No one disputes that the electricity generating sector of the US economy creates fewer carbon emissions today than it did a decade ago. What people do dispute is why that is happening. To listen to fossil fuel advocates, it is because utility companies are relying more on natural gas and less on coal, and that is certainly true. But what few recognize is that a sharp increase in power generation from renewables has been as important to reducing CO2 emissions as natural gas.
New research from Bloomberg New Energy Finance and the Environmental Defense Fund shows the impact renewables have had on power sector emissions, which fell 10% from 2007 to 2013. In its Sustainable Energy For America report for 2018, BNEF concluded for the first time that renewables played a larger role in reducing power sector emissions in 2017 that switching to natural gas. Those emissions dropped a hefty 4.2% in 2017.
Power generaton, which used to be the single largest source of US carbon emissions, is now second to the transportation sector. In all, total US emissions are lower than they have been since 1991. That is no reason for wild celebration, however. In order to meet the goals of the Paris climate accords, reducing emissions will not be enough. The world must actually find a way to stop all carbon emissions and actually devise a plan to remove much of the carbon dioxide that has migrated into the atmosphere over the past century.
The EDF study used what statisticians call decomposition analysis to look at several factors, including total energy demand, the share of natural gas in the fossil fuel mix, and the share of renewables and nuclear energy in total energy production. While conventional wisdom holds that lower emissions from the power sector are due to reduced economic activity after the greed heads crashed the global economy in 2007 and the influx of inexpensive natural gas from fracking, the EDF folks have a slightly different perspective. “Those…experts mostly overlooked another key factor: the parallel rise in renewable energy production from sources like wind and solar.”
Their numbers show that between 2007 and 2013, renewables decreased total carbon dioxide emissions by 2.3 to 3.3%. That is about the same as the 2.5 to 3.6% that shifting from coal to natural gas contributed. During the same period, nuclear added 0.6 to 1.5% to the decrease. “As the cost of renewables continues to decrease, it becomes increasingly relevant to track their role in CO2 emission trends,” the researchers say.
They also have an important insight with regard to using natural gas as a “bridge fuel to the future,” a claim that people in the fossil fuel industry make regularly. “However, it is important to keep in mind the role of methane leakage along the natural gas supply chain, which significantly reduces the net climate benefits of natural gas and the magnitude of which has previously been underestimated,” they write. Add in those methane emissions, and the euphoria about cheap natural gas evaporates as quickly as the vapor plume from the cooling towers at a coal-fired generating plant.