July 21, 2009 | General

Evolution of The Compost Windrow Turner

BioCycle July 2009, Vol. 50, No. 7, p. 44
One of the earliest Compost Science references to windrow turners describes a mechanical stirrer constructed from old automobile parts and scrap, including a 1938 Ford V-8 engine.
Nora Goldstein

TRACKING back through the pages of Compost Science from the early 1960s, there are references to equipment designed specifically to turn compost windrows. An article in the Spring, 1964 issue, “Oregon Farmers Save Money By Composting,” describes an operation on the Glaser family farm near Lebanon, Oregon. The farm grew English rye grass on its 1,000 acres. The Glasers had their own warehouse and seed-cleaning mill, which generated a large annual supply of seed screenings.
A compost pile was constructed with the screenings in late January; moisture was added if necessary. “About the third week in March, the pile will be stirred with a turning machine especially constructed for the purpose by the Glasers. This stirring will produce a heavy heat in the pile that very quickly kills all seed germination … Stirring is essential to introduce oxygen and to loosen the pile so that additional water may be absorbed…” As the annual volume increased, they “decided to build a mechanical stirrer to replace the slower method of stirring by hand. This automatic stirring machine was constructed in the farm workshop from old automobile parts and scrap materials for a very small cost. The machine is powered by a 1938 Ford V-8 engine and has a hydraulic raising and lowering mechanism.”
“The machine operates as follows: The stirring machine is moved forward into the pile with an M International tractor for a pusher. The revolving drum shreds and kicks the material onto a revolving chain conveyor which deposits the material to the side, rebuilding the pile to the same depth. Output of the machine is 110 cubic yards/hour, thereby doing the work in about five hours that formerly took two weeks to do by hand.”
An article in the Summer, 1965 issue, “Composting Fruit and Vegetable Waste,” described composting experiments done by the National Canners Association Research Foundation, located in Berkeley, California. Research trials blended fruit and vegetable wastes with various amendments, including sawdust and rice hulls. Among the composting methods studied was turned windrows. In a section titled, “Windrow Composting of Fruit Waste Solids (1963),” the authors note that “upon completion of the 1962 study, sufficient information had been accumulated from the bin-type experiments to allow expansion of the compost operation.” The project was moved to another location to enable field-scale experiments. “A program was initiated to evaluate windrowing as a composting method for the disposal of solid fruit waste … An area measuring 50 feet by 100 feet was prepared and covered with asphalt to serve as the actual working area. A machine initially designed to remove rock and gravel from quarries was purchased. It was modified for the purpose of mixing, aerating and turning the compost windrow. A windrow-former was constructed which shaped the compost into windrows as it was being turned by the machine. A front-end loader was used to initially form the windrows before adding the fruit waste …”
“The spiral screw feeds the material to the bucket elevator which carries the compost mixture to a conveyor at the top of the machine, which discharges it into the windrow-former … A tanker truck discharged the ground waste into a canal formed in the windrow. The mixture was then mixed and reformed into a windrow by the turner and windrow-former.”
A short article in the Spring-Summer 1966 issue of Compost Science described a municipal refuse composting facility in Boulder, Colorado that had opened in May 1965. The Boulder plant “handled most of the municipal refuse from the City of Boulder,” said Harry B. Gorby, president of Rich-Land Company, which owned and operated the facility. Waste was tipped into a hopper and then conveyed through a covered area where salvage and sorting operations removed metals, glass and other recyclables.
After sorting, notes the article, the waste “continues by conveyor to a giant 200 HP pregrinder before being transferred to a windrow area for processing. Composting is accomplished in a series of windrows. The process is said to be accelerated by the use of the ‘RichLoam Rapid Composter’ which travels through the windrows shredding, aerating and moistening the material in a single operation.”


In the very first issue of Compost Science in Spring, 1960, Royer Foundry and Machine Co. in Kingston, Pennsylvania advertised its Royer shredder. The photos in the ad showed the Model 36 being used at the Leaf Mold Division in Toronto, Ontario. The headline of the ad read: “Roy’er•te. 1. to shred, mix, blend, aerate and remove undesirable materials. 2. in Composting, to make marketable.” While not a windrow turner, it functioned to aerate compost piles and accelerate decomposition of materials. Materials could be discharged into a windrow-like pile.
One of the earliest commercially available windrow turners in the U.S. was the Cobey Composter. In the Spring-Summer, 1966 issue of Compost Science a photo and short paragraph titled “General Products of Ohio, Inc.,” stated the following: “The Cobey Composting system has been used near Crestline, Ohio for composting manure and other organic wastes. According to the company, organic materials such as garbage would be dumped by trucks in windrows. A bacteria-destroying liquid (similar to that used in sewage treatment plants) is then sprayed on the material, which is turned by a one-man operated machine at regular intervals as required. General Products of Ohio will contract for the compost produced – packaging and selling under their own or private label.”
The turner was designed and patented by Herbert Cobey of Galion, Ohio in February 1968. According to the website,, the patent filing described the machine as follows: “A compost turning machine which travels along the ground and straddles a compost windrow, and which carries a rotating drum for turning the composting material. An adjustable auger system is located outboard and ahead of the rotating drum to collect composting material and deposit it in the path of the rotating drum. Each auger is independently driven by a hydraulic motor and can be individually raised or lowered as required.”
A brief article in the Autumn 1967-Winter 1968 issue provided additional details about the Cobey Composter: “The new unit is now in use at the composting plant in Johnson City, Tennessee. The Cobey Composter, as the unit is called, is a self-propelled, diesel-powered machine that travels through windrows of materials dumped from a truck or ejected by truck-mounted packer units … The compost unit is designed to accept windrows of approximately 8-1/3 feet wide and 5-feet high. The patented design of the machine permits the material processed to reform into windrows for successive processing operations … The machine can turn, aerate and reduce particle size at the rate of 1,000 to 4,000 tons/hour depending upon density and weight of material.”
The cover of the May-June 1972 issue of Compost Science featured the Cobey Composter, with the following headline: “General Motors Enters The Composting Field.” The accompanying article announced that General Motors’ Terex Division of Hudson, Ohio was marketing the Terex-Cobey 74-51 Composter developed by Herbert Cobey “over a period of years.” The model was a tractor-mounted unit “with hydraulically-operated paddles which lift and cast materials from the front to the right of the machine as it passes through a pile, shredding, mixing and aerating them.” The unit was designed to handle feedlot manures and municipal refuse, and cost $89,000. (By 1978, the Terex 74-51 was no longer manufactured, according to an article on windrow systems in Compost Science.)

As the 1970s unfolded, a handful of other U.S. companies introduced windrow turners, primarily to process feedlot manure and municipal sewage sludge. All of these companies continue to manufacture and market windrow turners today, and include Scarab Manufacturing and Leasing, Inc., Resource Recovery Systems International, Inc., Brown Bear Corporation and Wildcat Manufacturing. Another company, Midwest Bio-Systems, introduced an Austrian-designed windrow turner to the U.S. market in the early 1990s; soon after, it began manufacturing its own unit. The Austrian machine was designed and built by Siegfried Luebke in 1974. Each company has its own interesting history of how it became involved in the composting industry. Those stories are presented below in chronological order.

Scarab Manufacturing and Leasing
Marvin Urbanczyk, founder and president of Scarab Manufacturing and Leasing, Inc. in White Deer, Texas, started his career in 1961 as a farmer. He developed his equipment design and construction skills early on by modifying farm equipment and manufacturing most of the farm’s implements. “In 1973, the high cost of fertilizers to replenish West Texas’ poor soil led to a joint venture between my farming company, Urban Farms, Inc., and a local cattle feedyard to develop a method of quickly and economically converting manure into a stable soil amendment for our own use,” recalls Urbanczyk. “The feedyard owner was to supply the raw material, and I was responsible for designing a machine that would efficiently break up and aerate large volumes of manure. I didn’t know of any existing technology to do the unique job I wanted to do, so I started from scratch and designed a straddle-type, rotating drum machine. That was the prototype for today’s Scarab windrow turner.”
Shortly after the first unit was placed into service, a local entrepreneur who had started a biodynamic composting business saw it and referred one of his California customers to Urbanczyk. An order was placed for a turner. “This time the customer wanted to manufacture large amounts of high grade compost for resale, not just agitate manure so it could be used as a fertilizer,” he says. Word spread, and machine orders began trickling in. In 1976, Urbanczyk and his wife Janet incorporated Scarab Manufacturing & Leasing, Inc.
All of the early models used a driveshaft, clutch and belts to drive the rotating drum. “While the system worked, it demanded more frequent maintenance, constant adjustment and operator competence than I could be satisfied with,” explains Urbanczyk. “I felt it was the weakest link in what otherwise was a trouble-free and easy to use product. I was using hydraulic pumps and motors to drive the turner’s wheel, and became intrigued with the possibilities of a hydraulic drum drive. My first experiments were discouraging as our particular application is very demanding.” With the assistance of some hydraulic engineers and vendors, he designed a hydraulic drum drive that worked well during factory testing. It was installed on customers’ machines, but didn’t hold up during day-to-day use. “I returned to recommending belts as the best currently available drum drive at the time,” he adds.
In 1984, with the proliferation of larger municipal composting projects, Urbanczyk once again tackled the belt versus hydraulic drum drive conundrum. “The idea of an 18-foot Scarab was a natural, but I recognized that the necessary increase in engine size – from 360 to 400 HP – would finally render belts unfeasible as a mechanism for transferring power,” Urbanczyk recalls. “It was apparent that the future of our business would be defined by my ability to master hydraulics. I reconstructed the problems and mistakes that had plagued me before and ultimately worked through the problem. We sold an 18-foot turner with the hydraulic drum drive to the Metro Wastewater Treatment Plant in Denver for its biosolids composting operation and it operated successfully, eventually leading Metro to purchase two additional turners.”
Today Scarab offers both hydraulic and belt driven models; several different flail designs, configurations and drum sizes; pull-type and straddle-type models; and numerous wheel and track driven models. “Our 38 years of experience are put into each Scarab designed,” says Urbanczyk.

Wildcat Manufacturing
Charles Melhoff, founder of Wildcat Manufacturing in Freeman, South Dakota, designed and assembled farm equipment. In the early 1970s, he was approached by a local organic farmer who wanted to start composting, and asked Melhoff to make him a turner to fit his tractor. “I sat down with him, figured out his needs and built the unit,” recalls Melhoff. “Word spread to other organic farmers, so we continued building and selling the turners.”
The drum-style turner was mounted on wheels and pulled by a tractor. It could pass through half of the windrow at one time. “Back then, the tractors weren’t large – about 70 to 100 HP,” he adds. “They didn’t have the power to turn a full drum, so we split the windrow in half.” Over the years, features such as a watering bar were added. Eventually, Wildcat introduced a straddle-type turner. “The design of our flails stayed the same, but we added another row of flails on the straddle turner, which spiraled around the drum,” says Melhoff. “That design worked very well.”

Resource Recovery Systems International, Inc.

Lester Kuhlman, a beef cattle nutritionist by training, was working as general manager for a cattle and sheep feeding operation in Colorado in the early 1970s. A late September snowstorm caught all the feedlots in the region by surprise, turning the cattle pens into mush, recalls Kuhlman. “This happened all over northern Colorado. Normal procedure in those days was to spread all the manure onto cropland, but the storm came so early and it was such a big storm, that all the feedyards in the area were backed up with manure. I figured there had to be a better way to manage all that waste material, either to beat the weather or clean out the pens using a different process. Composting seemed to be an option, but the feedyard was not interested in pursuing it.”
In 1975, Kuhlman decided to explore the composting route on his own and formed a company. His first customer was a farmer/feeder – a 15,000 cattle feedyard with 2,000 acres of land. “It is a very nice combination when the feeder is also a farmer,” he says, “because the best, most profitable market for your compost is your own crops.”
A year later, in 1976, Kuhlman formed a second company, Resource Recovery Systems of Nebraska. He was working with the Omaha Livestock Market (thus Nebraska in the company name), which was having a huge problem with its manure. “They were piling it up, so we looked at composting as a problem-solving exercise,” Kuhlman explains. “I used composting equipment that was available at the time. Because of our involvement with our own projects and custom composting at feedyards and city projects, we realized upgrades were needed in the current machines on the market. I wanted a more durable machine with more horsepower and introduced our own turner in 1981 – the King of the Windrow (KW).”
The first machine sold is still in use today, he adds. While improvements have been made, the original design concept hasn’t changed, except for offering several models and options for each machine as well as variations in drum designs. “We have three different styles of drums,” he says. “Two are good for chopping, e.g., leaves/yard wastes, animal bedding/straw, etc. A third style provides gentler action but equivalent capacity and mixing capabilities.”
In more recent years, Kuhlman and his wife Joan, have seen sales of their equipment increase in overseas markets, leading to the change of the original company name to Resource Recovery Systems International (RRSI). “The Middle East is really anxious for composting, so we are doing work there,” says Kuhlman. “The government can promote composting, and by and large, the compost will go back to agriculture.” As explained on the RRSI website (, Kuhlman has consulted with projects in many countries around the world.
He also sees growing interest in composting among farmers in the United States, especially as the cost of fertilizer has risen. “The ag market, especially where we are in Northeast Colorado and surrounding states, is booming,” he adds. “With high fuel and fertilizer costs, farmers, dairies, and cattle feedlots are now substantially involved in making and using compost.”

Brown Bear Corporation
Brown Bear was founded in 1961 by Roscoe Brown to manufacture products for pipeline and drain tile backfilling. One piece of equipment was a rubber-tired machine with an auger mounted on the front for backfilling pipeline and drainage trenches. Brown Bear had sold one of these machines to a contractor near Lincoln, Nebraska, who was using it to install drain tile along the side of the road. This road was traveled frequently by Dr. Leon Chesnin of the University of Nebraska in Lincoln, who happened to see the machine in operation. “He stopped his car and got out to watch the operator backfilling a ditch,” recalls Stan Brown, who had joined his father’s business in 1969. “Dr. Chesnin had been one of the early researchers on farm composting in the U.S. He asked the operator where he got the machine, and he told them it was Brown Bear. Leon thought the machine would be great for turning compost windrows.”
Chesnin invited Stan Brown to come over to the university where he was composting manure in windrows. “Basically, he would scoop up the manure with a loader, put it in the spreader, and let it go out the back to build the windrow,” says Brown. “He also used the loader to turn the piles. It was labor-intensive and expensive for the machinery. Leon convinced me to send a machine over to use in the composting trials, which I did in the summer of 1977. That was our entry into composting.”
He adds that the following year, Compost Science (then Compost Science/Land Utilization) held a conference in Omaha. “Dr. Chesnin was involved, and he got us involved as well,” says Brown. “That was our first exposure to BioCycle. We were one of five or six exhibitors!”
Experimentation with the solid continuous auger mounted on the front of the machine continued at the University of Nebraska for several more summers. In 1979, Brown Bear decided to try changing the rotors on the auger to paddles. “Leon and I realized that we could get a better mix with the machine if we used paddles,” he explains. “We thought we could call them continuous flails if we put a whole bunch together in a row. After a lot of testing and modifying, we came back with the design we have now – three rows of paddles on the smaller unit, and four rows on the larger unit. It was a compound helical pattern that works like an auger but is more like a flail so we get a lot more aeration. We were able to go from 125 rpm to 200 rpm. The increased speed and the change to the paddles or ‘inclined flail’ gave us a lot better machine for working with yard waste and green waste where you need more decimation.”
Although the turner was developed around manure composting, one of the first markets was in the wastewater treatment field. “We sold a lot of equipment early on for drying sludge,” says Brown. “Jack Dickens, an assistant equipment superintendent for the City of San Diego, saw our ad in a pipeline construction magazine for our trench backfilling machine and thought it would be great for mixing sludge that came out of the city’s digester with soil for landfill cover. He called and asked what I thought and I asked, ‘what is sludge and what is a digester?!'”
Fairly assured that the application would work, Brown flew to San Diego to assess the opportunity. The city decided to lease a machine for six months on a lease-purchase agreement. “It worked so well that they were done in a month instead of six months,” he recalls. “Jack was a backyard composter and he was friends with the head of San Diego’s Parks and Recreation department. At the time, Parks and Recreation was buying Milorganite [dried biosolids made by the City of Milwaukee, Wisconsin] by the train carload. So for the next five months, the machine was used to dry sludge that was stored in pits until the bottom became solid (about 40 to 50 percent solids), and then they would haul in leaves and grass clippings. The compost they made over the next five months replaced a lot of the Milorganite!”
While San Diego did not end up buying the machine due to a budget shortfall, it made its way to Phoenix for use in a similar application. “While the pits that Jack had in San Diego were 3-feet deep, the biosolids pits in Phoenix were 5 to 6-feet deep,” he notes. “We put bigger tires on the machine and it worked. The city bought the unit, which was our first sale in the environmental industry.”
Since that start, Brown Bear has gone on to develop and introduce several sizes of self-propelled composting units, as well as attachments for skid steer and compact track loaders, farm tractors and large wheeled and track construction type loaders.

Midwest Bio-Systems

To understand the history of Midwest Bio-Systems’ (MBS) Aeromaster windrow turner, one needs to go back to when Edwin Blosser began working for his father-in-law on his farm in 1984. “He had just learned about a new way of farming called ‘renewable farming,’ which was a slick way of saying that every year the farm gets more productive versus less productive,” recalls Blosser. “He said, ‘you are young, you can grow into this. I would like to have you learn as much as you can about soil fertility and the best management practices that end up making a farm renewable.'”
Blosser set out to learn as much as he could, testing all sorts of products and farming practices that claimed to boost soil fertility and productivity. “I had a lot of experiences – some good and some really bad,” he says. “By 1987, we were able to put together a systems approach to improving our soils, based on measuring soil tilth, balancing fertility, understanding which fertilizer materials to add to the soil, etc. Over the next several years, we were advising farmers in our community with a total of about 10,000 acres of active farmland.”
One significant remaining question was how the microbial products interfaced with the microbial aspects of the soil. “I knew there was life there, but I didn’t understand it,” he says. “I attended an ACRES conference in 1989 and met Amigo Bob Cantisano, who spoke with me about composting. It was the really the first time I had it explained to me. That winter, I learned about the Luebke family in Austria, who was doing work with enzymes, inoculants and composting. I ended up taking a trip to Austria and East Germany in 1992, where I met with Siegfried Luebke. He was a chiropractor who came to the conclusion that nutrition was the reason for people’s sickness or health. He bought a 37-acre farm and knew that he wanted to make compost. Luebke built a static pile with hopes that the material would rot. A year later, he found out the pile needed to be mixed better. He started using a pitchfork but that was very slow, so he made an agreeement with a local machine shop and built his first windrow turner. That happened in 1974.”
While in Austria, Blosser saw first-hand how inoculating the materials to be composted enabled the microbes to make use of the rotting materials to form long-chain polymers. That knowledge formed the basis of what MBS describes as “humus compost.” In May 1992, Blosser ordered a compost turner from the Luebkes. Soon after he developed the Aeromaster design and began to build and supply those along with auxiliary equipment and consulting services out of Tampico, Illinois. “We have a very simple proprietary system built into the drum that allows each particle to be treated individually, supplied with moisture, inoculants, and oxygen,” he explains. “We started with a 10-foot machine, then introduced an 11-foot unit. Today, Midwest Bio-Systems is on its ninth iteration of the drum, and there are over 400 of our turners in use in 20 countries.”

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