While the state is still a major polluter, Ohio’s shift away from coal has led to a significant reduction in carbon emissions.

Carbon dioxide emissions from Ohio’s energy sector fell by 50 million metric tons from 2005 to 2015, according to data recently released by the Energy Information Administration.

What happened in Ohio “is like a lot of places,” said EIA energy and environment analyst Perry Lindstrom. “You’ve replaced coal with natural gas.” Lindstrom’s December 11 Today in Energy report noted a nationwide trend in which all states except Louisiana and Nebraska cut energy-related carbon dioxide emissions over that ten-year period.

“Coal has gone from around 80 percent to 60 percent of our generation over the ten year time span, and gas from around 3 to 23 percent,” explained Andrew Thomas, an energy law and policy expert at Cleveland State University. Coal’s carbon dioxide emissions from Ohio’s energy sector fell by almost 47 percent during that ten-year period. Meanwhile, natural gas emissions grew almost eightfold, to 11.7 million metric tons.

“But you’re buying about twice the energy with that 11.7,” Lindstrom explained. The chemical structure of natural gas makes it “less carbon dense” than coal. As a result, “natural gas produces only about 45 percent of CO2 for the same amount of kilowatt hours produced.”

Natural gas plants also tend to be newer and more efficient than older coal plants, Lindstrom added. EIA data show that as of April 2017, the average age of coal-fired power plants in the United States was 39 years. Two power plants that are the subject of subsidy bills in Ohio are more than 60 years old.

Behind the numbers

“No doubt the steep drop in natural gas prices during this time period played a starring role in this change, forcing numerous dirty and uneconomic coal plants to close,” said Dick Munson at the Environmental Defense Fund. “Yet, despite recurrent challenges from state legislators, Ohio’s deregulated electricity market and clean energy standards are also to thank.”

“In particular, Ohio’s energy efficiency mandate has had some effect on CO2 emissions,” Thomas noted.

Despite Ohio’s huge cut in carbon dioxide emissions, 30 other states had lower per capita CO2 emissions as of 2014. And Ohio was still among the top ten producers of greenhouse gas emissions as of 2015. Nonetheless, in absolute terms, the Ohio energy sector’s carbon dioxide cuts rank it ahead of all other states for the same period, Munson said.

Some EIA data can be “notoriously simplistic,” warned energy and economy policy analyst Noah Dormady at Ohio State University. For one thing, the regional transmission organization working with two of Ohio’s four utilities changed between 2005 and 2015, making some comparisons like “apples to oranges.” Also, the EIA counted emissions at the place where electricity was generated, rather than where people used that electricity. So, a state with large cuts in emissions from generation might still use a lot of coal-fired electricity produced elsewhere.

Nonetheless, the trend in the EIA’s data and analysis confirm the big shift from coal to natural gas, which really “changes the game on CO2 emissions,” Dormady said. “I wouldn’t say that coal is being pushed out. But I would say there’s a move toward more parity between the two.”

Meanwhile, he said, carbon dioxide emissions from Ohio’s transportation sector fell by less than seven million metric tons from 2005 to 2015. In 2015, transportation produced about 30 percent of Ohio’s carbon dioxide emissions, second only to the energy sector.

Larger cuts from transportation might have been expected based on federal CAFE standards for fuel efficiency and other improvements in technology, Dormady said, especially since Ohio’s population grew about 1.3 percent during that decade.

Looking backward—and ahead

If one could travel back in time, Dormady wondered whether the data might have led lawmakers to make different choices. During President Obama’s first term, for example, Congress considered but failed to pass bills to limit greenhouse gas emissions. Given what happened in the years afterward, Ohio and other states now appear close to being on track to meet some targets from those bills.

Similarly, if 2005 were used as a baseline, Ohio companies might have profited from cap-and-trade programs, Dormady noted. Given the reductions that happened, “they’d be making money,” he said.

Looking ahead, coal still has some advantages over natural gas generation, and vice versa, Dormady added. Coal plants are “not curtailed when there are cold weather events” and have on-site fuel storage. In his view, both factors can help to meet large amounts of constant energy demand.

At the same time, besides having relatively lower greenhouse gas emissions, natural gas plants’ big advantage over coal is that they can be ready to run in minutes. “That ability to react to the stochastic, or volatile, nature of electricity demand is really important,” Dormady said.

But, he added, the job of managing markets to meet both baseload and variable energy demand is that of PJM and other regional suppliers, not individual states. Recent legislative and regulatory proceedings in Ohio have sought to subsidize companies with coal-fired power plants.

For his part, Munson would urge Ohio lawmakers to resist efforts to weaken competition in the state’s electricity market with reregulation or bailouts and to further weaken the state’s clean energy standards.

“Ohio made impressive reductions in its power sector’s carbon emissions from 2005-2015,” Munson said. “But many state utilities and lawmakers keep trying to mess with the market, and put Ohio back on a carbon-heavy diet.”