High Tech

Composting For municipalities

with0 ut wide-open

windrow com-

L-

m &p sel technology - 7 oftem an under-

the-roof option. But promises of ins- tant compost axe over stated and Mother Nature tolerates only so much nudging.

By Curt Harler

n top of the composting methods heap stands the high-tech alternative: in-vessel composting. Using the latest in controlled-environment technologies,

in-vessel composting provides an option for composters needing to speed up the process or with tight space restrictions

Unlike advising homeowners on backyard and neighbor- hood composting operations or windrowing, however, in- vessel municipal solid-waste systems require considerable planning, commitment, long-term management and fin- ancing.

Sadly, the United Stateslags behind the rest of the world in MSW composting. Governments and private corporations in Europe, South America and the Middle East built more than 100 such plants in recent years. Only about a dozen U.S. municipalities operate or manage in-vessel composting systems at present. But more than 100 facilities exist on the drawing boards

In-vessel systems consist of large, enclosed chambers which accelerate the composting process They digest material in two to 28 days depending, in part, on the design of the vessel. Final curing takes another month.

After the initial digestion period, operators still need to stabilize the material in piles or windrows A conventional, low-level windrow system, however, requires up to twice the time to make compost. The smaller amount of time spent in windrows allows the composters to use less total space for that portion of the process

Wright County, Minn., plans to begin processing material through it mixed-waste composting facility next year. When operational, i t expects the Monticello plant to convert 165 tons per day of municipal waste into humus or compost.

Buhler Inc. of Minneapolis designed the facility as well as manufactured the compost machinery and controls I t expects to complete the plant in 1992.

While Buhler includes more than 100 similar facilities worldwide on its design list, the Wright County operation represents only its second US. facility. It warns against claims of compost in just a few days from “accelerated pro- cessing.”

“Remember, the conversion of organic material into com- post is a biological process involving various microorgan- isms,’,” the company says “If left alone, waste gradually decomposes into simpler substances over aperiod of months or even years

“Commercial composting processes in use today can ac- celerate this process within certain defined limits by estab- lishing and maintaining certain factors during the decom- position phase. These factors are optimum for the microbial decomposition.

“Even under the best of conditions,’:’ Buhler maintains, “the time it takes to produce a mature compost product ranges up to 12 weeks”

Edward Janesz, organic recycling development manager for Kurtz Brothers in Cuyahoga Heights, Ohio, says good compost, produced by whatever method, must meet mini- mum quality standards

He says to shoot for a pH between six and eight. Keep percentage of glass fragments under 1 percent, and don’t let the heavy metalsreadingsgo above250partspermillion. Maintain a handle on lead and cadmium levels, he cautions

48 / May 1991 I RECYCLING TODAY

In some areas, salinity of the finished product presents a limiting factor, Janesz adds.

He says municipalities must watch other foreign matter -like plastic and aluminum - which creep into the com- post. He recommends passing all com- post through a one-half inch screen. “One-quarter inch for materialused on golf greens,” he adds

The Palm Beach County Solid Waste Authority, West Palm Beach, Fla., in- vested $1.4 million in a pilot in-vessel composting system designed to handle sewage sludge and yard waste. The county expects the four-bay, 324011s- per-day facility to begin accepting mat- erials during August.

According to Pat Byers, a represen- tative for the composting project, the system, manufactured by International Processing Systems, Glastonbury, Conn., processes a mixture of yard waste and sewage sludge into usable compost in 21 to 28 days

“We’re starticg with about 10 per- cent of the available material,” Byers says “In two to four years we expect to add 32 more bays to the project a t a cost of approximately $14.7 million.”

The mechanized compost turner (above) keeps the organic material aeration in the compost troughs (left).

The primary impetus for the project came from a desire to solidify the coun- ty’s waste water sludge rather than handle yard waste, Byers says.

“The county is also looking at other solidifiers such as paper, and we plan to conduct an experiment using refuse- derived fuel that we also produce here’)

In addition to helping Palm Beach County smooth out the bugs in the ac- tual process of producing the compost,

to aidinstudyingavailable marketsfor the material.

The best of technology, however, gets sidetracked by other considerations, as

Byes says he eq3i;eds th€ pil& px5mK-i

was the case just south of Palm Beach county.

Metro-Dade Solid Waste Manage- ment got involved in an inside compost- ing project in 1989. I t wanted to find anon-burn system to handle waste from the Miami area. After looking at several RFPs, it chose to go with Agripost of Pompano, Fla.

The County agreed to haul waste to the enclosed-building compost opera- +:,-...& ^--^- <-.:L-l.l. LIWII w i ~viiiov iiig uii~ulvduit: lndteriai - like propane tanks - from the waste. Agripost shredded, inoculated and win- drowed the material. The contract call- ed for Agripost to handle 800 tons per

RECYCLING TODAY / May 1991 / 49

obtained from the council’s‘ lbch

o prevent exposure of the waste to rain. ical nature of in-vessel systems, composters need

end maintaining moisture levels between 45 and 60 rsixfeetmust becompensatedforbylowermoisture

marketing patterns for the final product. notes that the burden is on the management team to know what

it is doing.

day at full operation, but the project never reached that level.

The system ran for less than a year. Some problems with the equipment in the facility arose, but odor became the real challenge.

“It was due to the weather,” says Ed West, president of Agripost. “It was a clean plant, but at times the smell was worse outside than inside.”

The company located the project on land leased from the state. When odor from the compost became noticeable, a nearby school and trailer court rais- ed major objections, and shut the pro- ject down. West emphasizes that he ex- pects to reopen the project as soon as he finds an answer to the odor problem. HEAVY WINDS. In that area of Florida, winds generally blow heavily from the Southeast. But in the fall, the wind re- verses itself, dies down, and the humidi- ty shoots up to near 100 percent. “You get temperature inversions in the ear- ly morning and evening,” West explains Odors get trapped.

West sees an odor-control system as a potential cure. Other compost opera- tions, including the Delaware Reclama- t ionhjec t , Wilminton, Del., found the systems worked controlling their odors West retained Odor Science and En- gineering of Hartford, Conn., which solved the Delaware Project’s odor pro- blem, to develop a system for Agripost.

Financial blocks appeared when the County Board of Commissioners vetoed signscant contract changes, recommended by the County manager and staff. The planned changes allow- ed for refinancing the project. It need the funds for several needed changes including an odor-control system and other equipment to allow the site to go to full capacity. HIGH TIP FEE. “There was a significant raise in the tipping fee,” West says While the project ran, waste collection presented no problems As the only body allowed to dispose of waste, the county’s facility, just south ofthe North Dade landfill, held a captive market.

West sees much of the resistance as political. He says the odor complaints began in late summer of 1989 for about a month. “We talked to the residents We’re friends today,” he says

Even many months after the event, and despite the problems it causedhim, West smiles as he recalls the appear- ance of the school’s principal with a

50 / May 1991 I RECYCLING TODAY

p u p of children singingrap-songcom- plaints about Agripost.

“So,” he says,”the contract changes were not done The future of the plant is in a cocked hat.” Agripost remains optimistic, however. A representative for the company expects a meeting scheduled for late April to provide relief for theproject. If the financing becomes available, the company intends to use the same chemical agent used by the Delaware project, but different mech-

anical equipment, says the represen- tative. Agripost also plans to examine the possible use of bio-filters, she adds.

Agripost marketed some of the mat- erial on its own while the plant oper- ated. It continues to turn the existing compost on a normal schedule.

Some people say moving the plant to aless sensitive site provides theanswer. West doubts the practicality of such a move The major expense of an in-vessel operation goes into site preparation

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which involves clearing the site, install- ing drainage, a foundation and prepar- ing the seven-acre floor space, he says.

“Moving the plant is impossible. There probably is not any location in Dade where you will site such a facili- ty,” says West. His advice to anyone con- templating a similar move: place re- sponsibility for the site on the govern- ment body. And don’t put such a plant near a residential area, he adds.

Dade County, however, continues to study a move.

CLARIFICATION C2S2, Seattle, Wash., developed the “Cost Analysis Of Backyard Composting Programs” includ- edwithPart1oftheComposting Series The analysis appeared on page 52 of the March issue of

cycling %day.

West believes including the cost of odor control in the tipping at the begin- ningprovides one way out of the finan- cing challenge By his estimates, less than $1 per ton covers the costs.

A request for proposal limit of $24 per ton, however, limited Agripost when it submitted its bid. The federal Solid Waste Management Act of 1988, whichrequired additional testing, made complyingwith that $%per ton tipping fee nearly impossible, says West.

The US. is a country built on legal precedent. “So if you close this site on odor, you have precedent to do the same thing elsewhere,” West worries But he has no obvious way out and must await the grinding of the legal mills. “There is no solution here without a contract with sufficient financial underpinning,” West concludes.

Such experiences concern municipal managers faced with mandated pro- grams forbidding yard waste and leaves from being added to county landfills. Still, in-vessel systems offer advan- tages, including control of run-off and a much higher quality end-product.

As more municipalities and counties produce compost, regionalmarketswill become increashg!y important, he says.

Strongsville, Ohio, where the author livesislongonspaceandshort on odors

RECYCLING TODAY I May 1991 I 51

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