BioCycle July 2004, Vol. 45, No. 7, p. 42
Facilities in New York and Massachusetts employ systems that increase recovery rate of wood, a high value material in the C&D stream.
LIOTTA Bros. Recycling Corp. in Oceanside, New York has its roots in the trucking business. Its fleet of dump trucks and walking floor trailers were used to haul waste materials, including construction and demolition debris, and make deliveries of end products, including topsoil and mulch. “We started realizing that loads we were hauling to the landfill and paying to dump contained recycled materials with market value,” recalls Vic Liotta, owner of the company. “About ten years ago, we decided to move into the recycling end of the business.”
The 3-acre facility on the south shore of Long Island takes in about 70,000 cubic yards of construction and demolition debris annually. In the fall, it also accepts leaves from area municipalities. The leaves are ground and transported to a composting facility owned by Liotta Bros. further out east on Long Island. Since the company shifted to a recycling operation, it has developed strong markets for natural and colored mulches and compost. “The primary markets for our mulch are nurseries, landscape architects and contractors, sold retail and wholesale,” says Liotta. “These products are sold to areas on Long Island, Westchester County, New York and Connecticut.”
WOOD SORTING VIA FLOTATION TANK
Upon entering the facility, the customer’s truck is examined to identify the type of material being dumped and the amount. The customer then is directed to a specific area to unload. The yard is divided into various sections (dump zones) such as aggregates, concrete, brick, asphalt, yard trimmings, clean wood, soil and C&D debris.
Most of the material received at Liotta Bros. is mixed C&D debris. “The main reason we got into C&D debris was because we felt the wood in that stream would make the best colored mulch,” he explains. “This includes pallets and kiln dried wood, which don’t cost as much to color. When we end up coloring wood from yard debris, there is too much moisture and fines, which doesn’t result in the quality of product we like to sell.”
In general, he adds, wood is the most important product to pull out of the C&D stream. “Wood is the highest percentage of material contained in the loads and we can make the highest profit on that material. So it comes in at a high dollar tip fee and goes out at a higher dollar value product, which is ideal. The key is get it clean during the sorting and screening processes in order to maintain its high market value. That means removing plastic, paper and dirt that is mixed in with the wood fraction.”
C&D debris is unloaded onto a concrete pad, where it is inspected to remove oversized items and any materials that could be hazardous to sorters and equipment. An excavator loads the remaining C&D debris into a two deck Erin Finger Screener with 3-inch finger spacing on the top and 1.5-inch square mesh on the bottom. The 3-inch plus material passing over the top is conveyed to a 5-foot by 60-foot picking station. “At this point, the clean wood, metals and aggregates are picked from the belt where they are put into separate bins,” says Liotta. “The remaining material – nonrecyclables – is dropped off the end of the belt into a 100-yard Spectech walking floor trailer and trucked to a landfill.”
The material falling through the 3-inch fingers and over the 1.5-inch square mesh deck (1.5-inch to 8-inch material) passes over a 4-foot air knife powered by a 10-horsepower, 26-inch Timberwolf blower. Plastic and paper in the sorted C&D stream is blown into a 14-inch by 4-foot hood, where the same size blower on the suction side pulls the contaminants through and blows them into a 40-yard container.
The next step in the process – a wet separation phase – both cleans the wood fraction and increases the material recovery rate. Material remaining on the belt after the blower drops onto a 30-foot cleated conveyor belt with a magnetic head pulley and drops into a 40-foot Flo-Cait tank that separates materials with different densities. A sort zone at the front of the tank helps separate the heavy and light fraction using a combination of varying conveyor belt speed and a pump that creates turbulence across the top of the water. Heavier materials fall to a conveyor at the bottom of the tank; the lighter fraction stays on the top conveyor.
At Liotta Bros., the wet separation tank is used to sort aggregates from the wood. “Before we installed the system, we would convey these materials to a second picking station where we would recover some wood, concrete and aggregate,” says Liotta. “Now, we have the ability to sort more recyclables – probably about 80 percent of what is going into the tank – whereas before, we were recovering about half that amount at best.”
The Flo-Cait machine separates the aggregates from the wood. The aggregates are processed in an Excel crusher and sold as road base. The tank uses about 350 gallons of water/day and processes about 600 cy/day. A drag link chain on the bottom of the tank cleans out any dirt that remained on the materials after the screen. Liotta Bros. cleans the tank twice a day -at lunch time and at the end of the day.
The wood – anywhere from 2-inches to 8-inches in size – is fed into a Diamond Z grinder with 1.5-inch screens. Wood recovered on the sorting line – the larger pieces over 8-inches – is ground as well. Next, the ground material is loaded into a Becker Underwood coloring machine to make various colors of decorative mulch. While the wood is slightly moist when it comes out of the tank, a fair amount of water still has to be added during the colorization process. “The kiln dried wood from the C&D stream is the ideal product to color because it has less fines,” he adds. “We use our trees and brush to make our natural brown mulch. On an annual basis, we produce about 43,000 cy of brown mulch, 17,500 cy of dyed red mulch and 13,400 cy of dyed black mulch.”
SORTING STRATEGY IN MASSACHUSETTS
While not in effect yet, it is expected that the state of Massachusetts will ban unprocessed C&D debris from landfills sometime in the near future (see “Sorting, Processing Wood At C&D Recovery Site,” January 2003). In addition, the Massachusetts Department of Environmental Protection has proposed a 70 cents/ton fee on C&D waste going into landfills, viewed by some as an incentive to recycle as much of that waste stream as possible.
Recently, a Waste Management facility in Raynham, Massachusetts installed a 50 tons/hour (minimum throughput) sorting line for mixed C&D debris with a goal of recovering as much wood, metal, cardboard, aggregate and other potentially recyclable feedstocks. An Action vibratory screen was installed at the front of the line to remove the 3-inch minus fines, followed by a magnet to pull out steel. Material then moves to a sorting line where pickers remove cardboard, wood and aggregate. The remaining C&D goes to a CBI heavy duty Magnum 4800 (steel rotor) horizontal grinder to produce daily land-fill cover. “For budget reasons, Waste Management didn’t install a shredder at the front of the line, but the concrete pad and other support infrastructure are in place so it can be added,” says Tim Griffing of CBI. “Shredding the material to a range of 6-inches to 24-inches makes it easier for the sorters to pull out the recyclables.” CBI also supplied the conveyors and magnet.
Chipped wood is sold for hog fuel. Waste Management is considering adding a screen to the end of the line to sort the finer, nonrecyclable material for use as landfill cover. “Landfills are getting more specific in terms of the alternative daily cover they need,” adds Griffing. “The smaller the material, the lower the tipping fee, e.g. one-inch minus material costs less to tip than 3-inch minus which costs less than anything larger. Adding a screen and capturing fines reduces the landfilling costs of the residuals fraction by one-third to one-half.”
RECYCLING AHEAD OF THE SORT FACILITY
A Somerville, Massachusetts organization, greenGoat, is working with construction companies and demolition contractors to recycle wood and other materials in the C&D stream back into other structures and even other industries. Last year, greenGoat advised Consigli Construction, Inc. on how to reduce C&D waste during renovation of the Cambridge (MA) City Hall Annex. A total of 112 tons of wood was recovered. About 15 tons were subflooring, which was sold to a local antique lumber operation that milled the wood into various construction materials. The project also recovered 29 tons of concrete, 15 tons of metal and one ton of asphalt roofing that was used in a road construction project. The results of this project and others that greenGoat has been involved with “gives added weight” to Massachusett’s proposed ban on unprocessed C&D debris, says Amy Bauman, president of the nonprofit group.
Recently, greenGoat received a grant from The Home Depot Foundation to highlight the ease of recycling C&D debris, using state housing projects as the example. “We gave the grant to greenGoat to promote the use of green building techniques, including the recycling and reuse of construction debris,” says Kelly Caffarelli, executive director of the Home Depot Foundation. “Our goal is to help ensure that homes are healthier for occupants, especially lower-income households.” GreenGoat has just completed a survey of local markets and manufacturers, confirming that new outlets for recovered C&D materials have emerged in previously untapped corners of the economy. “Often, it’s really just a matter of making an introduction,” says Bauman, “but we feel that finding outlets for used building materials is not a one-time deal. We work with architects, contractors and institutional land owners, taking a comprehensive view of development, using customized tools for each phase, from the bid spec to community relations. We also collaborate with manufacturers who use debris feedstocks in lieu of virgin materials.” For more information, visit www.greengoat.org.
July 1, 2004 | General
CAPTURING WOOD IN MIXED C&D DEBRIS
BioCycle July 2004, Vol. 45, No. 7, p. 42