Council committee eyes zero-waste option for city’s aging sewage sludge incinerator

A piece of biochar. (Photo courtesy Wikipedia)

It’s a fact of life that every municipality has to figure out a system for treating and disposing of human waste. For decades, the City of Edmonds has been separating the solid material from the liquids, flltering and pressing the material, and then incinerating it at the city’s wastewater treatment plant at 2nd Avenue and Dayton Street.

However, the city’s 30-year-old sludge incinerator “is really showing its age,” Public Works Director Phil Williams told the Edmonds City Council’s Parks and Public Works Committee Tuesday night. It’s becoming more difficult to find spare parts for aging components and it’s estimated the incinerator has five to seven years of useful life remaining. In addition, stringent and expensive new regulatory requirements for sludge incineration are virtually impossible to meet, Williams said.

After studying a range of options, Williams said, city staff have landed on what they believe is “the best for Edmonds” —  a two-step process that involves sludge drying and pyrolysis.

The second step — pyrolysis — is the chemical decomposition of organic materials at high heat with little to no oxygen. This creates both a dried product and a “biochar,” which Williams described as sterile and having the appearance of charcoal. The biochar byproduct can be used in city parks or sold as a soil conditioner or amendment, he said.

An equally important benefit of the process, Williams said, is that it is energy efficient and produces a reusable product, which will help the city meet its “zero waste” goals. “It’s a wonderful thing from an environmental perspective,” Williams said. “It dramatically reduces your carbon footprint.”

Williams also said the technology fits into the relatively small footprint of the city’s existing wastewater plant,

He cautioned that all of the alternatives studied — including this option — “are very expensive,” and estimated that the total cost of pyrolysis system would be in the range of $15 million.

The next step would be council approval of a $236,000 contract with Ameresco to conduct an engineering analysis and preliminary design for a system to replace the sludge incinerator, including a closer look at the pyrolysis option.

Given the significant cost of the project and other councilmembers’ interest in zero waste efforts, Parks and Public Works Committee members agreed that Williams should make a presentation to the full council prior to approving the contract.

This item was one of two that the committee referred to the full council for a future presentation. The second was a review of a professional services agreement for Civic Field design services, which staff is recommending be awarded to Walker Macy. That’s the same firm that worked with the community to develop the Preferred Master Plan for Civic Field.

In addition, the committee also referred the following items for placement on the next council consent agenda for approval:

– A contract with Dungeness Construction to complete the Seaview Park Infiltration Facility.

– Acceptance of final construction costs for the Frances Anderson Center Bandshell Replacement Project.

– Approval of a supplemental agreement with Murraysmith for the 2019 Sewerline Replacement.

– Approval to close out the Civic Stadium project demolition.

– Final acceptance of the 228th Street Southwest Corridor Improvements Project.

– Approval of city special event contracts, including the Classic Car Show, Fourth of July, Market and Taste.

– Approval of a resolution to submit five grants to the Washington State Recreation Conservation Office for two parks projects — Civic Field and the Edmonds Waterfront Walkway.

— By Teresa Wippel


5 Replies to “Council committee eyes zero-waste option for city’s aging sewage sludge incinerator”

  1. See this line by Williams “pyrolysis — is the chemical decomposition of organic materials?” What about the man made IN-ORGANIC persistent chemicals that he will not talk about? You know the ones that amount to 80,000 found in commerce and does not EVEN include compound chemicals.

    Every US industry connected to a sewer can discharge any amount of hazardous and acute hazardous waste into sewage treatment plants as long as they report it. Yeow right! There are over 80,000 chemicals in commerce and growing even today. It ends up in biosolids which is broadcasted over forest, farms and even bags taken to the consumer’s home and used in their garden.
    **US EPA Office Inspector General (OIG) Report # 14-P-0363 in 09/2014 / Google and read it for yourself. To sum up, industrial pre-treatment is not working and has never worked and nothing has been done about it. It ends up in biosolids and sewage plant effluent. “The priority pollutants list has not been updated since 1981”
    **So when you hear anyone from the multi-billion dollar sewage industry or anyone with monetary ties to any part of the sewage industry say the chemicals in biosolids are minimal and inconsequential or that they support composting with biosolids, ask them for any test showing the degree of hazard and concentrations of 80,000 chemicals that are found in biosolids or a composted biosolids like Milorganite from Milwaukee.
    **Chemicals that are persistent in the environment, bio-accumulate in people and/or wildlife, and are toxic are called Persistent, bioaccumulative and toxic substances (PBTs). With more than 80,000 chemicals being injected into our environment you and your family are at considerable risk of exposure. As long as they remain in commerce and may therefore be released into the environment, they will threaten the health of humans, wildlife including aquatic life.

    Cancer, Chronic Diseases, Birth Defect AND ALGAL BLOOMS complements of Williams extensive research on the process. NOT!

    Hows your health insurance?


  2. A whole lot of chemicals would be broken down by the heat, presumably, but that is a valid concern — just the other day I read an article about prescription drugs turning up in the Puget Sound because of treated sewage being released. Presumably this ends up in the solid waste as well?

    I hope the council will seriously investigate whether the benefits are worth the considerable cost. How are other cities of comparable size dealing with this problem? That is a question that’s definitely worth asking.


  3. Hopefully the $236.000 will address some of these issues. Sometimes it just seems like we have to pay money to figure out how to spend money. Is Ameresco’s study going to be part of the cost of the engineering of the project? Is this some new type of treatment method that requires this kind of outlay just to figure out if it will work? I don’t understand why we have to pay someone to see this.

    Put out a bid for companies to come up with a proven system. One that has been installed somewhere. I’ll bet there are a few that show up with a proven system. The engineering and environmental impact study already completed at another location. We could save millions of dollars in tax payer money by not trying to reinvent the wheel!


  4. Energy services contracts through the WA State process require that all funds expended will be recouped through the savings that derive from project completion. Pyrolysis (Two Greek words: fire, and cut apart) is not a brand new idea, and there are plants already producing biochar, so looking at other examples for best practices is a very good thing. This certainly does not preclude any novel or Edmonds-specific improvement in the process that comes along the way as the analysis and pre-design each progress.

    I was largely surprised at the harsh tone of the original comment here, and was left wondering how one gets worked up to the point of defining future algal blooms and cancer as Phil Williams’ doing. To the contrary, compliments of Phil, Edmonds has seen a full complement of terrific and sensible improvements over the last decade. Clearly, his goal is to leave Edmonds in a better place than when he came.

    I recognized NRDC and Sierra Club info within the material presented on the 11th, but I was also left wondering if the writer does understand chemistry. (What about the man made IN-ORGANIC persistent chemicals that he will not talk about? You know the ones that amount to 80,000 found in commerce and does not EVEN include compound chemicals.) This apparently defines that humans can only make inorganic chemicals. Courtesy of petrochemical engineering, almost everything we synthesize is organic by definition and is subject to pyrolytic degradation. Decades after its ban, there is still detectable DDT in Puget Sound, and it is this kind of pollution from an organic PBT compound in wastewater that pyrolysis can address.

    Speaking of nasty inorganic chemicals, learn more about the cover-up on dihydrogen monoxide (DHMO) and the myriad of ill effects from exposure to it here:

    It is true that we can never know everything that is contained in wastewater. At any time, individuals can also make significant negative impacts here via improper disposal of mercury thermometers, paint solvents and waste, rechargeable batteries, etc., so each of us needs to act responsibly. I am convinced Phil Williams is plenty capable and responsible to ask the hard questions about the relative safety of using biochar as a soil amendment, because life brings risk, and nothing can ever be proven 100% safe, not even DHMO.

    If the goal is to make Edmonds a zero-waste city, as the council has already determined, new ideas must be explored in earnest. All will come with pros and cons. As long as people poop, we need to look for ways to reduce the toxins we put straight into the environment via wastewater.


    1. Dihydrogen monoxide: Good one, Jim! A classic research topic from my middle school science teaching days – especially on April 1st.


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