Sweeping Debris Disposal
Screening Power Sweeper Debris
Good for the environment and a real moneysaver.by Ranger Kidwell-Ross
As America's available landfill space keeps shrinking, regulatory agencies are taking an increasingly close look at ways to reduce the material coming into them. One of the major guidelines which is now being used to reduce the volume entering landfills is prior identification of waste types which can be recycled elsewhere.
In at least one part of the country, Minnesota's Minneapolis-St. Paul area, sweeping contractors are being asked to screen out the dirt/sand component of their collected litter. Even where it is not mandated, however, screening of litter prior to disposal may well be to a sweeping company's advantage.
Harold Werkhoven, owner of Central Sweep, started his company's screening operation as a result of a letter from his county's Department of Health. They wanted him to to separate his litter so cleanly that it could be burned instead of landfilled, and then to start recycling the dirt component. Although Werkhoven is now entering his second year of screening, he says that fulfilling the 'ready to burn' requirement doesn't seem viable.
"Because of the fact that there is so much dirt caked onto the litter, at this point it just doesn't look possible to get it clean enough to take to the burner. I'm not sure that any system can be devised which will clean it up that well," says Werkhoven.
After looking around, he chose what is commonly termed a 'round head' screening system to do the job. It has a feeder on one end of a 50 foot conveyor that goes up into the air about 15 feet. The litter is fed up into a drum which is about 5' deep and 9' long, and which has a 2" wire mesh inside as a screen. The drum rotates and is at a very small slope. As it turns, the litter keeps tumbling over and over. The rocks and assorted litter fall out the end and the sand settles out through the openings in the sides.
Werkhoven feels that overall he reduces his landfill weight by about 80%, although much more during spring clean-up than at other times of the year. The screening unit ran "about $30,000, but it is pretty efficient. Now that we screen, we only have to haul about fifteen 10-yard loads out of here a year, at least five times less."
To get a feel for the difference in costs that this amount represents, we contacted Pamela Shaw, Industrial Waste Supervisor at BFI's Pine Bend solid waste landfill where Werkhoven takes his waste. She told us that screening brings two types of savings. "Because it is screened, the litter comes in at several yards to the ton, instead of in the area of one yard to the ton. Plus, it also falls into a much better disposal category in terms of cost per ton. Unscreened, this type of litter is $93.88 per ton at our facility, but screened municipal solid waste can be dumped for $61.98. [In this category, however, an out-of-county generator pays an extra $13.88 per ton, for a total of $75.31.] That's quite a difference."
Eugene Hansen, owner of Clean Sweep, Inc., and an NCSI Board member, has also been screening his company's litter almost 2 years. He started because "it is a more environmentally sound method of disposal. Although it is required in nearby counties, we're doing it in advance of regulations requiring such separation here. We like being out in front with a pro-active stance, and we make that fact known to our customers -- 'Okay, we may be a little bit higher, but how does your current contractor take care of your dirt? Are they disposing of it properly or are they dumping it into a ravine and next week someone's going to run across some of your stuff? Then you, as the initial generator of the material, will have the bad p.r. and also be responsible for the clean-up.' That's also another angle that can be used as a selling point."
Hansen figures that his company saves up to 90% of its landfill costs in the spring clean-up months. Since he is running 15 sweepers, that adds up. Even in the rest of the year the company's analysis shows that well over half, by weight, is separated out.
Once the litter has been screened, cans, bottles and other assorted trash are taken to a landfill site. Classified as solid waste, the rest may be used for fill in roadbeds and other underlayment uses. Because of his company's size, and the amount of litter which it must dispose of, Hansen is convinced that the operation will more than pay for itself in the long run.
To do the screening, Hansen says that "the company was fortunate to find a used conveyor head from a gravel pit screener for about $5,000. We welded some legs onto it and then used a sanding box from a state truck that had an old slide-in sand box to feed the materials onto the screener. Then we run the hydraulics off of one of our dump trucks. It happens to have a boom on it, so its oil reservoir is large enough to run both the sanding box, which feeds the screener, and the screener itself. Our system has a single screen, with 3/4" openings, and we've been satisfied with that. Some cigarette butts and a few straws sneak through, but it comes out pretty clean. We experimented with double screening, but found it wasn't worth the trouble.
"For our screening area, we built a retaining wall out of concrete blocks. Litter from the hopper goes onto the conveyor, which drops it to the head. The clean material falls down below and the assorted litter is discharged off the end. We feed it with either a loader or a Bobcat, and then pull it out with a Bobcat on the bottom. Ultimately I'd like to get another conveyor on the bottom so it'll stack such that we don't have to be moving it twice."
Scott McIntyre is Field Director for One-Way Sweeping. They run a total of 10 sweepers, 5 of which are air models, and have been screening for about 5 years. "We ended up making a 45 minute presentation to the city council in our area when we first looked into screening," McIntyre related. "We started by having to educate them about what sweeping even was; what we do, how we operate, even what it is that we pick up! Only then were we able to go on to our proposal to start screening. Their primary concern was possible leachate from our holding area, since houses are now being built near us. They required us to put a 6 inch clay liner under our storage area.
"Our approach was to build an 8 foot high bermed-up area, 100 feet by 200 feet. Then we put a 6 foot high fence around that, and a locked gate so that people don't try to dump their trash here. We dump all our sweepings into it, and then screen from there. The Council allows us to store it for up to 6 months in the winter, but once the weather breaks we are required to separate it out at least once a month."
The device One-Way chose for the job is a Read Screen-All, a machine which employs a two-deck screening system. One-Way goes with a 3" screen on one, and a 1" on the other.
So that the screening process can be done by one person, loading at One-Way is done with a 933 Cat loader. The material is dumped into the Screen-All, which separates it out into two piles: a garbage pile falls forward toward the loader, and the clean material falls toward the back. They get rid of the dirt in a variety of ways as solid waste fill, and the assorted litter is trucked to a landfill.
One-Way also makes an effort to sell its customers on its environmentally correct disposal methods. McIntyre says that they, too, are trying to be pro-active, to stay one step ahead of any regulatory requirements.
During spring sand clean-up the amount they save through separation "is quite high, and then lower during the rest of the year. When we do what we call our 'litter sweeps,' where we use backpack blowers to get the accumulation of assorted litter from all the planting and side areas onto the parking lot where our air sweeper can pick it up, then the percentage of dirt goes down accordingly. In those instances probably 75% is composed of garbage and litter material, and only 25% is sand and mud and rock. Still, even if it isn't required, why pay landfill charges for hauling in dirt and rocks?"
Shaker Buddy, Inc., is another manufacturer of screening machines suitable for the sweeping industry. David Lowrie, company president, sees sweeping as "definitely an emerging market for this type of equipment." Lowrie said that significant savings are quite possible, citing the case of a sweeping contractor who is currently using a Shaker Buddy screening machine. The contractor, who chose not to be mentioned by name, confirmed that he is happy with his choice of equipment, and that he separates his litter using a bottom screen that is one inch by one-half inch, and a top screen that is an inch and a quarter square. The dirt component he gets rid of as landfill cover. He reported "tremendous savings on the amount of dirt taken to the landfill, at $90 per ton. That more than covers my lease costs on the screener. Since I have the screening machine already, if there is as little as 30% dirt I separate it out."
Will screening become widespread, as landfill tipping fees increase and environmental concerns become more widespread? "The next 10 years will bring many possible changes," forecasts McIntyre. "We've had the EPA come down and look at our operation... In the next 10 to 15 years, I can see them really starting to tighten up on all this."
As the EPA, as well as the many other local regulatory agencies, become more concerned with what is going into landfills, it seems likely that industry screening may become a necessary way of doing business in the not-too-distant future. Clearly, there is a tremendous weight and volume savings to be gained by separating dirt from litter prior to disposal. And, as disposal costs per ton continue to rise, this option will become more cost-effective in many areas of the country even where it is not mandated.
This article is reprinted from American Sweeper magazine, v2n2 1992.
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