From coal and natural gas to renewables in the US

Two studies analysed the GHG emission reductions and health co-benefits that resulted from increased renewable energy use in the United States between 2007 and 2015.

The first study was an analysis of the effects from increased use of solar and wind power in the generation of electricity, which offset coal and natural gas generation at varying proportions. Between 2007 and 2015, the energy generation from solar and wind power increased from 35,000 GWh to 227,000 GWh per year. In 2007, 37% of wind generation offset coal generation and 62% offset natural gas generation. By 2015, 52% of wind power generation offset coal generation and 47% offset natural gas generation.

The second study analysed the effects of the Renewable Portfolio Standards (RPS), specifically one of the state policies in place to encourage the use of renewable energy. The state RPS is one of the policies in place to encourage the use of renewable energy and has been implemented in 29 US states, and in Washington D.C. the RPS requires electric companies to meet a growing portion of their load with eligible forms of renewable electricity.

Switching to renewable energy to meet the Renewable Portfolio Standards (RPS) obligations resulted in a 3.6% reduction in total US fossil fuel generation, equivalent to more than 2500 MW of fossil generation capacity, and reduced GHG emissions of 59 million metric tons of CO2 equivalent in 2013 alone. In the year 2015 alone, 147 million metric tons of CO2 emissions were avoided due to an increase in solar and wind power generation across the US.

Compliance with RPS obligations in the year 2013 alone led to estimated reductions of 77,400 metric tons of SO2, 43,900 metric tons of NOx, and 4,800 metric tons of PM2.5. These reductions are equivalent to 2% of the total US power sector emissions. It further prevented an estimated 320 to 1100 deaths; 160 to 290 emergency department visits for asthma; 195 to 310 hospital admissions for respiratory and cardiovascular conditions; 40 to 560 non-fatal heart attacks; and 38,000 to 64,000 lost workdays. Between 2007 and 2015, the increase in solar and wind power generation to replace coal and natural gas across the US resulted in a total of 3000 to almost 13,000 avoided premature deaths.

Between 2007 and 2015, the economic benefits of renewable energy power generation were estimated at between 30 and 100+ billion US dollars. This is only the benefits from air quality, but does not include the economic benefits of CO2, which were valued at an additional 5 to 100+ billion US dollars.

In 2021, about 61% of the electricity generation in the US was from fossil fuels, 19% from nuclear energy, and 20% from renewable energy sources. Therefore, the effects on health and CO2 emissions could be even greater if electricity generation from renewable sources were to increase and further displace fossil fuel generation. In 2017, approximately 47,000 (range between 16,000 to 86,000) deaths were attributable to PM2.5 exposure resulting from residential energy use, industrial processes, and energy generation, with coal use contributing to 9.3% of the total PM2.5 emissions, and oil and gas contributing to nearly 28% (McDuffie et al., 2021). In another study, it was also estimated that nearly 52,000 lives could be saved annually by transitioning from coal to photovoltaic-powered electrical generation, which requires 755 GW of US photovoltaic installations (Prehoda and Pearce, 2017).

The US introduced several policies to attract investment into the renewable energy sector. Despite these, there are still several barriers to uptake. For example, with the introduction of the Renewable Portfolio Standards (RPS) compliance obligations in 2013, the percentage of renewable energy that replaced fossil fuel generation varied widely between states in the US. There were marked differences between regions, with combustion-related emissions reductions higher in certain regions, namely the Great Lakes and Mid-Atlantic regions, Texas, California, Colorado, and Washington. For example, renewable energy generation replaced 0.1% of fossil fuel generation in the Southeast compared to 13.9% in California in 2013. This was due to varying levels of stringency in meeting the RPS standards between regions. Therefore for policies and regulation standards to achieve their potential impacts, procedures to ensure accountability, and compliance are required. In addition, current utility rate structures hinder the deployment of renewable energy, and a change in the system to distributed generation would be required. Standard procedures to connect renewable energy systems to the electrical grid are lacking and there may be limited access to renewable energy sources in remote areas (United States Environmental Protection Agency, 2021; Prehoda et al., 2019).

With regard to public opinion, a survey of over 1,000 adults living in the US conducted by the Yale Program on Climate Change showed that Americans strongly support policies aimed at increasing renewable energy use in the country. However, reasons motivating this support may differ between Democrats and Republicans. Republican support may be driven more by economic benefits, while Democrat support by concerns for global warming. Therefore, these variations in the drivers of public opinion should be considered when aiming to increase the investment and deployment of renewable energy (Gustafson et al., 2020). Possible spill-over effects should be considered in the scale-up of any action. In the case of the RPS obligation, fossil plant closures and resulting health benefits from reduced air pollution were shown to have occurred outside RPS compliant states. This is because some states meet RPS standards using renewable energy generated from non-RPS complying states, and the reduction of air pollutants was often beneficial across state borders. In addition, meeting RPS compliance obligations in 2013 also resulted in a reduction of power sector water withdrawals and consumption by an estimated 830 billion gallons and 27 billion gallons, respectively - equivalent to 8,420 gallons of withdrawal and 270 gallons of consumption saved per MWh of renewable electricity generation.