Grinding greenwaste not only keeps it out of landfills, but also creates valuable mulch for erosion control projects.

By Janis Keating

Greenwaste involves much more than residential grass clippings and dead leaves.

In areas of new construction, tons of greenwaste—unwanted brush and trees—must be cleared before building can begin, and much of that waste has traditionally ended up in landfills. Many MSW facilities now not only separate plant matter from the wastestream, but they also process it into valuable compost and mulch, which is in turn distributed to homeowners, government agencies, and landscapers.

PHOTO BANDIT INDUSTRIES

Stop and Chop
As home gardeners know, plant matter breaks down into compost much faster if it’s been chopped into smaller pieces. The same holds true for the greenwaste gleaned from construction sites. However, although a gardener can chop up shrub trimmings with a few swipes of the lawnmower, chopping a 5-caliper-inch scrub pine is a different matter, so MSW facilities use chippers, grinders, or trommels to get the job done.

South Bend, IN’s Environmental Services recycles yardwaste for its residents and those in neighboring Mishawaka. “We have once-a-week curbside pickup for city residents, and we also have account customers, such as landscape companies,” says Superintendent Ken Smith. “For the past three years, we’ve used the Bandit 3680 to grind all greenwaste and leaves, which we then windrow and compost.

“We screen and sell the end product as finished compost, but we also have ‘giveaway’ programs, for city residents; for example, if you load it yourself into your pickup, you get it free. In addition, city departments, such as the water, street, and park departments, also use this compost.”

Although South Bend’s Bandit 3680 is primarily used to grind greenwaste and leaves, Smith also uses it to reduce larger wood, such as tree removals and trimmings from the city’s parks department. “Local tree companies can also bring that sort of waste, but they are subject to a tipping fee,” he explains.

South Bend’s 3680 Beast Recycler, manufactured by Remus, MI’s Bandit Industries Inc. (banditchippers.com), is one of Bandit’s most popular waste reduction units. Available with a variety of power options with horsepower ranges from 350 to 645, the units can be purchased with 12- and 30-foot discharge conveyors, as well as a hydraulic thrower for loading end-opening vans or trailers. The 3680 can make short work of many projects, as it features a three-speed infeed conveyor drive and a two-speed discharge drive.

“We’d used a tub grinder in the past,” Smith reports, “but it required two guys to run it—one in the cab, and one at the grinder. The horizontal Bandit is more of a one-man operation, and we can run close to 120,000 cubic yards of material through it. We’re happy with the 3680—we get good parts and customer service from Bandit—they give wonderful service.”

PHOTO BANDIT INDUSTRIES

The Bandit 4680 is able to process entire trees.

PHOTO: CONTINENTAL BIOMASS INC.

CBI's 4000B Magnum Force grinds away in Warwick

Keeping Greens Out of the Wastestream
In some areas, MSW facilities don’t get the greenwaste, because the producers of the waste process it themselves. For larger projects, JEH/Volvo Rents in Memphis, TN, employs the Bandit 4680. “We grind greenwaste, trees, and stuff, mostly from land clearing—and we also did some grinding in Florida last year after the hurricanes,” says Eric Hinshaw. “Using a 6-inch screen, we ground up trees damaged by the hurricane that went through Pensacola, Florida. We were working for Florida DOT, which then used the ground-up waste for various erosion control purposes. Here in Tennessee, many mulch suppliers get their ‘ingredients’ from us.”

Bandit’s 4680 Beast Recycler, which offers horsepower options up to 860, features a 57-inch-diameter mill that’s 63 inches wide, with a 40-inch-high by 60-inch-long opening. Stumps and logs 40 inches in diameter and larger are no problem for the machine, which is also excellent for processing whole trees—up to 500 cubic yards of material per hour. Bandit’s unique patented cuttermill allows materials to be cut, split, or ground, providing various types of end products. Although the 4680 weighs 73,000 pounds, it’s easy to transport and can be set up for operation in just 10 minutes.

Chestnut Mountain, GA’s A+ Lanier Tree Service finds use for both a Bandit 3680 and 4680.

“The units produce different horsepower, and there’s a tremendous difference in their grinding abilities,” says owner Kelly Smith.

“When I first started out, I was clearing individual house lots, and needed to get into smaller spaces. The 3680 is a smaller machine, horizontal, so it’s easier to get into tighter spots, and it didn’t throw chips around, making for easier cleanup. For bigger jobs—let’s say, clearing sites 6 to 8 acres and bigger—I use the 4680. It’s an impressive piece of machinery. We took our 4680 to Florida in 2004 for hurricane cleanups.”

Turning “grindings” into “mulch” arose as a cost-saving measure. Builders in the area, which is 50 miles from Atlanta, first made the connection that cleared greenwaste could have a purpose. “It’s very expensive to haul off the grindings to a landfill,” Smith explains.

“We were grinding it for less than if they hauled it, and the builders now have a good-looking mulched product around their landscaping. They also realized that mulch is one of the things used for erosion control. We grind up the trees and shrubs they’ve knocked down, and they use the grindings as mulch behind silt fences.” Certain parts of the year, the woodwaste can be incinerated in a pit burner, but during burn ban season (May 2–September 30), A+ Lanier Tree Service uses the Bandit 4680 to quickly grind flammable waste.

Smith prefers Bandit’s products for several reasons. “Beast grinders, compared to tub grinders, use a lot less fuel,” he says.

“Although some are self-propelled machines, I have tow-behinds, which are about the length of a tractor trailer. However, both machines are overwidth, so I need permits to move them on the roads.

“Another thing I like about Bandits—the infeed slot sits low to the ground, allowing me to do a better cleanup with a crawler/loader,” he goes on. “My usual procedure is to use a backhoe or trackhoe and crawler/loader to bring the scrap to the grinder machine. Although they may be good machines, some other manufacturers’ grinders’ infeed tray sits about 3 feet higher in the air, which would prevent me from using crawler/loader—resulting in more time, and more labor costs.”

A+ Lanier Tree Service has used Bandit machines for nearly four years. “It’s the only kind I’ve ever operated,” Smith reports. “I know how to use it. I think most people who get involved in grinder business start out with a machine and if it suits their needs, when they learn it, they usually stick with it. People have tried to sell me other machines but I know where I am with Bandit, and I’m sticking with it. Plus their sales reps all do a good job—they want to know about your satisfaction with their machines.”

As its name states, Newton, NH’s Continental Biomass Industries (cbi-inc.com) produces grinding machines primarily for greenwaste disposal. The City of Warwick, RI, uses a CBI 4000B Magnum Force grinder to compact greenwaste and create mulch and compost. Specifically designed for super-high production of yardwaste and throughput of uniform, high-quality mulch, CBI’s 74,000-pound, road legal, 4000 series features 860- to 1,030-horsepower Cat electronic engines and built-in pre-screeners, and some of the machines’ operations are radio controlled.

PHOTO: PETERSON PACIFIC

“We grind leaves into compost with our CBI 4000B Magnum Force,” says Joel Butler, a senior equipment operator for Warwick’s Highway Department. “We not only process residents’ waste, but also that from about 45 local landscapers. Landscapers bring in a lot of the grass, brown [dead bushes, leaves, et cetera], and greenwastes. We grind the material, put it in windrows, and flip it with payloaders once it reaches 130 to 140 degrees. We screen it too, to make it a nice uniform size, and get it ready for sale in about nine to 12 months. The city makes use of this compost; sometimes the state takes a few loads as well. Our city residents get it free, although landscapers have to purchase it from us.”

Warwick’s Highway Department, which has been composting for a decade, purchased the CBI 4000B in fall 2004, when it “outgrew” its former grinder. “The CBI distributor is only two hours away, and I liked the machine,” Butler says. “It was more money than some other brands, but worth it.” Alluding to CBI’s corporate logo, which includes a large bear, Butler suggests that operations needing to “go big, go ‘grizzly.’ You can’t fill it up; it’s hungry!”

Grinding Green and Grey
In Tennessee’s Williamson County, the Solid Waste Department grinds greenwaste and construction-and-demolition (C&D) waste with CBI’s 5060 Grindall. Due to its tolerance to metal and aggregate, the Grindall can grind C&D waste down to a fine, uniform 3-inch product. This vertically fed rotary hog, available in both portable and stationary units, comes equipped with Cat engines ranging from 860 to 1,030 horsepower.

PHOTO BANDIT INDUSTRIES

PHOTO BANDIT INDUSTRIES

“We started our grinding program five years ago; at that time, the landfill here had a very short life,” explains Solid Waste Director Lewis Bumpus. “We started a clean woodwaste—storm debris, development waste, Christmas trees—program immediately, to help lengthen the landfill’s life.”

Bumpus explains why his operation chose the Grindall: “We wanted the one machine because it does both jobs. Generally, a vertical grinder will halve less long pieces of wood better than a horizontal grinder will. We find the Grindall works well for both our C&D and clean woodwaste programs. When we take logs and stumps we use a shear with a hydraulic thumb, and we haven’t found wood we can’t bust. We make the wood the size for our grinder; the wood has to go over a conveyor, in up to 8-foot pieces, although it’s usually 6-foot.

“We then class the wood mulch into whatever application we need it for. With a four screen, the grinder makes a good erosion control mulch end product—a second pass-through is not required.”

Much of the mulch and compost Williamson County Solid Waste creates is used onsite. “We use it a lot for vegetative growth and erosion control,” Bumpus says. “There’s a lot of bioengineering on this site. For example, Tennessee ordinance 303 had listed one of the streams on our 408-acre site as ‘impaired from original use.’ Since we’ve used trees/mulch for silt control, the state has delisted the stream at the landfill, since the stream has been returned to ‘pristine condition.’ One now even supports 26 species of fish!”

A mulch berm was part of the solution. “Our stormwater is directed into a mulch berm 15 feet wide on a 4:1 slope. The berm, which has a fall of 1%, is about 5 feet tall and 800 feet long.

“Stormwater leaks through, but the berm stops the silt from reaching the stream. We cut down on downdrain down the hill, cleaned all the silt of out the drainage. This produced a 6.5-acre aerated bioreactor, which, three years later, was covered with a foot of mulch. When the EPA came out to monitor the site, it found 98 different species of plants grew here, and we hadn’t sown anything! Some were native plants, and one was even on the endangered list. Now that’s progress.” Bumpus also reports that the Tennessee DOT has approved three of the site’s different engineering practices for mulch for state highway projects.

Williamson County, some 30 minutes south of Nashville, is home to many internationally known country and western music stars, and new housing developments are always underway.

“With C&D wastes, we pull out metal, brick, cement, and carpet, and compost the rest,” Bumpus says. “We’ve been experimenting with taking some sheet rock waste and putting it with clean tree waste, to see if the lime will change the pH of the waste.

“We run over the C&D with a Cat 826 with chopper wheels, then screen it. The screening plant we have is on tracks, much like a rock crusher, if you can picture that. When C&D waste is composted for six months, it takes on more dirt-like qualities. With the green-/yardwaste, we put it into windrows and let it cure 180 days.

“We don’t like to turn material loose earlier than that if it’s going to be for vegetative purpose, because we don’t want to ‘burn’ the plants.”

At this time, Williamson County’s compost/mulch is only sold to large construction outfits. “We put it into class 8 trucks with a 12-foot-wide bucket to haul it out,” Bumpus says. “We’re trying to get to a program where residents can have it, but right now the compost is moving as fast as we can make it. When construction in this area slows down, maybe we can get it to smaller customers.

“Maybe by this July we can sell to landscape markets.”

Janis Keating is a frequent contributor to Forester Communications publications.

MSW - May/June 2005