The making of a big ash deal

Incinerator ash and the long, winding, pun-packed road from by-product to “buy product”

Ash is the by-product of incinerating biosolids, the organic material extracted from sewage during the wastewater treatment process. Our Southerly and Westerly plants use different methods of incineration, hence the different ash consistencies.

It took a while, but we finally pulled the best idea out of our ash: Reuse it.

After being little more than an incinerator by-product for more than 80 years, ash from two of our treatment plants is now reused in top soil and concrete mixtures thanks to combination of creativity, coincidental timing, and collaboration. The result is saving money and the environment.

“This is an exciting time,” said Manager of Regulatory Compliance Robin Halperin. “It’s been years in the making and these benefits are real.”

Since 1936, the Southerly Wastewater Treatment Center incinerated its biosolids. The industry standard for managing the organic material extracted from sewage during the wastewater treatment process, incineration burns the dampened biosolids (or sludge) down to ash.

In 1978, the District began pumping the ash over to nearby lagoons on the treatment plant’s grounds. Excess ash was placed into an on-site fill area adjacent to the lagoons. Until it was closed in 2006.

Ash lagoons at the Southerly Wastewater Treatment Center, Cuyahoga Heights.

Incineration would continue, but what about the ash? Ohio didn’t have processes or permits in place to allow beneficial reuse; very few states did at the time. The next best option was to haul truckload after truckload more than 40 miles away to a landfill to the tune of 33,000 cubic yards a year.

There had to be a better way.

When Robin joined the District in 2008, rather than accepting bids for an ash lagoon cleaning contract as had been done for years prior, she worked with Operations & Maintenance to instead solicit proposals for an “innovative, cost effective and environmentally responsible approach to cleaning of the ash lagoons and the reuse of the ash material.”

It would become the Beneficial Reuse of Ash Pilot Project at Southerly. The rest became sustainability history.

A few redirects along the way altered project schedules. Southerly’s incinerators underwent a redesign, a new renewable energy facility was built, all while data continued to be collected to demonstrate using ash as a soil additive had an environmental benefit.

Part of that research involved “test plot” boxes, filled with either regular top soil or some combination of top soil and the phosphorus-rich incinerator ash. Early on, if not for the labels, no one would know the difference between our ash and a hole in the ground. But once the boxes began sprouting, it became clear that the soil with ash additives was producing fuller and taller grass. It was what the team was hoping for.

“We had to prove the ash didn’t pose an environmental risk,” Halperin said. “And, it couldn’t be neutral, there had to be a benefit. The ash had nutrients that were making a difference.”

The District reached an important milestone in 2014 when it took an even closer look at the physical and chemical composition of the ash for beneficial reuse, considering its uses beyond topsoil such as concrete, low-strength mortar, and more. The results showed the potential was there. The ash had value.

Landscape supplier Kurtz Brothers, a neighbor less than two miles from Southerly, approached the Sewer District in 2015 with an interest in conducting a new pilot study now that the new incinerators had been up and running for a few years. Kurtz wasted little time and hauled ash, a truckload specifically, for experimenting to see what options for reuse might be available.

Southerly incinerator ash as seen waaaaay up close.

In response, the District solicited proposals the next year for phase two of the pilot project: select the preferred beneficial reuse options, and obtain the associated approval from Ohio EPA. That’s when everything finally came together, including a number of good viable beneficial reuse options, and a new Ohio EPA permit process, making reuse of the ash a reality. The District sought a long-term relationship with a partner to begin hauling ash and reusing it in an economical, sustainable, environmentally sound matter.

Kurtz signed the contract in 2018, not long after Ohio EPA issued Kurtz the first biosolids incinerator ash reuse permit in the state under the new program.

It’s a feel-good story all around, and the benefits are both environmental and economic.

The District saves significant money in hauling costs, not to mention cutting greenhouse gas emissions by more than 96% by eliminating an 80+ mile landfill round-trip with every truckload. The contractor gets the ash, District customers save dollars, and reduced landfill contributions make a dent in our carbon footprint.

“We are no stranger to meeting our permit obligations,” said Halperin. “Incineration has its benefits, but when the chance comes to improve and to be more sustainable, it feels good to see plans realized. It’s good for us, our customers, and the region.”

Updated in 2022.



Northeast Ohio Regional Sewer District

Official Medium channel of the Northeast Ohio Regional Sewer District in Cleveland, OH