The implementation of “clean energy” sources is an important component of the government’s plan to mitigate climate change, but what makes an energy source “clean” is a contentious topic. The Senate’s Clean Energy Standard Act of 2012 defines a clean energy source based on carbon emissions (with unclear thresholds) and focuses only on electricity generation. The EPA is more broad in its definition, and includes energy efficiency and combined heat and power, as well as renewable energy sources, as clean energy sources. In a recent presentation I attended by Jose Zayes, the Program Manager for Wind & Water Power Program (a part of the DOE), he said that “clean energy” is often stretched to include nuclear energy, fossil fuel combustion with carbon capture and sequestration, and natural gas, since these sources have lower carbon emissions than traditional fossil fuel energy sources.

If defined this broadly, what are the implications for energy policy? With the focus on clean energy in the face of climate change, rather than sustainable energy for the purpose of long-term energy security, it is easy to overlook the broader impacts of our energy sources. Nuclear energy is “clean” in terms of emissions, but what about the radioactive waste produced? Natural gas burns cleaner than coal at the plant, but methane leaks from pipelines and drilling operations can have a large impact on short-term global warming potential. Combustion with carbon capture and sequestration is not well developed and introduces the problem of finding somewhere underground to store the carbon, with the risk of the carbon making its way to the surface and atmosphere after ground-shifting.

Even renewable fuels can have large carbon footprints in the production stage, despite having low or no emissions during actual energy production. Energy efficiency, in some cases, has been shown to backfire as people use the technology more and negate the savings. For example, more efficient vehicles are cheaper to drive, so people are may begin to drive more and cancel out the savings. This phenomenon is termed the “Jevons Paradox”, and while it certainly does not hold true in all situations it is important to keep in mind when creating policy to encourage energy efficiency.
If we are to effectively address climate change in the near future, we need to be sure that we are judging energy sources based on the impact of the entire system. We also need to give priority to energy sources that are not only clean, but sustainable over the long term.