BioCycle July 2007, Vol. 48, No. 7, p. 51
Most mixers for the composting industry have their roots in animal feed preparation and rationing. Several units are targeted at biosolids processing.
Nora Goldstein

AMONG the workhorses of the composting and organics recycling industry are mixers – equipment to size reduce and blend feedstocks for composting and/or stabilization of biosolids. Many of the manufacturers surveyed for this month’s What’s New? report have their design and application origins in the animal feed (rations) industry. Augers or screws with knives to cut up hay bales while mixing in other feed ingredients, and discharge chutes that can be directed to fill troughs, have a direct application to composting. The cutting and turning action of the mixers helps to size reduce feedstocks such as yard trimmings and corrugated cardboard, while blending materials to achieve an optimum mix. The discharge chutes can be modified to unload directly into windrows. Equipment mobility – many of the manufacturers offer trailer and truck-mounted units – accommodates materials handling needs of composters and biosolids recyclers.
The transition from agricultural to industrial applications (typically the product category in which manufacturers have their composting equipment listed) has required some modifications to the mixing equipment. “Because the material is typically more dense, and the throughput requirement is often more aggressive in the industrial setting than with our more traditional agricultural customers, we have seen the need to provide heavier drive systems and heavier duty mixing components,” says Chris Searles, Product Specialist in Kuhn Knight’s Industrial Division.
Most manufacturers surveyed offer a number of designs and models, with a full range of throughput capacities. Several mentioned that they custom design mixers, e.g., varying placement and number of discharge doors. A key factor when selecting a mixer is the need for size reduction and breakage of feedstocks. For example, a biosolids composting facility with a set recipe of sawdust and wood chips, and a steady flow of materials, is well-suited to a stationary mixer that specializes in blending. Conversely, a food waste composting facility receiving a variety of feedstocks that include cardboard boxes, whole melons, roughly ground yard trimmings, etc., may opt for a mixer with cutting knives on the screws or augers.
“Questions we ask customers when they are determining which mixer to buy are how much volume per day they expect to handle, the size of the materials they will be mixing, and whether they will need size reduction and blending, or blending only,” says Garland Smith of Roto-Mix. “Answering those questions guides what type and size machine is needed to get the job done.”
In addition to identifying the appropriate mixer for the client’s materials handling needs, manufacturers use their experience to help composters get off on the right foot with their feedstock recipes. “We work with our customers’ recipes to get the right mix for their particular need, such as moisture level, porosity and C:N ratio,” says Jim Reed, Industrial Sales Manager for Patz Sales, Inc.
Ten manufacturers of mixing equipment responded to BioCycle’s What’s New? request for information. Summaries of their responses are below. The accompanying directory of manufacturers includes website addresses, where more specific details can be obtained.
EQUIPMENT OVERVIEWS
ALLU: The ALLU Group markets a Screener Crusher for mixing and blending materials prior to composting. The unit can be attached to skid steers, excavators and wheel loaders. A rotating drum mixes and blends materials; the drum has hammers for breaking and crushing larger particles. There are 48 different models and capacities, from 0.5 cubic yards (cy) to 4 cy on one bucket. “The smallest unit handles approximately 32 cy/hour, while the biggest model has a throughput of about 250 cy/hour,” says Marko Melto of ALLU. In addition to composting facilities, the screener-crusher is used at a number of soil remediation sites. “A unique feature of the ALLU SM Screener Crusher is that the operator can choose an end material size from 1-inch minus to 4-inch minus,” adds Melto. “The type of hammers on the drum can be changed as well.”
Cementech: Cemen-tech, Inc. specializes in alkaline systems for the treatment of wastewater biosolids. It makes continuous mixing soil processors, available in stationary and mobile units (the latter are self-contained mixers on a trailer). The units have a single-shafted, high sheer paddle mixer with hard wear blades. Volumetric proportioning is used to prepare the mix of materials accurately. “All types of dewatered biosolids can be processed using our mixers, including primary and waste activated,” says Marc Nusser of Cementech. “Capacities of the various models range from 5 wet tons/hour to over 75 wet tons/hour, depending on the technologies incorporated and the feedstocks used.”
Recently, the company introduced the Alka-Tech system, which includes custom-engineered equipment, technology and services, he adds. “The system approach provides one source for biosolids processing, including mixers, proportioning equipment, receiving stations, bulk storage and conveyance systems, fugitive dust control, PLC control and SCADA coordination. We have more than 50 installations in five countries.”
DuraTech: DuraTech Industries International Inc. manufactures horizontal and tub grinders for organics processing. Its Haybuster division offers products geared toward agriculture, including a vertical mixer. Designed for feed processing and rationing, it can be used for mixing of feedstocks for composting. The CMF-425 has two augers equipped with knives. It has 425 cu. ft. of mixing capacity, which can be expanded to 524 cu. ft. with a 12-inch extension. A 36-inch discharge conveyor can be set up to unload to either side of the mixer.
Helm Welding: Marketed under the Luck/Now brand, Helm Welding manufactures four auger and vertical mixers in stationary, trailer or truck-mount versions. Models range in capacity from 300 cu. ft. to 900 cu. ft.. All units are built with on-board scales. “We have numerous models, from a regular ‘read up-read down’ system to a programmable indicator with computer software packages enabling the customer to track and cost out materials being mixed,” says Grant Helm. Throughput of the mixers depends on the density of materials and capacity of the mixer, he adds. “For example, our 450 cu. ft. model can mix approximately 35 tons/hour.”
Since the early 1990s, Helm has utilized Engineered Compost Systems and Green Mountain Technologies as its distributors in the composting market. “We have been manufacturing mixers designed to their specifications for compost systems,” says Helm.
Kuhn Knight: Kuhn Knight Inc. offers a wide range of mixers for organic residuals processing. Its Reel Mixer Series (capacity ranging from 150-950 cu. ft.) features a large reel that turns slowly, lifting material up into two blending horizontal augers. The lower auger moves material forward, and serves as the discharge auger while the upper auger moves material rearward. Knives on the augers size reduce the feedstocks in the mixer. The Biotec 4-Auguer Mixers have four horizontal augers; the Vertical Maxx units have a single vertical auger for smaller capacities (270-430 cu. ft.), and there are twin vertical auger models in a full range of sizes (320-1,000 cu. ft.). All mixers are available in tow, truck-mount and stationary models.
Electronic digital scales are standard with all units. Truck-mounted models have an indicator in the cab as well as on the mixer. Chris Searles says that for its industrial customers, “we have more requests for unique features.” These have included tow models with extended tongues to accommodate a diesel or electric motor; belt conveyors of various lengths mounted at the discharge of the mixer, as well as an adjustable height on the auger discharge to enable construction of windrows while discharging; and complete stainless steel chamber due to the pH of the material being mixed. Kuhn Knight also has manufactured a truck-mounted mixer for collection of food scraps (see “Trucks With An Appetite,” January 2003); a tote-lift system was adapted to the mixer to unload containers of food waste. Wood chips or other amendments are added into the mixer prior to construction of the windrows. On its website, the company features the Reel Auggie “Scrapper,” a towable self-contained mixer package (5.4 cubic yards) used for combining food scraps or other waste materials with amendments prior to composting. It is powered by its own gasoline engine, and is available with electronic digital scales.
McLanahan Corp.: McLanahan Corporation manufactures the Blendmaster pugmill mixers in seven sizes, ranging in capacity from 15-425 tons/hour, at 50 lbs/cu. ft.. The mixers are typically used for biosolids applications to mix bulking agents for composting or to incorporate alkaline products such as lime or kiln dust for stabilization. The pugmill mixers use paddle shafts of structural steel pipe with replaceable bolt-on screw flights at the feed end only. The paddle bases are welded to the shafts. Three McLanahan 36-inch by 18-inch Blendmaster pugmills were installed at the City of Philadelphia biosolids composting site in 1987. Each unit was sold to mix 130 to 200 tons/hour of dewatered biosolids with wood chips and sawdust.
NexGen: NexGen Composting Ltd. manufactures ribbon and twin auger mixers, both in stationary (electric drives) and mobile (diesel engines and PTO). The ribbon mixers use a number of adjustable paddles made from wear alloy; the paddles are radially adjustable to ensure optimum clearance settings. The twin auger units are available with or without cutting teeth, to chop and mix the waste streams. Both mixers are constructed from steel; the ribbon mixer has a low friction polyethylene liner to minimize wear on the inner face of the vessel, and reduce power consumption.
Depending on materials and mixing requirements, the 5.2 cubic yard (cy) hopper on the ribbon mixer can process up to 10 batches/ hour, says Steve Kroening of NexGen. The twin auger units, with a 26 cy hopper, process up to 52 cy/hour. Weighing systems with load cells and electrical controls can be fitted to both types of mixers, he adds. In addition to raw material mixing, the ribbon unit also can operate as a final product blender, mixing sand and slow-release fertilizers with finished compost.
Patz Sales: Patz Sales, Inc.’s Industrial Division manufactures horizontal auger and vertical single and twin-screw mixers. The horizontal model is available with three augers, ranging in capacity from 185-380 cu. ft., and with four augers (940 cu. ft.). Knives are mounted to the augers. The Model 800 single screw stationary vertical mixers (available in 270 cu. ft. and 350 cu. ft. models), and the Model 800 twin screw mixer (620 cu. ft.) are the newest units in the Patz industrial mixer line. The Model 2400 has capacity of 1100 cu. ft..
Patented “Weigh-Tronix” 3- and 4-point scale systems are available to weigh materials as they are loaded. There are stationary, mobile and truck-mounted units. On the vertical mixer line, buyers have a choice of door locations. Jim Reed of Patz Sales says that on the Model 1100 Single Screw Vertical Mixer, the company offers “a ‘cafeteria style’ system whereby purchasers can choose from a variety of options to build a mixer that best meets their mixing requirements.” The single and twin-screw models offer 12-inch and 21.5-inch knives.
Roto-Mix: ROTO-MIX, LLC offers a horizontal mixer and blender with capacity ranging from 13-34 cy, and vertical dual auger mixers with 15-50 cy of capacity. All are available as stationary, trailer or truck- mounted. “Both the horizontal and vertical mixers and blenders will process any compostable materials,” says Garland Smith. “The difference in the two is the vertical gives size reduction and the horizontal mixes and blends already presized materials. As such, the horizontal units can process at a much faster rate than the vertical.” Smith adds that facilities using the horizontal unit for mixing only should have amendments with particle sizes under 4-inches.
The staggered rotary design in the horizontal mixer resembles a paddle wheel that enables faster processing and “improves mixing and tumbling action with less wear and fuel and lower maintenance costs,” he says. They will mix and unload their capacity eight times/hour. The vertical mixers will mix and unload their capacity three times per hour. All mixers are equipped with “Digi-star” scales. Units can discharge directly into compost windrows, and also have been used in compost spreading applications, e.g, to construct filter berms and apply compost blankets. The company is assessing use of the truck-mounted mixers for food waste collection.
Supreme International: The Supreme International Ltd. website states that the company was the first in North America to design, test and manufacture a vertical processor for the animal feed industry, along with the first vertical twin screw design. Recognizing an opportunity for its equipment in the waste recycling industry, Supreme researched how to efficiently process and blend different waste commodities of varying densities and moisture content in one machine. The result was the Enviro Processor Series, developed for the composting industry, which features 16 models of mixers in three categories. The units can be used for mixing/cutting, or for blending only (without knives on the augers).
The processors – with a vertical auger(s) with cutting knives mounted on the auger flighting – are manufactured in stationary, pull-type and truck-mounted models, and range in size from 300-1,400 cu. ft. “All Supreme Enviro Processors will now come standard equipped with our patent-pending Tub Mounted Interference Knife Package for faster processing of feedstocks,” says Sylvie Nadeau of Supreme International. The truck-mounted models are offered only with twin screws and range in capacity from 549 cu. ft. to 1163 cu. ft.. Throughput is entirely dependent on the loading process, but standard mixing time is about three minutes, adds Nadeau. All units come standard with an electronic scale system.
Directory
ALLU Group
700 Huyler St.
Teterboro, NJ 07608
800-939-2558
www.allu.net
Cemen Tech, Inc.
1700 N. 14th St.
Indianola, IA 50125
800-247-2464
www.cementech.com
DuraTech Industries/Haybuster
P.O. Box 1940
Jamestown, ND 58401
800-243-4601
www.duratechindustries.net
Helm Welding
86386 Lucknow Line
Lucknow, ON N0G 2H0
Canada
519-529-7627
www.lucknowproducts.com
Kuhn Knight Industrial Div.
1501 W. Seventh Ave.
Brodhead, WI 53520
608-897-2131
www.kuhnknight.com
McLanahan Corp.
200 Wall St., P.O. Box 229
Hollidaysburg, PA 16648
814-695-9807
www.mclanahan.com
NexGen Composting Ltd.
P.O. Box 435
Timaru 7910, New Zealand
(64)36874437
www.rotocom.com
Patz Sales, Inc.
P.O. Box 7
Pound, WI 54161-0007
920-897-2251
www.patzsales.com
Roto-Mix, LLC
2205 E. Wyatt Earp Blvd.
Dodge City, KS 67801
620-225-1142
www.roto-mix.com
Supreme International Ltd
4710 56 St.
Wetaskiwin, AB T9A 2R3
Canada
800-563-2038
www.supremeinternational.com