January 25, 2009 | General

Historical Perspective: Grinders, Chippers, Shredders

BioCycle January 2009, Vol. 50, No. 1, p. 16
BioCycle looks back at the development of size reduction systems that have helped to grow the organics diversion industry.
Rhodes Yepsen and Nora Goldstein

SIZE reduction equipment is used on the front line of the organics recycling industry, processing wood, yard trimmings, agricultural waste, C&D debris and more into feedstocks for composting, mulch, biomass fuel, etc. Modern grinders, shredders and chippers are powerful and efficient, evolving from much smaller machines manufactured for various industries. The first tub grinders and stump grinders came out of the agricultural sector, whereas other companies approached the industry from the forestry or land clearing businesses, starting with delimber-debarkers and then expanding into whole tree processing.
Several common threads emerged as interviews were conducted for this article: Many manufacturing companies that started in the 1940s and 1950s are led by family members of the founders; grinding and shredding concepts that went into original designs are still in use today, albeit with heavier duty components and bigger engines; and servicing customer requests led to many company entries into the organics recycling market. This historical perspective on the size reduction industry starts in the agricultural arena, then moves through forestry and land clearing. Company histories in each section are presented in chronological order.

W.H.O. Small grinders were often used in the 1940s for processing hay and alfalfa into feed. “My grandfather, Walter Henry Oberwortmann, invented the tub grinder back in 1945,” says Jon Littler, grandson of W.H. Oberwortmann and President of W.H.O. Manufacturing. “He was grinding hay and alfalfa into feed meal using a small grinder, sacking it in 100-pound bags and shipping it to cities like St. Louis on the train.” A desire to streamline this process led to the invention of the tub grinder with a rotating tub that feeds the hammermill. According to Littler, “Walt was looking for a more efficient way of grinding feed. Loading the small grinders with pitch forks was a slow process and a lot of work, so he invented the tub grinder as a way of speeding this process up.”
The first W.H.O. grinder was a model P12, and had between 150 and 175 HP. W.H.O. held a patent on the tub grinder from 1952 until 1969, leasing the right to manufacture to other companies. A customer request led to manufacturing a line of industrial wood waste grinders. “In 1980, a customer who processed walnuts asked for a grinder that could handle the walnut limbs,” says Littler. “The style of the grinder was fine, but it needed heavier steel and cylinders, since wood is harder on the equipment. It took about four years to perfect the modifications for the wood grinder.”
Vermeer: Vermeer Manufacturing Company also has its origins in 1940s agriculture, looking at ways to make operations more efficient. Gary Vermeer entered the manufacturing world in 1948, inventing a wagon hoist. “The wagon hoist had a cable to lift the wagon, using gravity to unload the contents,” says Jerry Roorda, Environmental Product Specialist for Vermeer. “Prior to that, material had to be scooped out by hand.”
Vermeer then developed a stump grinder, to remove stumps from farm fields. This process was labor intensive, and became more of an issue with the spread of Dutch Elm disease across the U.S., leaving large numbers of problematic stumps. “Gary Vermeer worked with local farmers to develop a PTO [power take-off] stump grinder,” says Roorda. “Initially this was a thrashing rotor mounted on the back of a tractor. However, innovation really came by accident – the tractor was driven forward and backward to get the stump out, but during a test a farmer accidentally hit the brakes, causing the stump grinder to go sideways. It cut about five times faster, leading to a major innovation in the way the commercial stump grinder was developed.”
Vermeer is still family owned – Gary’s son Gary Vermeer and daughter Mary Andringa are co-CEOs. The third generation works for the company as well. Vermeer entered into the wood waste recycling industry in the 1980s, introducing a tub grinder. “Gary Vermeer was concerned with the safety of tub grinders, and the liability of thrown objects,” recalls Roorda. “He decided that if the company couldn’t design a safer tub grinder, it wouldn’t develop one at all. This was the birth of the two-piece thrown object restraint system, and later the rotor guard.”
DoppstadtUS: Werner Doppstadt, an agricultural company, was founded in Germany in 1965. “Prior to that, the Doppstadts were agricultural contractors, taking equipment to local farms for soil processing etc.,” explains Shane Donnelly, Sales Manger for DoppstadtUS. “Existing equipment was not up to their standards, so they decided to design and build a grinder for their own use.” The first grinder was a 250-HP high-speed flail hammermill, tolerant of tramp metal. “This initial Doppstadt grinder was taken to a trade show for demonstration purposes, and somebody purchased it, leading them into manufacturing more grinders,” adds Donnelly.
After the high-speed grinder, Doppstadt introduced a trommel screen, followed by a slow-speed high-torque grinder in 1996. “There were other slow speed grinders on the market in other industries, but ours was the first for the green waste and composting industry,” observes Donnelly. “With fuel prices already high in the mid 1990s, there was demand in Europe for the slow-speed grinder, which is more efficient and has less wear. It has a true direct drive, not a hydraulic drive, meaning there is a more efficient transfer of power, and thus higher fuel efficiency It also makes a coarse product, ideal for promoting aerobic conditions in the composting process.”
One challenge with a conventional direct drive is that it cannot reverse, meaning that if a contaminant becomes caught, it jams the machine. “Joseph Doppstadt adapted a breakaway, pressurized comb for single shaft,” he says. “This allows material to pass through under normal conditions, but at a certain pressure, when contamination enters the grinder, the comb breaks away, allowing the problematic material to drop out; the grinder resumes operation once the material has been removed.”
DuraTech: Joe Anderson, a farmer and rancher in Woodworth, North Dakota, started J&J Manufacturing in 1966 to build tub grinders. He found that other grinders on the market were too large and expensive for the average farmer, so he sought to build one that would be a better fit for the agricultural industry. Later named Haybuster Manufacturing Company, the first model offered was a PTO tub grinder for processing hay, which ran off an 80- or 100-HP tractor. The company was subsequently renamed DuraTech Industries International, Inc. Ownership remains in the Anderson family.
“In the late 1970s and early 1980s, people were using hay machines for grinding other things, so we built several mills for grinding newspaper,” says Al Goehring, DuraTech’s Marketing Manager. “This was the start in the recycling market for Haybuster. There was a need for heavier, more durable grinders to handle green waste, etc., and throughout the 1980s, we increasingly focused on the development of an industrial line of products as the need for recycling and composting emerged.”
Everything on the original equipment had to be adapted in order to process wood, green waste and C&D. “Basically, we had to make everything heavier, and with more horsepower,” explains Goehring. “Innovations for the grinder continue to come from the agricultural side though, such as putting on electronic governors, etc.”
CW Mill: In 1967, Clyde Wenger started CW Mill, a factory for making alfalfa pellets, using a homemade grinder. He started manufacturing grinders for sale in 1976. “These were stationary electric grinders for alfalfa pellet mills,” says Tim Wenger, Clyde’s son and President of CW Mill Equipment Co., Inc. “In 1978, we introduced a large portable diesel unit, and then a smaller tractor PTO model to compete with others on the market.”
Its move into heavier-duty grinders happened in the late 1980s, when CW Mill sold a grinder to Land Reclamation in Portland, Maine. “We had built them a stationary double hammermill tub to grind rolls of damaged paper from a nearby plant, and they asked us to design a heavy duty wood grinder so they could process a wider range of materials,” recalls Wenger. “We basically doubled the size of everything on the hay grinder, which was already pretty thick. A vendor’s salesman said that it was a monster machine, and since wood grinders were often called hogs, the name HogZilla was born.”
CW Mill continued to make larger HogZilla wood grinders, and then a customer complaint about the dry clutch not lasting long enough led the company to look for alternatives. “The rock crushing industry was using torque converters instead of clutches, which were tougher and gave better production and fuel economy,” notes Wenger. “We redesigned our grinder around the torque converter in 1993, introducing the TC series. Our business took off, because the organics recycling industry was willing to pay more for a tougher grinder, unlike the agricultural industry.”
Rotochopper: In 1982, Vince Hundt started Poplar Coulee Ridge (PCR) Inc. to import and market forestry equipment from Finland, including skidding winches and wood chippers, sized to handle wood lots on Midwestern farms. In the 1980s, recycling mandates were being passed, which led the company into manufacturing a machine that could process old newspapers. “I put together a John Deere hay baler, the wood chipper from Europe, and a sheet metal cyclone for a machine that could make farm-sized bales of chopped newspaper,” says Vince Hundt of Rotochopper, Inc. “The PCR Newspaper Bedding System was an instant success, and led to a partnership with Fred Peltz to make bigger recycling equipment, sold under the name Rotochopper.” Up until that time, Peltz had been manufacturing equipment for the turkey production industry. The first Rotochopper Newspaper Bedding System was introduced in 1990, and had a 30-HP electric motor on a newly designed paper chopper.
In 1992, Rotochopper designed a machine specifically to grind wood pallets into boiler fuel, making a uniform particle size in one pass. This machine used a wide horizontal rotor that could take a whole pallet at one time. It also employed a closed grinding chamber design. “Then, in 1994, we introduced the MP-156, a 180-HP horizontal grinder that weighed 18,000 pounds,” explains Hundt. “This was a huge leap forward for the industry, achieving particle size requirements that a tub grinder couldn’t manage, and in a machine that addressed the safety concerns customers had with tub grinders.”
In 1997 Rotochopper put an AutoBelt Drive (ABD) on its MC-166 grinder, a clutchless power transfer system. “Most large grinders at the time had friction clutches, just like a Model T,” says Hundt. “The ABD replaced this clutch, which was prone to failure, and one of the biggest maintenance problems in grinders. There are no complex parts – it’s all out in the open and very operator friendly. This is one of the most important features of the Rotochopper grinder.”
Komptech USA: In 1987, Josef Heissenberger and Rudolf Pretzler started Heissenberger & Pretzler GmbH, an engineering firm in Austria for agricultural machinery. “In 1990, we designed a windrow turner for the treatment of waste streams in the agricultural industry,” says Todd Dunderdale, Director of Sales for Komptech USA. “In 1992, we began manufacturing the windrow turners in house, to ensure a higher degree of quality control, and marketed them as the Komptech Topturn.”
Komptech’s entry into the grinder industry came through its involvement in organics recycling and composting. “Our Crambo filled a void in the market, because it was designed specifically to grind green waste and wood for large-scale commercial composting facilities,” explains Dunderdale. “This makes our equipment different from machines that were developed from other industries to fit the organics recycling market. Although there were other low-speed, high-torque grinders on the market in Europe, they were based on processing MSW and were more volume reducers. The Crambo, on the other hand, has a dual shaft designed to aggressively grab wood, and easily changeable screens to make a uniform product.”
One of the main influences for innovations with Komptech has been the rules and regulations in Europe, e.g., noise requirements and landfill bans, along with high fuel prices. “This has led our equipment to be compact and efficient, using torque instead of massive amounts of horsepower,” he adds. “We also designed our machines to be modular, so that owners can easily change the chassis of any machine. For instance, a Crambo mounted on a trailer chassis can be unbolted and reattached to a chassis with tracks, making it a very versatile machine.”

Morbark: After serving in World War II, Norval K. Morey returned to Michigan where he and his brother started a business harvesting and selling cedar timber. A chance meeting with Robert Baker about a decade later laid the groundwork for what today is Morbark, Inc. Baker had a scale model of a machine designed to peel bark from pulpwood logs, a task traditionally done by hand, but didn’t have the capital to manufacture the machine. Through the winter of 1957-58, Baker and the Moreys worked to develop a full-scale prototype debarker. After numerous challenges, the Morbark Portable Debarker Company was founded. “That post peeler was built primarily for ranchers and farmers using cedar posts,” says John Foote, Morbark’s Vice President of Sales. After the post peeler, Morbark started building other sawmill equipment such as chippers and screens.
During the 1970s, continues Foote, Michigan was faced with the Dutch Elm disease. “Huge Elm trees were dying and municipalities had no way to dispose of these trees other than burning them. In 1971, Morbark was the first company to develop the portable whole tree chipper. This was really our introduction into recycling and waste management because it was our first size reduction piece of equipment. Since we utilized our sawmill chipper on these portable whole tree chippers, pulp mills soon discovered that in-woods chipping could produce a product for their pulping and wood energy applications.” This led Norval Morey to become a strong advocate for wood energy.
“My father showed me over 30 years ago that wood energy was the right thing to do for our country and for Morbark,” notes Lon Morey, Norval’s son and President of Morbark, Inc. “I also saw demand for recycling wood debris into other markets such as compost and mulch to be just as valuable for the waste management solutions provided.” Morbark expanded into the hand-fed chipper market using the same technology, but on a smaller scale. “The introduction of the hydraulic feed wheel with the safety control bar on hand-fed chippers revolutionized that industry,” explains Foote. “It made feeding a chipper much safer than ever before.”
In the late 1980s, land clearing customers asked Morbark to develop a machine to process stumps. “The disposal costs at local landfills were escalating and some landfills even refused to accept stumps,” Foote recalls. In 1990, Morbark introduced the Waste Recycler, a 650-HP portable machine capable of processing stumps through an 8-foot diameter grinding disc. “This was our introduction into the emerging green waste recycling and mulch market that we understand today,” he adds. “Morbark’s strength has always been that its roots were in forestry and sawmill businesses as opposed to agricultural applications. We understand the demands of processing wood on equipment longevity.”
West Salem: Founded in 1947, West Salem Machinery Co. traces its roots back to Carl Gerlinger, Sr., who emigrated to Oregon at the turn of the 20th century. He was a machinist by trade who was very familiar with steam power. “He did a lot of work for the railroads and some of the logging operations that used steam power,” says Mark Lyman, current President of West Salem and Gerlinger’s great grandson. “There was an industrial accident when Carl was in his mid-20s, and he lost an arm so he was no longer able to work as a machinist. He started a small business in Dallas, Oregon, and eventually started a number of companies throughout the state, all related to the metal trades and generally associated with manufacturing. West Salem was one of his business offspring.”
In the early 1960s, the company began building waste wood chippers for the sawmill industry in the Pacific Northwest. From there, and through the 1960s and 1970s, West Salem grew and did quite well servicing sawmills. “Our line included chippers, vibrating conveyors, chip screen, disc screens and bark hogs,” says Lyman. “But when the 1980s hit, it became a brutal time for the sawmill industry. Interest rates jumped up to 16 to 17 percent to crush inflation, and there was a crash in the housing industry. New machinery sales to sawmills went to zero.”
Lyman joined the company in 1983. His goal was to diversify West Salem’s products and markets, which is a continuing theme today, he notes. “Our first diversification was throughout the wood products industry. We sold equipment to particle board plants, medium-density fiberboard (MDF) plants, the paper mill industry and to biomass power plants. As we moved into new markets, we identified new applications, e.g., we expanded into our shredder and hammermill lines for the fine grind, especially for the particle board and MDF industry.”
Another development for West Salem has been to supply more than just a grinder, he adds. “We are a systems provider at this point, using more of a turnkey type approach. We can supply a complete machinery package that delivers a specifically sized product in an efficient manner.” Having been in the industry for so many decades, the company is tapping into the resurgence in biomass power. “We can service the biggest plants in the world, with grinders up to 1,500 HP,” says Lyman.
Bandit: Bandit Industries, Inc. started in 1983 with the introduction of the Model 100 Brush Bandit chipper. “Mike Morey, Sr. introduced the original 12-inch capacity hand fed chipper,” recalls Jerry Morey, Bandit’s President, who joined the company in 1987. “It was targeted mainly for the tree care industry, including utility companies, parks and recreation departments and tree service firms. Prior to introducing the Model 100, chippers for that application were simple drum chippers. Bandit incorporated a feed system that would collapse and crush the limbs, eliminating the need to trim everything prior to chipping.”
In 1989-1990, Bandit developed whole tree chippers designed for processing land clearing waste and larger diameter materials at landfills. “We introduced the first whole tree chipper that was self-propelled,” says Morey. “The chipper could be taken to the trees, versus having to forward that material to a central spot when clearing.” The machine became popular for clearing rights of ways, such as for gas and oil pipelines. “Back then, most operators just blew the chips back onto the ground,” he adds. “In this day and age, the whole system is changing as people want to collect what they clear for biomass fuel.”
In the mid-1990s, Bandit introduced the Beast Recycler, one of the first horizontal grinders on the market. “Our process is uniquely different,” according to Morey. “We use a cutter mill that is very versatile and easy to change to a different style of cutting, e.g., chip, split, grind or just hog up. A set of teeth can be changed in 30 minutes.”
Three years ago, Bandit expanded its line of horizontal whole tree chippers to service the biomass energy industry. Fuel source processors or the biomass facilities can modify the chipper to meet the needs of their particular system, e.g., chunkier material versus a chip versus ground wood. “We have a number of teeth available that gets them the fuel product they want,” says Morey. “We are selling a lot of chippers to Europe and into Canada.”

Peterson: In the 1950s Wilbur Peterson & Sons was a heavy construction company, clearing land and building roads up and down the West Coast. A major market was land clearing for flood control dams along the south Willamette River area in Oregon. “For instance, one project was clearing 100 miles or so for a right of way, cutting down lodge pole pines in eastern Oregon,” says Dave Benton, Marketing Manager for Peterson Pacific Corp. “The trees were too small for sawlogs, so they purchased a chipper and sold the wood to hog fuel markets. Peterson realized that if the bark could be taken off before chipping in the field, it could be sold as clean pulp wood, at a higher value.”
The initial expansion into manufacturing was to develop equipment to suit Peterson’s land clearing and construction needs. The first machine was a chain flail delimber-debarker that could sit behind the chipper. It used short lengths of chain on a shaft that acted like a wire brush, beating the bark off. “The delimber-debarker took small diameter ‘waste’ trees and made them into a high value product, increasing the amount of useable fiber per acre,” explains Benton. “Other companies heard about the device and wanted them, which led Neil Peterson, Wilbur’s son, to start the manufacturing business in the mid 1980s.” Peterson’s first commercial delimber-debarker was sold in 1987.
The machine opened up a new market niche for the company. “In the field, the delimber-debarker produced a lot of bark,” says Benton. “Operators were putting the bark into tub grinders and selling it as hog fuel, but tub grinders can be very dangerous, throwing material when they get close to empty.” There was a need for a grinder that could produce the same material more safely. Around 1990, a customer gave Neil Peterson a sketch of grinder on a scrap of paper, which became the basis for the horizontal grinder.
A major innovation for Peterson’s horizontal grinder was the development of an upturn rotor in the mid 1990s. “We redesigned the grinder chamber itself, changing the direction of the rotor, as well as switching to an open-hopper, with a drive chain pulling continuously,” explains Benton. “The standard horizontal grinder has a downward swinging rotor, which moves against a fixed anvil. Our redesign has the rotor impact wood on the upstroke, breaking it up before it hits the anvil. This redesign increased the efficiency and reduced the number of fines, making our horizontal grinders competitive with the tub grinder on a horsepower to production basis.”
Diamond Z: Marty Zehr and his father founded Diamond Z Manufacturing in 1989, after 20 years of using hay grinders to make cattle feed. “The Zehrs were always modifying and fixing the grinders, so they made their own,” says Pat Crawford, Vice President of Products at Diamond Z. “People saw it and were impressed, and asked them to make a grinder for the wood grinding industry. In 1989 they made the Diamond Z Model 1463, a 90,000-pound tub grinder for stumps with 750 HP. This was the largest on the market.” The company went national in 1990, and became a success in 1992 after Hurricane Andrew, getting involved with disaster debris cleanup.
Modifications made to the tub grinder to service the wood grinding industry included replaceable hammer tips. “Hammermills were all swing hammers at that point, and they would break down and need be fixed at the end of a full day,” says Crawford. “They were tired of working all day, welding all night, so they bolted on replaceable tips. Then they introduced a fixed hammer for increased productivity, and used hydraulics instead of chains.”
CBI: Anders Ragnarsson came to the U.S. from Sweden in 1983 and started a land clearing business. Although clearing land was the company’s primary service, Ragnarsson recognized that wood waste produced could be converted into a useable product, such as biomass fuel. The existing equipment didn’t seem rugged and efficient enough for the job, so in 1988 he and his wife Amber Bell founded Continental Biomass Industries, Inc. (CBI). Over the next two years, the company worked to engineer a durable grinder that would turn wood waste into a biofuel, resulting in the 1990 release of the Grizzly Mill. “This was a stationary grinder that operated at a lower rpm than a traditional hammermill hog, using a patented offset-helix, high-inertia, solid-steel rotor that was easy to maintain, had low power consumption and was tolerant to rock and steel contamination,” explains Aaron Benway, CBI’s Northeast Regional Sales Manager.
Still a standard CBI product today, the first Grizzly Mills were located at sawmills, pulp mills and stand-alone energy plants. They were used to grind wood waste into boiler fuel for cogeneration (to produce heat and electricity). In 1991, the Grizzly Mill became the basis for CBI’s first mobile grinder, the RoadMill. In 1995, CBI developed a new style of horizontal-feed wood grinders, called Magnum Force. “Although a lot had to be invented for the move into horizontal grinders, there was some carry over too,” explains Benway. “One of the major innovations in our early grinders was the clamshell opening, which provides easy access to the rotor and screen for quick maintenance and repairs. This feature remains unique to CBI, and was transferable to our horizontal grinders.”

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