New technologies turning Edmonds wastewater plant from sewage incinerator to green biofuels producer

Edmonds Wastewater Treatment Plant Manager Pamela Randolph points to the plant’s footprint on an aerial photo. One big advantage of the Ecoremedy system is that the equipment can fit into this footprint. Other alternatives would have required a new building to house the equipment, for which no space exists.

Sewage treatment is not a topic that normally generates excitement. Quite the contrary, when we flush the toilet, we just want it to go away and not think about it further. But the hard truth is that there is no “away”– it all has to go somewhere, and traditionally that somewhere is in the air as greenhouse gases such as carbon dioxide (CO2) and either landfilling or surface spreading the solid portion.

But that is about to change in Edmonds with the addition of new equipment being installed the in city’s wastewater treatment plant. Pioneered by Pittsburg-based Ecoremedy, it promises to cut CO2 emissions to near zero, reduce the plant’s electrical consumption by a third, eliminate the need for fossil fuels necessary for the old incineration process, and convert residual solids into a marketable product that will not only stay out of landfills but will provide Edmonds with a new revenue stream.

An additional plus: The new process is self-sustaining, meaning that it produces more energy than it uses, turning what was once a sewage sludge incineration plant into a city-owned renewable energy producer.

Ecoremedy President Dave Mooney walks participants through the various stages of the process.

In a presentation last Friday – appropriately timed for Earth Day – representatives of Ecoremedy met with staff from the City of Edmonds and other partner jurisdictions to provide an overview of the process and explain what to expect when the new systems comes online later this year.

Dedicated in 1991, the Edmonds wastewater treatment plant has served Edmonds and other partner jurisdictions for more than 30 years. But the plant’s aging incineration equipment, as it reaches the end of its useful life, is increasingly expensive to operate and maintain. And because it was designed for a different time, it does not fit with Edmonds’ current environmental goals to reduce the city’s carbon footprint, address global warming on a local level, and reduce municipal waste.

“We’ve known for at least a decade that we’d have to replace the waste incinerator,” explained Wastewater Treatment Plant Manager Pamela Randolph. “But it was delayed due to the need to sequence this work with other projects that are part of Edmonds’ Pathway to Sustainability.”

Dedicated in 1991, the Edmonds Wastewater Treatment Plant is in the process of a major upgrade where new technologies currently being installed will expand its capabilities, cut greenhouse gas emissions, and produce marketable biochar products.

With the need to replace and update this equipment becoming more critical each year, city officials opted not to simply replace what was already there. Instead, Edmonds began seeking new answers that would better fit the environmental needs and priorities of the city, the region and, indeed, the planet.

In June 2020, city staff presented their findings to the Edmonds City Council, and in October of that year the council passed an ordinance authorizing nearly $14.4 million in revenue bonds to finance the project. The measure increases the sewer rate for the average single-family residential Edmonds homeowner by 88 cents per month — from $45.84 to $46.72.

While the total cost of the project is $26 million, three other partner jurisdictions that send their sewage to Edmonds for treatment and disposal — the City of Mountlake Terrace, the Olympic View Water and Sewer District, and the Ronald Sewer District — will pick up the remainder of the costs.  Edmonds will pay approximatly 51 percent, the partners 49 percent.

“This is the best technology to meet Edmonds’ environmental goals,” added Randolph. “With this new system, our plant can now remove things from the wastewater stream that were beyond the ability of the original incineration setup including microplastics, pharmaceuticals and PFAS.  We were most impressed that the Ecoremedy solution treats for these substances that the plant was not originally designed to address but are increasingly inherent in our waste stream.”

PFAS stands for Per- and Poly-Fluoroalkyl Substances, a broad class of chemicals that don’t break down easily, build up in the environment, and are detrimental to many plants and animals. They include things like cleaning products, waxes, paints, degreasers, food packaging and fire-fighting foam. Traditional sludge incineration does not destroy these, and their presence in traditional incinerated waste severely limits disposal options. (Learn more here.)

Ecoremedy’s patented process replaces traditional incineration with gasification and pyrolysis. Through this system, a range of wastes — including components like PFAS that traditional incineration cannot break down — are subjected to high temperatures in the absence of oxygen. The extreme heat breaks the chemical bonds, a process known as lysis. Since oxygen is not present, nothing burns, so no CO2 is produced.

Ecoremedy president and CTO Dave Mooney points out what is happening in each phase of the Ecoremedy process.

“Our system deals very effectively with PFAS, microplastics and pharmaceuticals,” added Dave Mooney, Ecoremedy president, chief technology officer and inventor of the process. “Our gasifier heats the waste to 1400-1700 F, which destroys these substances by breaking the chemical bonds with heat alone.”

Mooney went on to explain that the process is designed to create its own fuel, and once started is self-sustaining, requiring no outside energy source – such as fossil fuels — to keep it going. The system runs around the clock, using the incoming waste as the sole source of thermal energy without any supplemental fuels such as wood chips or fossil fuels. (A complete explanation of how this works is available here.)

The anaerobic process also yields a mix of combustible gases — mostly hydrogen and carbon monoxide – collectively called “syngas,” which again does not burn in this phase of the process due to the lack of oxygen. This syngas is not released into the atmosphere as a waste product like CO2 in traditional incineration, but instead is reclaimed and cycled back into the system where –with the introduction of air later in the process — is combusted at very high temperatures (2000-2200 degrees F). The result is a clean, renewable thermal energy with no waste CO2. Captured by heat exchangers, this energy can be used to produce steam, hot water, hot air or even refrigeration.

“Unlike incineration which requires a constant energy input to keep it going, once the gasifier is started biosolids are the sole energy source for the process,” Mooney explained. “When fossil fuels are burned [in traditional waste incineration], they add CO2 to the environment from carbon, which was previously sequestered below ground [e.g., as coal, petroleum, etc.]. In contrast, biosolids are already present above ground, and therefore already a part of the carbon air balance. (Learn more about the carbon cycle here). By converting biosolids to usable thermal energy without fossil fuels, Ecoremedy contributes no additional carbon to the overall CO2 balance.”

This rendering shows the final configuration of the Ecoremedy system after installation. It’s a tight fit, requiring a new second floor in the equipment room, which is currently under construction.

When the Ecoremedy process comes online in Edmonds later this summer, the plant’s net CO2 emissions will drop to near zero, eliminating the huge carbon footprint of the city’s former waste incinerator. And the carbon footprint of waste incineration is considerable. According to a 2006 scholarly paper published by the United Nations Intergovernmental Panel on Climate Change, traditional sewage incineration releases between 0.7 and 1.2 Mg of CO2 for every 1 Mg of incinerated municipal waste.

In addition, the Ecoremedy process eliminates the need to landfill or otherwise dispose of the ash waste that is the end product of traditional incineration (in the case of Edmonds all ash waste was landfilled, none surface spread). Instead, it produces a marketable biochar product called FlexChar that can be sold to an array of industries from agriculture to water purification to cement manufacturing — opening a new revenue stream for the City of Edmonds.

While the market is still evolving, FlexChar is already finding uses. Its natural ability to retain water has been recognized by the agriculture industry for reducing irrigation needs by up to 30% when used as a soil amendment. And the cement industry uses it as a substitute for fly ash that makes concrete less permeable to water, a boon to homeowners plagued by wet basements. It is also finding a role as a filtration agent.

New uses and markets are being researched and developed both in industry and academia, and it’s a good bet that the value of Edmonds’ FlexChar will increase as these come online. As these markets emerge and evolve, Edmonds’ Ecoremedy plant can respond to produce a range of FlexChar compositions with varying moisture and carbon content to precisely meet the customers’ needs

“We can literally alter the composition of our FlexChar on the fly,” explained Mooney. “It takes about 15 minutes to adjust the operating parameters. We don’t have to stop and retool.”

A strong incentive for industry to switch to FlexChar is the recent EPA ruling declaring the Ecoremedy process a renewable energy producer and not a waste incineration process. This distinction means that it is exempt from EPA’s Sewage Sludge Incineration (SSI) regulations, and that FlexChar is officially recognized as a green renewable product and not a byproduct of waste incineration. This allows companies that purchase and use FlexChar to declare it as an offset to help meet their carbon footprint reduction goals.

Viewed from the partially completed second floor, the Ecoremedy equipment first-floor components are largely in place.

“Compared to land application of traditional sewage incineration waste, [selling these products] also offsets air emissions associated with truck traffic from hauling sludge by approximately 95%,” Mooney added. “Furthermore, by eliminating land application [e.g., landfills and spreading], Ecoremedy reduces harmful air emissions associated with the decomposition process, which releases methane gas, a greenhouse gas that is nearly 27 times more harmful than CO2.”

Because the Ecoremedy system is self-sustaining, producing more energy than it consumes, the flexibility is there to use the excess energy in creative ways. One of these will ensure that Edmonds citizens and visitors can continue to enjoy their Puget Sound views.

In explaining this, Mooney pointed out the tendency of people to “smell with their eyes, not their nose” when they observe a plume of white steam rising from an industrial plant.

“While this is merely water vapor – the same thing you see coming out of your laundry dryer vent – we recognize that people don’t want to see it, so we’ve taken the extra step to not introduce this into the visual environment in Edmonds,” he explained. “Since our process yields an excess of energy over what it consumes, we use some of this to superheat the steam as it exits the plant. This makes it invisible at the point of discharge, allowing it to condense higher in the atmosphere where it won’t mar anyone’s view of the Sound and mountains.”

According to Randolph, construction will be ongoing through July and August.  The Ecoremedy equipment is being installed by Ameresco, the official project provider, and if all goes as anticipated the process will come online and receive final EPA certification later this year.

— Story and photos by Larry Vogel

  1. Well I hope it works as described and I hope they can develop a market for the waste. My concern would be I heard it reduces capacity by 1/3 and with a growing population will it be able to handle the flow? I think just recently they had a problem that discharged raw sewage into the sound I know it seems every year Seattle has had capacity issues resulting in the release of untreated waste. My question then becomes is it more environmentally friendly if we have double the number of raw sewage discharges because of capacity issues?

  2. Growing up as a kid on the East side I remember not being able to swim in Lake Washington because in some places it just wasn’t safe. Fast forward 40 years and the lake, for the most part is in much better shape and that is with more residents living in the area. This responsibility fell on the shoulders of government and local and state government addressed the issues and cleaned it up.
    This project is similar and makes sense in regards to stewardship of our city and region. Cost can be an issue and capacity may be limited in regards to total volume but it is the right direction to go towards if we have the ability to do so. That being said we have the ability to make this change and implement this solution.
    This is a great example of the private industry coming up with a solution that makes sense and the government purchasing the solution because they can. I can get behind something like this because it makes sense. But please don’t force me to buy a $80k+ Tesla for environmental reasons (I don’t have that kind of money and I am still concerned about where we are dumping all those batteries when they no longer function).

  3. This project intrigued so I did some sleuthing into the pyrolysis processes and came across a couple of interesting links to share:


    Hopefully the above are one offs..

    Overall, other links are very positive…

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