5 January 2017
By Britt Faulstick
When the Environmental Protection Agency finalized the Clean Power Plan in 2015, the agency exercised its authority to regulate carbon dioxide emissions to protect public welfare. The Plan, now the focus of escalating debate, also put the nation on course to meet its goals under the Paris Climate Agreement. Given that other pollutants are emitted from power plants—along with carbon dioxide—research has shown that carbon emission standards for the power sector benefit human health. But new research shows they would also benefit crops and trees.
The new study, recently published in the Journal of Geophysical Research: Atmospheres, is the first to model the ecosystem impact of contrasting policies, one of which was similar to the Clean Power Plan.
According to the study, which included an option similar to the Clean Power Plan, the corresponding reduction in carbon, nitrogen and sulfur emissions from coal power plants would also mean a decrease in ground-level ozone—a known inhibitor of plant growth. And by modeling these reductions in the year 2020, the researchers found that they would provide a significant boost to the productivity of key indicator crops, such as corn, cotton, soybean and potato, as well as several tree species.
“Our findings suggest that crops like corn, soybeans and cotton could benefit from substantial productivity gains under moderate carbon standards for power plants,” said Shannon Capps, an engineering professor at Drexel University in Philadelphia and lead author of the new study. “With policies similar to those in the Clean Power Plan, we’re projecting more than a 15 percent reduction in corn productivity losses due to ozone exposure, compared to business as usual, and about half of that for cotton and soybeans. Depending on market value fluctuations of these crops over the next few years, that could mean gains of tens of millions of dollars for farmers—especially in areas like the Ohio River Valley where power plants currently contribute to ground-level ozone.”
“Our work shows the importance of considering the co-benefits of our nation’s energy policies going forward,” said Charles Driscoll, an engineering professor at Syracuse University and co-author of the study. “These benefits to people and plants are nearly immediate and occur in urban and rural communities across the U.S. We know from this and other studies that the economic value of the added benefits from power plant carbon standards are large and exceed the estimated cost of implementation.”
Crops and ozone
The team used three policy scenarios that encompass a range of emissions targets and reductions measures, and they compared each policy scenario with a “business-as-usual” reference case that represents current clean air policies, as well as energy demand and market projections.
Then, using a computer model widely employed to help guide state-level decision making for compliance with the National Ambient Air Quality Standards, the group generated a detailed projection of what the surface-layer ozone would look like across the country under each policy scenario through 2020.
The team looked at the consequences of lower ozone for five crops whose primary growing season is June through August, the period when ground-level ozone is at its peak. They also evaluated the consequences for 11 tree species, including eastern cottonwood, black cherry, quaking aspen and several species of pine. These crops and trees are used as standard indicators in environmental research. Based on previous research by crop and tree scientists, the team could relate their models’ ozone-exposure findings to the productivity of crop and tree species.
“The option most similar to the Clean Power Plan has the greatest estimated productivity gains for the crops and trees that we studied,” Capps said. “The improvement in crop yield and tree growth was strongly tied to the level of carbon dioxide emissions reductions and adoption of cleaner energy achieved by the policy.”
Under the business-as-usual scenario, the productivity of soybean, potatoes, and cotton is reduced about 1.5 percent, with only slight impacts on corn. These levels of production only slightly improve under a policy scenario that includes only “inside the fenceline measures” such as improving the efficiency of coal-fired power plants.
A second scenario, that most closely resembles the Clean Power Plan and includes demand-side energy efficiency, substituting lower-emitting natural gas plants and zero-emitting solar and wind power into the energy mix—produces larger results. The potential corn production lost to ozone exposure in the reference scenario is reduced by 15.7 percent, soybean losses are reduced by 8.4 percent and cotton losses are diminished by 6.7 percent.
Under the third scenario, which reflects putting a price on carbon, and achieves similar emissions reductions as the second scenario, the researchers project slightly lower reductions in ozone-induced losses for corn (12.1 percent), soybean (6.6 percent) and cotton (3.8 percent).
Members of the team are also analyzing the co-benefits of power plant carbon standards for reducing regional haze and acid rain and conducting new research on the co-benefits of the final clean power plan as compared to different energy policy futures.
—Britt Faulstick is the assistant director of media relations at Drexel University. This post originally appeared as a press release on the Drexel website.