PHOENIXVILLE — Everything old is new again, at least at the Phoenixville Wastewater Treatment Plant.
There, a “new” technology whose actual discovery dates back to before World War I is getting ready to revolutionize the treatment of sewage sludge by creating a safer and more sustainable byproduct from what Phoenixville residents flush down the toilet.
And just to give things an international flavor, it is being helped along by some Swiss technology to boot.
The process is called “hydrothermal carbonization.” According to the borough website, it “uses heat and pressure to mimic the way nature produces coal and other fossil fuels, but we are using chemistry to speed up the process from 250 million years to a couple of hours.”
“Waste enters the system and goes through a reactor that pressurizes and heats it until it can be separated into process water and one of several very useful bioproducts.” The solid bioproduct that is created can be used as carbon carbon-neutral, clean biofuel called “hydrochar.”
2 Kinds of Sewer Sludge Treatment
Current wastewater treatment technology across the United States uses “anaerobic digestion,” by which wastewater is kept in large pools to be “digested” by microbes, a process that can take weeks. Then that product is settled, the water is siphoned off, treated and returned to the Schuylkill River. What’s left behind is called “bio-solids” among professionals, but is called “sludge” by pretty much everyone else.
The problem with sludge is that it is very wet and, in that state, many of the organic pathogens and germs remain, making it something troublesome to get rid of.
Instead, hydrothermal carbonization makes sludge into something useful and sustainable.
“Right now, we have three basic solutions (for sludge) in the United States. We incinerate it; we send it to a landfill where it releases either carbon dioxide or methane; or we use it as a farm application to grow animal feed crops,” Dan Spraklin explained during an event Thursday at the Phoenixville Wastewater Treatment Plant on Second Avenue to introduce the new process to the public.
Spraklin is the founder and CEO of SoMax BioEnergy, the company that brought this technology to Phoenixville and convinced the borough council to make Phoenixville the first town in North America to test it out. He said it will “do the heavy lifting” in helping the borough to reach its goal for all borough facilities to use 100 percent clean energy by 2035.
In 2017, Phoenixville became the first town in Pennsylvania to make that commitment. Council committed $3 million to this project. It has since received $402,000 in grants from Chester County, $650,000 from the Commonwealth, and another $250,000 from the U.S. Department of Energy.
One of several problems with the standard anaerobic digestion technology is that it completely ignores all the other things that go through the sewer pipes other than last night’s dinner.
“Think about all surfactants in the shampoo we use, the makeup we wash off. What about the pharmaceuticals we ingest, but our body only partly absorbs. Think about the microplastics from certain fibers. It all ends up here, at the plant,” Spracklin said.
And anaerobic digestion does nothing to grapple with that growing environmental problem.
So when sludge is landfilled, those pollutants end up in the landfill leachate — which gets treated again with the same sewer technology that does nothing to remove it from the environment — or as landfill gas, which is either released into the environment or burned.
When sludge is applied to farm fields, it transfers those pollutants to the soil, where it accumulates and is ultimately absorbed by the plants grown there. Then feed animals eat those plants, thus moving those pollutants up the food chain into us, the people who eat those animals. After we eat, we send it back to the sewer plant, a perfect circle of pollution.
Breaking Down Molecules
One of the primary advantages of this newly introduced technology is that the sludge goes through a chemical process in the digester, not a biological/physical process.
Rather than get rid of the water in sludge — a process which requires the use of polymers, a kind of plastic, in the traditional treatment method — the water present is used in the digester as part of the chemical reaction caused by the heat and pressure that breaks down those pollutant molecules, even the plastics, into their base components, Spracklin explained.
The remaining water, now much cleaner, goes back into the feed water that goes into the traditional sewer plant and is cycled through the system again.
Two Kinds of ‘Coal’
As a result, the biochar product that comes out the other end of this new process lacks those pollutants and can be burned for fuel, like traditional coal.
However, this substance is unlike traditional coal in that the carbon dioxide it gives off was already present in the biosphere.
“We’re making use of it twice. We’re eating the carbon in our food for energy, and then we’re using it again to make energy,” said Spracklin. The coal that comes from the ground, on the other hand, was sequestered and away from the biosphere for millions of years. So when traditional coal is burned, it is emitting carbon dioxide that had been removed from the present environment, and adding more as an additional load, contributing to climate change.
The volume of combustible by-product produced by Phoenixville’s new process can provide 150 percent of the electricity needed to run the entire sewage treatment plant, which is the largest energy user among the borough’s facilities. In fact, it can produce so much power that it can put power back into the grid, Spracklin said, offsetting other, dirtier methods of power generation.
Alternatively, the end product can be used as a cleaner soil additive on farms that puts no poisons into the soil or what grows in it; or it can even be used to make things like bricks and concrete, which is another method for sequestering carbon and making a useful product in the process.
Pushing Through the Paperwork
While the science of this new system is very simple, with few moving parts to break down, the bureaucracy of getting it up and running is not, said Phoenixville Council President Jonathan Ewald.
“We knew this was new technology, so we’ve worked with the Pennsylvania Department of Environmental Protection from the start. It’s new technology, and so it will need a whole new kind of permit. We’ve dealt with lots of complicated questions over the past year,” he said.
The new facility has been test-run for proof-of-concept, but is not yet being used daily to treat Phoenixville’s sewage. Ewald said the borough hopes to have it up and running in the first quarter of 2026. “We knew it was a risk, but we’ve proven it can be done. I can’t wait until it’s up and running.”
Ready to Take More
The new facility is purposefully built over-capacity, and only about 25 percent of its capacity is needed to process Phoenixville’s sewage. Spracklin and Ewald both said they hope that once it is up and running, it can be used to process Phoenixville’s food waste as well, thus keeping it out of a landfill and avoiding the carbon dioxide release that comes from composting. “Anything that’s organic, it will process,” said Spracklin. “That includes food waste, animal waste, and yard waste.”
Added Spracklin, “This has so much capacity, it can act as a regional solution.”
An Old Discovery for New Technology
The hydrothermal carbonization process was discovered in 1913 by the German chemist Friedrich Bergius. “But then we had two world wars, and the division of Germany into East and West, and so his papers were lost to history,” Spracklin said. The papers and the process they described were rediscovered at a Max Planck Institute in Potsdam, Germany, in 2006.
It was at a conference in London, said Ross Lee, a professor at Villanova University, that this “long dormant” technology began to get more attention, and “we quickly realized it is cost-efficient and good for the environment,” Lee said.
After Thursday’s tour of the facility, officials held a panel discussion at Phoenixville’s landmark Colonial Theater, hosted by Mayor Peter Urscheler and Niclun Jäger, Swiss ambassador consul general, out of New York.
Jäger said the technology, new to Phoenixville, is already in use throughout Switzerland, and he praised the partnership that brought it to the United States; a partnership represented by Spracklin, Lee and Andreas Mehli, founder and CEO of GRegio Energie, based in Chur, Switzerland.
Ross heads a special program at Villanova called the “Rise Consortium,” which pairs industry with graduate students from cross-disciplines to address problems in manufacturing and sustainability.
“Dan came to us in 2014 with this question: how can we turn sewage sludge into something useful?” Lee said. The team eventually settled upon a very old idea, but a very new technology, hydrothermal carbonization.
“I was sold on the process because it just works and it’s so simple,” said Spracklin. “Whether we burn it for energy, bury it in bricks or concrete, we’re preventing CO2 from going out into the atmosphere. It’s effectively offsetting a lot of emissions in Phoenixville.”
“Sustainable energy has focused on solar and wind for now, but they can be intermittent,” said Lee. “What’s exciting about this technology is its working out of abundance, a source that has not been tapped for energy.”
An International Accent
In addition to the machine used to press the processed sludge at the end of the hydrothermal carbonization process being of Swiss design and manufacture, it was Spracklin’s visit to the “sustainable energy park” Mehli built in Chur that inspired him to move forward with the project. “He is really much further along than anything over here,” Spracklin said. “The magic was there.”
“If you ever go, you really should see that place. He has all kinds of sustainable energy models,” Spracklin said of Mehli, in whom he found “a kindred spirit” who not only wanted to provide a better solution, but who realized to get the full benefit, it must be “spread all over the world.”
“We are facing a climate crisis, and today, we are seeing here how we can face this problem together,” Jäger said. “Pennsylvania is in a unique place, as a center of industry, agriculture, home to 52,000 farmers, and a natural gas producer that can move us toward a sustainable future.”
“It is a place where we can be not just innovative, but visionary in turning waste into something highly valuable.” He said the Phoenixville effort can serve as a “model for other municipalities in the United States and around the world.”
“Phoenixville is a community that takes protecting the environment seriously,” said Urscheler. “We are proving that small towns can lead the way with bold and sustainable solutions.”
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