November 18, 2011 | General

Mixed Waste Composting Facilities Review

BioCycle November 2011, Vol. 52, No. 11, p. 27
BioCycle’s 2011 MSW Composting Survey finds 10 facilities reporting continued success, while one is transitioning to refuse-derived fuel production only.
Dan Sullivan

ALTHOUGH there are only a handful of facilities across the country doing mixed solid waste (MSW) composting, each has its own way of dealing with the particular challenges it faces. What these facilities have in common is that they’ve all reached the conclusion that collecting single-stream municipal solid waste and sorting out the organics for processing makes the most sense both logistically and economically. Each also operates in service to the dual goals of maximizing recovery of organics and diverting material from the landfill.
Some facilities we talked to cocompost the organic fraction of their MSW with biosolids. Some are assisted by curbside single-stream recycling and some collect source separated organics (SSO). BioCycle has been tracking these projects for more than two decades, with eleven facilities in nine states weighing in for 2011.

Last year the Z-Best Compost Facility reported an uptick in throughput over the previous year, in large part due to the addition of multifamily (apartments, condos and townhouses) materials coming from San Jose. That stream will continue, says Michael Gross, marketing manager for Z-Best parent company Zanker Road Resource Management, Ltd. (Zanker). “Currently we’re at about 83 percent diversion – we hover around that,” he says, adding that increasing that number presents a continued challenge. Its capacity for MSW organics is 400 tons/day.
Markets for finished MSW compost, which incorporates food residuals, include landscape applications and non-food agriculture. Compost made with only agricultural and other green waste – which accounts for about 85 percent of the volume Z-Best produces – goes to food production agriculture including USDA Certified Organic farming (Z-Best receives about 800 tons/day of yard waste from predominantly curbside collection programs). Compost is produced in aerated static piles enclosed in CTI bags.
Zanker is a partner with GreenWaste Recovery to construct a dry fermentation anaerobic digester and composting facility adjacent to its operations in San Jose. Zero Waste Energy Development – the name of the partnership – received a 15-year contract with the city of San Jose to process commercial organic wastes (see “Creating Infrastructure for Commercial Waste Diversion,” August 2011). The digester and composting facility, ultimately with the capacity to process 270,000 tons/year of commercial organics, is being built in phases. The first phase, designed for 90,000 tons/year, is scheduled to open in the fall of 2012. However the contract with San Jose starts next July, so in the interim months, commercial organics (being collected by Allied Waste Systems) will go to Z-Best for processing. While this contract will ultimately take away a large percentage of the 400 tons/day of MSW organics that Z-Best currently composts, Gross says there are plenty of residual organics to be sourced elsewhere.

When Greg Ollivier, solid waste manager at Mariposa County Landfill, Compost Facility and Recycling Center, took over the operation a few months ago, he immediately identified a problem. “The first time I saw some of the compost, I said ‘are you serious? Why is that in there?'” The challenge in producing clean compost, he says, stems from a history of trying to fit a square peg into a round hole by running a composting facility that, based on an accurate assessment of the waste stream, should have been built as a materials recovery facility (MRF).
“Specifically what happened was a [consultant’s] waste characterization study prior to this facility being built told them they had 69 percent organics in the waste stream,” explains Ollivier. As a result, the county built an $8.2 million facility – with USDA subsidized loans and $1.2 million from nearby Yosemite National Park – with the idea that a focus on composting organics would allow it to meet the state’s mandated diversion rates. “They thought the most efficient way to go would be to build a composting facility,” says Ollivier. “But somewhere along the way, either the waste stream changed drastically or else the information wasn’t right in the first place.”
This was made abundantly clear when the State of California selected Mariposa County randomly for its own waste characterization study in 2008. “It wasn’t released publicly, but we did get the data,” Ollivier adds. It showed organic materials at about 30 percent. “It was designed and built to be a compost facility, not a MRF,” he says. “It’s not really user friendly for a sort-line situation. But we have to focus on what we have.”
One bright star in the program is DNC Parks & Resorts at Yosemite, Inc., the official concessionaire at one of the country’s most-visited national parks. “They are making a tremendous effort to sort compostable materials, especially their food waste,” he says. “We’re dealing with the issue now of how we can get that material here.” The county facility processes a fluctuating volume of between 30 and 100 tons a day, the high number bolstered by the park’s some 3.8 million visitors. “Other than peak season, the volumes don’t justify separate collection,” Ollivier adds. One solution to collect the separated organics has been to have haulers load easily identifiable clean compostables at one end of the truck and mixed solid waste at the other.
The clean organics can go straight to composting. While the separating of compostable organics is a big help and other food purveyors in the area are being encouraged to follow suit, it’s a small part of solving the facility’s challenges, says Ollivier. “We were not putting enough focus on pulling out other materials so we can divert and recycle them.”
No matter how clean the compost feedstocks may get, much of the end product will likely continue to be used predominantly as alternative daily landfill cover (ADC), he adds. “As a rural mountain community, we don’t have a lot of dirt at the landfill. We have to import dirt to use for cover, and that is very expensive.”
Operationally, a big question was whether to invest in a second crew to try to manually recover more material or to change the process. The immediate solution has been to run the material through the sort line twice, with the first pass focusing on removing bigger trash items. “The bags get broken open and anything that is easy to pick off the line that’s big and bulky – and that we know is not going to be composted or recycled – is taken out. We run it through again and do a finer sort.”
Equipment at the facility includes SV Composter stationary vessels supplied by Engineered Compost Systems and a front-end preprocessing line supplied by Bulk Handling Systems (BHS). Total retention time in the vessel averages 20 days, after which material is placed into aerated static piles.
Programs have been implemented to encourage recycling so that materials can be collected and brought to the county facility, which has a certified buy-back program. “We have a Bin Buddies program with receptacles in the parks and at strategic places around the community for the residents and the millions of tourists that come through,” he says. The county partners with nonprofits and school groups in the area to facilitate recovery. “They collect and redeem the materials, providing the manpower to source separate in order to cut down on recycling that comes in to our plant with the waste,” explains Ollivier. “Cluster bins placed throughout the community accept cans, bottles and paper. We have a recycling coordinator who educates residents and businesses as to how they can save money and how separating out materials helps them and helps us. We’re aggressively working at it, and we’ll get there. Total diversion at the facility is at 64 percent. We’re being effective at creating some good diversion. It’s a work in progress.”

“It seems food waste processing is getting bigger and bigger,” says Philip McCarthy, president and manager of the Marlborough composting facility operated by WeCare Environmental, LLC. McCarthy says the Massachusetts Department of Environmental Protection (MassDEP) is proposing to add food waste to a list of items banned from landfilling, a move he says could increase that volume exponentially. The challenge will be meeting any organics diversion mandates, presently proposed for 2014, with the necessary infrastructure. “MassDEP is anticipating 600,000 more tons of organics could be diverted from Massachusetts landfills when the program is fully implemented,” he notes.
Currently the Marlborough facility processes about 55,000 tons annually of biosolids and MSW organics for composting. About 22 to 25 percent of the compost feedstock is biosolids from Marlborough’s easterly and westerly wastewater treatment plants, approximately 40 percent is source separated organics and food waste from supermarkets, and the remaining 40 percent comes from unsorted curbside MSW from the city of Marlborough (which contains approximately 40 percent recoverable organic material). “We process everything except mattresses, couches, etc.,” says McCarthy. “That material is transferred out.”
In 2010, the facility reported about an 8 to 10 percent drop in volume due to a sluggish economy. “We’re back up to permitted levels for 2011 and it looks to stay there for some time,” he adds. Once in awhile, the facility needs to turn away a wet load in order to balance moisture content. “If somebody calls with a truckload of watermelon or some other load we know is going to be all water … we have to balance that input to the overall plant moisture balance,” he explains. “We are contracted to take the biosolids and unsorted MSW from Marlborough. That doesn’t really change. We can only bring the moisture content up so high before we have to divert the sludge. WeCare manages other regional biosolids facilities and can divert if necessary.”
The average tipping fee for both biosolids and food waste is around $85/ton. “The ‘trashier” you get, the higher the fee,” McCarthy says of the organics loads. “If it’s cleaner and can go straight to composting, we [discount] for that.” The biosolids market fluctuates between $70 and $90/ton, he adds. “We continue to look for new food waste sources and have a couple of new grocery chains moving in that we’re going to go after … If Massachusetts continues on its path with a food waste [landfill] ban, it will be interesting to see where that all goes.”
Materials are processed in a rotating drum, then placed in aerated windrows. “Food waste is heavy to begin with, and it’s very odorous,” says McCarthy, adding that initial processing in a rotary drum helps address these challenges. Finished material goes mainly to contractors and landscapers. “The housing market is still down in terms of how companies are blending and their needs for new loam products,” he says. “But we keep pushing and expanding markets, finding new uses. We’re in pretty good shape now.”

The big news at the Nantucket landfill, MRF and MSW composting facility managed by Waste Options, Inc., is that the company has now mined 300,000 cubic yards of material (in three years) out of an old unlined landfill. “We’re recovering metals that are being sold as scrap steel, and we’re recovering structural-grade soil and reusing that to raise the grade of the property,” says Waste Options partner Nelson Widell. “Plastics are also being recovered and stored, and we are looking at closed-loop energy systems that might be complementary to what we’re doing there.” This would include gasification, not incineration, he adds. “Being able to use unrecyclable plastics in a positive environmental fashion is what we’re exploring.”
When Waste Options took over management of Nantucket’s waste stream 15 years ago, mining the old landfill was part of the deal. It’s a scenario that doesn’t make sense everywhere, says Widell. “There are no industrial 55-gallon drums of mysterious liquid or things of that nature. Every 1,000 cubic yards of mined material has to be tested. And Nantucket over the past several decades has been pretty clean, which is not the case with many other landfills.” A newer lined landfill accommodates those items that still require disposal, including what is mined but not recoverable. “They will never be able to build another landfill, and there are some things that still have to be disposed,” he notes, adding that the state had initially mandated closure of the landfill altogether. That would have cost the Island’s residents and businesses dearly. “To collect waste on a truck, put the truck on a boat and haul it to another place is a huge expense,” Widell says.
With all its initiatives, Nantucket’s diversion rate has soared to a record 92 percent. Organic material is initially processed in a Bedminster rotary drum, then finished in aerated static piles under a fabric structure. During the summer tourist season, the facility processes about 80 tons/day of MSW, decreasing by as much as 20 percent during slower parts of the year.

When BioCycle spoke to Mark Bauman, director of Prairieland Compost Facility, he was awaiting the finalversion of a contract for Refuse Derived Fuel (RDF) that would likely lead to the shutdown of the facility’s composting operation.
“We’re probably going to end up phasing out the composting portion of our facility,” he says. “The equipment is 20 years old and needs replacing. We thought instead of replacing it that we would go to RDF production.” The RDF contract is with the Xcel Energy power plant about 40 miles down the road. “They burn RDF, and the organics would go to waste to energy,” explains Bauman, adding that the Prairieland facility is currently at about 80 percent recovery, producing both compost and RDF.
“We use basically the same equipment we do for composting; we shred the garbage and machinery takes out the glass and grit. We have ferrous metals recovery, and a trommel screen sizes the material. We can use all of that equipment to produce fuel and can discontinue composting. Economically, it’s using less electricity, less water, and the equipment isn’t going to be nearly as expensive to replace or maintain.”

“One new development this year is that we’re diverting all of the tires out of the waste stream,” says West Yellowstone composting facility manager John Burns. A tire recycler makes a five-hour drive from Polson, Montana, to haul back between 800 and 900 tires left behind by tourists at one of three service stations in West Yellowstone, typically between Yellowstone National Park’s operating months of May through October.
The West Yellowstone composting facility deals with all the park’s trash and is holding steady at about a 38 to 40 percent recovery rate. “Our waste stream is pretty routine now,” says Burns. “This is our eighth year processing the park’s trash.” Prior to the composting facility being built, MSW was brought to a transfer station, loaded onto semi trailers and either landfilled or incinerated (the incinerator has since been shut down). “We are getting 100 percent of the trash coming to our compost facility now,” Burns says, adding that this does not include several roll-off containers set up for maintenance shops and mechanics to dispose of large noncompostables, such as vehicle parts, that go directly to landfill.
Only one hotel/restaurant, located in West Yellowstone, is currently source separating organics. “They started halfway through the season last year, in late July, and this year as soon as the park opened up for business,” says Burns. “I would say [the amount diverted] has doubled, percentage-wise.” The source separated organics (SSO) are able to go directly into a four-auger mixer, bypassing a presort on the floor and a wet mill that break open bags and separates compostables. One conveyor belt goes into mixer, and any plastic bottles, cans and other materials that have snuck passed the park’s aggressive recycling campaign get processed out the end of the wet mill and shipped to the landfill. “Another advantage of them bringing SSO is that we can offer them a lower rate,” he adds. The savings are substantial: $35/ton instead of the usual $125.95/ton (clean wood is $40/ton). Once a year, usually after the park shuts down, the facility hires a contractor to chip woody debris to add as an amendment to the compost. The fact that the landfill is 122 miles away was a main driving force for building the composting facility.
Roughly half of the MSW unloaded on the tipping floor is suitable to go through the composting process. “We have a screen with 3-inch by 6-inch openings that runs the entire length of the wet mill,” says Burns. “Anything that comes out of that bag that is able to fit through the holes, that’s what gets diverted into the compost stream. Pens, swipe cards, toothpaste, razors, you name it, if can fit through that size hole it gets into the compost stream. Once that material is removed [from the finished compost] that accounts for another 12 to 14 percent diversion loss.”
West Yellowstone utilizes the SV Composter tunnels from ECS for the initial phase of composting. “We have seven vessels that we fill about three times each season, producing the 22 windrows of compost,” he says. “The organic material is unloaded from our vessels onto a uring floor. We make windrows and leave them on the curing floor for a minimum of six weeks. We turn each windrow once a week and add water as necessary. After the six week curing period, we can then screen each row.”
About 1,200 yards of finished compost are produced annually. With housing starts and other new construction down, the operation is not selling as much compost as is typical to contractors, Burns says, but the Petra Academy, a private boarding school in Bozeman, Montana, recently took delivery of 400 yards for a new soccer field. “They integrated a compost layer in between some of the sandy soil they had to help hold in the moisture,” he explains.
Something perhaps unique to the Yellowstone facility is bison mortality composting. “We have 13 bison currently composting onsite,” Burns says of the three-year-old program. “The previous manager, Kathy O’Hern, implemented this because a number of bison get killed each spring by using the highway as a transportation route during spring migration from the park to their traditional calving grounds. We use the same method as a lot of highway departments use for road kill: lay the dead bison on a layer of wood chips, cover them with more wood chips mixed with a small amount of compost and let nature do the rest. We do not sell this compost or use it anywhere else except reusing it in composting the next incoming bison. We average 12 to 22 bison a year, depending on the severity of the winter.”

“It’s been a steady state from a materials handling standpoint with no modifications or changes to our operations,” says Delaware County Department of Public Works Solid Waste Director Susan McIntyre. “We did exceptionally well with sales of material. It’s somewhat interesting, as when the economy tanked in 2008, we haven’t seen any drop off [in product demand]. Maybe it’s because we compete so well. We had a banner year.”
Most of the compost is brokered through WeCare Environmental for large landscaping projects, roadside remediation and realignment projects, bridge work and to establish landfill vegetative cover, McIntyre says. In 2011, a substantial amount of material went to convert a brownfield along the Hudson River into a recreation area in the town of Beacon, New York.
“Total input last year was 29,500 tons,” says McIntyre. “Of that, about 22,600 was MSW and the balance was biosolids.” While the facility wanted to begin taking in more food waste, the initiative hasn’t gained much steam. “We have agreed to receive compostable diapers from an experimental project in the New York City metro area,” she adds. “I understand as part of their permitting, the authority wanted to make sure they were going to a facility with well-documented temperature control. We were approached by several groups to receive SSO, but none have actually worked out. It’s a function of geographical distance and the fact that most of the [vendors] have volume far exceeding our excess capacity. The last thing we want to do is take on material and create problems. I think there are viable opportunities if it’s a good fit. But we’ve been talking about more volume than our little plant can handle.”
A project with the local soil and water conservation district to compost invasive weed species such as Japanese knotweed water hemlock is going well, says McIntyre. “We got a call from somebody in North Carolina looking at controlling invasive species down there. I think it was Kudzu. They read about our project in BioCycle.”

“About a third of the loads that come to our processing facility have no recyclables,” says Medina County Solid Waste District Coordinator William Strazinsky. “We try to determine what materials are in each truck. If there are no recyclables in the load, we send it to the east side of the facility.” That waste is loaded into transfer trailers. The west end of the facility handles the clean loads, which include recyclable materials. The clean loads go onto a series of conveyors for processing and extraction of recyclables. “We exercise flow control in Medina County, so all of the county’s MSW from residential, commercial and industrial firms is brought to our facility – about 550 to 575 tons per day.”
In Medina County, 53 percent of all MSW is reclaimed for recycling and composting, with the balance going to a landfill, adds Strazinsky. Waste goes through a trommel screen, which opens up garbage bags. The first 20 feet of the trommel contains holes that are 2 inches in diameter. About 50 to 55 tons of 2-inch material or “fines,” roughly 10 percent of total volume, are recovered from the waste stream in this manner. The MSW compost is turned once or twice a week and when finished is used for alternative daily landfill cover. An additional Class 4 compost facility processes yard waste only.
Strazinsky estimates that for 2011 “we’ll have about 130,000 tons coming in here, which is probably about 2 percent better than 2010, which was 2 percent better than 2009. I would say that the [population] growth of the county is offsetting some of the economic woes. We’ve grown almost 50 percent in 21 years. We were at 122,000 in 1990, and we’re at 180,000 in 2011.”

The only adjustment to the operation at the Rapid City solid waste composting facility has been to change the design of the biofilter to make it more efficient and allow for quicker rebuilds. “Because the media breaks down, it was taking too long to clean out, so we came up with a different design to speed up the process,” says project manager Mike Oyler. The configuration was changed to larger wood media with a perforated membrane between the wood media and rock media. “It’s worked so far,” he reports.
The facility is still processing about 180 tons of MSW and 60 tons of biosolids a day. About 40 percent of the total MSW is diverted from landfill. The MSW organics are mixed with the biosolids in two Dano drums, then composted for four weeks in nine Siemens-IPS agitated bays. The facility produces around 50 tons/day of compost, which is used for public works projects, by contractors for new construction and by homeowners. About every two to three weeks, the facility receives a semi-load of single-stream recyclables from Gillette, Wyoming, which it trades for compost.
Some recyclables are also recovered from the MSW waste stream (the facility operates two sorting lines: one for curbside recycling and the other for MSW). “The [MSW] line is moving pretty fast, so for the safety of employees we get what we can target and see,” says Oyler. “It’s always a challenge just to get people to participate in recycling, but things are working pretty smoothly.”

Sevier County’s MSW composting facility run by Sevier Solid Waste, Inc. (SSWI) continues to recover from a 2007 fire that destroyed most of the operation (see “Tennessee Composting Facility Rises From the Ashes,” November 2007). As testament to the facility’s resilience, the rebuilt facility hosted the Rotary In-Vessel Users Group meeting in 2010 and was honored with that year’s Eweson Award for Facility Excellence.
Since BioCycle last checked in with SSWI (see “Tennessee Composting Facility Makes Full Recovery,” November 2010), throughput has remained steady at around 275 tons/day of MSW and 60 wet tons/day of biosolids. “We haven’t really gained or lost any volume, we’ve kind of stayed flat,” SSWI Manager Tom Leonard says of the material mostly coming from the communities of Sevierville, Gatlinburg and Pigeon Forge.
MSW is loaded into one of five rotating drums for three days, screened through a Doppstadt trommel and a Li-well flip deck screen,then composted in windrows under one of four Norseman Structures fabric buildings. Piles are turned two times a day with a Backhus windrow turner. The facility is also receiving SSO from the University of Tennessee, other local colleges and commercial cafeterias, and commercial food processors such as Green Mountain Coffee. “Everything is mixed in the drums,” says Leonard. “We are now taking all of the cafeteria waste from JTEK, an automotive parts supplier. We have more people wanting to bring in material. As long as it has a pretty high organic fraction, we’ll take it. We’re owned by the three cities in the county, so there is not a lot of leeway on processing out-of county waste. Politically, we want to deal with waste we generate in our own jurisdiction.”
Leonard admits that can be a bit frustrating when it comes to turning away clean loads of organics. “I told them, ‘this is all going to compost in our process, why not take it?’ The electricity [to run the drums] costs the same, and whether it’s 100 percent organics or 50 percent organics we’re going to charge the same price.”
The rebuilt plant’s footprint has more than doubled, from 88,000 square feet to 190,000 square feet. “We’re really trying to perfect what we’ve built back and have gotten things in pretty good shape as far as working the way we want,” says Leonard. “We’ve had a few minor glitches with some of the equipment we put in. We had a conveyor where we didn’t get things sized right and ended up having to upsize. Mostly it has been minor stuff. We’re producing about 3,500 to 4,000 tons of compost a month and haven’t had a lot of downtime or even problems. It’s been really good.” Finished compost goes straight to farms, soil blenders and contractors and to large commercial projects such as sowing grass at a new industrial park. Diversion from landfill is at 60 percent.

With a recovery rate still hovering around 50 percent, the Columbia County Recycling and Waste Processing Facility is turning out about 3,000 tons of compost annually for use by area landscapers and farmers. The facility collects MSW – between 75 and 80 tons/day five days a week – from all cities and towns within the county. “We took in 14,158 tons last year,” says Bill Casey, director of the facility. About one third is organics that are recovered. Other diverted materials include appliances, tires, recyclables, fluorescent bulbs, scrap metal and drain oil. “If you go by volume [our diversion rate is] about half; if you go by weight it’s about 60 percent,” he adds.
Any material that’s not recovered gets shipped to a landfill 60 miles away. The organic fraction of the MSW is processed in two 250-ton capacity rotating drums for five days, then screened and windrowed for eight weeks. A leaf-only compost is available for purchase by area residents. Commingled recyclables, about 4,500 tons over the past year, are collected curbside, brought to the facility, compacted and shipped to John’s Disposal in nearby Whitewater, where it is sorted and baled at a volume of about a semi truckload a day. “They broker it out to different places,” says Casey.

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