BioCycle October 2007, Vol. 48, No. 10, p. 28
Partnering with a system designer, a Washington state rancher now processes up to 84,000 tons per year of biosolids, yard and food residuals plus MSW in an aerated static pile facility.
Rhenda Meiser

“FOR ME, starting a composting business was a personal, social and economic decision,” says Greg Schoenbachler of Silver Springs Organics in Rainier, Washington, who has been in the farming business his whole life. His family-run ranch on 1,100 acres produces all-natural, grass-fed and grain-fed cattle. The need to import nutrients for agricultural production got him to consider adding a large-scale composting facility to complement other activities at his ranch.
“On a personal level,” Schoenbachler continues, “I wanted to be sure that there would be a sustainable farm for my children to operate if they chose. This required finding new revenue streams for the farm. And, on a social level I wanted to solve a community problem. We could take relatively unstable waste products and convert them through natural biology to become an asset for the environment and for agriculture.”
He pursued the permits with Thurston County to process farm waste and yard waste, and discovered the hard realities of setting up a composting facility. He found the industry to be well controlled, with high barriers to entry, unlike agriculture. But, he adds, like agriculture, he has since found competitors and industry people ready to help each other out.
Right away, Schoenbachler faced two major hurdles. The first was regulatory. County code required recycling facilities (including composting) to operate under a roof to contain wastewater and odors. This meant constructing a building, which would automatically spike costs. Permitting also required that a business have customer contracts in place, but many local waste streams were already tied up with competitors.
Schoenbachler landed a deal to handle municipal yard waste that would become a starting point. “At that stage I came to the realization that I would need to assume the financial risk out of pocket, and develop the market along the way.” Once the market was developed and permitted, Silver Springs moved on to construction.
He partnered with Seattle-based Engineered Composting Systems (ECS) on system design. ECS develops systems to compost organic feedstocks such as biosolids, food waste, manure, yard waste and MSW. The company offers whole systems and components for in-vessel and aerated static pile (ASP) facilities. “We worked with ECS because our needs were very site-specific,” he notes.
ECS had already piloted its AC Composter at Silver Springs and other sites. The system has four major components: 1) an impervious cover; 2) an automated aeration control and monitoring system; 3) a negative-only aeration system; and 4) a biofilter for odor and emission control. The cover is designed for negative aeration with single-direction air inlets.
Together the cover and negative aeration contain and capture the VOCs and NH3 emitted by the composting process, and scrub all of the process air through a relatively small biofilter.
Silver Springs filed for a variance from the code, citing evidence that the AC Composter cover and airflow system would meet the code’s intent. The county granted the variance to do an open-air covered ASP.
One problem was solved. But Shoenbachler faced a second hurdle: cost. He could go with an 80,000 square-foot, below-grade aeration floor made with pipes cast in concrete and stainless steel covered trenches that distribute air and collect leachate. These systems were tried and true, but were too expensive for his business model. Or, he could choose a typical above-ground system with perforated pipe to aerate the compost piles. The latter option costs less but had operational hazards: it was very labor-intensive and required heavy machinery and a lot of space to move the 90-foot pipes. Pressured by price, Schoenbachler chose the above-ground system.
ADAPTING MACHINES TO MEET NEEDS
Farmers are used to making the best of tight resources and adapting equipment to meet specific needs. Schoenbachler still worried about the operational challenges of managing the pipes with heavy machinery. Using farmer’s ingenuity, he considered the idea of a pipeless aeration floor. Schoenbachler brought up the concept with ECS’s CEO Tim O’Neill and Business Development Manager Steve Diddy. At ECS, engineers had also been thinking about aeration floors without pipes.
Together they brainstormed. They speculated that coarsely ground yard waste (compost) placed on a form and allowed to settle would hold the shape of a form once it was removed. The void space (or aerated vault) could be used as an aeration plenum that would replace the need for perforated pipe.
ECS and Silver Springs tested rigid forms to prove the theory. Then the ECS engineers came up with the idea of an inflatable form. The first prototype looked like a 30-foot hotdog, both in color and shape. Although the shape ultimately changed, the name CompDog stuck.
After nine months of field trials, ECS engineers finalized the design of a rugged form that could be inflated to form the vault and then deflated to facilitate removal, and withstand the rough service found at compost facilities. The CompDogs are constructed of heavy-coated, double-walled, field-repairable material. The “Dogs” at Silver Springs are 100 feet long. When inflated, a cross-section resembles an arch with a broad, stable base.
DESIGN ALONG THE WAY
“There’s been a learning curve,” admits Schoenbachler. When the team first tried to pull the CompDog out of the pile to create the vault, it stuck. The inventors tested a different fabric that was less sticky, and now know that the compost immediately surrounding the CompDog must be fine-grade, with minimal large sticks or objects to create resistance. The shape of the CompDog also evolved, from a simple inflatable cylinder to a form with an arched top and wide base comprised of three inflatable chambers.
Schoenbachler and ECS are improving handling of the covers. It takes a team of at least three men to manually move the 400-pound covers over 10-foot piles of compost. With wind, the job is even trickier. So they have worked with Danzco, Inc., a local designer and fabricator to develop a self-propelled machine prototype that uses hydraulics to spool and wind covers. The machine reduces the labor requirement to one man and performs four functions: setting and pulling the CompDogs and setting and pulling the covers. The machine is in early testing: “Development and testing is going well – we should be homed in on a final design within a month or two,” says Schoenbachler.
The collaboration between Silver Springs and ECS has resulted in technology that puts the operator’s needs at the forefront.
“We are always impressed with what operators can teach us about how to improve our designs,” says O’Neill. “Working with Silver Springs has been a great partnership.”
HOW THE FACILITY IS WORKING
Silver Springs opened as a commercial entity in April 2007, with the start-up capacity to handle 7,000 tons per month of food, yard, wood, agricultural and industrial-waste feedstocks. Revenue targets are on track.
Technically, operations have been smooth. Odor is being effectively controlled. “The covers and biofilter system are tried and true,” says Schoenbachler. “The only time we have odors is if we don’t put the covers on promptly.”
Silver Springs projected a Phase II expansion in its business plan for 2011 or 2012, enabling the facility to reach volumes of 120,000 tons per year. The facility currently has 24 zones that process compost; each one is 100 feet by 30 feet. According to Schoenbachler, the facility is now on track to expand early: adding 28 more zones by 2010 that will more than double its size.
Customer response has been good, and Silver Springs is pursuing business with food service entities including hospitals, retirement homes, schools, supermarkets and municipalities. In the spring of 2007, it completed a food waste pilot with the City of Olympia and other contracts are in negotiation.
“Initially I wanted to be a composting facility for municipalities. It took five years, a degree of maturation, and working with the people at ECS to flesh out the vision of what we are today,” says Schoenbachler. “Now the facility’s built, and we’re ready to adapt. There are always ways to process waste better and more efficiently. Making this a success will give my kids an opportunity to take it to the next level.”
Rhenda Meiser is a freelance writer living in Seattle, Washington. She can be e-mailed at trrim@msn.com.
FOOD RESIDUALS COMPOSTING LOGISTICS
SILVER Springs Organics is pursuing contracts with various food services entities, including supermarkets, municipalities, hospitals, retirement homes and schools. Phase II of the company’s business plan includes expansion to collect 120,000 tons/year by 2011 or 2012.
Silver Springs receives food waste from various haulers, including LeMay, Inc. It accepts both preconsumer and postconsumer food waste and all that entails, including cardboard (waxed and unwaxed), soiled paper and pallets. Incoming feedstocks are offloaded onto a paved tipping area. “The food waste is tipped onto a bed of bulking agent, such as wood waste, ‘overs’ from wood waste compost or anything else that is suitable,” says Greg Schoenbachler, of Silver Springs. “The materials are mixed immediately, and then put into the compost process.”
Depending on the load, some size reduction and grinding is included in the mixing process. The company has been using a front-end loader for mixing, and a Komptech Crambo 5000 for grinding. In the future, it plans to use the Crambo unit for both grinding and mixing.
The City of Olympia, Washington worked with Silver Springs on a pilot program with area schools last year. Food scraps were collected once a week and delivered to Silver Springs. The City of Olympia is developing a residential commingled curbside collection program, with routes that would eventually extend to commercial sources. This is part of the city’s Zero Waste Resolution, adopted by the Olympia City Council in 2006, which spawned a six-year plan to achieve that goal. – R.Y.
HOW THE UNIT WORKS
THE CompDog (patent pending) is placed into the end of an AC Composter™ aeration header, stretched to full length, and inflated. Typically two CompDogs are used for each ASP zone. The wheel-loaders drive between the two Dogs and bury them. After staying buried for 12-24 hours, the compost has settled and the aeration vaults are formed. The CompDogs are deflated, wound onto an In-Deflator retrieving spool, and stored for the next use.
The aeration vaults connect to aeration systems and run the length of the pile. Operators then put the AC Composter covers in place and complete the zone for composting using the CompTroller automated control system. During composting, fresh air is drawn through the air inlets in the cover to provide oxygen to the feedstock. The air flows out the vault and through a volume damper into above-ground, stainless-steel, aeration plenums. Each group of 12 zones is serviced by a single fan that runs at an average continuous power of 15 HP. Additional fresh air is mixed in as necessary to keep the temperature of the air exhausted through the biofilters below 40°C.
The position of the dampers and the output of the fans are automatically controlled by the ECS CompTroller system. The operators use the software to monitor the process, to record time/temperature data files for regulatory compliance, and to input process setpoints used by the automatic controls. Real-time technical support is available via Web access.