Mitigation Math: Hypothetical Answers

Roger Pielke Jr. has an outstanding post titled US Mitigation Math where he shows the general sources and sinks of US energy and resulting GHG emissions. He also throws out some reduction scenarios and concludes that they cannot come close to meeting an emissions reductions goal of 14% below 2005 levels by 2020.

So he closes with a challenge: “… present a scenario combining decarbonization of the energy supply and efficiency gain that has a realistic chance of succeeding in meeting a 14% emissions reduction (below 2005) by 2020.”

It’s a busy week for me so I haven’t had time to work out some complete solutions, but I took a shortcut and asked myself how much CO2 I could reduce if I took all of the Obama administrations projected $645B in revenue from emissions allowances between 2012 and 2019 and applied it to various solutions.

Since I’m living in a hypothetical world, I’m going to take a couple of liberties. First, I’m going to assume that I’ve either got access to all of the money on the first day of 2012, or I can get the average amount of $80B/year for a long time to come. Second, I’m going to ignore the physical and temporal realities of implementing my solutions - in my world I’ve got the full support of the nation and they’ll do everything they can to implement these ideas. Finally, I’m going to conveniently ignore the emissions required to implement these solutions.

Solution 1: Buy Lots of Prius’s

In this scenario I’m going to buy 25.6M Prius cars at an estimated 45MPG and replace 25.6M gas guzzlers at an average of 15MPG. At 12K miles/year each, we’ll save 533 gallons of gas per car per year, and at about 20 pounds of CO2 per gallon, that’s about 4.8 metric tons of CO2 per car per year. Grand total savings: 122MMt/year, or a 2% savings from 5991 MMt.

Solution 2: Go Big on Today’s Solar

That didn’t work so well, so let’s take the money and go big on solar. This project outside of Phoenix looks pretty cool, and the article reports that we can get about 870M kWH/year (70K homes at 12,424 kWH/home) at $133M cost/year. For $80B/year for 30 years we can invest in 707 of these plants. eGrid says that AZ emissions rate is about 1,200lbs/MWh, so if we replaced that with 707 plants worth of carbon-free solar power, we’d save about 335 MMt/year, or 5.5% reduction from 5991 MMt.

Solution 3: Go Big on Future Wind

Getting better, but still not there. Since we’re being hypothetical lets not limit ourselves to current technologies, but instead bet on 2012 wind power. The Large Wind Technology Project at DOE is shooting for $0.035/ kWH by 2012, so lets assume they are successful and we’ll buy it up with our $80B/year of carbon auction dollars. That give us 2.3T kWH/year. Replacing a national average of around 1,300lbs/MWh, that yields 1350 MMt/year, or a 22% reduction from 5991 MMt.


  • Its worth noting that the difference between the solar and wind solutions lies in the cost/kWH of the two solutions I somewhat randomly picked. If I’d picked other projects, these two might have come out closer.
  • One question I’ve had is whether the cap and trade system has enough economic impact to meet the targets being laid out solely through investment in new energy sources. Since the actual plan involves using some of the money for tax breaks, and since the system won’t be as effective as my “direct spend” approach, I conclude that the answer is a solid “no” at the projected carbon prices.