Myth: Primary sources of electricity (wind, nuclear, solar, hydropower) are carbon-free and thus do not contribute to climate change.
The hydroelectric facility at the Aswan High Dam, Egypt.
Evidence: The potential contribution of a source of electricity to climate change is measured but the quantity of greenhouse gas (GHG) released per unit of electricity generated. The units are grams of carbon dioxide equivalent per kilowatt-hour (CO₂-e/kWh). CO₂-e is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO2 that would have the same global warming potential.

Fossil fuels are hydrocarbons and release significant amounts of CO₂ when burned. Nuclear burns uranium, and wind, solar and hydropower burn no fuels at all.  But are they "carbon-free?" The appropriate way to compare technologies is with life cycle analysis (LCA), which assesses the GHG emissions at all stages of the fuel cycle: exploration, construction, operation, and decommissioning. The "cradle-to-grave" approach is important because GHG emissions occur in every stage.  For example, all energy technologies use some fossil fuels to construct their physical plant: a furnace in the case of coal, a turbine in the case of wind, a dam in the case of hydropower.  In addition, reservoirs behind a dam can flood soil and biomass, and flooded biomass decays aerobically--producing carbon dioxide--and anaerobically--producing both carbon dioxide and methane. Similarly, the mining, milling and enrichment of uranium in the nuclear refuel cycle release GHGs.

Several recent assessments have compiled the various LCAs for power generation technologies.  They indicate the following GHG emissions: lignite releases between 1100 and 1700 g CO₂-e/kWh, coal between 800 and 1000 g CO₂-e/kWh, oil between 700 and 800 g CO₂-e/kWh, natural gas between 360 and 575 g CO₂-e/kWh, nuclear between 10 and 130 g CO₂-e/kWh, photovoltaics between 43 and 73 g CO₂-e/kWh, wind between 8 and 30 g CO₂-e/kWh, hydropower between 1 and 34 g CO₂-e/kWh, and biomass between 35 and 99 g CO₂-e/kWh.

Thus, it is fair to say that nuclear and renewable power sources are low--perhaps very low-- GHG emitters compared to fossil fuels.  But they are not "carbon free" technologies.

Verdict:  False

Sources

• Weisser, Daniel, A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies, Energy, Volume 32, Issue 9, September 2007, Pages 1543-1559.
• Lenzen, Manfred, Life cycle energy and greenhouse gas emissions of nuclear energy: A review, Energy Conversion and Management, Volume 49, Issue 8, August 2008, Pages 2178-2199.