Here’s a new idea to save jobs in coal and steel country: Spin it into carbon fiber, a lightweight, sturdy building material. The pitch-black stuff derived from long-dead forests could become the backbone of spacecraft, airplanes, cars, and bikes. With a lightweight body, those vehicles would theoretically need less fuel to get moving — meaning fewer greenhouse gases polluting the atmosphere, despite more people back at work taking coal out of the ground.
Demand for U.S. coal has plummeted in recent years for a multitude of reasons. Coal production reached 35-year lows last year, related in part to bargain-basement prices for oil and natural gas. Demand has also dropped as utilities look for energy sources that produce fewer greenhouse gases, and as the prices of wind and solar power have fallen. As a result, coal jobs have taken a hit, a narrative that appeared throughout the 2016 presidential election and continues in its aftermath.
Trump's misleading coal promises
President Trump and his administration have fixated on restoring these jobs by rolling back regulations, including signing an executive order to withdraw the Obama-led Clean Power Plan, which would have frozen construction of new coal plants and closed hundreds of existing ones. The plan was a keystone piece of the Paris Climate Agreement, a landmark accord that calls for coordinated global action to combat greenhouse-gas emissions. But Trump and other Republicans also incorrectly argue that climate change is not happening or is not caused by human activity.
Trump also eliminated a stream protection rule that took years to write but was finally implemented in the waning days of the Obama administration. Environmental groups decried that move, saying wetlands and streams will now be at risk of pollution by coal companies.
Trump said such actions would bring coal jobs back, but states and the federal government were taking other, more progressive steps toward coal’s future even before the Trump administration began.
Using science to find answers
The Obama administration’s POWER initiative designated $28 million for coal-impacted communities, and some of those funds were directed to the University of Utah, which is leading a research effort that includes scientists and engineers in other coal-seam states like Kentucky and Tennessee. Researchers started working on their new project last month, and they hope to transform coal into an affordable precursor for carbon fiber. It would be a boon not only to coal country, but to manufacturing and the environment — if researchers can get the recipe right.
It’s harder than it may seem, according to Ahmad Vakili, a mechanical engineering professor at the University of Tennessee Space Institute. “Carbon fiber has properties that, pound for pound, are lighter weight and stronger than steel. But there are a bunch of catches involved,” he said.
Chiefly, the catches are price — it’s still prohibitively expensive to do this for anything other than aerospace technology — and quality. As of now, coal-based carbon fiber isn’t strong enough to compete with the more common kind, made from polymers.
For several centuries if not millennia, humans have burned coal to produce heat, and later to generate electricity. When coal is heated without oxygen, the hydrocarbons within it can be captured instead of released. This material is called pitch. Because it’s carbon-based, this raw waste material can be refined and spun into carbon fibers.
Environmental groups like the Sierra Club argue that any use of coal harms natural resources, because the process of extracting and using coal is rife with pollution. But Sierra’s Beyond Coal campaign, which advocates for alternative energy sources, has not yet studied the effects of using coal to produce carbon fiber, according to a spokesman. Similarly, advocacy groups like Citizens Coal Council say the research is still new and have not taken a position on it.
Most carbon fiber is typically made from a petroleum-based compound called polyacrylonitrile, or PAN, which has long strings of molecules bound tightly by carbon atoms. These are combined into larger filaments, which are wound together in a bundle called a tow or a ribbon. A single tow with 24,000 filaments in it would be about the diameter of a pencil, says Matthew Weisenberger, associated director at the Center for Applied Energy Research at the University of Kentucky in Lexington.
“You can take a 24,000 filament tow, and you can tie it in a knot and pull the knot tight, with a PAN-based fiber. They can handle high strain without breaking, so they’re used in airplanes, cars, in sensitive structures,” he said. Pitch-based, not so much. “It could be twice the length of a PAN-based rod and still say straight, but it will snap like a twig. It’s going to weigh nothing, but if you tried to tie a knot and pull it tight, it’s going to break. It can’t handle the strain.”
This has to do with the size of the crystals in the material, and the sizes of the gaps between them, he said. Figuring out how to alter these crystal structures requires better understanding of the coal itself, explained Vakili. Coal is mostly plant matter that has been compressed and carbonized over the eons. But different plants grow in different parts of the world, in the deep past as they do now.
Pitching new coal products
“Coal coming out of the ground from Kentucky is different from coal coming out of the ground in different parts of the country. They are not the same coal mine, so they are going to be different,” Vakili said. “The processing takes into account all those differences.”
Eric Eddings, a professor of chemical engineering who leads the research team at the University of Utah, says his team will analyze the makeup of Utah coal to figure out how it can be used in pitch precursors. They will deliver them to Weisenberger’s team, who will spin them into carbon fibers.
Vakili adds that the refining process is competitive, and different labs have their own techniques. His lab holds a patent on a process that he says can produce fibers more cheaply than other groups. While the precursor material is already cheap, because it’s left over from the process of petroleum refining or coal production, it’s the processing that gets expensive, Vakili said.
“Typically, lower end products are the cheapest. You can buy pitch for like 50 cents a pound, or 20 cents a pound,” he said. “So if you can use this effectively to convert into carbon fiber, with some extra processing, then you get cheap carbon fiber.”
Mitsubishi already uses a form of coal-derived pitch to produce carbon fiber for robotic hands, disc brakes, and satellites. But improving the refining and spinning process to make this less expensive will take time and work, not to mention additional government funding, Vakili said.
If researchers can make coal-based carbon fiber more cost-effective, they’d be solving several problems at once: Increasing demand for coal jobs, removing hydrocarbons from the ground and the atmosphere, and producing a strong, tough material that can improve fuel economy for gas-guzzling vehicles in the skies and on the roads.
“You certainly don’t want to dump it; it’s polycyclic aromatic hydrocarbons. If you can utilize it for something that’s high value, that’s awesome,” Weisenberger said. “If we can get there, we’ll start to garner a lot of attention.”
Rebecca Boyle is an award-winning freelance journalist in Saint Louis, Missouri.