil, and other fossil-fired generation in place) would be monumentally expensive.

Using EIA fuel cost estimates, we can do some ‘back of the envelope’ calculations. Replacing all 1.68M GwH of coal generation with next-generation natural gas turbines, using carbon capture and sequestration (CCS) technology, could cost roughly $157B — ignoring any retirement or grid improvement costs, which would likely push costs much higher. Using only renewables could cost somewhere between $145B and $439B — again, ignoring any secondary costs (which are likely to be much higher with intermittent renewable technology).

In 2012, US investment TOTALLED (in all sectors) about $2T. In other words, we’d have to spend 10% to 20% of our TOTAL annual investment just to update our electrical generation capacity. Upgrading the grid is likely to add much more to the cost.

In other words, decarbonization is a monumental and expensive problem, one that is unique in the modern industrial world. However, retooling our energy mix is a problem we must solve — we likely don’t have a choice.

Image Credit: By Randy C. Bunney; Great Circle Photographics (Own work) [CC-BY-SA-3.0 (], via Wikimedia Commons


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