Since 2019, vibrantly painted shipping containers have been popping up around Pittsburgh outside office buildings, hospitals and community buildings.
Inside these reused containers are Zero Emission Upcycling Systems (ZEUS), Ecotone Renewables’ patented system that breaks down food waste through anaerobic digestion, turning it into a liquid fertilizer and renewable energy.
Food waste is responsible for about 10% of global greenhouse gas emissions. A study by the University of Pennsylvania found that if all food waste in the U.S. were diverted to alternatives like composting and anaerobic digestion instead of landfilling, it could avoid nearly 40 million metric tons of carbon dioxide equivalents per year.
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Ecotone Renewables started out as a group of students from Carnegie Mellon University, University of Pittsburgh and University of Michigan building a small-scale aquaponics system. This sparked an interest in food waste solutions, which evolved into on-site anaerobic digesters.
They asked a company to fabricate their first prototype of a digester, but found it difficult to operate. CEO and cofounder Dylan Lew said they saw an opportunity to create a more reliable and cost-effective solution.
“There are these two barriers to adoption for food waste solutions,” he said. “It’s like a smelly, gross feedstock, and people are struggling to find reliable solutions for it, and then the second piece is the financing. A lot of the time…sustainable food waste solutions have been more expensive than landfilling.”
While anaerobic digestion is not a new technology, Ecotone seeks to improve upon it by “right-sizing” and automating the technology, according to Lew.
Most of their clients — which include places with a commercial kitchen like coffee shops, restaurants, hospitals and senior centers — lease the ZEUS, making fixed payments over three to five years. The cost, Lew said, is offset by reduced waste hauling bills.
“This is actually usually a net cost saver and bottom-line improvement for partners that we work with,” Lew said. “Then we do all the operations, maintenance, repairs, upgrades and retrofits.”
How it works
Anaerobic digestion uses microbes to break down food waste in the absence of oxygen. The ZEUS uses microbes, bacteria, and fungi to break down food waste, turn it into a slurry, and then digests it over time, usually about a two to three-week period, according to Lew. He compared it to a stomach.
“This is to some extent a form of biomimicry,” Lew said. “We’re finding a natural process and we’re replicating that at a larger industrial and commercial scale.”
Lew said he and collaborators wanted to make using the digester easy for the user, which is why they automated much of the process. All site workers need to do is collect their food waste in compostable bags and drop it into the chute located on the side of the ZEUS.
“[Automation] is what enables the user experience to just be throwing food waste in a trash chute, walk away and forget about it, and the system’s doing automated dosing, feeding, temperature and pH regulation,” Lew said.
The food waste ends up in a holding tank. It’s mixed with rainwater collected from a gutter system on ZEUS’s exterior and ground into a slurry before being sent into the digestion system, which consists of two tanks: the dosing tank and the stomach tank.
Lew compared the process to how our stomachs work, breaking down food waste into two byproducts, which, for ZEUS, takes two to three weeks.
“So that is like a fertilizer byproduct. It’s poop for humans or actual stomachs, for us it’s ‘Soil Sauce,” he said. Soil Sauce is Ecotone’s liquid organic fertilizer that it sells to half a dozen farmers directly and about 50 retail locations across Pittsburgh.
Biogas is the second byproduct.
“So again, for stomachs and humans, that’s people farting. For our digester system, that’s a high methane concentration biogas that we actually use to help power the system,” Lew said.
Lew estimates each system diverts between 120 and 130 tons of CO2 equivalents per year. “We’re actually seeing this is already kind of like a carbon sink,” he said.
Hoping to change the ‘culture of restaurants‘
One of the ZEUS units installed in Pittsburgh can be found at the Energy Innovation Center for food waste from its commercial kitchen. Case Specific Meal Prep, one of its tenants, prepares healthy meals for individual delivery or pick up and for several cafes across the Pittsburgh area.
Dominick Grande, the company’s head chef, estimates that he and his team fill up 10-15 bags of food waste per week.
“We make upwards of 2,000 breakfast sandwiches a week, so that’s a lot of eggs, also, you know, just food waste byproducts from different proteins that we’re using or produce or that we’re using, so we fill it up pretty frequently,” Grande said.
Before the ZEUS unit was installed, all the food waste produced by Grande and his team was thrown in the garbage and landfilled. He said using the digester is ”incredibly easy.”
“We just fill up those [compostable] bags, tie them up, and take them to the digester at the end of the day. It is really that simple,” Grande said. “I don’t fully understand it, but I like the results.”
Grande said he was happy when the ZEUS system was installed.
“You think of how many restaurants are located in Allegheny County and how much food waste that actually is, just having devices like this…It just makes it easier to [recycle food waste] and make that more a part of the culture of restaurants.”
Ecotone’s future plans
Ectone Renewables has grown to 12 full-time employees and has deployed 12 ZEUS digesters, six of which are located in Pittsburgh. By the end of the year, Lew said they will likely have close to 20 systems operating in the field.
In addition to raising $4 million in private investment, the company was the recipient of a $2.2 million grant through the United States Department of Agriculture’s Fertilizer Production Expansion Program and $130,000 through Pennsylvania’s Agricultural Innovation Grant Program. Funding also came from the Richard King Mellon Foundation, according to Lew. (The foundation has also funded The Allegheny Front.)
In 2023, Ecotone also won $300,000 from the University of Pittsburgh’s Sustainability Challenge.
The company’s goal is to have 10,000 systems deployed and build up manufacturing capacity, particularly as sales increase in New England and Southern California, where waste hauling landfill costs are higher.
“It’s going to take us a few years to get there, but that’s kind of the first goal,” Lew said. “And then long term, we’re thinking very big about food waste solutions globally. So this is something we could have millions of systems around the world processing food waste and turning it into value-added fertilizer.”
CORRECTION: 9/18/25 This story has been updated to reflect the correct amount of funding Ecotone has acquired.
