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New technologies and innovative practices are paving the way toward more efficient use of a community’s resources. By Peter Hildebrandt In years past, nearly everything headed for the landfill. Nowadays, solid waste can be shredded, ground, compacted, mulched, or recycled. Some landfills are having life spans extended because of space-making equipment, while others are witnessing the drive to go green through more recycling. Distributing mulch can also take the pressure off acreage, reducing the amount of passes compacting vehicles must drive over the tops of the landfills. With all the new options on the market when it comes to dealing with waste material, some manufacturers and their clients explain how dynamics are changing. Shredding and Reducing Since the area’s landfills are essentially “landlocked” and cannot grow any larger, O’Brien’s initial idea was to reduce the volume to get a better density, a better compaction rate, and, in the end, a better volume. “So far it seems to be working out that way for us,” says O’Brien. “Our 770 is a primary reducer, shredding everything from trees to lawnmowers—you name it, we throw it in it. My asset is my volume, and the more I can fit in my landfill, the more income I can make.” Trees account for some 30%–35% of the material handled by Rosencutter Brothers. Simply by reducing the trees down to pulp or shredded timber as opposed to limbs and branches, the company is able to fit far more into the landfill. The rest of the material being landfilled is construction-and-demolition (C&D) waste. “By primarily reducing it, this machinery takes the volume down by 40%,” adds O’Brien. “With our two D-9 Caterpillar dozers (a D-9R and a D-9L), without shredding, it was taking me 12 to 14 passes to get things to the density we needed. With the use of the shredder, we can compact in about four to five passes. With fuel where it is right now, this was the right decision, even if it was done for nothing else besides the fuel savings.” There is a fuel cost and an operator cost associated with the shredder. But the fuel cost is roughly one-half that of running a D-9 dozer, according to O’Brien. “Our dozers consume some 10 to 12 gallons of fuel per hour per vehicle, whereas the compactor with the loader we have on it takes roughly 6 gallons of fuel per hour,” he says. “I’ve had it in service for six to seven months so far, and those are the numbers we’ve calculated so far for fuel usage. The decision to use shredders has been a good one thus far.” Fuel Prices Come Into Play
There continues to be interest in shredding at landfill sites; however, it’s generally limited to C&D landfills, according to Terri Ward, solid waste product manager for SSI Shredding Systems Inc. in Wilsonville, OR. The bulky, unwieldy nature of C&D means the cost of shredding can be offset by better in-place density, efficiency gains in material handling, reductions in compactor maintenance, and revenue from metal recovery. In some cases, shredding can also convert incoming C&D into roadbed material or alternative daily cover. “The main drivers to shredding waste material continue to be reduction in transportation and disposal costs, as well as landfill diversion through recycling,” adds Ward. “Fuel costs are at an all-time high, providing a great incentive to maximize payloads on every load going to the landfill. “Depending on the region and type of trailer being used, this can be difficult to do with unshredded bulky waste and C&D. In addition, some landfill operators prefer shredded material and may offer a reduction in disposal fees, providing further incentive to shred. In areas where landfill space is at a premium or where recycling is mandated, shredding can be a key part of diverting material from landfill disposal. “As automated sorting technologies advance for recycling, so does the need for preshredding of C&D, bulky waste, and even MSW. Whether mechanical screens, air-density separation, float tanks, or optical sorting are used, most work more efficiently with the consistently sized, homogenous material stream that shredding provides. Even manual sorting of C&D can be improved by preshredding, as long as the material isn’t overprocessed, becoming too small to handpick. Our PRI-MAX primary reduction technology offers a very coarse shred at about 24 inches, optimal for hand sorting. “Alternative fuels are currently underdeveloped in the US, therefore, the combination of landfill diversion and reducing the need for foreign oil is making RDF [refuse-derived fuel] more attractive these days. Shredding is a key element to preparing waste for conversion to fuel.”
Composting also comes into play as a viable alternative to landfilling. Since organic material can be converted into usable compost, efforts continue to harvest this resource rather than send it to landfill. As with fuel, size reduction is a key element of the compost process. SSI specializes in low-speed, high-torque shredding technology. “It’s what we’ve done very well for over 25 years,” Ward says. “We pride ourselves on our multiple product lines, patented features, and significant technical capabilities to tailor our solutions to each customer’s unique needs. Low-speed, high-torque shredders are the best tool for mixed waste-streams—especially where metal contamination is present. Unlike high-speed grinders, we have the ability to effectively shred most any material while offering low dust, low noise, low power/fuel consumption, low maintenance costs, and very high online reliability. “More specifically, our PRI-MAX product line delivers all of the benefits of low-speed technology while delivering the high output capacity previously only available with high-speed grinders. The shred size is coarse but ideal for volume reduction/densification.” These units are used by C&D landfill operators, C&D recycling facilities, transfer stations, drop-box companies, haulers, scrap metal yards, mulch processors, demolition contractors, waste-to-fuel processors, and the like. “In the late ’80s, we developed a preload compactor for transfer stations that loads, compacts, and ejects a preweighed, untied bale into a long-haul transfer trailer to maximize payloads of MSW going to landfill,” Ward says. “This line has been successful, particularly in the Northwest and in rail-haul situations where net payloads up to 62,000 to 70,000 pounds are allowed. It also works well on lighter waste that can’t otherwise be toploaded to achieve maximum allowed payloads. Another application is handling bulk recyclable commodities, such as newsprint, which can be more efficient than baling.” With the big emphasis lately on making machinery and products as environmentally friendly as possible, Ward points out that SSI’s low-speed shredders are inherently eco-friendly because of the work they do and because of their minimal environmental impact when compared to alternative technologies—low dust and noise emissions, energy-efficiency, high reliability, and good safety record. Taking the Landfill Out of the Equation This compactor system was installed in February 2006. Prior to this, the company had a manual system that ran a transverse conveyor over the top of open-topped trailers, allowing the product to flow directly into the trailers. “What we had before did not use our transportation abilities to their fullest,” adds Grossen. “We always sent light loads to the mill because we were unable to compact the material to a density able to generate enough weight to reach the point at which these trucks were at their greatest hauling capacity. Now we have a direct economic benefit in being able to haul more with each load and do fewer loads in the long run, a clear advantage in light of increasing fuel prices.” Screening and Recycling “As they say in politics, all waste is local,” says Lyman. “You can’t afford to haul it long distances. In any area you must evaluate what the landfill costs are, what the markets are, and which are available for recyclables, and then see what makes sense to put into place from a recycling standpoint.” For C&D debris, WSM offers grinders for processing that material, and it is also getting involved in working with system suppliers who will provide a complete processing solution. “Where we are a bit different from other companies is in the fact that, due to the range of products we offer and the experience we have with all our years of operation since 1947, we are very much application-driven,” he says. “We don’t just build a machine and say, ‘Here it is—this is the extent of what we’re going to build,’ but instead we can customize solutions based on the feedstock the customer has and the markets or the products that he’s trying to produce for his end market in efforts to convert that waste product into a recyclable.” A current project being done in California involves the handling of a foodwaste system. WSM will be supplying screening and size-reduction equipment for a foodwaste-to-compost operation. “This is the niche in the solid wastestream involving materials that can be separated, processed and then converted into recyclables,” Lyman says. In the C&D arena, WSM has a number of systems throughout North America. It’s also working on a project in Singapore, where the C&D material is sorted into different fractions, and such recyclables as cardboard, paper, plastic, stone rubble, or wood are removed. “On the energy front, what we are working on is urban wood fiber that is collected and has many viable markets as boiler fuel, particle board furnish, or mulch-type products,” adds Lyman. “There are good markets for any of the wood-fiber materials, and they form the main part of our business. We cut our teeth in the wood products processing industry; all of our equipment is designed for mill duty–type construction 24 and seven and is quite heavy-duty, necessary in the recycling industry as well.” Lyman has observed that these recycling applications really come into play over the past 20 years. The trend has been that, as time goes by, the waste industry figures out how to collect and correctly source some of the waste materials and then allow the recycling process to be done in an efficient manner. “Then it becomes economical to collect these materials,” he says. “I think now with the higher energy prices there is a desire for us to produce our own energy and reduce our dependence on foreign sources. More and more people are starting to look at the wastestream as an energy resource.” The real benefit WSM brings to the industry is its knowledge of applications and being able to deliver a customized and economical solution for any material or location. “Certain materials are only recyclable in certain places,” adds Lyman. “We’ve been supplying the processing systems to the big biomass facilities for 30 years. We have a long track record and have supplied our equipment to some of the largest biomass facilities in the United States.” One of the big trends Lyman sees now is the push to switch large grinders from diesel to electric power. “The cost of diesel is now so high that by going with an electric system you eliminate diesel emissions, reduce power costs, improve the machine reliability, and reduce your cost per ton to process material,” says Lyman. Going along with this idea, WSM has just introduced its largest horizontal feed-grinder, the model 6070 with dual 500-horsepower electric drive motors to the grinder shaft, electric-driven equipment. “We’re seeing operations lately that want machinery that is overbuilt to minimize maintenance and have a machine with a 20- to 30-year lifespan with proper protection,” says Lyman. “Some guys go through a portable engine in about five years, but they’re hugely expensive. This 75-ton machine will be installed and be operated for many, many years.” Balance “I’m still in an area of the country where our volume and marketplace are so competitive—my tipping fee is $17 per ton—that I can barely keep waste coming into the site,” says Papin. “With tipping fees that low, layering in an additional mitigation such as shredding municipal solid waste does not seem to be something someone would want to do just because of the added expense, especially when we have such a plentiful amount of airspace and at such a great price.”
All the yardwaste in Greenville County is accepted at the landfill facility without a tipping fee in lieu of tax revenue received from the county. “We take this material at no charge, so that’s a very competitive tipping fee,” says Papin. “But I have not noticed a reduction at the landfill. We’re at about 50,000 tons per year in what some refer to as greenwaste. We do have a mulching operation on the site and of the 50,000 [tons] grind or mulch about 20,000 tons, which is distributed back out to residents at no charge.” If the landfill was able to get an increase in its tax revenue or be able to charge a tipping fee, Papin feels it would be in the same position as the private sector and be able to find an effective end use for that material. Desirable yard trash, such as branches and limbs, is separated from the more mixed wastestream and mulched. The rest of that mix, including plastic bags, goes into the C&D landfill. “I think the same basic theory exists—that we’re at such a competitive rate that it’s not practical at this point for someone to come in and do a large capital investment, take the stuff from me for free, and reduce our size,” says Papin. “It’s one of those things everyone would like to see a reduction in or see go back on the ground to replenish the natural resources, such as the topsoil. “Also, with the advent of the big grinders, we’re seeing a product now we’ve never seen before: land-clearing debris. As we’ve pinched out the ability of land-clearers to obtain permits, they are going to chipping and grinding. The fact that I’ve only been able to give away 20,000 tons of yardwaste per year is tied into the fact that it’s never really been viewed as a desirable product. It contained plastic and other debris. If it had been land-clearing debris, double-ground, I could probably give away every bit of that.” When It Comes to Tires ... The system can process 100–150 tires per hour and shreds them into 2- by 6-inch chunks.
“It’s high-torque, not high-speed, but it can move some product,” says Franczyk. “Its price is competitive, and it weighs some 8,000 pounds, making it somewhat portable, and it runs virtually maintenance-free. You simply make sure the bearings and zerk fittings are greased. Two electric, 8.3-horsepower motors run using counter-rotating shafts with cutters for shredding the tires.” The design capabilities point to the machine shredding 90,000–100,000 tires with little more than general maintenance, according to Franczyk. “Shredding reduces the cost of handling tires by 80% because that much more material can now be placed on a truck,” he says. “There’s more weight, but there is also much more material which can be packed onto the truck, compared to whole tires. Also, the machinery is quiet—it can be run inside—and can also be run in the worst of conditions. There are no fumes or environmental problems. If your business is shredding even as few as 100 tires per week, you will probably be able to recoup the cost of this machine in cost savings within eight months. “Landfills could use this equipment to increase their space, as the compaction rate is greater for shredded tires, or this material could work as well as roadbed material. This equipment could be designed to shred smaller, but for now this is a less cost-prohibitive option for tire shredding.” Peter Hildebrandt is a writer specializing in science and engineering topics. MSW - September/October 2007
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