Dealing With Greenwaste

May 1, 2000

Spurred by state mandates barring the landfilling of greenwaste, the processing of these organic materials increased greatly in the last decade. Larry Burkholder of Morbark Inc. in Winn, MI, estimates that 70% of all the landscape clearing materials in the state of Florida are no longer being landfilled; they are processed and reused as soil amendments or energy fuel or are left onsite. Moreover, yardwaste is now being routinely source-separated, collected, and recycled in many parts of the country. The trend is so pronounced that it is changing the support industry. Dave Benton, marketing manager for Peterson Pacific in Eugene, OR, recalls that just five years ago, 80-85% of his company’s sales of grinding equipment were with the forestry industry, with just 15-20% of equipment being sold for recycling. Today that ratio is almost completely reversed. “We’re still in the forestry market,” he says, “but today most of our equipment is being sold to recycling yards, landscapers, clearing contractors, or solid waste facilities.”

“This trend is quite logical,” contends Morbark’s Dan Brandon. “This type of organic waste represents 30% of the entire wastestream, and it is the easiest portion to remove and recycle. It has helped a number of communities meet or come close to meeting their diversion requirements at a cost they could afford.”

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations.  6 Tips for Excellence in Landfill Operations. Download it now!

These diversion regulations, as well as the outright banning of landfilling greenwaste imposed by some states, undoubtedly launched the trend toward recycling greenwaste, but landfill operators were quick to see the profit potential of alternate disposal. Bruce Rizzoli of Cold Canyon Recyclers in San Luis Obispo, CA, explains why: “We’re in the landfill business, and we charge a tipping fee for every pound of waste that comes in. If we can mulch, compost, or otherwise process that greenwaste so that it can be reused, we get those tipping fees without using up valuable landfill space. The trick is to do that processing at a reasonable cost.”

Conserving Landfill Space

Cold Canyon Recyclers tries to reuse every bit of greenwaste that comes in. The pallets, lumber, and tree branches that are delivered go into a wood pile and then are ground up by a Peterson 2400 grinder with a 4-in. screen for cogeneration fuel. The yardwaste goes into a separate “green” pile. It too is ground by the same grinder, but because residents often throw metal and other contaminants in their yardwaste bins, Rizzoli cleans up the ground yardwaste with a Wildcat trommel.

“We screen after the grind with a 2-inch-minus screen, which removes this trash and a lot of the high-carbon shrubbery material. [The trash is discarded and the other overs are used for a mulch product or combined with the wood for cogeneration fuel.] We push the screened yardwaste into 4- by 12-feet windrows that are 500 feet long. Using a Wildcat 117 turner, we turn the windrows twice a week, adding water when necessary. After 90-120 days, we perform the mandatory pathogen reduction test and then a maturity test. When the compost is ready, we rescreen it with the Wildcat trommel with a 3/8-inch-minus screen.

“It’s an expensive process, but it produces such a good-quality product that we can easily sell it. The process doesn’t make a profit, but it is a break-even proposition. Best of all, it gets rid of all the greenwaste so that we save that landfill airspace. We calculate that this approach will extend our landfill life by 12-14 years.”

Darrell Hournbuckle, assistant city engineer for the City of Jamestown, ND, has calculated the economic benefit of extending landfill life. The Jamestown operation is similar to that in San Luis Obispo, except that it uses DuraTech equipment (tub grinder, trommel, and windrow turner) and gives its compost to residents at no charge. Even so, he claims, the operation pays off.

“The landfill tipping fees are $30 per ton,” he explains. “This cost includes operation and maintenance, amortized capital costs, and long-term set-asides for closure and postclosure costs. Our 1998 costs for the yardwaste program were $45,000 for collection and $15,000 for composting 2,000 tons. Thus, the cost was $30 per ton—the same as the tipping fee. However, the avoidance value of the compost was approximately $44 per ton. This is the cost of the tipping fees, the transportation costs, and the loss of interest if the yardwaste was placed in the landfill as an alternative cover. Thus, the composting operation costs are significantly less than the avoidance costs.”

Of course, Jamestown’s composting operations (and costs) are helped considerably by the fact that DuraTech supplies a grinder and the labor to grind up the greenwaste and lends the city a trommel to screen the compost. Hournbuckle estimates the value of this support at about $25,000. Still, the composting operation pays off handsomely. For every year the construction of a new cell can be delayed, the city earns approximately $17,000 in interest. In addition, the city can place waste for additional years using existing facilities. Hournbuckle estimates that if just two years of landfill life are added, the city will gain $1.5 million in additional revenues for other waste that can be added to the landfill at a $30/ton tipping fee.

It wasn’t economics that drove Pennsylvania’s Derry Township to process greenwaste; it was the sheer volume of the leaves that fell each autumn. For years, the township just let them lie where they fell on town property, but the rate of decomposition was simply too slow. In 1994, the town built a new facility to compost leaves, recalls Public Works Director Tom Clark. The quality of the compost was inferior, however, and the town couldn’t give it away.

“That created a bigger problem than ever,” Clark says. “Each fall, our five crews would pick up 4,500 cubic yards of leaves over a six-week period. It wasn’t long before we were almost literally buried in leaf compost that we couldn’t dispose of fast enough. Finally, we realized that we would have to improve the quality of our compost if we were to get rid of it. We bought a DuraTech leaf turner, and that made all the difference.

“Now each fall, the trucks bring in their loads of leaves to form a windrow 10-12 feet wide and 5-6 feet high. Then our leaf turner goes through this square windrow and turns it into a mounded row, fluffing and shaping the pile in the process. It turns the windrow once a week. Within six months (four, if it’s a wet year), we have a usable product that we give away to residents and to the township for use on its athletic fields. For the athletic-field application, we screen the compost with a DuraTech trommel to remove any large chunks. Conversely, the residents take the compost just as it comes off the windrow.”

Clark also has a system to make mulch from woodwaste. For this, he uses two DuraTech grinders in series to grind tree trimmings, brush, and yardwaste to produce “a nice double ground waste in about two months.” As with the compost, this mulch is very popular. Residents come to the center and either bag it or shovel it into their pickups.

“All in all, we produce about 3,500 cubic yards of compost and mulch,” Clark reports, “and no longer does it pile up on us. I suppose that we could sell it instead of giving it away, but this way we’re meeting our requirements to reduce the amount of plant material going to the landfill and we’re providing a service for our residents.”

Savings Without Revenues

One of the largest greenwaste programs that does not seek revenues from its processed products is in Los Angeles. The city generates about 1,800 tons of yard trimmings each day, which are mostly processed by subcontractors in various areas. The city, however, has one facility that processes more than 200 tpd of yardwaste in addition to about half as much woodwaste from the city’s tree trimming program. Started in 1994 when it produced just 9,000 tons of mulch, this operation produced 83,000 tons of mulch in 1999 (at least 300 tpd). And despite this volume of quality mulch, it gives every bit of it away free.

currently operating at a site owned by the Los Angeles Department of Water & Power (DWP), the Van Norman Yard Trimmings Recycling Project, as it is known, produces two products: (1) fines consisting of grass, leaves, and other 3-in.-minus greenwaste and (2) a coarse mulch product consisting of the 3-in.-plus yard trimmings and the brush and tree trimmings ground to a spread-ready size and condition. Every day, project personnel truck the fines to citrus growers, avocado growers, and other farms in southern California. The mulch is distributed to other city agencies, including Recreation and Parks, Street Services, and the DWP, for weed abatement, erosion control, and beautification. There is no charge for either the mulch or the trucking services, although the DWP provides the use of the project site in exchange for the mulch and the spreading of the mulch on its property.

The operation of this large project is quite straightforward. Incoming yardwaste is dumped into a Morbark 7-ft.-wide x 37-ft.-long trommel, which separates the fines and aerates the mulch. The 3-in.-minus fines are then loaded on trucks for delivery to agricultural users. The overs are conveyed to a covered Morbark picking station where a crew manually removes contaminants introduced in the curbside collection.

“This is by far the most labor-intensive part of the process,” says Greenwaste Recycling Coordinator Matt Wood. “It takes a crew of 14 pickers to pull out all the trash, which may consist of rocks, metal, tires, and hubcaps. We have four 40-yard rolloff bins under the picking station, and we have to dump these at least twice a week.”

The cleaned greenwaste and log/brush feedstock is then placed in two Morbark 1300 tub grinders that turn them into a spread-ready mulch. There is no need to rescreen the mulch for the markets currently being served. The mulch is placed in a pile from which project personnel make deliveries to agencies using the material.

“We have developed an extremely efficient operation that we hope will be the model for other city projects of this kind,” Wood remarks. “We really have a bare-bones staff, consisting of just four equipment operators, a maintenance laborer, and me, plus the 14 pickers and seven truck drivers who drive an average of 300 miles a day to deliver the product to users. We are the largest greenwaste processor in California, yet our cost to process all of this greenwaste and tree trimmings is just $18 per ton. That’s a total of $1.5 million per year to yield $2.5 million in annual tipping-fee savings alone. And that doesn’t reflect the value to the city of the mulch used by other city agencies.”

The Need for Revenues

That would appear to be quite a good payback just from cost avoidance, but Howard Fiedler for one doesn’t think recyclers can or should base their operations on cost avoidance alone. The executive of Erin Systems Inc. in Portland, ME, insists that “the only operators who can succeed are those who can generate profits from the processing itself. They must develop the markets for supply as well as for product so they can economically get a reliable, steady supply of feedstock and then get the finished product off the site without delay. Today, planning operations solely on the basis of getting positive revenues from tipping fees is a recipe for disaster.

“More and more, our customer base is composed of ‘mini factories,’ [with operators] that are interested in equipment that can produce all day, every day, and in all conditions in order to keep up the production levels required for maximum return and efficiency from that equipment. In this business, the companies that understand producing at the lowest cost per yard or ton manage to make the greatest margins and survive and prosper in what can be a very tough environment.”

Erin manufactures a product called a Fingerscreener that is designed to screen the roughest infeed materials, including stumps, construction and demolition (C&D) debris, landfill debris, contaminated soil, woodwaste, and rough topsoil. Its self-cleaning finger screens enable it to separate these materials at a high production rate without clogging.

Erin also manufactures a Starscreener that can be used to separate and size a variety of organic materials, including compost, woodwaste, bark, mulch, manure, and topsoil. It uses specially designed, long-lasting rubber stars mounted on a series of high-speed rotating shafts. As a result, it can screen greenwaste and composts with as much as 60% moisture content without clogging. Organic Resource Management Inc. (ORMI) of St. Louis, MO, uses a Starscreener at the end of its compost pile instead of a trommel. ORMI President Jim Wolterman remarks, “The Starscreener was particularly helpful this past spring when we had a heavy moisture content. We could still screen materials at 0.5 inch minus and maintain production rates all day, every day.”

Morbark also embraces this factory concept for the processing of organics. According to Burkholder, operators are looking for value-added processing, over and above just grinding for volume reduction. They’re trying to squeeze the last dollar out of any equipment they buy. “To meet those needs, we have developed an integrated system that combines a tub grinder, a trommel, and a color machine to produce colored mulch. We have matched the speeds of these three modules so that even though the grinder is grinding C&D and white wood materials at as much as 90 tph, this output does not overload either the trommel or the color machine. Conveyors simply send the material on to the next module without stopping. Thus, the operator handles the material just one time rather than six. That saves time as well as labor costs.”

Profits As Well As Revenues

Tim Jelus is one operator who believes in this high-production factory approach to processing. His Melbourne (FL) Landfill and Recycling Facility was originally a 20-ac. C&D landfill that he expanded to a 40-ac. Class III landfill and began recycling operations. Today he receives three wastestreams: clearing debris from land-clearing contractors, new construction debris in rolloff boxes from contractors, and greenwaste and residential yardwaste from Brevard County.

“After being cleaned, the clearing debris and the construction woodwaste are processed for recycling,” Jelus explains. “They are ground in a large Morbark 1400 tub grinder whose output is conveyed to a three-deck trommel screen that separates the material into three products: (1) 0.5-inch-minus fines, which are then mixed with the greenwaste for composting; (2) greater than 2-inch material that is sold as a low-cost mulch; and (3) 0.5- to 2-inch mulch that is conveyed to the Morbark coloring machine. This colored mulch is then sold to a bagging plant that supplies Home Depot.

“The composting process involves first mixing the greenwaste and the wood overs and grinding them. After mixing in the fines, we place the blend in a static pile. We water it occasionally, but in this humid Florida climate, it pretty much decomposes on its own in 60-90 days. Then we run it through the trommel screen, and the result is a decent bedding topsoil product. We don’t aerate or turn this compost because my experience is that every time you touch a compost pile, you spend money, and for us it just isn’t worth it.”

Jelus has only been recycling since August 1999, and he confesses that he still makes most of his money from landfill tipping fees. Still, less than six months after obtaining the Class III permit, the facility is turning a profit on its recycling operations. And since he just received approval to add another 30 ac., he will be able to expand these operations. “Turning a profit so quickly on the recycling operations is phenomenal,” he says. “Now we’re getting a profit on the outgoing as well as the incoming material, we’re producing an environmentally sound product, and we’re conserving landfill airspace.”

As Jelus expands, he might well look at the Monterey (CA) Regional Waste Management District, which earned SWANA’s award for the best solid waste system in North America in 1998. As part of its recycling operations, the district creates a variety of landscaping products from the woodwaste and yardwaste it receives. From the yardwaste grind, the district produces fines, mulch, and ground cover. From the woodwaste grind come small wood chips, used for decorative landscaping (in natural or colored versions) and large wood chips, which may also be sold for landscaping or biomass fuel or used as a bulking agent in the sewage-sludge composting process. According to Site Superintendent Jim Griffith, the district diverts 100% of the greenwaste that comes on-site.

The grind itself is an assembly-line process. “The greenwaste is dumped on a walking floor and is fed up an inline conveyor,” describes Griffith. “It then passes through a shaker screen to get rid of dirt and inerts and drops onto a feed conveyor with magnets that remove any ferrous metals. The cleaned material then drops into the Peterson grinder that grinds it down to 2-inch-minus material. The ground material then drops onto another magnet-equipped conveyor, which takes it to a trommel screen that separates it into 0.75-inch-minus mulch. [The 0.75-in.-plus overs are sold as ground cover for vineyards and bedding for dairy farms or blended with the dry wood line for cogeneration fuel.]

“The material stays off the ground from the time it is dumped onto the walking floor until it is a finished product. It only takes one loader operator to feed the walking floor and one operator to monitor the entire operation.”

Mobility Is Key

For most operators, equipment mobility is key to revenues and profits. Jeff Brown, whose father owns Nature’s Earth Products in Arlington, TN, says the company uses two Diamond Z tub grinders to support the tree-trimming, land-clearing, and sawmill industries. The grinder processes trees into raw mulch material. Then the demolition screen is removed and replaced with a smaller screen, and the material is reground. “Then we age it six to eight months,” Brown reports, “and we have a dark, fine mulch that people buy for their flowerbeds and general beautification. It sells very well. Why, we’ve shipped four truckloads to Memphis in the past two days.”

One of the grinders is based in Arlington, although it goes from place to place to do contract grinding for such organizations as a pallet company and municipalities. In addition to doing the grinding, Nature’s Earth Products hauls the ground mulch back to Arlington for a second grind and preparation for sale. “Where possible, we sell finished mulch in those same areas,” Brown says. “That way we have a useful backhaul rather than an empty truck.”

Brown’s other grinder is located an hour’s drive from Arlington. It supports three sawmills, going from one to another as needed. Two employees stay with the grinder, operating a dozer and an excavator. Here, too, the company trucks the ground material back to Arlington where it is reground and processed into mulch. “Between the two grinders, we can cover a 100-mile radius,” Brown estimates. “We use Diamond Z 1262 and 1352 grinders rather than the bigger ones so that we meet highway regulations. They’re easier to get around, and they do a great job wherever we go. We don’t storm chase, though; we’re just too busy locally. Why, there’s one outfit down in Mississippi that’s had brush piled up for a year, but we’ve been too busy to get down there and grind it.”

ORMI’s Wolterman says his company grinds off-site too. “About 60% of our volume here comes in the fall, so we have spare capacity at other times of the year. Our Morbark 1300 tub grinder is quite mobile, so we can do contract work off-site for extra income.”

Kenneth Patterson, president of Packer Industries in Mapleton, GA, sees another market for operators or contractors, assuming they have mobile grinding equipment. “EPA and most state Environmental Protection Divisions have approved letting developers and building contractors leave woodwaste on-site when they complete a development or a home. That means that rather than having to truck all that debris and pay for its disposal, a contractor can have scrap plywood, two-by-fours, Sheetrock, and assorted woodwaste ground up on-site and spread as mulch there. Full-size tub grinders would be too big for this job, we reasoned, so we developed a little 125-horsepower machine that can easily be transported to a home construction site. Then, after it has cleaned up that site, it can be moved on to the next one. Recyclers can perform that function, and we’re seeing cleanup contractors buying the machine and working for eight to 10 builders.”

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations. 6 Tips for Excellence in Landfill Operations. Download it now!  

Fully Utilizing Equipment

Patterson also believes that grinders are being underutilized in many operations because they are only used for greenwaste. “Smaller operators might just grind greenwaste periodically. Our 400-hp machine can grind the entire greenwaste output of a 100,000-resident community in about six weeks. So if that community collects yardwaste weekly, it will just store it until there is enough to make a run. Now, that same machine could be also be used to grind C&D debris, asphalt paving, asphalt shingles, gypsum, and industrial woodwaste and make a usable sellable material from each. Today the Roofing Manufacturers Association is doing a lot of educational work in an attempt to get used roofing materials back into the asphalt mix. This is a natural market for a recycler.”

It would appear that the recycling industry has come a long way from just grinding organics to allow a more efficient packing of landfills. At the very least, recyclers are processing greenwaste so that it doesn’t get into the landfill except perhaps as alternative daily cover. Will the industry as a whole take the next step and expand this type of recycling into integrated, financially viable operations? Myron Holzwarth of Wildcat Manufacturing in Freeman, SD, sees promising signs to this effect. “We’re seeing a difference in the way many operators do business. They’re becoming more professional in their approach, investing in equipment that might cost more but is more productive. The key word is investing as opposed to just buying or leasing. Also, we’re seeing more regional operations that are replacing small municipal operations that can’t afford the investment needed for a viable operation. And best of all, the markets seem to be expanding to justify the needed investment. We’re moving forward.” 
About the Author

Charles D. Bader

Contributor Charles D. Bader is with Dateline II Communications in Los Angeles, CA.

Photo 39297166 © Mike2focus |
Photo 140820417 © Susanne Fritzsche |
Microplastics that were fragmented from larger plastics are called secondary microplastics; they are known as primary microplastics if they originate from small size produced industrial beads, care products or textile fibers.
Photo 43114609 © Joshua Gagnon |
Dreamstime Xxl 43114609