North America generates more than 80 million tons of organic waste each year. Through organics waste recycling, some solid waste operations are turning that trash into treasure.
Written by Carol Brzozowski
About one-third of municipal solid waste in the United States is organic, including foodwaste, yardwaste, and woodwaste. Some 65% of yardwaste and 2.5% of foodwaste in the US is now being diverted from disposal.
According to the USEPA, converting waste into valuable raw materials through recycling creates jobs, builds more competitive manufacturing industries, and adds significantly to the US economy.
“Organics processing is crucially important to our environment and efforts toward sustainable living,” says Nick Korn, regional sales manager for Rotochopper. “Organics processing and composting can also be a very profitable business venture.”
Shane Donnelly, general manager for Doppstadt USA, agrees that organics processing offers an opportunity to turn part of the wastestream into revenue.
Calling greenwaste an “intelligent use of a renewable resource,” Donnelly points out that the beneficial reuse of materials can be used as a fertilizer, soil amendment for decorative use or in the case of fuel, the minimizing of more contaminating or less environmentally friendly materials for the production of energy.”
Korn lists several benefits in diverting such organics as greenwaste, foodwaste, and animal waste from landfills:
- Dumping organics in landfills creates dangerous methane deposits as they decompose in the absence of oxygen. “Methane is one of the most harmful greenhouse gases,” Korn points out. “Diverting organics from landfills reduces methane deposits.”
- Diverting organics from landfills saves landfill space.
- Composting organics results in a nutrient-rich soil amendment, enriching the soil and feeding the plants that grow in it.
- Composting organics promotes sustainable living by closing the life cycle loop on the plant and organics nutrient cycle.
- Composting organics and creating a nutrient rich soil amendment can be a profitable business, helping waste handlers diversify market opportunities in addition to conserving landfill space.
“The demand for compost, mulch, and soil amendments seems certain to continue growing,” says Korn. “The limitations on water usage that some local governments are imposing may help to further increase demand for compost.”
One of the largest efforts in organic waste recycling is being undertaken by Waste Management. The company’s most recent foray into organics recycling is in south Florida, where the company established the Okeechobee Organics Recycling Facility in late 2011 in partnership with the Publix supermarket chain. Its establishment followed a year-long planning and implementation process.
“Our customers are asking us for solutions to their environmental problems and we do bill ourselves as the nation’s largest environmental solutions provider,” says Dawn McCormick, spokesperson for Waste Management.
“Our customers are demanding innovative solutions to managing their waste in the most environmentally responsible way possible. We’re getting more customers asking us about organics recycling.”
Situated on 8 acres adjacent to Waste Management’s Okeechobee Landfill, the organics recycling facility uses a forced aeration system with computer controls to regulate airflow and air treatment to process such preconsumer foodwaste as produce, bakery, and floral items with yardwaste into organic compost products.
During the program’s first phase, Waste Management trucks have collected and transported organic material from 40 of the supermarket stores in Miami-Dade and Palm Beach Counties. The company has entered the second phase to incorporate an organics waste collection from additional stores in Broward County.
The Okeechobee facility is permitted to accept up to 30,000 tons per year, including 15,000 tons of foodwaste and 15,000 tons of yardwaste and is part of Waste Management’s strategy to expand organics recycling in Florida and throughout North America.
Garick, a subsidiary of Waste Management that manufactures, markets, and distributes organic lawn and garden products, is producing the products from the Okeechobee composting facility. The bulk of it is being purchased by area farmers and ranchers.
“We are investing in and debuting organics recycling facilities nationwide. The Okeechobee facility was our first dedicated comprehensive site in south Florida,” says McCormick.
Waste Management operates some 155 recycling facilities that process approximately 10 million tons of recyclables per year, halfway to its goal of managing more than 20 million tons each year.
The effort is attracting other customers, including 10 Whole Foods Market stores, as well as a local hospital.
The organics recycling facility helps entities such as Publix meet corporate sustainability goals, McCormick points out.
“They’re looking to less landfill usage, so it meets their goals of repurposing their organics,” she says. “We’re investing in many different technologies in order to better use waste and to turn it into an end use.”
That includes not only mulch, but alternative fuels and petrochemicals.
It’s the direction in which the industry is ultimately headed, McCormick says.
“Waste Management’s tag line is we want to ensure that waste no longer goes to waste,” she says. “There’s a value there. Where we can, we’re taking materials out of the wastestream and recycling them, whether it be household recyclables or construction material such as metals, asphalt, concrete and cardboard.
“We’re also recycling organics as there is another technology that allows us to do that and create an end-use compost. We’re going to continue to move towards less in the landfill, but extracting a value from the materials we manage.”
Organics recycling is deemed by many to be as important as any other recycling effort, says Travis Lint, large equipment sales manager for Bandit Industries.
“Instead of simply letting organic materials decompose naturally, they can be utilized in many positive ways, from aiding and promoting new growth as mulch or compost to providing renewable energy,” he says. “And the recycling of organic matter is actually one of the simplest forms of recycling.”
To that end, Bandit Industries has tweaked tooth designs, mill speeds, and other machine configurations on its horizontal grinders for the woodwaste recycling segment for better production in organic waste recycling.
Bandit Industries’ Beast Recycler uses a cuttermill design to reduce material. Designed for versatility, the Beast Recycler can recycle shingles for an hour, process construction debris for another hour, and then work on organic waste recycling in the same day, Lint points out.
Maintaining the Beast’s performance entails changing teeth, making sure it is greased properly, and maintaining the engine.
Compost and landscape mulch are the largest value-added products from organic green waste, Lint says.
“It's extremely easy to produce and simple to work with,” he adds.
Diverting material away from the landfills is the largest benefit of organics recycling, Lint points out.
“Why let the material decompose uselessly in a landfill when it could be used to help new trees or gardens grow healthy?” he adds.
The Southeastern Oakland County Resource Recovery Authority (SOCRRA) in Michigan comprises 12 municipalities covering 75 square miles and serving 283,000 people.
The operation takes in about 130,000 yards of material a year and utilizes the Beast Recycler to grind up everything three times.
SOCRRA makes its rows at a 3:1 ratio—three parts leaves to one part grass.
“Every year is a challenge,” notes Dave Powe, compost site supervisor. “The weather plays a big factor in how we do things. With this early spring, it’s definitely going to affect us. We’re probably three weeks ahead of schedule, which is going to make our season three weeks longer. I’m going to have to adjust and figure out a way to incorporate more grass. I may have to go to a 2:1 ratio this year because of the early spring.”
After processing organics waste, some of it is sold to landscapers. Most of it is distributed to the communities that encompass SOCRRA.
SOCRRA chose the Beast three years ago after seeing a demonstration of three other units, Powe says. The return on investment came within the first year through significant time efficiencies, he adds.
“It saves a tremendous amount of landfill space, which is good for everybody,” says Powe. “The reason we chose the Beast is we don’t have to run a screen in it. Our production rate is much faster. The other issue is the remote control. The Beast is on a remote-control track unit, and it’s very effective for us making windrows. We can make the windrows as we go.”
Tim Wenger, president of CW Mill, the company that manufactures the HogZilla line of tub grinders and horizontal grinders, says he believe many smaller municipalities are still burning or burying organic material.
“Bigger markets have embraced grinding and composting, but a lot of the smaller markets are probably still disposing of it in the same way,” he says. “There’s growth potential to it, but for the most part, most of the bigger markets in the bigger cities are online currently to handle that in some way, shape, or form.”
Meeting the upfront costs becomes a challenge for small operations and may find it easier to privatize that type of operation, Wenger adds.
“I think there are a lot of small municipalities out there that could be doing something, but they’re just struggling to meet the demand of their current bills and expanding their green waste program isn’t a high priority,” he says.
“It becomes a Catch-22 for the city trying to maintain a service at a reasonable expense, but then it becomes a burden on their ability to pay other bills and if they privatize it, it opens it up to the free market,” Wenger says, adding that sometimes the free market may not be the best option when some companies operate from an element of “greed.”
One-third of CW Mill's clients are involved in the greenwaste sector. They derive revenue streams from land clearing, tire recycling, cleaning up after wind-driven weather events such as hurricanes and tornadoes as well as creating products for the mulch and landscaping season and fuel production.
The markets for the end product depend on the material, Wenger says.
“Grass and leaves get composted. The wood product can get turned into a mulch. Some municipalities give it away to their residents. Some garden centers dye the material different colors and sell it for $30 a yard for landscaping material,” says Wenger, adding that the landscape sector seems to be the biggest market for processed organics.
“Some of it is processed for fuel and turned into electricity,” he adds. “If there’s a wood-burning power plant in reasonable distance, some of it gets used as a bulking agent. Customers mix liquid food waste with ground-up wood products for a bulking agent. The majority of it gets composted for dirt products or turned into a mulch product or a fuel.”
The city of Murfreesboro, TN, bought a HogZilla tub grinder in 2005.
In Murfreesboro’s greenwaste collection, the solid waste department runs knuckleboom trucks along with garbage trucks, picking up tree limbs, brush, grass, and leaves.
Last year, the solid waste operation collected more than 31,000 tons of yardwaste, processing it through the HogZilla, which the workers nicknamed “the hog.”
“We do a passive windrow system here, and it keeps increasing every year,” notes Joey Smith, director of the city’s solid waste department. “We do a second-grind cut during the fall when we have an active leaf season. We collect almost 900 tons of leaves and we windrow them along with our static piles.”
There are eight static piles located on a concrete pad; the public is invited to pick up free second grind mulch. This year, Murfreesboro gave out more than 8,000 cubic yards of the mulch on a first-come, first serve basis starting March 1. The green waste program is well-received by the public, Smith says, adding that the city’s goal is to be able to extend the second grind mulch give-away to April 1.
The city of Murfreesboro also uses the mulch in its municipal landscape operations.
“We mulch the trees in our yard and the parks and recreation department uses it in landscaping projects,” says Smith. “It’s a win-win for the city as far as being able to save money.”
Changing weather patterns necessitate the need to be prepared to deal with greenwaste, Smith says.
“You’re always having to deal with the variables from the weather,” Smith notes.
The city’s Christmas tree recycling program generates a great deal of greenwaste, Smith says. The trees are mixed in with the other greenwaste material.
No sooner were the Christmas trees processed than the city’s greenwaste program was inundated with yardwaste due to an early arrival of spring.
In the solid waste industry, a tub grinder is one of the expensive pieces of equipment to maintain, Smith says.
“There are so many moving parts on a tub grinder, from hydraulic stabilizers to the tips,” Smith says. “There are the belts. You have to make sure that the hammers and the mill itself is maintained. There’s the torque converter. We go through about three to four sets of tips each year in the grinding process.
“It’s one of those things that is the cost of doing business. Just on the wear parts alone, we probably spend about $7,000 a year. It’s just the cost of doing business. It looks like you’re spending quite a bit, but once you maintain it and keep it up, it works out in the long run.”
Because of the maintenance program, the HogZilla has held up well, given what it’s gone through over the years, Smith notes.
“All of the mechanics have been trained from the factory,” he says. “Every 250 hours, we go through oil changes. Although some people think it’s not cost-effective changing out the hydraulic oil, we’ll do a hydraulic oil flush each year just in case something got contaminated.”
The HogZilla was put to the test in 2009, when the Good Friday tornado that hit Murfreesboro subsequently created 10,000 tons of waste that was processed over three months on the machine.
“Our normal rules and regulations say eight inches in diameter and 10-foot lengths. We were picking up pine trees, oak trees, and everything else,” Smith says. “The year after that, we had the floods, which impacted more of the county than it did us but we still had a lot of material came in from that.”
In 2011, the area was hit with straight line winds of 60 to 70 mph, creating 6,000 tons of extra yardwaste for pickup.
“One of the things that predicated us getting a tub grinder was, in 2003, we had a major storm come through,” says Smith. “At that time, we just had a little horizontal grinder. We found out real quick that we needed something that could do logs, stumps, and everything else”
Until 2006, Murfreesboro’s solid waste program existed on an eighth of an acre.
That year, the city purchased a 15-acre plot of land. A 5.5-acre concrete pad serves as the host for the mulch processed by the HogZilla.
“Every year, we have CW Mill come up here and do a yearly check on our tub grinder. They love working on something on concrete that’s clean. It’s not on the side of a mountain or swamp,” says Smith. “It’s also helped the general public to be able to come in and drive on concrete, not on the dirt or gravel. A lot of the program’s success has to do with how you set it up and the ease of your trucks being able to come in and dump and the general public’s access as well.”
In addition to the solid waste department’s collection of 31,000 tons of greenwaste, the department also collected 35,000 tons of garbage.
Murfreesboro’s landfill costs are $35 to $40 a ton. The greenwaste was diverted from the landfill, given away free to the public, or taken away by those who color it for landscape purposes or take it to a borer for use as an alternate fuel source.
Donnelly points out that some of challenges associated with the processing of organics range from contamination in the waste stream to cost-effective processing of the material.
“Doppstadt offers a full product line of fuel efficient shredders, screens, and grinders to ensure the right mix of machinery to process the range of material that comes as part of an organics wastestream,” he says.
The machinery is designed to be operated by a single operator and for ease of maintenance, Donnelly says, adding the company’s product offering allows for the application of specific machinery for specific applications.
The fastest-growing segments for use of organics materials are the compost, mulch, and soil markets, Donnelly says.
With proper maintenance, the machines can appropriately handle quantity and quality, Donnelly notes.
“Outside of normal engine maintenance such as replacing filters and changing oil, each piece of machinery requires different maintenance, from changing of teeth on the slow-speed shredders and grinders to the replacement of brushes on a trommel screen,” he says.
A typical ROI on the machine varies according to the market, “but there are not many markets where you can receive revenue for your raw material as well as the finished product,” Donnelly says.
Ed Donovan, general manager for Continental Biomass Industries (CBI), observes other types of value in organics recycling.
“If done properly, selective thinning management and removal of logging residues helps make for a healthier forest without threatening the nutrient retention arguments that come with processing the tops and stumps,” he says. “Also, organics are truly renewable and if done properly, small tracts of land can perpetuate benefits for years to come and improve the overall quality of the stand.”
There is another benefit through lowering the US dependence on foreign oil by utilizing the energy value of material that otherwise decays and acts as fuel for wildfires, Donovan says.
“Everyone with any level of understanding knows that not touching the forest is not management,” he says. “Trees are just like any other crop. When they are mature, they should be harvested before they become over-mature and not only deprive the other trees around them from the available groundwater but when they become over-mature, they start to rot from the inside out. That is why big old trees fall on a house during the big storms.”
One of the biggest challenges in addressing organics recycling is being able to process the biomass material into a usable product.
“The material doesn’t have enough value in a lot of markets unless you can process it for less,” Donovan points out. “CBI’s entire design mentality is to manufacture equipment that will more efficiently process these materials in higher volumes for a significantly lower cost per ton.”
That’s achieved in the offset helix rotor pattern on the company’s wood grinders, which maximizes the efficiency of the hammer by only having one hammer in contact with the material at a time, he says.
“This focuses the inertia and maximizes the horsepower for more efficient processing of the material.,” Donovan says. “Also, horizontal grinders are more efficient than tub grinders at processing material because part of the energy on a tub is used with the hammer pushing the material away rather than processing it.”
The horizontal grinder’s grinding chamber is enclosed to limit the danger of launching debris out of the tub and causing an unsafe area all around the equipment, he says.
“With horizontals, the only place material can leave the grinding chamber is out the front, so you set up your operation to eliminate this danger,” Donovan says, adding that CBI’s systems also have a metal detection system.
CBI designs its systems with components necessary for maximum uptime and minimal maintenance on a per ton basis, Donovan says.
Transportation is the single most expensive component of a chipping or grinding operation, Donovan says.
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Photo: Okeechobee
The Okeechobee Landfill uses a forced aeration system to regulate airflow through its compost. |
“Additional horsepower and a smarter design get the trucks filled and on the road faster,” he says. “We recently designed a Chain Flail Debarker and Disc Chipper to produce clean chips for the pulp and paper industry. This concept is not new, but the inefficiencies of the current machines available were well known and the machines failed to truly improve on a technology of more than 20-plus years.”
Maintenance involves tending to hard surfacing wear areas as needed and changing wear components such as tips, screens, wear plates, knives, and belts.
“Any time you introduce material into a grinder or chipper, you will have maintenance schedules that must be adhered to,” Donovan says. “By being able to process more material per hour, you give your people more time to successfully perform their duties. Also, use the components that are required so they don’t need to be maintained or replaced prematurely.”
Biomass is the largest market for processed organic waste, Donovan says.
“The fact that owner Anders Ragnarsson named his company Continental Biomass Industries 23 years ago gives you an idea of his level of understanding of the markets available worldwide,” he says. “The most efficient use of wood is for heat generation. If it gets used to build a house first and doesn’t get utilized until the house gets torn down, that is okay. As long as we use the material that is available to ultimately serve its best purpose, then we have done our job. By not ultimately realizing the benefits of the organic materials in whatever form they present themselves, we are doing a disservice to future generations.”
The typical ROI on green waste processing equipment depends on what the machine is capable of processing and how an operator can make money doing so, Donovan says.
“Railroad ties are a perfect example,” he says. For those, CBI offers the Magnum Force Model 8400-P Horizontal Grinder.
“It is more than capable of processing green waste, but in order to achieve the ultimate ROI, you have to have a machine that can enable you to service several markets,” he says. “The 8400 is not only an extremely efficient grinder in construction and demolition debris, but can be converted to a chipper to make perfect fuel chips out of green waste or even uniform micro-chips for the pelletizing industry.”
The entire line of CBI’s downturn horizontals—the 5400, 6400 and 8400—can all have two different grinding and two different chipping rotors.
Andreas Schwartz, president of Lindner America, points out that because organics “are typically wet and of low caloric value, they are not a desirable part of alternative fuel. We typically remove it from the process so it can be composted or landfilled.”
The biggest challenge in size reduction is the high volume of material that needs to be processed, he says.
“Many require two-inch minus fractions at a rate of 20 to 50 tons per hour,” Schwartz says, adding his company has developed shredders to handle that kind of volume.
“Our secondary shredders have a unique rotor design that allows for very high output while making fractions as small as one-half inch,” he says.
The shredders are designed for maximum up time and minimum maintenance, he adds.
“We have a maintenance flap that allows quick and easy access to the cutting chamber without spilling the entire load,” Schwartz says. “This comes in handy when trapped metal has to be removed. It also makes tool changes easy.”
With the equipment’s adjustable counter knives, the life of tools can be stretched out while maintaining good output, he adds.
Composting done incorrectly can be a “dirty and smelly job,” Rotochopper’s Korn says.
“Proper processing techniques—grinding material to the correct size, aerating the ground organics pile—results in a premium finished compost product without the unpleasant odors,” he says. “Grinding is one of the most important steps in organics processing.”
One of the biggest challenges is the moisture content of typical organic waste sources, including yard waste and food waste, says Korn.
“As moisture content increases, horsepower efficiency often decreases,” he says. “High moisture feedstocks do not pass through screen openings as easily. Additionally, high moisture materials may cause buildup. Some organic waste materials, such as municipal yardwaste, may contain higher levels of abrasives than wood waste and other feedstocks, increasing wear rates.”
Rotochopper grinders are built to consistently process large quantities of gritty, abrasive organic waste and do so “perfect in one pass”, says Korn.
“Numerous Rotochopper customers process hundreds of tons of organics per day, ranging from green waste to wood waste to fruit, vegetable, and bakery food waste,” he says. “A grinder that produces a consistent finished product helps ensure that organics will break down consistently and completely.”
Korn points out that versatility is essential as waste handling companies continue to diversify into different recycling markets with different raw materials and end products.
The Rotochopper horizontal grinders are designed to allow operators to quickly and easily switch feedstocks and end-product specifications.
“You can grind wet green waste for compost in the morning, and within minutes, change screens and be grinding wood waste into colored landscape mulch in the afternoon,” Korn says.
Tracked mobile grinders allow easy moving around large recycling yards. A line of electric grinders are designed for stationary operation to offer a cleaner, simpler operation that can be integrated with sorting systems, material handling systems, and other equipment, he adds.
The primary maintenance components in organics grinders are the teeth, which do the grinding, and the screens, which do the sizing. All high-speed, horizontal organics grinders have teeth and screens.
“Wear costs of different grinders will vary based on the number and style of teeth, size of screens, and direction of grinding rotor rotation, such as up-swing versus down swing,” says Korn, adding that Rotochopper grinders have designs tailored for the urban and municipal waste streams for lower operating costs.
Compost is the most common end market for Rotochopper systems.
“The soil is the best final location for processed, composted organic waste,” says Korn. “For waste streams comprised primarily of woody debris, many businesses grind and color wood waste into colored landscape mulch. For green waste streams, many businesses blend green waste with dry construction wood for a boiler fuel product."
The typical ROI on investing in green waste processing equipment varies on location, local landfill dumping fees, local competition for the waste streams, and the local options for other compost, mulch, and soil amendments, says Korn.
“Most businesses aim for an ROI of three to five years, although a well-run facility with good inbound tipping fee revenue and healthy end markets can see a more rapid ROI,” he adds. “The combination of inbound tipping fee revenue and end product sales revenue makes recycling an attractive business opportunity whether it's food waste recycling, wood and green waste recycling, or scrap metal recycling.”
The ROI varies widely with regional commodity markets, Korn says.
“Some regions throughout the United States have very mature compost markets that are comparable to landscape mulch markets, while other regions show very little activity in markets for compost made from organic waste,” he says. “The undeveloped compost markets are starting to grow in some regions in much the same way as the colored landscape mulch markets.”
What do MSW operations need to consider when deciding what equipment they need and how to enter the organics recycling market? Korn suggests:
How much organic material is available in your market?
How many tons per day can you capture?
What are the local landfill dumping fees? The higher the landfill dump fees, the higher price you can charge at your own site, says Korn.
Where will you locate your operation? “Each city, county, and state has zoning, permitting, and environmental requirements to comply with,” Korn says.
What end products will you produce—compost, colored mulch, boiler fuel?
“Raw material volume and end product requirements, including particle size, help determine size and horsepower requirements,” Korn says. “Because of the high moisture content of organic waste, clean operation and ease of maintenance access are important.”
Donovan adds a few more questions: Where is the market? What size end product is needed to produce? What level of contamination is there? How will a machine handle contamination? Is there an effective means to protect the machine from heavy contamination? How is the machine built?
Adds Lint: “All operations need to look at overall value, their production needs, resale values, and the manufacturer's reputation for taking care of their customers.”
Efficiency is the primary consideration in entering the organics processing market, Donnelly says.
“The cost of organics processing can be steep if the wrong equipment is applied,” he points out. “The answer is not horsepower which can send your diesel bills soaring but is handling different feed streams with the correct equipment. Organic material can hold a lot of moisture, which is not suited to a rigid hammer arrangement in a grinder.
“For composting, use a slow speed shredder to handle the material on the front end. Making the product a little coarser allows air and moisture to move through the material, allowing Mother Nature to allow the product to decompose and mature as opposed to using a high-speed grinder with more significantly higher operating costs that also makes the product too fine and will require more handling and cost to aid in decomposition.”
Schwartz says MSW operators should look for an experienced supplier with references that match a particular project.
“One cannot assume that if a supplier can do 5 tons per hour that he can easily scale up to 20 tons per hour,” he says.
Powe’s advice to others is to operate a windrow turner and a grinder.
“We run our grinder too much and are using our grinder as an aerator. We need a machine just to aerate,” he says. “Our next purchase is going to be is a windrow turner to cut down on the amount of grinding time.”
Factors that solid waste operators need to consider when choosing recycling equipment center on productivity, Wenger says.
“They don’t want to spend 24/7 trying to process their material,” he says. “They certainly want to get something capable of doing the job and not constantly having more material coming in than they can process.”
Reliability and machine longevity is another consideration, Wenger says. When an operation is investing a lot of time in recycling materials, but is doing so with a less expensive machine, it may break down more often and in the long run, the operation is losing time and money in fixing the machine, he adds.
Choosing a machine size depends on the type of material being processed.
“If you’re looking to grind bigger materials such as stumps and if there’s a chance of contamination of metal and rocks, you’re better off to buy a used big machine than you are to buy a smaller new one,” Wenger says.
“It depends on how many hours they’ll be using it and the amount of material coming in,” he adds. “Some customers don’t have enough material coming in to justify a $600,000 grinder but they can justify a $200,000 used one.”
Before Murfreesboro started its greenwaste operation, the city put out specifications and hosted six machines for demonstrations, something Smith advises any MSW operation to do if considering such a program.
“Not everybody is going to get a Diamond Z or a HogZilla or a DuraTech—it’s really going to matter on what they’ve got and what they’re willing to do,” says Smith. “When we got the machine in 2005, it was a half-million dollars then.”
Smith also advises visiting different cities to see their operations.
“There also are a lot of private industries that do this and they do make money,” says Smith. “Sometimes it might not be in the cards to do it yourself, but it may be from a joint private/public partnership. There are so many different options out there. You don’t have to leave any stone unturned.”
Delaware Solid Waste Authority
The Delaware Solid Waste Authority is a full-service solid waste management facility that even at the time it was constructed in 1986 was starting to recycle items such as tires and other waste, notes James Vescovi, facility manager.
“Over time, we have expanded the focus of other recycling, adding drywall, propane cylinders, electronics, and other recycling,” he says. “We’ve gone through the traditional expansion and changes in focus of service for solid waste management.”
Part of that transition entailed diversion of construction and demolition waste, which the facility labels as ‘dry waste’.
For seven years, the dry waste was being handled by an offsite contractor who had beneficial use approval from the state of Maryland for alternate daily cover.
The Delaware Solid Waste Authority took over that part of the program in 2007, making its own ABC rubble.
“We thought we could a lot more,” says Vescovi. “At that time, it was about 25,000 tons. We thought we had 50,000 tons available, so we decided to buy the equipment for ourselves and get a higher percentage of the waste stream.”
The Delaware Solid Waste Authority purchased a Continental Biomass Industries machine, choosing it among three high-speed machines in a demonstration.
“One of the chief reasons we picked the CBI machine was because it was going to produce a material that was similar to the material we had already approved through the other vendor for an alternate daily cover,” says Vescovi.
The slow machines produce a more coarse material, he notes.
“I did a field trial onsite with a slow-speed machine, which was a nice machine, but it had a lower capacity of tons per hour,” Vescovi says. “We were looking at going 25,000 to 50,000 tons a year. This machine was a little bit slower and we didn’t think it would be able to stand up to it.”
The CBI machine processes 50 to 75 tons an hour. The Delaware Solid Waste Authority has discovered items it will not process well, such as palm trees, which gum up the screen, Vescovi says.
A high-speed machine can be high maintenance, Vescovi says.
“There is significant maintenance for wear and tear,” he adds. “We’re replacing strikers. We were doing it manually and we eventually switched over to using pneumatic tools for changing the strikers. We tried aftermarket strikers compared to original equipment manufacturer strikers. Depending on the types of material you’re using would determine the OEM strikers are about as cost-effective as the aftermarket ones. We look for aftermarket supplies because those are predominantly big expense items.”
There also is a magnet that came with the original purchase that has become a maintenance item. “It has all kinds of trash on it if you don’t maintain the belt and put some additional guards on it,” Vescovi says.
Vescovi says the Delaware Solid Waste Authority has had a good experience with CBI.
“All machinery of this nature is expensive,” he says. “The machine we have was relatively new at the time. We’ve had problems with it, but we’ve had adequate technical support in a timely matter.”
The Delaware Solid Waste Authority derives a revenue stream from some of the steel, Vescovi notes.
“We have a material handler with an orange-peel grappler and by virtue of feeding it or sorting the material with the orange-peel grapple, we are able to recover steel and yardwaste,” he says.
The Delaware Solid Waste Authority also pulls out drywall, with Vescovi pointing out that the facility’s H2S numbers increased with drywall recycling.
Vescovi says the Delaware Solid Waste Authority uses the same machine with the same strikers to produce an end product.
“We don’t change the strikers for shredding yard waste because it’s used onsite,” he says. “Yardwaste runs through it like butter with the C&D strikers. It’s not to our economic advantage to buy a set of wood strikers and shred and change the screen and produce a high-quality wood product, which I’m sure we can with the machine.
“We don’t produce a high-quality shredded product because we use material onsite. We have a small portable composting system. We run the unscreened, shredded yardwaste through that system, and then we use that as a soil amendment for establishing vegetative cover at the landfill. We can use 100% of that onsite.”
In previous years, the Delaware Solid Waste Authority sold surplus to other composters who needed a carbon material to augment their biosolids.
“We continue to divert some of our yardwaste to them, but it’s not to our economic advantage to spend money on the labor and purchase the extra screen and extra strikers,” says Vescovi. “We have a lot of undigested wood trash in the compost, but that’s OK by us. We’re just combining it with topsoil and using it as an anti-erosion component in the topsoil cover.”
The Delaware Solid Waste Authority has done an economic analysis on the cost of purchasing to own the equipment and the operation of the ABC process as a whole.
“We evaluate that periodically to determine if it’s cheaper to landfill the C&D and other dry waste components versus diverting the dry waste to produce an alternate daily cover,” says Vescovi.
That evaluation encompasses 12 components, including airspace, solid waste, the cost of soil to replace the alternate daily cover, and the cost of the equipment.
Fixed costs such as labor and variable costs such as fuel are tracked monthly. The Delaware Solid Waste Authority periodically reviews the costs.
“It’s still to our economic advantage to use the alternate daily cover as compared to landfilling it,” says Vescovi. “One caveat with that is the additional hydrogen sulfide that you may or may not create by grinding the dry waste versus just landfilling the dry waste.
“You can’t quantify it because you don’t know how much more hydrogen sulfide you’d get out of a pound of drywall if you shred it in the ABC versus just landfill; I don’t think there’s any state of technology that can tell me what the difference is. We’re sensitive to whenever we’re thinking about grinding the dry waste, but at this point, there is no way to quantify it.”
Carol Brzozowski specializes in topics related to waste management and technology.