“Obsolescence is a factor which says that the new thing I bring you is worth more than the unused value of the old thing.” – Charles Kettering
I am the blacksmith at a historic village. I burn coke, coke I make right there on the forge. I start by laying bituminous coal around the coke fire. The heat from the fire drives off impurities in the form of a thick, oily green smoke. This approach allows me to smith with the coke fire while coking enough coal to work for the rest of the day. Once the smoke is gone, the fire doesn’t smoke anymore for the rest of the day, and I have almost pure carbon to burn.
I am grateful that my 1901 Sure Draft chimney does a good job, because that smoke is nasty. I am also grateful that a Saturday and Sunday afternoons’ production of smoke, which contains hydrogen, methane, ammonia, hydrogen sulfide, and coal tar (a carcinogen), can be measured in grams, not tonnes. Historic villages are not about nostalgia, but perspective. The good old days weren’t that good. As someone who has made nails one at a time, I am grateful that when I need a 5-pound box of nails, I can go to the hardware store.
I need coke, so I can demonstrate how blacksmithing was done in the nineteenth century. I’m not sure industry still needs coke, especially given the costs.
What Is Coke?
Unlike the coke I make at the forge, industrial coke is the product of intense heating in an oven kept free of air. Keeping it free of air allows the oven to produce coke without converting the carbon to carbon dioxide.
As a fuel, coke had the distinct advantage over coal that it was “smokeless”. Not because the smoke, with all of its dreadful components, weren’t produced, but because they were produced elsewhere.
Back in the eighteenth century, coke makers used the same process I use today, but on a larger scale known as the hearth process. In the nineteenth century, however, as coke became essential to the steel production driving the industrial revolution, coke makers switched to beehive ovens. The size of individual beehive ovens was limited, so scaling meant building rows and rows, “batteries”, of beehive ovens. The president of the University of Wisconsin, Charles van Hise, described “long rows of beehive ovens from which flame is bursting and dense clouds of smoke issuing, making the sky dark. By night, the scene is rendered indescribably vivid by these numerous burning pits. The beehive ovens make the entire region of coke manufacture one of dulled sky, cheerless and unhealthful.”
Coke ovens being restored at Redstone photo by Jesse Varner from Boulder, Colorado, USA Cropped and color-corrected prior to upload by Daniel Case, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=18260958
It was into this environment that coke-making began in Clairton, Pennsylvania in 1901. In 1916, in the midst of the First World War, U.S. Steel opened the Clairton Coke Works.
The Clairton Coke Works
U.S. Steel switched from beehive ovens to by-product ovens, which could collect the coke gas and use it as a chemical feedstock. In April 2023, U.S. Steel closed three coke batteries—Batteries 1, 2, and 3—leaving seven coke batteries in operation (Batteries 13, 14, 19, 20, B, and C, with Battery 15 in hot idle). Reportedly, U.S. Steel closed the three batteries, built in the 1950s, because of environmental concerns.
On Monday, August 11, 2025, an explosion at the Clairton Coke Works severely damaged Batteries 13 and 14, killing two and hospitalizing 10 others.
Speculation About the Cause of the Explosion at Batteries 13 and 14
When I first heard about the explosion, I heard speculation that it was a combustible dust explosion. Later, having watched a video of the event and given what I knew from experience about coking, I had my own speculations. A friend asked me what I thought. This is what I told him:
I’m waiting for more information. Guys like me are typically too quick to offer their expert opinion.
That said, however, let me offer my “expert opinion.” What I have gleaned from news reports leads me to guess that coke gas, which is a mixture of hydrogen, methane, carbon monoxide, and other flammable stuff, ignited. My guess is that air leaked into the system somewhere, which would be necessary to form a flammable mixture. The coking oven itself is hot enough to ignite such a mixture, although something else could have been the ignition source. There was a single explosion at Battery 13/14, followed by overpressure at Battery 19/20, which noisily lifted the relief valves (giving neighbors the impression of three separate explosions).
For now, that’s my best guess.
As is often the case when we jump to conclusions without investigating the facts, my guess was wrong.
Preliminary Findings
Four days after the explosion, U.S. Steel reported that the explosion happened while crews were flushing a coke gas valve in preparation for planned maintenance. Pressure behind the valve caused it to fail, releasing coke gas into the area and forming a combustible mixture, which then found an ignition source.
There is not much detail there and certainly little guidance for those of us who are interested in preventing reoccurrences of similar events.
Fortunately, the Chemical Safety Board has deployed to Clairton, so we can hope for a thorough investigation and report. Assuming, of course, they get it done before the White House succeeds in shutting them down.
Nothing Lasts Forever
The Clairton Coke Works was at its highest employment of 7000 in the 1970s and has been in decline ever since. The facility itself is aging and in need of significant overhauls to its equipment and controls. Equipment does not last forever; eventually it comes to the end of its useful life and ultimately needs to be retired. It can be taken out of service, or as the August 2025 explosion demonstrated, it can take itself out of service. At the cost of human life.
U.S. steel production reached its peak in 1969 or 1973, depending on whether one considers just steel, or steel and iron. At the time, steel was primarily produced in blast furnaces fired with coke. Now, 70% of steel produced in the U.S., and 30 to 40% of the steel produced in the world, is made in electric arc furnaces (EAFs). EAFs are the technology that make mini-mills economical. There are other steelmaking technologies emerging as well, such as electrolysis and hydrogen DRI (direct reduction of iron).
Invest In The Future
Does it make sense to continue to invest in a dirty, obsolete technology?
The objective of the Clairton Coke Works has never been coke, nor the jobs it created to produce that coke, but the steel that coke made possible. It may have made sense to continue running the Clairton Coke Works as long as it remained operational, to squeeze a little more productivity out of a facility that was over a century old. At this point, however, we should remember that the Clairton Coke Works is not a historic village, operated so visitors can see how things were done “back in the olden days.”
Every facility operates with the implicit promise that it is a safe place to work and that whatever local harm it does is more than offset by the good it does to society as a whole. That is not a promise that the Clairton Coke Works can make or, apparently, keep. Rather than continue to invest in a technology of the past, it seems that it is time to redirect investment into the technologies that will carry us into the next century and train people to run those future technologies.
