Making coal cleaner

Situated along the Allegheny Mountains in the west and from Hazleton to Pine Grove in the east, Pennsylvania’s expansive coalfields make the Commonwealth the third-largest coal producing state. Despite its mining production capacity, the state’s reliance on coal for energy production fell to 39 percent in 2013 from 60 percent in 1990 while reliance on other energy sources such as nuclear power and natural gas have increased, according to the U.S. Environmental Protection Agency (EPA).

The move away from coal-generated electricity is in part due to the Clean Power Plan, finalized in 2015, which aims to gradually reduce emissions across all states through 2030. Pennsylvania was tasked with reducing carbon dioxide emissions by about 33 percent, according to StateImpact Pennsylvania, a National Public Radio news reporting initiative focused on Pennsylvania’s energy economy.

Coal is often charged for a large portion of carbon dioxide emissions in the state due to its composition of primarily carbon and its traditional majority share of energy production in Pennsylvania, according to StateImpact Pennsylvania.

“We should stop talking about getting rid of coal and start talking about what [we] really want to do which is to have available, cheap electricity with a significant reduction in the environmental footprint,” said Jonathan Mathews, a professor in the College of Energy and Mineral Sciences (EMS) and co-director of the EMS Energy Institute’s Coal Science and Technology (CST) program.

Mathews and Sarma Pisupati, also an EMS professor and CST co-director, understand the desire for clean energy with a reduced environmental impact, but argue that how coal is used, not the use of coal, is the problem.

“Where the disconnect is, is a lot of people are saying ‘let’s get rid of coal,’” Mathews said. “But, what they really want to do, what they’d like to achieve, is decarbonizing the emissions and if we can do that with coal—and there’s several ways of achieving that—then coal should have the ability to meet those demands.”

Making coal clean

Mathews’ current research centers on exploring ways to capture and store carbon emissions, also known as carbon sequestration, along with examining coal behavior during use. His research has identified ways to improve carbon sequestration through the application of stress fields and creating new fractures within coal using microwave bursts.

“If carbon sequestration can be achieved commonly, then coal will continue to have a role to play and we will achieve reduced carbon dioxide emissions,” Mathews said. He has published some of his result in recent issues of Carbon, Fuel, and Fuel Processing Technology.

The potential for carbon sequestration in a given type of coal can be predicted through x-ray imaging of a sample along with molecular-level modeling of coal’s structure and interaction with atmospheric gases. Both Mathews and Pisupati are particularly focused on how carbon can be captured during coal burning and effectively stored instead of being released into the atmosphere.

“Some of the reasons why coal is not environmentally friendly are because what we put back in to the environment in either gaseous or solid form is not acceptable. But, if we turn those wastes in to resources, then they would be environmentally friendly,” Pisupati said.

Pisupati said that rethinking how coal byproducts are handled can help coal become a more environmentally friendly resource. Currently, char, ash, liquid, and gaseous byproducts are often discarded by returning them to the earth. Discovering alternative ways to capture and discard those byproducts are challenges Pisupati views as integral to an engineer’s job.

“If we don’t want to touch a problem, what is there for us to solve as engineers, as designers, as scientists?” Pisupati said. “If we don’t want to do research and find new things, then what is there?”

Coal ash, in particular, includes multiple high value, critical elements including vanadium and nickel that if extracted could offset the market’s demand while reducing the environmental impact of coal combustion wastes, Pisupati said. Learn more about Pisupati’s research into recovering rare earth materials from coal on nine.

Clean vs. cleaner

Current electricity generation figures suggest that clean energy production is preferable to fossil fuels like coal. In 2010, almost half of Pennsylvania’s net energy was produced by coal compared to natural gas’ share of 15 percent. By 2017, coal’s role decreased to about 25 percent and natural gas use grew to provide almost one third of the state’s net energy production. During that same period between 2010 and 2016, the most recent data available, carbon dioxide emissions in Pennsylvania dropped about thirty-nine million metric tons, according to the U.S. Energy Information Administration (EIA).

Pisupati and Mathews caution consumers and policymakers from viewing increased reliance on nuclear and natural gas energy along with the decrease in carbon emissions as further evidence that coal has the largest impact on the environment.

“No energy is clean. It’s hopefully cleaner,” Mathews said. “Everything is going to have an environmental impact and I think it’s a good conversation to have, regarding what’s acceptable and how do we get down to those levels? We need to be careful that we don’t make electricity so expensive that we have to choose between electricity, heat, and food. We have to keep a balance.”

Mathews and Pisupati also want the public to recognize that energy from natural gas and renewables like wind and solar have shortcomings too. 
“There’s a reason we’re not using wind, there’s a reason we’re not using solar historically to generate all our electricity,” Mathews said. “These are more sustainable energy sources but they’re currently still more expensive than coal in generating a consistent large-scale supply of electricity. ”

While the technology and methods to reduce carbon dioxide emissions during coal-fired power generation are being tested and added to existing plants, carbon production from coal plants has decreased since its peak in the mid-2000s. According to the EIA, carbon emissions associated with coal plants fell by about forty-two million metric tons in Pennsylvania from 2005 to 2016.

Even after efforts to reduce emission levels, Pennsylvania remains third behind Texas and Californiain energy-related carbon dioxide emissions. However, it is important to note that the term “energy-related” refers to all energy produced in the Commonwealth including energy sold to neighboring states. Annually, Pennsylvania is the nation’s second largest energy exporter. When considering per capita energy-related carbon dioxide emissions, Pennsylvania annually ranks in about the middle of all fifty states.

“We need to look at the overall environmental footprint,” Mathews said.

“If we bring coal out, why is it not environmentally friendly? Because what we put back in to the environment is not acceptable either gaseous form or solids that we send back. But, if we turn them in to resources, [then they would be environmentally friendly].” 
— By Sarma Pisupati

Local consumers do have the option to vote on which local utility serves their area or remodel their home to use a different energy source, but the cost and availability of energy sources are influenced by a state’s legislature, utility companies, and market prices which limits a consumer from selecting an energy source over the other based on environmental impact.

However, Mathews said homeowners should not be forced to rely solely on renewable energy sources or any one type of energy because of the fluctuation in and unpredictable nature of resources. He worries about Pennsylvania’s growing reliance on natural gas for heat and a push for residents to use renewable energy as their dominant power source.

“Natural gas certainly has a role to play but we need to have a mixture of energy supplies,” he said.

Mathews believes energy policies are in a transition period from relying on a single resource to having multiple sources available to best meet an area’s needs “not just on a sunny day or a windy day, but in the darkest winter vortex.”

Both researchers agree that coal fired-plants can become more sustainable by upgrading plants with new carbon capture and storage techniques along with creating better methods to reuse and dispose of coal byproducts, all challenges Pisupati says engineers are ready to solve. Despite the shift toward carbon-free energy production, coal still has a role as a “base load” energy generator Pisupati said. He said coal will continue to power residential areas and supply industries with byproducts to some extent in Pennsylvania and abroad.

“I can very clearly see that coal will not go away in the foreseeable future,” Pisupati said. “Coal will play a role in our nation’s energy scenario but, the question is how big of a role or what kind of role. We should be looking at coal as more than just an energy source for power generation and more as a resource to help us to a sustainable future.”

Learn more about the sustainable energy research being conducted at the EMS Energy Institute in our summer edition of Energy Innovation.