VERSATILITY IN APPLICATIONS

LIVE BOTTOM TRAILERS FIND NICHE IN ORGANICS RECYCLING

ATERIALS handling con- siderations typically are fo- cused on the internal work- ings of a composting or mulch production site -for example, moving feed- stocks from the drop-off

area to the grinding or mixing area. But as operations get into handling larger and larg- er volumes, they quickly face the reality of having to purchase or lease vehicles to haul in amendments or deliver finished product. One category of vehicles that increasingly is found in the fleet of trucks at composting and organics recycling facilities are trailers with moving floors, or "live bottoms."

Generally speaking, the live bottom trail- ers being used in the organics recycling in- dustry fall into two categories: continuous belt floor systems and slatted, live floors (sometimes referred to as "walking floors," which is a patented brand name but a com- mon description in the industry). Trailers come in a range of capacities. The bodies are made of aluminum, steel or fiberglass rein- forced plywood. The walls and floor can be coated with plastic, which reduces adher- ence of particles and accelerates unloading.

The belts in the conveyor floors are sold in a variety of widths. With the wider belts, the walls taper to meet the edges of the belt. With the live floors, the whole bottom moves; the side walls are vertical to the floors.

Transporting greater volumes of material, and better mobility a t sites w i th overhead wires and trees, are t w o advantages cited by users of trai lers wi th moving floors.

Nova Goldstein

Live bottom floors and trailers have been used to haul fertilizers, soil amendments, agricultural products, aggregates and solid waste for many years. More recently, manu- facturers have been targeting composters, mulch producers and others in the organics recycling industry. At the same time, busi- nesses that own live bottom trailers for other purposes, e.g. hauling agricultural crops, are discovering the adaptability of this equip- ment for composting and organics recycling.

TRAILER OPTIONS The two manufacturers of continuous belt

floor systems interviewed for this article - Red River Manufacturing and Trinity Trail- er - concur that the wider belts in their lines are best suited to organics recycling applications. Red River, which recently was acquired by Trail King Industries (owned by Carlisle Co.), has the Super Hi-Lite series designed for high volume, lighter weight materials like compost and mulch. The com- pany recently introduced a conveyor with 63-inch wide rubber belt segments. These trailers have an aluminum floor with a plas- tic liner (the floor tapers to the belt at a 45- degree angle). "When dealing with compost feedstocks like green waste, the wide belt can be better so you don't have tunneling," says Dean Badinger of Red River. Capacity of the trailers range from 45 cy to 120 cy and come in lengths from 37-feet to 52-feet long. Unloading time, he adds, can be as little as two minutes. cost of the. trailers are in the $40,000 to $50,000 range.

The Trinity Trailer self-unloading units have flexible steel bodies, making them durable for off-road use such as farm fields. Its 41-inch and 61-inch wide belts (the latter being a new product for the company) are the most effective for compost, says John Christofferson of Trinity. "They move the whole load as a big loaf and work well with

m- Images courtesy of Tr nlty Tra ler Mlg.. Inc.

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materials like chopped hay and compost, as well as garbage and bulk commodities." The side slopes of the trailer are lined with high molecular weight plastic; the trailer bottom is lined with ultra high molecular weight plastic. The standard unloading time is four to eight minutes, depending on the length of the trailer and the type of hydraulics, notes Christofferson. The cost of the trailers range between $40,000 and $70,000, depending on belt width and trailer options. Capacity ranges from 106 to 133 cy.

The Keith Walking Floor systems are made of aluminum floor slats. There is no set length as the company custom builds the floor for trailer manufacturers. Most trailers have 24, 3.5-inch floor slats spanning the width of the trailer. To load or unload mate- rials, the floor moves in four stages (see dia- gram). In each of the first three stages, a third of the slats move forward ten inches while the other two-thirds are stationary. In the fourth stage, all slats move to the rear of the trailer, moving the load with them. "With slats spanning the entire width of the trailer floor, there is no bridging in the load," says Bob Moore of Keith Manufacturing, adding that any type of product can be hauled. (Bridging is when the load gets "jammed" in- side the trailer, forming an arch over a tun- neled out segment.) The company's litera- ture notes that a 45-foot trailer can be unloaded in under five minutes. The system comes with an option to reverse direction.

Vermont Natural Ag Products, Inc. in Mid- dlebury, Vermont has a 26-foot, 50 cubic yard (cy) box with a Keith Walking Floor system; the box is mounted on a tri-axle truck. "We're able to use the truck for loading and unload- ing pallets, which is very beneficial for deliv- eries to customers without loading docks," says Jim Foster. "The pallets are walked to the rear and then removed with a fork lift."

All three vendors note that their trailers can handle wet loads without experiencing leakage, either by using seals or attaching a water catcher to the gate. The trailers all can be equipped with hydraulic lift gates.

UNLOADING FLEXIBILITY The consensus among all composters and

mulch producers interviewed is that a main motivation for using live bottom trailers is the flexibility they offer in unloading. "The prob- lem we encountered with dump trucks was that in residential areas, overhead power lines and trees were a challenge," says Jack Hoeck of Rexius Forest Products in Eugene, Oregon. 'We couldn't use a dump truck." Jim Foster of Vermont Natural Ag Products had

- similar experiences. "Now we can go into places like smaller nurseries where there are

A main motivation trees on a side hill, wires and so forth," he says. "It is risky to unload there with a dump

for using live truck but with our live bottom box, we can back right in and walk the material out."

bottom trailers is California Bio-Mass, Inc. (CBM), based in Bloomington, California, uses live, slatted the flexibility they floor trailers to transport unprocessed yard

Offer in unloading trimmings aswell asfinished product. The company has two transfer dump trucks that it uses primarily for deliveries to residential and commercial businesses such as golf courses, where there is not a lot of room to bring in a live floor trailer. "The primary con- sideration is the space available at your typ- ical customer site," says David Hardy, presi- dent of CBM. "We find that live floor trailers are great for agriculture because there is usually a lot of room to dump and store."

From a weight standpoint, he adds, the two types of vehicles hold about the same tonnage of compost - roughly 24 tons (1,300 lbslcy of compost). The transfer trucks take longer to load, however, in order to minimize spillage of material. "Overall," notes Hardy, "we have found that the live floors handle mulches the best because they can carry over a hundred yards of light material, and the transfer trucks handle compost, or small particle size, heavier materials, better."

CBM has seven slatted, live floor trailers in its fleet (the Imco and Fruehauf brands), some with floors designed for light materi- als and others with heavy duty floors. Hardy, who prefers the heavy duty floors, says that a "good live floor trailer costs about

The slaited Walking Floor system from Keith Manufacturing moves in four stages (below) to load or unload the trailer (right).

The f~rst slat group (every lh~rd slat) The second slat group (every third slat) moves to the front (Load does not move) moves to the front. (Load does not move)

The thlrd slat group (every tn~rd slat) A I slat groups move to the rear moves to tne front (Load ooes not move) (Load moves rearward)

$40,000. Then, of course, you need the diesel tractorltruck to pull it, which costs between $50,000 and $80,000. A good transfer truck and trailer cost about $80,000."

INCREASED HAULING CAPACITY The Street Tree Division in the City of Los

Angeles' Bureau of Street Services operates

INNOVATIVE COMPOSTING APPLICATIONS ... AND MORE

0 RGANICS recyclers are known for adapting equipment from one application and using it for an-

other. Moving floor trailers, because of their materials handling capabilities, are no exception. For example, the Broad Creek Wastewater Treat- ment plant in Hilton Head, South Car- olina installed a Dynatherm in-vessel composting system essentially made from two slatted, live floor trailers stacked on top of each other. Fairfield Ser- vice Co. in Marion, Ohio d i d the installation. Biosolids at about 18 to 22 percent solids are mixed with sawdust, wood chips screened from finished compost and recycled compost. The batch mixer has a screw that feeds the mix into a bucket elevator, which in turn loads the top reactor. The floor moves

ing the mix. The targeted moisture con- tent for the initial mix is 42 percent. Broad Creek also has storage bins to keep the amendment dry.

Vermont Natural Ag Products, Inc. in Middlebury, Vermont uses its truck with a walking floor box to build windrows when it isn't being used for deliveries. "Usually, we mix the manure and amendment with a bucket loader

on the compost pad and then scoop it up and take it to our static pile bays or windrows," says Jim Fos- ter. "It's a lot faster if we can haul it out in the truck than by the individual bucket load." When build- ing the windrows, the truck backs up to where the pile ends and then the material is walked off and the truck keeps creeping forward. The piles are about seven- feet high.

Foster also is looking into forward a half-foot each The Broad Creek putting a live floor hopper time a load is put in. "As plant composts in the bagging plant. The the compost moves from biosolids in two live material would be metered the top reactor to the bot- reactors- out onto the conveyor that

Materialisloaded f eeds thebagger . tom One l it passes intothetopreactor, through a shaft with tines then gradually currently load whatever is to break up the clumps," moves through that being bagged into a ce- says Eric Dean, opera- unit and into the ment bay and then using a tions manager. "Process bottom reactor. skid loader, fill the hopper air is treated through an Total retention time is that feeds the bag plant," ammonia scrubber." Total 14 days. he explains. With a live retention time between bottom hopper, the un- the two reactors is two weeks. loading and reloading step could be

The system processes about 10,000 eliminated. wet tons/year of biosolids. It began op- Bob Shillington of CSC Farms saw a erating in 1990. Capital costs were just compost application demonstration under $1 million, and included a belt recently where a spreader was at- press. There hasn't been any corrosion tached to a 20-foot potato box with a and the interior is "in pretty good shape conveyor belt in the floor. "They got after all these years," says Dean. "None about 30 feet of coverage," he says. of the slats in the floor have had to be "Right now, we unload from our trailer replaced. We do a lot of preventive and then reload into a manure box to maintenance and upkeep of the sys- spread the compost. It would be a slick tem." When the facility first started op- deal if we could find a way to spread erating, there were some problems with the compost right off the trailer, using the initial mix being too wet, making it the hydraulics of the tractor to run the difficult to load the material into the top belt. That would save us lots of time reactor. That was corrected by adjust- and energy."

a green waste processing facility that re- ceives about 400 tonslday of material. When the program first started in 1994, i t only took materials from its own division - pri- marily tree trimmings, brush and logs gen- erated by city crews. Since then, the site has been getting brush and logs from the Los Angeles Department of Water and Power and its contractors, as wel1.a~ from the city's parks and recreation department. "We also get 300 tonslday of curbside collected yard trimmings," says Matt Woods, the Street Tree Division's green waste recycling coor- dinator. "We prescreen them to separate the trash from the meen waste stream, which produces a 3-inih size fines product. Then we grind the overs with the brush and logs to make a coarse, six-inch minus mulch."

Because of permitting and where the fa- cility is located, the Street Tree Division isn't able to compost at its processing site. Therefore the product goes out fairly green. "The fines product primarily is used by small composting operations that incorpo- rate it into their mix," says Woods. "The coarse product goes mostly to citrus and av- ocado growers who use it as sheet mulch."

Two types of trailers are used to deliver the mulch: horizontal discharge or push-out trailers with a ram, and live bottom trailers with a conveyor system. The push-out trail- ers were inherited from the city's Hyperion wastewater treatment plant, where they were being used to haul ash from the biosolids incinerator. "They were going to salvage, so we took them for our operation," explains Woods. "The main problem we have with those is volume. They don't hold enough for what we need. In addition, the cylinders on the truck are extremely high maintenance; the dust particles from the mulch tears up the seals on the cylinders."

To address the situation, the operation purchased four Red River trailers with the 63-inch wide belts. "We've been able to dou- ble the volume we can haul," he says. "We wanted the wider belt because of the type of material we are hauling." The trailers take about 1.5 minutes to unload. At times, the 3- inch size mulch product can be very high in moisture, upwards of 70 percent during the rainy season. The trailers have rubber seals around the back gate and the bottom edge and no leakage has occurred.

The trucks cycle four to five loadslday, and so far, notes Woods, maintenance has been minimal. "There are only a few mov- ing parts per se and everything is accessi- ble for adjustments. And if a part of the con- veyor belt tears, only that one segment has to be replaced."

FROM POTATOES TO COMPOST Bob Shillington, owner of CSC Farms in

Jerome, Idaho, has adapted with the times. Originally a potato farmer, he has been switching gradually to growing silage for the booming dairy industry in southern Idaho. The dairies increasingly are in need of acreage to manage their manure in order to comply with the state's nutrient manage-

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Deadline for abstract submission - on climate chailge

August 31,2001 Bioreinediation of contaminated soils, ecological engineering

Notice to authors of acceptance or rejection of Role of composting in modern landfills proposed papers; Instruction to accepted authors Animal manure composting/nutrient for manuscript preparation - management and sustainability October 31,2001 Soil quality and productivity; erosion control

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Photos courtesy of Red River Manufacturing

ment requirements. This situation has cre- ated an opportunity for CSC Farms. "Basi- cally, what we are doing is growing corn silage for about ten local dairies," says Shillington. "One of the dairies is composting the manure. We take the compost on the back haul and apply it to our fields. The dairy pays for the silage and the hauling fee, and does not charge us for the compost because it can use our acreage in its nutrient manage- ment plan. This year we will have hauled 25,000 tons of corn silage to the dairies and about the same amount of compost back. It's a deal that works for everyone."

CSC Farms has three self-unloading Ea- gle Bridge trailers, supplied by Trinity Trailer, that have a flap-type conveyor belt in the floor. Each trailer has a different width belt (24-inch, 31-inch and 36-inch). "We've been using trailers for about 14 years, and as we've been switching over from growing potatoes to silage, we've had to switch the types of trailers and width of the belts," he says. "The narrowest belt is specif- ically for hauling potatoes, and the two wider belts are good for corn silage and com- post. If the belt is narrow, the material wants to form a tunnel when unloading and you have to get in there and shovel it out. The wider belts are really good to avoid that. Trinity has a new 61-inch belt that I've been tempted to try for that exact reason."

The compost and the silage are pretty dry, although Shillington said they have gotten some wet compost over the past six to eight weeks and there is only one day that the ma- terial bridged while unloading. The silage is lighter than the compost, thus CSC Farms can load the 49-foot, three-axle trailers al- most to the top, getting about 30 tons in. With compost, the trailer is filled to about two feet below the top. The silage takes about four minutes to unload, while the com- post takes slightly over five minutes to un- load. Essentially, the load comes out with little or no material left in the trailer. The wider belt trailers cost about $42,000, he re- calls, and the maintenance has been mini- mal. "The 36-inch belt trailer we are trans- porting compost with hauls two to three loadslday," he says. "That is about a 22-mile haul, six dayslweek. Since we started last

The walls of the Red River trailer angle down to meet the conveyor belt (above), facilitating unloading of materials such as green mulch (top).

November, we haven't missed any days be- cause of maintenance."

OPERATOR INSIGHTS Rexius Forest Products has a fleet of trucks

that includes 14 slatted, live floor trailers (with Hallco floors) and 11 blower trucks with conveyor floors (from Western Trailer). The trailers are used to haul bark and soil amend- ments and compost that is screened and fair- ly dry. The company prefers the live floors for wood shavings or wood chips that are very light and not free flowing, according to Jack Hoeck of Rexius. It also uses those to trans- port unground yard trimmings. However, with its mulch and compost blower trucks, Rexius uses truck and trailers with a belt con- veyor because they are more economical. "There are less moving parts and it is easier to maintain," he says.

The belt floor unloads more quickly than the slatted, live floor (five versus 15 min- utes, typically), which become a factor when using the trucks for short hauls. "That may make a difference of delivering one more load a day," he adds. "For long hauls, how- ever, an extra five to ten minutes to unload really doesn't matter."

Having used live bottom trailers for a number of years for organics recycling oper- ations, Hoeck has some operator tips:

Bridging: Bridging is not much of an issue with the newer belt trailers. There are lots of home remedies to make sure the material doesn't bridge, including spraying the sides of the trailer with vegetable oil before loading. Loading the center of the trailer - versus loading the side - also seems to help. If you do get a bridge, it may be necessary to get into the trailer with a pitchfork and start working with the bottom sides to find the pinch points that relieve the pressure.

Loading: While it depends what is being loaded, typically heavier products won't fill up the trailer. If the product is really light, like wood shavings, you can fill up the truck and still not hit the weight limit.

Freezing: Leave trailers empty a t night when the weather is cold. Wet material and freezing temperatures yield a big ice cube that will not come out easily. Even if the trail- er isn't loaded, it's advisable to keep it cov- ered with the tarp so that water or moisture doesn't get in and freeze the moving parts in the floor. Belt floors seem to have fewer prob- lems in cold weather.

Cleaning: On slatted, live floor trailers, you can use a tarp mounted on a heavy board and walk it from the front to the back to pull out any materials. With the belt, usu- ally if it is run long enough, all the material will come out. And then there's the broom method - getting into the trai ler and sweeping i t out. This may be necessary when a back haul is involved, e.g, hauling mulch or compost in one direction and or- ganic pumice in the other. The pumice leaves a sand-like layer in the bottom of the trailer and if the next load is bark mulch, it would be coated with white specs if the trail- er isn't swept out with a broom.