In 2008 I predicted that 2007 would prove to the be peak CO2 output for the USA (I termed it “peak carbon”). Checking in on the 2010 results published by the EPA we see that my predication has held up, but seeds of its possible undoing have been sown.
The total US CO2 emissions rose over 2009 levels, but is still solidly below the CO2 emission levels in the years from 2003 through 2008. As the graphs on the EPA website show, the uptick in emissions (expectedly) followed an increase in US industrial production, and the resulting increase in energy usage.
What was less expected was the increase in carbon intensity of the US energy supply (i.e. the amount of GHG emissions per unit of energy delivered went up), and in particular the carbon intensity of electricity production (tons of CO2 per kWh). If the economy continues to improve and energy usage grows, this is the key number to watch.
Presumably we’d all like to see the economy grow, but that will put us in the following race: can we bring on line lower carbon electricity sources faster than the increase in electricity demand that the economy is driving. Cleaner electricity could come from wind or solar, but it could also come from natural gas or nuclear, which are both far cleaner than coal.
In 2010 we did not win this race. The figure below from the EPA site shows that most of the increase in electricity usage was fueled by coal, followed by natural gas and (a distant third) renewables. As a result, the carbon intensity of US electricity delivery went up in 2010.
In addition to the growth of the economy, there’s one other driver of electricity use that we need to be aware of. As I have discussed previously, switching from gas to electric cars does not necessarily result in a reduction of emissions when the electricity is primarily sourced from coal. And as 2010 shows, when we increase electricity usage today, most of it is coming from coal.
The 2011 numbers will be out in mid-2012, and it will be interesting to get another look at the economic growth, the increases in energy and the sources of that energy.