MSW Composting in the United States

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Courtesy of BioCycle Magazine

Massachusetts became home to two new composting facilities that process MSW and biosolids. Nationally, the total number of operating plants is 19.

Since the mid-1980s, BioCycle has been conducting an annual, nationwide survey of municipal solid waste (MSW) composting facilities. From the late 1980s into the early 1990s, when it was projected that landfill capacity would drop and tipping fees would skyrocket, interest in MSW composting was high. About two dozen companies were marketing systems and equipment, and cities and counties around the country were expressing interest in starting a project.

As it turned out, the landfill crisis passed, tipping fees dropped and remained fairly low, and with the Supreme Court ruling striking down flow control in 1994, proposed projects had difficulty guaranteeing MSW throughput. Despite these odds, composting has been able to establish a niche, albeit a small one, in the solid waste management arena. Operating facilities have established a track record, meeting the needs of the communities they serve.

BioCycle’s 1999 Survey of MSW Composting covers facilities that are designed to handle mixed and/or source separated solid waste, along with other residuals such as biosolids. To be part of this survey, projects must include the residential MSW stream. This year, there are 19 operating plants, and six projects in various stages of development (see Table 1). Two plants are closed and may resume operations. In 1998, BioCycle identified 18 operating MSW composting projects, 15 in development or consideration (two in construction, both of which began operating in 1999) and one closed. This year, projects in Clinton County, Iowa and Vilas County, Wisconsin were not included in the survey because their MSW processing method use of a rotating digester, screening, and use of the fines as landfill cover does not build in an actual composting step. The following is a project round-up.

COBB COUNTY, GEORGIA

Last year at this time, the MSW composting project in Cobb County was just starting to slowly get back on-line after two separate fires caused a multiyear shutdown. Designed to handle 300 tons/day (tpd) of MSW and 20 wet tpd of biosolids, the facility is now fully operational, but the original operator Bedminster Bioconversion Corp. isn’t running the plant any longer.

“It was a mutual parting,” says Joe Accortt, head of the county’s solid waste program. “But there’s no question that the county wanted to run the facility.” After two months of performance testing was completed satisfactorily in April, the county assumed control.

Prior to the fire, the biggest problem with the facility involved odors. The plant, which is located close to a fairly large population base, experienced problems during its initial start up. Much of the work completed after the fire involved improving the odor control system.

That work has paid off. “It’s not totally odor free,” says Accortt. “But it’s day and night from what things were like during startup Now we have odor ‘puffs’ occasionally. But thanks to the redesign, we can now operate day in and day out.”

The time spent rebuilding the plant also aided in finding markets for finished compost. “We have approval from the Georgia Department of Agriculture to sell the compost as a soil conditioner and from the Department of Environmental Protection to use it as landfill cover,” says Accortt.

One operational plus about utilizing the compost as landfill cover is that it needs less curing time. “We can take the compost straight from the plant,” says Accortt. “When it’s used for landscaping, it requires four or five months of additional curing.” The county is using the bulk of the compost for the closure of three of its own landfills, as well as several others in the state. It also has a giveaway program that allows residents to pick up compost at the facility two days each week.

MARLBOROUGH, MASSACHUSETTS

If taking a cautious approach to startup can keep little problems from turning into bigger ones, then the latest MSW composting project to go from drawing board to operation doesn’t have much to worry about. The 120 tpd facility in Marlborough isn’t in any hurry to get to full capacity.

The plant began accepting MSW from the city at the end of August, but is only taking in about 25 tpd. “We are being prudent,” says Bob Spencer, who manages the project for Bedminster Marlborough LLC. The idea is to run the operation at a reduced level while the bugs are being worked out. And so far, there have been minimal problems. “There have been a few mechanical and electrical glitches,” says Spencer. “But it’s better to correct them now while we have the time.” The city is pleased by what it has seen so far. “It’s doing what it’s supposed to do,” says Doran Crouse, who oversees the project for Marlborough.

The next bump in throughput was expected in late October, when the plant will be taking all of the city’s MSW. That would put the facility at approximately half capacity. Plans are to be fully operational, processing 120 tpd of MSW and selected organics, and another 60 wet tpd of municipal biosolids, in early 2000.

Bedminster is employing a waste broker to search for the other half of the feedstock needed to bring the plant to 100 percent capacity. The principal target is organic-rich residuals from places like grocery stores, cafeterias, restaurants and office parks. Enticements are offered: While the tipping fee at the gate is $75/ton, loads with ten percent or less inorganic content will pay $60/ton. Loads with 20 percent or less inorganic content will pay $66/ton.

“We can justify the lower fees,” says Spencer, “because it means we have less contaminant residue to deal with.” Those residues are handled by the same firm, Penn Atlantic Group, Inc., that is obtaining feedstock for the plant. “Actually, that’s how we got together in the first place,” says Spencer. “We were looking to have someone handle our residue. Now they’re really into finding those organics for us.”

The Marlborough project has benefited from the experience Bedminster has garnered over the years from its other projects, which include Cobb County, Sevier County (Tennessee) and others. The plant, located at the city’s wastewater treatment facility, is using two digesters to mix and initially process the MSW and biosolids. The garbage is fed to the digester via a hopper, but to aid in minimizing odors, biosolids are pumped directly from the dewatering room into the drums. “Originally, we were going to use overhead conveyors to move the biosolids,” adds Spencer. “But we decided to go with an underground delivery system to reduce odors.”

After three days of retention in the drums, the composting mixture is run through a 1.25-inch trommel and then sent for curing on an aeration floor similar to the one used in Sevier County. The windrows are turned with a front-end loader. After this curing phase, the composted material is put through a final screening and destoning operation, with the final product finished to three-eighths inch. Because Bedminster isn’t allowed to store any material outside, it has contracted with third parties located off-site to provide staging and curing areas.

Odor control was a major concern for the city because it had operated a biosolids composting facility with all sorts of odor problems. “We really have a multifaceted odor control program here,” says Spencer. “The biofilter is the most visible component, but it’s just the final stage.” That biofilter consists of five separate bays, each with an 18-inch base of stone under a mixture of softwood chips and mature yard trimmings compost. “Each bay can be operated independently and we can run (at full capacity) with three of the five,” he notes. That allows the media in a bay to be changed without disrupting operation of the plant. The biofilter is housed in a building that contains emissions, which are introduced to the atmosphere through five dispersion fans on the roof.

While the biofilter offers “end of pipe” control, point sources of odors also have been targeted. Collection ducts are located over points such as the feed hoppers and digesters. Those ducts feed two 55,000-cfm water absorption-type scrubbers that pretreat the air prior to it going to the biofilter.

NANTUCKET, MASSACHUSETTS

In Nantucket, Waste Options, Inc. is putting the finishing touches on a facility capable of composting 125 tpd of MSW and biosolids. According to Jeff Willett, director of public works, the facility was scheduled for a three-week shakedown period after going on line at the end of October. Under the agreement with Waste Options, that company is responsible for the financing, construction and operation of the facility. The Town and County of Nantucket will pay a fee of $90/ton for the material that is processed. While that fee may sound high to people in many parts of the country, Nantucket located on an island represents a unique situation. “Off-island options were in the $140 to $180/ton range,” says Willett.

The initial phase of the project was construction of a MRF that handles recyclables from the island’s mandatory recycling program. That facility was actually built as part of a previous agreement with Daneco that Waste Options assumed when it took over the project.

For the composting component, Waste Options chose the Bedminster drum technology. After processing in the drum, material will be screened and further composted in aerated windrows, then screened and destoned. To cut down on the amount of plastic film in the finished material, the town is discussing the possibility of replacing clear plastic garbage bags with biodegradable bags.

Because the island has a tremendous fluctuation in population (from 60,000 in the summer months to roughly 7,000 in the winter), for much of the year the facility will have a significant amount of excess capacity. To utilize some of that excess, the public works department is looking at the possibility of processing waste that can be mined from an old landfill.

Waste Options is ultimately responsible for compost marketing, although the town will share in the sale of material. According to Willett, the marketing program is largely targeted to on-island uses, since there is a great need for organic material to improve the soils. However, he does anticipate some material being sold off the island as well.

SUMTER COUNTY, FLORIDA

Sumter County has been composting MSW since 1988, which makes it one of the oldest such facilities in the country. Although in its early years the Florida facility had its problems producing a viable product, the county has battled through them and continues the operation today.

In 1996, the county embarked on a $5 million upgrade of the facility, which included installation of a new sorting system, a digester and a composting building. The facility now can handle approximately 100 tpd of MSW. Up-front sorting is done manually to recover glass, corrugated cardboard, newspaper, plastic bottles and film plastic. Steel cans are extracted with magnets, while aluminum is removed by an eddy current separator. Other noncompostables are removed in the upfront system as well.

The resulting feedstock is then conveyed to the 185-foot-long rotary digester, where it remains for approximately three days. The feedstock is then put through a two-inch screen and transported to a covered windrow composting area. It stays there for approximately 20 days, then is screened again and windrowed on an open pad for another three to four months.

Last year, the county completed an analysis of the sorting and composting systems. The study, performed by TIA Solid Waste Management Consultants of Tampa, showed that the amount of recyclables removed in the sorting system ranged from 13 to 23 percent of the total amount of material processed. Residuals removed up front ranged from eight to 14 percent. In both cases, variation in the amount recovered was largely attributable to the number of sorters working on the line. Analysis of the composting system showed that 30 to 35 percent of the material entering the digesters is residuals removed through the primary and secondary screening systems.

CRISP COUNTY, GEORGIA

May, 1998 marked what was to be the startup of the biggest MSW compost facility this country had seen since the Dano facility in Portland, Oregon, which shut down in the early 1990s. The Solid Waste Management Authority of Crisp County project was designed to process about 1,700 tpd of MSW, and compost about 420 tpd of the organic fraction. To date, the composting system hasn’t come close to handling that amount. What’s more, after several months of operation and an evaluation of the processing facility, the authority now believes that its capacity is closer to 800 tpd. These shortcomings led it to dismiss the original management team and replace it with a new firm, ERR, last February.

According to Robert Sears, who oversees the compost operation, the initial management of the process was lax. “There was no record of windrow temperatures, when windrows were turned, or when water was added,” he says. “There were no quality control measures in place until September, 1998.”

Not surprisingly, these management shortfalls contributed to odor problems. And even though the plant is in a rural setting, that translated into complaints. After improvements in recordkeeping and management, the number of odor complaints fell from an average of three times a month to zero since January, 1999.
 
 Further, the sorting and processing system prior to composting also had not been doing well. Sears notes that workers on the picking lines were letting many recyclables slip through, particularly glass. When the first compost was analyzed, it was found to contain upwards of 12 percent glass. An evaluation of the system from December, 1998 to April, 1999 led to better trained sorters and improved equipment performance. There has been a drop in the amount of residue going to the landfill and fewer noncompostables going into the windrows. Glass content is now 1.5 percent. The amount of film plastic in the compost also has dropped substantially, according to Sears.

The facility is currently accepting about 650 tpd of MSW, of which about 35 percent is landfilled. Since the process has been retooled, the amount of material composted has increased from an average in April of 110 tpd to just short of 150 tpd in September. Compost has been distributed primarily to farmers and homeowners; some has been used in land reclamation projects as well.

O’NEILL, NEBRASKA

Last October, Great Plains Recycling, Inc. in O’Neill began operating a city owned processing facility that sorted out recyclables and composted the remaining organic fraction. Less than a year later, the facility was turned over to the city, which had financed its development.

“They just couldn’t keep up with the payments,” says Kevin Seger, who now manages the facility for O’Neill. “The tipping fee ($37.50/ton) is too low to support the mortgage payments each month. Most of the landfills in the area are in the $45 to $48/ton range.” On September 22, the city continued the operation, rehiring 25 of the people who had been working there.

The $2.7 million facility is taking in between 65 and 100 tpd, predominantly from Waste Connections, which collects garbage from nearly 50 communities in the O’Neill area. “This is largely a manual operation,” Seger says of the processing system. After the garbage is dumped, corrugated cardboard, large metal items and noncompostables are pulled at the tipping area. The feedstock then goes through a linear picking system designed and installed by Wildcat Manufacturing. The MSW is put through a drum bag breaker, then goes onto the picking line where plastics (#1 & 2) are pulled manually, along with aluminum cans. Ferrous metal is taken off via a crossbelt magnet.

At the end of the line, the remaining material is processed through an Ariens grinder and deposited on the floor. From there it is loaded into a silage wagon and taken transport to the compost area. O’Neill uses an Ag-Bag composting system, which employs elongated plastic sleeves to contain feedstock during the process. The compostable material is loaded into 200-by-10-foot plastic tubes, which each contain an aeration hose fed by a blower and have a capacity of approximately 100 tons.

OTHER OPERATING PLANTS

The following is a summary of the other operating MSW composting projects:

Lake of the Woods County, Minnesota: The amount of MSW processed at the county’s facility has increased a bit over the past year, creeping up from three to almost four tpd. A maintenance building has been added, opening up space for household hazardous waste storage. “That means we don’t have to service equipment in the same area where we shred material,” says Gary Lockner, the county’s solid waste officer.

Expansion of the curing pad’s length from 300 feet to as long as 600 feet is in the works for next year. Although a marketing study revealed that a farmer would use all of the compost generated at the operation, the county has just about nothing left over after using it internally for landfill cover. “We defer the costs of buying black dirt, which is worth more than what we could get by marketing the compost,” Lockner explains.

Pennington County, Minnesota: Tough times are continuing for the county’s pioneering MSW composting site, which started in 1987. Three years ago, the facility suffered a devastating fire. The contracted site operator recently was hit with significant fines. And in the past year, throughput has dropped from 25 to 11 tpd. “The company that’s been operating the plant for us lost most of its garbage contracts,” says Howard Person, who supervises the plant for the county. “We had about 25,000 tons per year of MSW coming in, and now we’re at about 10,000 tons per year.”

Markets for fuel pellets and compost produced by the operation have been poor, resulting in a large stockpile of finished product, a little of which has been taken by businesses trying it out. Some compost that has not been run through the destoner to remove glass and metal fragments will likely be used in gravel pit reclamation. The remainder might be mixed with yard trimmings compost and given away to county residents, adds Person.

Truman, Minnesota: A fire last year that destroyed several pieces of equipment led to a dramatic marketing turnaround for the Prairieland Solid Waste Board’s MSW composting operation. To replace its gutted trommel, the board purchased a Bivitec dual-stage vibratory screen. It previously had to pay $3/ton to have the compost trucked and spread on agricultural land. Now the board sells the compost for $6/ton (and pays for freight). “After we put in a different screen, the product became more aesthetically pleasing,” explains board official Mark Bauman. “It takes out more inert material. I think we’ll be able to sell pretty much all of our compost.” The facility produces about 4,000 tons/year of compost.

Mackinac Island, Michigan: “We’re all about volume,” says Bruce Zimmerman, director of the island’s Public Works Department. Over the past year, throughput has increased at the site from four tpd to about five tpd. A small amount of the MSW and biosolids is being diverted to a pilot vermicomposting operation. Selling for $10/cubic yard (cy), about half of the finished compost is bought by businesses such as hotels and golf courses, with most of the rest going to residents and community groups. A little is sold to landscaping businesses. “We marketed all that we wanted to last year,” notes Zimmerman. “We sold 800 cy and reserved 200 cy for landfill cover.”

Hot Springs, South Dakota: A few changes over the past year have enabled a decrease in operating hours on the materials sorting line at the MSW composting facility from 40 to 32 hours/week. Some plastics are allowed through the Ariens grinder, with the vast majority taken out later by a Wildcat trommel screen, says Steve Moir, facility manager. “We also used to spend a lot of time pulling dirty cardboard off the line,” he adds. “Even though the market was good for cardboard, we ended up with a lot that was not recyclable. If it’s clean, we save it; if not, we grind it.” Significant amounts of compost have been used on athletic fields, but most is given away to residents. This summer, the facility started turning a profit for the first time since starting in 1993.

Sevier County, Tennessee: The only change at the county facility has been an upgrade to larger wheel loaders. Although the volumes of MSW and biosolids are similar to last year’s amounts (240 tpd of MSW and 100 wet tpd of biosolids), the bigger machines were acquired to keep up with the total increase over the past several years, explains Tom Leonard, who began managing the project a few months ago. Another possible change is an expansion of the aeration floor to handle more compost. Professional Services Group, the facility operator, is responsible for marketing the finished product, which is delivered to nurseries and farms for the cost of hauling it.

Lexington, Nebraska: The Lexington Area Solid Waste Authority has taken over marketing of recyclables from the former contractor after he retired. The board of directors has discussed slowing down the sorting line to recover more plastic on the front end and improve compost quality. Compost is given away to residents and will be used by the City of Lexington for application in parks and other areas that can use it.

Buena Vista County, Iowa: Things are running smoothly at the county’s facility. Some compost has been applied at public ballfields and flower beds of new parks. The rest is mixed with equal portions of dirt for daily landfill cover. Testing of the product is being conducted on farmland to evaluate increases in organic matter content, but a lack of volume is inhibiting more widespread use of the compost. A Rotochopper was purchased to grind wood for mulch given away to the public and used in conjunction with road work.

Swift County, Minnesota: Not much has changed at the MSW composting facility, says Scott Collins of Swift County. About 85 percent of the roughly 1,400 tons of MSW compost produced last year is being used as a soil amendment on county grounds, with the rest snapped up for free by residents. “We’ve talked about selling the compost,” says Collins. “But for a program where residents are asked to source separate, at this volume, we think it’s better to give it to them.”

Columbia County, Wisconsin: MSW volume has increased a bit to roughly 63 tpd at the county facility, which will have its first shutdown in the spring to conduct preventative maintenance, says Bill Casey, the county’s solid waste director. Finished compost is currently land applied on agricultural land, but plans are afoot to meet interest in the product expressed by landscapers, nurseries and a few homeowners. “We’re going to clean up the compost a little more before trying to sell it,” says Casey. “We’re looking at doing some things on the front end, like buying a machine to open and separate bags of MSW and get some of the glass out.”

Pinetop-Lakeside, Arizona: Due to population growth in the area, the operation has outgrown its cocomposting digester. “We are in the process of adding a dehydrator to handle sludge that we can’t process in the digester,” says Phil Hayes, who supervises the facility. “That material will be blended into the compost.” All compost is sold to a contracted company for $7.01/cy, which is more than what was paid by the prior business. The facility produces about 1,100 cy/year of compost, most of which is used by residents.

Fillmore County, Minnesota: After a prior dip in feedstock, MSW volume has stabilized at six tpd for the county’s operation, one of the country’s longest running MSW composting projects. Finished product is sold to residents and nurseries for $1/cy.

East Hampton, New York: MSW composting was temporarily suspended at the municipal site in July due to an order by the state to deal with the stockpile of yard trimmings. “When we get caught up on our yard waste, the state will allow us to do MSW composting again,” says David Paolelli, manager of the facility.

Medina, Ohio: Operated by Norton Environmental, MSW composting continues at the Medina County Class 1 Compost Facility. The operation generates 92 cy/day of fines (two inches or less) from its MSW processing line, which are composted with yard trimmings and bulking agents in a 4:1 ratio, processing a total of 460 cy/day.

FUTURE PROJECTS

Financing is being sought for a $7 million MSW composting facility using Bedminster technology in Iberia Parish, Louisiana. “It’s in the preliminary phases right now,” explains David Suire, project manager for Wayne M. Labiche Engineering, the parish’s consulting engineering firm. “We’re hoping at the beginning of next year to select a contractor and have plans and specifications completed.” The facility, designed to handle 50 to 75 tpd of MSW, would consolidate the parish’s garbage and recycling programs. Once it begins, construction is estimated to take up to 18 months.

In Mora, Minnesota, the East Central Solid Waste Commission is looking into the possibility of restarting its composting plant. According to Al Christensen, interim director, the commission may operate a scaled-down version of the project that was most recently overhauled, but never operated, by Microlife, Inc. One possibility would be to process ten to 30 percent of incoming material through a picking line and then compost the fines from a screening operation. But ultimately, the commission may be looking for another vendor to do a full retrofit of the plant. “There’s nothing concrete now,” says Christensen. “But processing is definitely in the future.”

Several years ago, Rapid City, South Dakota developed a solid waste management plan that called for a yard trimmings composting system and a MRF, as well as an MSW organics composting plant. To date, the city has put in place the yard trimmings composting and MRF. Additionally, it has constructed the front end of the MSW composting plant, installing a digester salvaged from the defunct Dano project in Portland, Oregon, which is currently used to reduce the volume of material going to its landfill. Because of problems that its wastewater treatment plant is facing in regard to land applying biosolids (which would require upwards of 900 additional acres of farmland), the city is investigating the possibility of processing biosolids in the digester with MSW, and then composting the mixture. In order to cocompost, the city would have to spend at least $6 million for improvements to the $13 million facility, which began operating in 1997.

During the past year, Mariposa County, California selected Herhof composting technology for the development of a 100 tpd facility. If grant funding can be secured, the $5 million project can get off the ground as early as mid-2000.

Harvey County, Kansas has awarded a contract to Agranom, Inc. to build an MSW composting facility that would process 60 to 70 tpd of source separated organics collected primarily from residents. Currently in the design phase, the county expects the facility to be completed by 2001.

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