April 30, 2012
Have US Emissions Peaked?
This trend is principally the result of the ongoing transition from coal to natural gas in the electric power sector. Coal, long the dominant power source in America, has faced a tightening gauntlet of pollution regulations in recent years while hydraulic fracturing in shale has expanded the nation's natural gas reserves and driven prices to record lows. Consumption of gas-fired electricity, which emits roughly half as much CO2 as coal-fired generation, increased 2.5 percent in 2011. Coal use, meanwhile, shrank 4.6 percent. Coal now supplies less than 40 percent of total electricity generation in the United States -- the lowest levels seen in 33 years. Natural gas reached the highest consumption levels seen since 1973, when the EIA began recording data.
Cheap, cleaner gas means effectively flat emissions growth in the coming decades, according to EIA estimates. Emissions in the United States peaked in 2007 at 6.3 billion metric tons and then immediately plummeted under the pull of the Great Recession. The ongoing transition from coal to gas, however, is projected to keep US CO2 emissions below the 2007 peak over the coming decades, even as the economy recovers. According to the EIA, emissions in 2011 shrank 1.9% below 2010 levels despite twelve straight months of economic growth. The EIA projects 2020 emissions at 8.1 percent below the 2007 peak, and 2035 emissions 3.9 percent below -- a return to growing emissions, yes, but very slow growth by historical standards.
It's clear that deeper emissions reductions will hinge on the development of affordable, zero-carbon power technologies as well as substitutes for oil in the transportation sector. In their projections, the EIA assumes a "policy-as-usual" scenario, without further tightening of air pollution or CO2 regulations and with only incremental technical improvements to clean energy technologies. Any strengthening of US clean energy policy -- for example, the institution of EPA regulations on CO2 emissions from existing power plants or an acceleration in clean tech innovation investments -- could push domestic emissions on a permanent downward trajectory.
Electricity generation from renewables increased by 12.9 percent in 2011 -- impressive, yes, but considering that added generation from all renewables combined was about half the absolute increase of natural gas alone, it's clear that solar, wind, next-gen biofuels, and other zero-carbon alternatives have a long way to go. As the shale gas revolution demonstrates, sustained public and private investment in next-generation energy technologies can hasten the pace of advanced energy innovation and deployment. The magnitude of total emissions reductions achieved this century will depend on the scale and efficacy of these investments.