The daily grind: asphalt shingles, drywall and wood burning power plants create new markets for secondary grinding equipment.

For recyclers looking to make a marketable end product from recovered material, secondary grinding equipment plays a vital role in the industry. Even with the growing popularity of slow-speed, high-torque shredders as primary processors, tubs and horizontal grinders remain essential in the growing wood waste and construction and demolition debris market.

While wood debris is still the strongest market for secondary grinding equipment, the machines are making forays into other C&D-related materials as well. Secondary grinders are being used to process a variety of materials, including asphalt shingles, mixed C&D, drywall, municipal solid waste (MSW) and organic debris.

These and other growing markets--like wood chips for wood burning power plants--have been driving the market for secondary grinders.

THE LONG AND SORT OF IT. In many of the markets where secondary grinders find use, the latest trend has been using the grinder in tandem with a primary shredder. Recyclers who are after a high-end product--usually clean mulch for landscaping--employ a number of sorting techniques when using two processors in a system.

Cody Peterson, sales coordinator at Peterson Pacific Corp., Eugene, Ore., recommends three methods of sorting between a primary and secondary processor, depending on the material being ground.

Peterson recommends screening equipment for the removal of abrasive material that can be damaging to the grinder, magnetic separation equipment for the removal of metal and pneumatic equipment for the removal of unwanted paper or plastic material.

Sorting between processors is essential to eliminate any chance of metal contaminants ending up in the high-speed grinder, says Bob Strahm of DuraTech Industries International Inc., Jamestown, N.D. "Certain sizes of metal typically do not bother [the grinder] if it is mixed in with the wood, such as conduit copper pipe and gutter material," Strahm says. "But a thicker, heavier piece of metal can be catastrophic."

In addition, sorting stations between a primary shredder and a secondary grinder should be in place to remove stone, block, carpet, shingles and other materials that, though unlikely to harm the grinder if they've been through a primary shredder first, still must be removed for a clean, value-added end product that can be used for mulch, compost or animal bedding," says Mike Byram, senior director of environmental solutions for Vermeer Manufacturing Co., Pella, Iowa.

In end-markets that demand the cleanest product--like mulch and animal bedding--Tim Griffing, systems engineer for Continental Biomass Industries Inc. (CBI), Newton, N.H., recommends positive sorting of the wood for the best results.

Each market is different, Griffing says, and boiler fuel will not carry the same kind of quality expectations as other products. "It all depends on how strict the specification is," he says.

SIZING IT UP. The tandem setup is particularly popular in the mixed C&D market, says Jerry Morey of Bandit Industries Inc., Remus, Mich. However, in the wood market, the trend is toward bigger machines with more horsepower "because it's the only machine being used, the one that's doing all the grinding," Morey says.

"The trend in the United States is primarily toward larger grinders due to economies of scale in production," Byram agrees. "With labor being one of, if not the, greatest cost of grinder operation, some wood waste processing companies purchase larger grinders to increase production while essentially using the same labor requirement needed to operate smaller grinders."

However, the trend toward larger, more powerful grinders isn't absolute, many manufacturers say. "In the past, the larger grinders were typically the only machines built heavy enough to take the rigors of this application, but today some mid-sized grinders are built for [heavier applications] and offer options to upgrade the machine into a primary grinder configuration," says Peterson. "In regards to the right size grinder, facility size or production requirements will dictate this."

The wood waste industry is growing, says Byram, and attracting companies that might not be able to afford a big grinder when first entering the business, increasing demand for smaller machines. "Additionally, as fuel costs continue to rise, more companies may look at the cost of operation and determine that smaller grinders are less costly to operate."

And in today's market, customers often don't have to just decide between large and small--manufacturers say grinders can be tailored to pretty specific needs. "People used to have to guess more," says Vince Hundt, director at Rotochopper Inc., St. Martin, Minn. "But there's been further refinement in the grinder business where you can tailor the machine specifically to the ton-per-hour throughput that's being anticipated by the recycler."

Dan Brandon from Morbark Inc., Winn, Mich., says some companies, Morbark included, do onsite demonstrations of a particular machine for customers before they buy to make sure the grinder is the best match for a given operation. "It's not like buying a car where you take a test drive and say, 'Yea, I like that one,'" he says. "There's a lot of experimentation when it comes to getting the best end product."

Brandon also suggests leaving some room to grow when buying a grinder. "Think about buying one size larger than you think you need, because your business is going to grow," he says.

GROWTH PATTERNS. Markets for secondary grinding equipment are growing across the board, manufacturers say. Some private contractors and homebuilders are even in the market for them, although manufacturers recommend they should carefully weigh their options before making a big investment.

"In considering the purchase of a grinder, contractors should consider two criteria--the scope of the wood waste processing project and reduced transportation costs by grinding on site vs. hauling wood waste to another location," says Byram."

Ralph O'Donnell, western regional sales manager for Sundance Equipment LLC, Newton, Kan., agrees and says that homebuilders and private demolition contractors can save on both transportation and labor costs by investing in their own grinder. "You can get up to three or more times more material in a truck in a ground condition than you can in the original condition. For homebuilders, many times the ground wood can be left as mulch for the new homeowner."

Land clearing has remained steady business for secondary grinders, and the wood waste market has gotten a recent boost from an influx of biomass burning power facilities, especially in the Northeast, says Hundt.

"The fuel market is going to drive the expansion," Morey agrees. "The rule of thumb has always been anytime oil is above $30 per barrel, wood looks like a real viable alternative, and nobody is predicting oil dropping below $50 per barrel any time in the near future."

The need for alternative daily cover (ADC) for landfills has opened up a new niche in the market for secondary grinders, Peterson says.

Peterson also says that grinders are being put to work grinding MSW with greater frequency. "Increased compaction rates and transport load weights are achieved by grinding the material," he says.

The biggest trend, says Hundt, is that C&D facilities are all focused on making consumer quality products from wood waste. "Recyclers are zeroing in on equipment that can give them that."

RELATED ARTICLE: Horizontal vs. tub.

Horizontal and tub grinders each have their own strengths in the market, although some manufacturers say horizontal grinders are gaining in popularity over their tub counterparts. "The trend is more toward horizontal," says Jerry Morey of Bandit Industries Inc., Remus, Mich. "You have more control over the feed. You can regulate particle size, as well as speed it up with lighter material and slow it down with heavier."

Horizontals have a slight advantage when it comes to control over material flow, and they also have an edge when it comes to safety, says Vince Hundt, director at Rotochopper Inc., St. Martin, Minn. "They are far safer to be around--they don't throw material in the air," he says. This reduced thrown object zone comes in handy for companies that work in residential areas, says Mike Byram, senior director of environmental solutions for Vermeer Manufacturing Co., Pella, Iowa.

Horizontal grinders also tend to be within road travel width and easier to transport, says Ralph O'Donnell, western regional sales manager for Sundance Equipment LLC, Newton, Kan. "The loading height of a horizontal grinder is much lower than a tub and the operator has more control over the feeding operation," he adds.

Tub grinders do have their niche, though. They are designed to handle bulkier material, according to O'Donnell. "A distinct advantage of the tub grinder is the ability when grinding extra-large pieces of material to chew off what it can handle and let the remainder move on to the next round," he says. And recently, some tub manufacturers have addressed the safety issue by adding covers to keep material from flying out of the tub, O'Donnell says.

But there are variances within horizontal grinders to consider as well, says Tim Griffing, systems engineer for Continental Biomass Industries Inc. (CBI), Newton, N.H. Recyclers should pay attention to whether the machine uses upswing or downswing rotors, he says. Griffing says cutting down tends to slow the rotor down, which saves wear on the equipment. "Wear is directly related to speed," he says. "The higher the speed, the more wear."

Other standard practices also help operators save on their wear parts. Many manufacturers say the key is keeping abrasives out of the equipment.

"To keep your machine running well, the best answer is to keep as much dirt and sand out of your debris," says Bob Strahm of DuraTech Industries International Inc., Jamestown, N.D. "This material causes excessive wear on your tips and screens."

Hundt agrees. "There's nothing that aggravates tooth wear more than trying to grind dirt," he says.

Common sense also goes a long way in saving on wear costs, says Brandon. "Monitor the material," he says. "A good operator isn't going to drop an engine block in there."

Keeping the feed constant also helps, according to Shane Donnelly of DoppstadtUS, a Lakewood, Ohio-based manufacturer of slow-speed and high-speed grinders. "Let material work on material as well as steel," he adds.

Byram also suggests maintaining a wear pattern and following the maintenance schedule recommended by the machine's manufacturer.

This feature originally ran in Construction & Demolition Recycling magazine. The author is assistant editor of the Recycling Today Media Group and can be reached at [e-mail].