While curbside collection of recyclables and greenwastes will get you close to your diversion requirements, construction-and-demolition waste materials are where the heavy tonnage exists.

By Lynn Merrill

There can be no question that the typical rolloff coming from a construction site is a literal treasure trove of recyclable commodities. Unlike a load of MSW, construction-and-demolition (C&D) wastes are composed of materials that are highly recyclable. But because of the nature of that material, it tends to be heavy and bulky. It's not something that would be run easily through the typical material recovery facility (MRF).

The Zanker Materials Processing Facility's overall view, sorting trommel, and material recovery apparatus.

According to the Construction Materials Recycling Association in Eola, IL, C&D makes up approximately 25%–45% of the wastestream, and approximately 25% of the C&D wastestream is recycled. A study for the EPA in 1996 by Franklin Associates estimated that 136 million tons of building-related C&D debris were generated in 1996. Of this total, 58 million tons were generated from residential sources and 78 million tons were generated from non-residential sources. Demolition accounted for 48% of the C&D wastestream, while 44% of the wastestream was due to renovations. Surprisingly, only 8% of the wastestream is generated by new construction.

Woodwaste, from framing, is the largest commodity generated at construction and renovation sites. Concrete is the largest material generated at demolition sites, resulting from the removal of slabs, foundations, and walls during teardown. Other materials found in quantities at either demolition or construction sites include asphalt from parking or road reconstructions, gypsum, or wallboard from finish construction or demolition, and asphalt shingles from roofing.

C&D waste, much like curbside recyclables, has generated debate over the effectiveness of single-stream versus source-separated materials. While some programs separate material on the job site, the trend in the C&D industry tends to favor the "load it all in one bin and separate it somewhere else" approach. For contractors at the job site, training the various trades to take the time to separate materials and to move these materials to multiple locations for recycling adds time and cost. Given that many of the trades are specialized subcontractors, the challenge multiplies exponentially while the ability to control the actions of the work force decreases, making onsite recycling programs a challenge at best.

Because of these concerns, the trend in the industry is to develop C&D processing facilities that can handle the volume of materials while dealing with the dust, noise, and processing issues associated with the material stream. Think of today's C&D processing operations as a MRF on steroids.

San Jose Deposit Program

To encourage the development of an active C&D diversion program, the City of San Jose, CA, implemented the Construction and Demolition Diversion Deposit (CDDD) program in 2001. "We did a number of studies back in the late '90s that led us to believe that there was a considerable amount of C&D material ending up in our landfills here," says Stephen Bantillo, C&D program manager with San Jose's Environmental Services Department. "In our strategic plan to council we put implementation of some type of C&D recovery as a high priority. We furthered our studies by doing gate surveys to identify how the material was getting there and those vehicles that were bringing loads there."

Using California's beverage container recycling deposit program as a model, the city began thinking of a similar program for C&D materials, "the concept being that all the folks here who recycle their material get all of their money back, with the focus being on developing the infrastructure and not so much the generators," Bantillo says. "The contractors were the first group to tell us that they weren't recyclers by trade. They're in the business of tearing things down and building things up. We knew there were too many issues with trying to force them into recycling, and that's not what we want to do anyway. We rely on an incentive-based system for all of our programs, sort of an extension of the pay-as-you-throw model. In this sense, we thought what we can do is give them a financial incentive to divert their C&D material."

The program involves three steps. When a contractor applies for a project permit, the city assesses a deposit based on the square footage and type of work, such as new construction, alteration, or demolition. Then, during the project, the C&D materials generated must be recovered or recycled. The materials can either be reused or donated, taken to a CDDD-certified facility for recovery or recycling, or a combination of both strategies. Once the project is completed, the contractor submits documentation to the city showing that at least 50% of the waste generated by the project was diverted from landfill disposal.

Developing a viable and robust infrastructure to handle the C&D materials became another priority for the city. "Our focus was on coming up with an infrastructure that would be able to handle the material," Bantillo says. "One of the things we did after building support through our stakeholder process was to offer up three-quarters of a million dollars in C&D infrastructure grants. We wanted to seed this system with some money so that the processors knew that we were very serious about moving forward with the program, and would begin to see the value in enhancing their operations and increasing the overall C&D processing capacity in town. We have a number of facilities that are not in San Jose, but we've certified them as well because they demonstrated they can accept a significant amount of material from San Jose. We gave out these grant funds over a period of two years."

Morbark's Predator.

The facilities are motivated to participate, Bantillo says, because the city told them it would assess a deposit and issue 10,000 permits a year to contractors in need of a place to take their debris. The city ended up with 22 certified facilities that could handle C&D materials.

One facility that received certification from the city is the Zanker Road Landfill. Zanker owns and operates two waste-recycling and -disposal facilities in San Jose. The Zanker Road Landfill is a 46-acre facility and the Zanker Material Processing Facility (MPF) is another 46-acre facility located approximately 3,000 feet west of the landfill, which opened in 1999. The landfill receives up to 1,300 tons of Class III waste daily, while the MPF can accept up to 1,250 tpd.

Peterson's 4710 (top) and HC 74000 processing rail ties.

According to information provided by Michael Gross of Zanker, most of the waste received at these facilities is mixed C&D debris that comes from contractors or is hauled to the site by contractors or residents. To process the C&D materials, Zanker uses a screening system and unique float tank designed by the company specifically for separating wood from the rest. Mixed C&D is first screened to recover soil from the waste and sorted to remove large pieces of metal, wood, and trash. The remaining mixed materials are then fed into a special "float tank" where the wood is separated. The wet wood is then combined with other recovered wood. The sinking concrete, asphalt, bricks, mortar, metal, glass, and soil are also recovered, separated, and then processed further into usable materials.

Woodwastes are the largest component of the incoming debris at the Zanker facilities, making up 32% of the construction stream and 50% of the demolition stream. Zanker also accepts clean wood and brush loads, and separates wood from incoming mixed loads, as well as processes bulky wood items such as large stumps, limbs, and tree cuttings. All of the recovered wood is ground and then screened to meet market specifications. The finished wood products are then sold as mulch, biomass fuel, and soil amendments. Clean concrete, reinforced concrete, asphalt, bricks, and porcelain are screened and crushed. Steel—including rebar and other loose metals, wood, plastics, and trash—is screened and separated before and during the crushing processes. The finished material is a high-quality Class II base rock. The base rock is sold mostly to construction and paving contractors and used as Class II aggregate or as engineered fill that meets California Department of Transportation specifications. The company also produces a variety of finished products, principally hog fuel, cover soil, and base rock.

Williamson County, TN

While the San Jose programs discourage using processed C&D materials for alternative daily cover (ADC), the C&D program at Williamson County generates materials that are used for various landfill programs, including erosion control and vegetative purposes. "Williamson County is a very high-income county," says Lewis Bumpus, solid waste director for the county. "It's served by a lot of retail, a lot of office, and a lot of service-type businesses. There's very little industry. We are very close to the music industry; in fact, there's probably more music stars in this county. Although Nashville is recognized as the music city, Franklin is really the home of a lot of the music people."

The county operates a variety of solid waste transfer operations, as well as a C&D waste landfill. "When I came here, it had about five years' life," Bumpus says. "I've been here six years and with the program that we've set up, I'm hoping to make it last about 40 years and will in C&D recycling. Necessity is the mother of invention. The first thing we did was a waste audit to study what all was coming into the county so we'd know our wastestream and some possible uses of it. We first started off with woodwaste. I had 75 acres of cap we had to build out here on the site and we took the mulch that we made and we used it for vegetative cover. We just spread it real thin over a lot of the acreage here."

After identifying needed equipment, Bumpus sought a portable grinder that could do C&D woodwaste. "We've used several different pieces of equipment, but we ended up buying the vertical grinder because it could be the one machine that could handle all of our material. We pull all the clean woodwaste out of the C&D. We bought a star-type screen machine where we can change different dials to make different sizes of mulch for whatever your application. A lot of mulch is going to be used for vegetative [purposes]. Thus far the large jobs, state road projects and landfills, have taken up all the material and I haven't had to develop markets, but we have plans to serve some of the landscapers. There's a lot of landscaping in this county."

Because of the high content of clay in the native soils, Bumpus had to develop a three-way screening machine that could stand up to the clay while screening the C&D materials for end uses. "We've got a machine that was put together by several of us that … requires no picking station and will work in Tennessee red clay," he says. "In the Northeast or West Coast, there's a lot of C&D recycling that they used to trommel but they have sand and sand works good in trommels. Red clay doesn't work; it sticks to anything. We took the frame of a rock crusher. It's a spring system to keep the vibration from shaking the machine apart. Then, secondly, it works on the same principle as a combine in that it has finger decks that it shakes and drops down to a lower deck. The major difference is we put a tilt bed on it like you see on rock crushers and some of your woodwaste machines. What it does is, when you drop the material on that deck and flatten it out, you don't have elongated pieces going down through the fingers like a piece of rebar because it's laying flat when it sifts over on it. We pull out any metal that we see while we separate. The material is flat and we run it through the screener and, depending on the material, we get anywhere from 60% to almost 80% that comes out a 2-inch screen. Then, we're getting about 20% that comes out the screen that's about 6 inches to 2 inches. That material will go into the grinder and be ground down. We try getting all of the loose dirt out because dirt and silica are terrible on grinders. They just wear them out all to pieces."

Bumpus has identified three markets for his materials. "I'm trying to develop a market for vegetative and drainage layer to cap landfills and that's the experiment we're doing. We've got the approval on doing the ADC, and I've got a contract in place on that for the ADC. The third thing we're doing—and again, we've only done this in pilot projects, but it seems to work well—is reclaiming some of the old construction and demolition sites by mining it out."

Phoenix C&D Recycling

In Des Moines, IA, C&D material is heading to markets from the mixed materials delivered to Phoenix C&D Recycling Inc. "We receive around 300 tons a day and we accept it commingled and process it into different markets," says Rob Hosier, senior vice president. "We pull out wood and metal, cardboard, concrete, and we make an alternative daily cover. That's our single largest commodity. We find ourselves landfilling somewhere between 10% to 15% residuals."

The company uses a finger-screen and conveyor system that divides the material in thirds, then each of the fractions goes through a series of processes to an end product. "The bottom third, which is a 2-inch-minus material, will go all the way around the system and pass underneath a magnet that pulls out all the ferrous metals," Hosier says. "The middles line, which would be 24-inch to 2-inch, passes underneath the magnet and it pulls out the ferrous metals. It also goes across the picking station, where we pick trash and wood. The overs line, which is 24 inches up to 8 feet long, goes across a picking station and we actually handpick all those commodities, such as the metal. We don't use a magnet at that fraction. After that there is a concrete pick and then anything on that overs side that we don't pick will actually go into a grinder and it gets reduced into alternative daily cover. Typically, we're going to grind all the bricks, all the block, small pieces of concrete, wood, and some smaller pieces of cardboard. The system will process up to 50 tons an hour. After the grinder, it'll go to another magnet to separate any additional ferrous metals and then from there the material goes into a storage building. On one side of the building is the alternative daily cover, and it gets screened out with a star screen. The overs, which is basically anything larger than 2 inches, will go to the other side, and then that's a different product."

The company sells the ADC to three local landfills, so it's concerned with meeting the needs of these customers. "We try to stay away from brush and trees," says Chris Reynolds, vice president of operations. "The reason is, on our alternative daily cover, there's a spec on it and we're trying to keep the organics low. We don't process the tree limbs. Other than that, they can go ahead and bring the carpet and the gypsum, and what we'll do is we'll pull that out. If it's large enough, we'll do a kick sort where we pull it off on the front end and that'll be landfilled. Most of our wood, however, goes to a local company that supplies a furniture company with particleboard wood."

Lynn Merrill is director of public services for the City of San Bernardino, CA.

MSW - January/February 2005