BioCycle March 2007, Vol. 48, No. 3, p. 22
Screen manufacturers approach the challenge of separating larger particles from smaller particles in myriad ways. Equipment options fall into two basic formats – trommels and decks.
THE WORLD of organic materials recycling has a wide range of equipment available for screening raw material and final products. Screens are virtually indispensable for converting organic waste into organic products, as well as processing soil, rock, asphalt and concrete. Factors manufacturers and buyers take into consideration when evaluating screens include rigorous specifications for particle size and contaminants; safety of operation; energy efficiency; portability; processing capacity, particularly with wet materials; ease of maintenance; reduced air emissions; warranties; and, of course, price.
This third article in BioCycle’s What’s New series reports on responses to a survey sent to screen manufacturers/distributors marketing in North America (see accompanying Screen Directory). Vendors were asked to describe their screen’s primary applications, new screens they have or are planning to introduce in 2007, new applications and features, and technology improvements.
Screen manufacturers approach the challenge of separating larger particles from smaller particles in myriad ways. One pass through a screen can often yield two or three products. Screens tend to come in two basic formats – decks and trommels. Deck screens are equipped with a variety of shaking and snapping motion screen panels, or cloth. Discs are also incorporated onto decks, spinning in a manner that keeps larger material on top with product dropping through. Decks also include star screens, a variation with an array of star-shaped discs that spin in a manner that larger particles stay on top and smaller ones drop through the stars. Significant advancements are being made by providing a second or third screening deck, enabling production of three or four products in one pass through the screen. The other primary category of screens is the rotary trommel, which tumbles material through a spinning, cylindrical screen. For all screen designs, various “grizzly” bars prescreen large, potentially damaging objects out prior to reaching the decks or trommels.
A European influence on screens is the horizontal trommel, as opposed to the inclined trommel, a design that seeks to increase contact time of material on the screen, and hence throughput. One U.S. company recently added internal flails to its inclined trommel to pulverize materials, reduce rejects and enable use of a smaller drum. Advances in plastic and metal materials are resulting in more robust screen discs and stars, reducing maintenance. Easily interchangeable drums also are being found on more models, and larger trommels.
Another overseas influence is windsifters, a European term for vacuum or air classifiers that operate alone or in conjunction with other screens, pushing or pulling a stream of air through the material to remove light contaminants, such as film plastic. An American company also has developed a wet separation system for removing stones from bark and wood.
The screen industry is continually making improvements to its equipment that is resulting in more cost-efficient compost, mulch and soil production, along with higher quality products. On the front-end of the processing line, especially at construction and demolition waste recycling plants, screen innovations enable improved sorting and recovery operations.
SCREEN EQUIPMENT ROUND-UP
BioCycle received responses to our What’s New survey from the following 19 screen vendors. The information reported here was supplied by the manufacturers and not independently verified by BioCycle editors.
Aggregates Equipment, Inc.: The Banana bivi-TEC was introduced in 2006, referring to the curved deck with a steeper screen inclination at the feed-end of the screen than at the discharge end. The new screen is designed to better maintain a consistent bed-depth of material throughout the deck, and increase screen capacity by 10 to 15 percent. A dual-vibration principle is applied to polyurethane panels, causing material to bounce across the screen, with smaller particles falling through a range of screen openings. Bivi-TEC screens are used primarily as finishing screens for compost and topsoil.
ALLU Group: This unique front-end-loader bucket has a built-in crusher at the base of the bucket, and got its start in the mining industry, crushing rock in Finland. The SM model replaces the standard bucket on a front-end-loader with a bucket that is both a crusher and screener, dropping its contents out of the bottom of the bucket. A new, 3/4-inch screen attachment is now available to be used for finished compost. For composting and soil manufacturing, the ALLU bucket is particularly useful for breaking up clumps, mixing feedstocks and agitating compost. Aeration of contaminated soil and clay is another application, as well as mixing of soil products.
Bulk Handling Systems: The company started 30 years ago providing screens to the wood products industry, and has expanded to yard trimmings composting and C&D applications with deck screens. The newest innovations for its “tri-disc” design are intended to improve the wear quality of the discs, which can be manufactured from steel, rubber or polyurethane. BHS has patented its “tri-shape” disc, as well as the “in-line” fit of the screen shafts (versus the offset of the shafts in other disc screen designs). This combination of disc shape, durable construction of rubber and metal discs, as well as “in-line” mounting on the shaft are intended to keep material from wrapping and jamming. “Less wrapping and jamming results in workers not having to climb onto screens to remove jammed material,” says Donna Walters of BHS. Improved safety features include emergency stop devices, system programming, enclosed guards and more accessible maintenance doors.
CBT Wear Parts, Inc.: The company’s unique screening method employs single or double rotor shredders ahead of a trommel screen in order to break up clumps and open up the flow of materials headed to the screen. This design is intended to enhance screening of wet materials. “It greatly reduces the necessary screen space while significantly enhancing screening efficiency,” says Mark Heffernan, President of CBT. The shredder also allows the screen to blend soils with finished compost and other materials. “In one pass, soil and compost clumps are broken apart, roots and rock are separated from the good soil, the soil ingredients are blended together, and the finished product is screened,” he adds. “The machine also can be used for its blending capabilities alone. This system is being used to blend biosolids with sawdust, so the machinery has utility at both the front and back end of the composting process.”
In soil remediation applications, the shredding breaks down soil particles and removes rocks in order to blend the soil with compost for biological remediation, or prepare it for thermal treatment. “For thermal treatment, the soil particle size must be small enough that the heat of the thermal unit can drive out the entrained contaminants and vaporize them,” Heffernan explains. “In the case of biological treatment, the soil particle needs to be small enough (smaller than thermal requirements) for bacteria to get to and consume the contaminants. The power of the shredding chamber of our machinery is capable of getting contaminated soils to the required small particle size.”
Construction Equipment Co.: For the past 15 years, CEC has manufactured a variety of screens for use in the forest products and sand and gravel industries, notably its Screen-It line. A new product, CEC 5×12 Three Deck Screen-It, is now being offered for use in compost and soil manufacturing. The three decks will generate four products. The top “breaker” deck has a 2-1/2 to 3-inch screen, the middle deck has a 3/4- to 3/8-inch screen, and the bottom deck has a 1/2- to 1/4-inch screen. The overs from each screen are kept separate for additional processing if desired. A new feature is a ball deck on the bottom deck for self-cleaning of the smallest screens, which are most prone to blinding. Users can customize the size and make of screen cloth to be installed in the CEC screen baskets. “We added the third deck in response to customer demand to make another product,” says Pat Andrew, Vice-President of Sales. “For example, when screening compost, the coarser product may be used as fill, the middle product for biofilter media, and the finer product as potting soil.”
Another new introduction to the screen market is the RWS 2000 Separate-It, a trailer-mounted water bath system for recovering stone from wood. The all-in-one unit includes a diesel engine, hydraulics, 2,000-gallon water tank, water jet, drag line and water recirculation system. Andrew claims this “rock water separator” achieves 99 percent separation of rock from wood at feed rates of 70 to 90 cubic yards/hour. Prescreened wood with rocks is loaded into the tank where a powerful water jet propels the floating wood across the water surface and onto a conveyor, allowing rock to sink to the bottom of the tank. Approximately 300 to 400 gallons of water are used in a typical day of processing. A small amount of fine material (about 10 cubic yards) is pulled out by a drag conveyor.
The Separate-It is designed to further refine the overs from a screen that has already removed the fines from a lumber mill yard cleanup, or a stump recycling operation. “The Department of Environmental Quality here in Oregon is seeking cleanup of sawmill yard stockpiles that contain a mix of wood bark and rocks,” says Andrew. “This machine allows those cleanups to recover wood for mulch and fuel, and rock that can then be crushed and sold.”
Continental Biomass Industries, Inc.: CBI has many different screens for different applications – from sorting construction and demolition waste to screening finished compost. For some C&D materials, CBI offers an octagonal trommel – eight sides with individual screen panels on each side. “This design allows for easy replacement of each panel rather than the entire screen,” says Tim Griffing, Systems Engineer for CBI. Screen panels are bolted in, five panels on each of the eight sides of the trommel. These can be replaced in less than one hour, notes the manufacturer. According to Griffing, the octagonal shape works best with C&D material since it does not roll tarps and sheet plastic into “Tootsie Rolls” as cylindrical trommel screens may do. The unit is covered for dust control, and is only built for stationary applications, most of which are C&D recycling facilities. Size of screens recommended for C&D applications are 1/4-inch to 1-1/4 inch. Larger screen openings in a trommel tend to create problems with objects spearing through the screen.
Another new product in the line is the Action Vibra Snap deck screen, designed to handle wet compost, as well as aggregate, auto fluff and C&D. For this screen, CBI partnered with Action Conveyors of Newberg, Oregon to use a screen cloth made with polypropylene. The vibration of the deck allows the screen cloth to flex continually and keep the deck from blinding. It is available in different deck sizes, and is only made for stationary applications at this time.
Action Conveyors also manufactures CBI’s Action Taper-Slot Screen for the C&D market. The patented screen design minimizes spearing, says Griffing. A 2-inch size material comes out with minimal amounts of objects greater than 2-inches in length. “The screen is a balanced action,” he explains. “Unlike the centrifugal motion on conventional screens, this allows the unit to be turned on and off without adversely impacting the screen box or the operation each time it is restarted.”
CBI also offers a mobile Prescreener typically used in the land clearing business. A large hopper feeds a heavy-duty disc screen to scalp off dirt from the stumps and brush, which then passes the larger size material over a picking conveyor to allow manual labor to pull off rock, metal or other items for recycling, or to remove items prior to grinding.
Doppstadt US: A new trommel screen, the SM 726, will be introduced in 2007, on both a wheeled and tracked undercarriage. Doppstadt has a patented load sensing system that controls the feed to the drum of the trommel screen in order to optimize screening efficiency. For an operator, this can minimize the loss of efficiency associated with over loading a screen since the sensor will reduce the rate that material is fed to the drum. The SM 726 will have a processing capacity of up to 350 cubic yards/hour, depending on the material being processed. The unit has a low load height and does not require a ramp for a front-end loader to feed the screen.
Another design enhancement is a drum changing system that allows the drum to be changed in less than 15 minutes. For ease of maintenance, the engine swings out at 90 degrees; the cleaning brushes on the drum are raised and lowered hydraulically.
The Doppstadt trommel also uses a horizontal drum with a flight system to move materials along the drum, as compared to an inclined trommel that relies on force of gravity. The drum has metal ridges (“flights”) designed to reduce spearing. “This rolling of material – as opposed to the lifting and transfer motion of conventional trommel screens – allows material to be in contact with the screening surface for an extended period of time, leading to increased production capacity and alleviation of potential for speared or elongated material to be discharged in the fines fraction,” explains Joan Ritchie, sales representative.
Another new addition to the Doppstadt line in 2007 is a star screen to be used on the standard unit in place of a drum, a design intended to handle higher moisture materials, in excess of 40 percent. “Materials such as compost, remediated soils and very specific blended soil mixes are likely applications for a star screen,” says Ritchie. She points out that although star screens have such strong advantages, their major limitation is production capacities compared to trommel screens, which also have “dramatically decreased maintenance requirements.” A star screen attachment also will be available to mount over the hopper of the trommel screen so that grinders and shredders can discharge directly to the star screen, and then to the trommel, producing two specification products in a single pass.
Extec Inc.: The company manufactures a range of mobile screening equipment, including single deck screens, double screens, finger screens and scalpers. It plans to unveil three new products at Bauma 2007 in Munich, including a new S-6 screen with the following features: Longer side conveyors that feed straight into a cone-shaped pile and a longer tail conveyor, both allowing for higher stockpiles; Faster running belts to increase throughput up to 700 tons/hour; Double screen box that yields three separate product grades coming off three conveyors; and Screenbox lift mechanism to facilitate changing of the screen mesh. For safer maintenance and ease of changing of the screen mesh, the S-series of screens includes hydraulic walkways.
According to Roger Murrow of Extec, a double screen box creates over 20 different screening angles. “Screening efficiency is maximized as material flow is directed by the angle of the screen box,” he says. “This results in a steep angle for the primary screen box, which ensures that the majority of the material is processed in the initial impact area, and the majority of the undersize material is removed during that initial impact. Only near-size material passes to the secondary screen box, which is set flat enough to ensure any remaining material is screened efficiently.”
Extec also announced the new E-7 tracked screen, a heavier duty, self-propelled screen built for the recycling and quarrying industries. It has the ability to mix a variety of screening surfaces, including fingers, bars, meshes and punch plate.
Komptech: New for 2007 is the Multistar L3 “Windsifter,” a three fraction star screen with light fraction plastic removal on both the middle and over fractions. A windsifter or plastic cleaner has previously been offered on the Hurricane screen, but this is the first star screen with a windsifter to be marketed in the U.S., says Todd Dunderdale, Sales Manager. He acknowledges that the windsifter cannot distinguish between light materials. “However, the suction of the windsifter is adjustable, as is the distance above the star deck,” he explains. “This allows operators to fine-tune for the material they are running.”
The unit offers throughput of up to 220 cubic yards/hour, with primary applications for screening wet compost, mulch or soil. There are two star screening decks that are adjustable – from a fine fraction down to 1/2-inch minus, a middle fraction of 1/2- to 2-inches, and a third, larger fraction. The star shaft speed can be adjusted on the machine while it is running in order to increase or decrease the fraction sizes, with faster speeds producing smaller sizes. As with other Komptech screens, the new line includes the self-cleaning “Cleanstar,” which is intended to prevent wrapping and buildup of material when processing food waste or other contaminated material. An even higher capacity Multistar XXL also is being introduced in 2007, with throughput of up to 520 cubic yards/hour.
McCloskey International, Ltd.: Since 1985 McCloskey has been manufacturing trommel screens, vibrating screens, stacking conveyors and picking stations. New this year is the 4×4 733 Trommel, the company’s largest portable trommel screen, which now incorporates the patented Drum X-Change System. With a 33-foot long and 7-foot diameter drum, it is designed for high volume processing, especially for prescreening and large custom composting applications. The Drum X-Change System utilizes a wheel drive in place of traditional chain drives, which facilitates quick changes of the screening drum – less than two hours using a wheel loader or excavator to lift it out, says the company. According to Andy Krol, Chief Engineer, “By eliminating the chain drive, we also eliminate the number one maintenance item on the machine. With the chain drive out of the way, we were able to relocate the engine compartment and the diesel tank down to ground level instead of 9-feet above ground, making engine maintenance more efficient and safer.”
Krol adds that the new 733 also has a larger feed hopper than previous models, which, along with redesigned drive hydraulics, further increases throughput and production efficiency. The 733 is powered by a 205 hp Caterpillar diesel engine that is Tier 3 (air emissions) compliant, meeting more strict air quality regulations such as those in California and Florida.
Multitek Inc.: The company’s newest trommel screen is the M650B, designed for high moisture soil applications. The unit incorporates 32 shaft-mounted flexible flail hammers on the inside of the screen that are designed to pulverize organic material while in the screen. The flails clear just a half-inch above the screen. This additional processing allows for a shorter drum, only 6.5 feet in length and a 5-foot diameter. According to Dale Heikkinen, whose father founded the company, this unique design results in far less reject material from the Multitek trommels – about five to 10 percent reject. “To give you an example, topsoil with clumps of sod are pulverized by the flails, with the majority of the soil product passing through the screen rather than coming out as reject,” he says. Another advantage of the flail is the mixing that occurs in the drum. “We are seeing applications of the screen in bagging soil and compost since it mixes the product and breaks up clumps while screening it,” he adds.
To keep the trommel screen clean, patented hydraulic-powered, 13-inch diameter cleaning brushes are also inside the trommel screen. A 16-inch nonpowered idler cleaning brush sweeps the outside of the trommel drum screen.
N40, Inc.: For 2007, N40 is adding Terra Select trommel screens to its product line. (Terra Select was formed by three Farwick brothers, who broke away from Komptech-Farwick). Its trommel screens are mounted horizontally, not at an angle. Material is moved through the drum by a helix mounted inside the drum, which assists material in contacting the drum for a longer period of time, and hence increases throughput of the screen. Lyndell Pate, N40 Sales Manager, explains this concept as follows: “Screening only occurs when the material is in contact with the drum, and therefore inclined drums with devices that cause the material to be airborne are not as efficient at screening. The Terra Select trommel moves the material while allowing it to maintain contact with the drum. Typically, the fines from a horizontal drum screen are cleaner and contain fewer spikes than their inclined drum brothers.”
The trommel design also includes digital controls, a “roll out” drum for changing screens, hydraulic drive with remote control, and hydraulic brush controls. A new fuel saving feature monitors the level of material in the feed hopper; once the hopper is empty, the control automatically stops the drum and conveyors, and engine speed is reduced to idle (700 rpm). This feature reduces fuel consumption of the trommel while the operator is doing other tasks, and then once the hopper is filled again, the screen automatically restarts and the engine accelerates to normal speed.
N40 also distributes the Backers star screening equipment, which includes both two and three fraction star screens in a variety of drive configurations, i.e. wheeled, tracked, and the 3-MBT model which offers both wheels and tracks in one unit. Windsifters can be added to the trommels and star screens; a stand-alone W6 Wind Sifter is also available.
Neuenhauser, Inc.: While no new screens are being introduced in 2007, Neuenhauser noted in our survey that features on its equipment are extending wear-life. The company’s Superscreener is a star screen used to process a wide range of materials, including aggregate, asphalt, C&D, chicken litter, shredded gypsum wall board, green waste, topsoil, wood chips, sludge, incinerator slag and paper/cardboard. According to Mark Leuner of Neuenhauser, typically star screens have had a bad reputation with sticky and gummy materials, as well as excessive wear. “What has evolved with our machines are incredibly good wear on our stars, typically 2,000 to 3,000 hours with aggressive materials,” he says. “This is due to the rubber compounds we are using on the stars.” Another advancement was to add more hydraulic power to the screen decks. “On the 230 star deck, for example, there are four hydraulic motors, rather than just one, so the screen does not stall, and is able to move material along,” adds Leuner. Other features include combs that wipe the shaft clean so material does not build up. The company also uses Caterpillar Tier 3 compliant engines.
The screens are available with tipping grids that can be remotely activated from the excavator so that rocks, logs and other large objects are thrown off prior to the star screen. For material that tends to be sticky, a vibrating tipping grid that shakes like a sieve is available.
Orbit Screens: The “Orbital Action” screen utilizes the principles of centrifuge, gravity and particle size separation by rolling the material so that large particles rise to the surface and tumble out over the lip of the screen, and smaller particles drop to the bottom and through the screen. The Orbit Screen has a unique self-cleaning feature whereby screen holes rotate continually, exposing a new side of the screen hole to the flowing materials. This action helps by wiping off some of the moist materials, small sticks, grass, etc. from the wire screen. “As the sheet of screen turns the hole is also turning and with each turn of the screen dish, all four sides of the hole are presented to the material flowing over the hole,” explains Brad Schnitjer, Sales Manager. “If a stick gets into the hole, the stick is soon brushed off the hole, which after a half turn is now the top edge, with new material flowing across it.”
A new, Model 68A Screening Plant features several improvements and options. A hopper extension increases hopper capacity from 1.8 cubic yards to 4.5 cubic yards, which allows use of larger loader buckets, and therefore improved productivity through the screen dish. Another option now available is a Grizzly with a standard bar width opening of 7.5 inches. Other spacing options are available, and the Grizzly will work with any screen opening size. The screens can be towed with a pickup truck, and have a nominal processing capacity of 50 cubic yards/hour.
Powerscreen: Two new models are being offered by Powerscreen, the Phoenix 3300 Trommel and the Chieftain 1700 deck. The 3300 trommel has a 30-foot, 7-inches by 7-feet, 7-inch drum. It has a hydraulic folding tail conveyor that can stockpile material to a height of 12-feet, 5-inches. The Chieftain 1700 comes in either two or three decks, and has increased stockpile capacity for the fines fraction. New features being offered on the Chieftain 2100X include a two or three deck option, a mounted auxiliary conveyor, and a new power unit.
Screen USA: This manufacturer of portable screening equipment recently introduced a portable box screener designed for small to medium users. The BOX810 is designed to use with topsoil and compost, and is equipped with a 10-foot wide by 8-foot direct feed screen box. New features on existing products include “severe shake” shaker screens for heavy-duty materials such as land clearing debris, C&D, asphalt and concrete. These track-mounted screeners also offer optional longer overs conveyors to feed directly into a grinder, rather than having to move the overs twice for further processing. Technology improvements include changing the rubber feeder conveyor belt on the shaker screens to a heavy-duty steel apron feeder. This design change is intended to eliminate the possibility of ripping a feeder conveyor belt.
Terex Finlay: The company is making improvements to the Finlay 883 Reclaimer, which will result in greater stockpile capacity, two speed track movement, and easy interchange top deck system on the screen to enable changes from mesh to punch plate, or fingers. Increased ground clearance is also a new feature.
United Rotary Brush Corp.: While it doesn’t sell screens, United Rotary Brush manufactures a critical screening component – the brushes that clean trommel screens as they work. For the most part, the brushes are custom-fit for each user. Brushes are typically supplied as a complete assembly, with the brush mounted on a core with a through-shaft. The brush also can be supplied as a loose coil that is mounted to the shaft by the end user. “Once a design is created, an item number is assigned to that brush,” explains Jeff Ghilani, General Manager of Engineered Products at United Rotary. “The screen owner can use this item number to reorder his or her ‘standard’ brush. We now offer a blanket/stocking program. Customers can have us build and hold a predetermined number of brushes in our warehouse. This reduces delivery time, and also offers a cost savings based on a quantity commitment.”
He notes that the two most frequently used filaments for trommel brushes are Nylon Type 6 and polyester. While nylon has greater abrasion resistance and durability and thus is more likely to last longer under the stress of brushing debris, nylon absorbs more water than polyester (maximum of 9 percent versus up to 0.5 percent for polyester); this retention creates a loss of stiffness in the Type 6 Nylon. “Because of this, polyester is the preferred filament for wet screening applications,” says Ghilani. “Since many screen users process both wet and dry waste, polyester filament provides the greater versatility and is most commonly used.” Brush replacement is needed when the filament becomes shorter and cannot flick or clean as effectively. In addition, for brushes to clean efficiently, they need to rotate smoothly with the screen. “If the brushes are not rotating smoothly, it is usually due to bad or dirty bearings,” he explains. “Proper maintenance and replacement of the brush bearings will ensure smooth operations.”
West Salem Machinery: West Salem manufactures oscillating, vibrating, trommel and disc screens. It recently introduced a portable disc screen to process preshredded wood. This eliminates the need to regrind material that is already “to size,” resulting in substantial energy savings. The disc screens can process up to 600 tons/hour of material, and have been used for hog fuel, C&D, shredded tires, compost, plastic, paper and OCC.
Wildcat Manufacturing: While not introducing new models in 2007, this trommel screen manufacturer has added new features, including tracked units, dust control devices, better clearance above the collecting conveyor, the AmeriMulch colorizer system, and a specialized feeding mechanism that includes a high frequency vibrating grid over the feed hopper. Technology improvements include remote controls capable of greater distance from the machine, more efficient hydraulic systems, a more efficient bag ripper, and an engine diagnostic system.
Tim O’Hara, Sales Manager, describes the bag ripper as being more efficient since it uses several different size ripper teeth for picking up and catching more bags. Other design features on the trommels include a radial stacking conveyor that swings up to 200 degrees, reversible drum and feed conveyor, optional stainless steel construction for acidic environments, a low feeding hopper so no ramp is required, and brushes that can be adjusted from ground level. Regarding the reversible feed conveyor, O’Hara explains that “it is used only to clear jams, but the reversible drum can be used to rock the barrel and clear a plugged drum. It can also be used when the drum is empty, to clean off the screen panels if the material is wet.”
Robert Spencer is a Contributing Editor to BioCycle. An environmental planning consultant, he is based in Vernon, Vermont.
Screen Directory page 26
Aggregates Equipment, Inc.
9 Horseshoe Road
Leola, PA 17540
700 Huyler Street
Teterboro, NJ 07608
1100 Holland Rd.
Suffolk, VA 23434
Bulk Handling Systems
Eugene, OR 97402
CBT Wear Parts, Inc.
13658 Hilltop Valley Road
Richland Center, WI 53581
Construction Equipment Company (CEC)
PO Box 1271
Lake Grove, OR 97035
Continental Biomass Industries, Inc.
22 Whittier Street
Newton, NH 03858
11299 Bass Lane
Caldwell, ID 83605
1030 Jaycox Road
Avon, OH 44011
EarthSaver Equipment, Inc.
P.O. Box 7325
Kalispell, MT 59904
P.O. Box 355
Essington, PA 19029
McCloskey International Limited
#1 McCloskey Rd. RR #7
Canada K9J 6X8
700 Main St.
P.O. Box 170
Prentice, WI 54556
N40 Inc. (Backers, Terra Select)
P.O. Box 1330
Rockwell, NC 28138
PO Box 1340
Greer, SC 29652
505 3rd Street
P.O. Box 345
Delhi, IA 52223
11001 Electron Drive
Louisville, KY 40299
March 23, 2007 | General
BioCycle March 2007, Vol. 48, No. 3, p. 22