July 2004
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It was Henry Ford who once said, “You can have any color you want, as long as it’s black.” Of course, he was referring to his mass-produced Model T Ford. A lot has changed since then - including the color of mulch. From the customary Earth tones to shades not found in nature, today’s mulch buyers can have nearly any color imaginable.

Colored mulch originated in 1990 near Cleveland, Ohio. At the time, it was no more complicated than handfuls of iron oxide thrown in a cement mixer with a small load of fresh grind. “It was crude,” said Vince Hundt, owner and CEO of Rotochopper, Inc., in Saint Martin, Minnesota. “But it worked. Colored mulch came out, and we took notice,” he said.

Not long after, several companies were building wood grinders suitable for blending colorants into the mulch they produced. “It was important to buyers to have product with a uniform color. It’s the adhesion and consistency of the color that made colored mulch attractive to retailers and homeowners alike,” he continued. “The finished product must meet the standards and expectations set forth by the market. It was input from customers that drove the early product development process and led to many of the innovations we see in equipment today,” said Mr. Hundt.

In 1997, Rotochopper, Inc. was awarded a U.S. patent for introducing liquid mulch colorant directly into the grinding chamber of their wood recyclers.

Over the past few years, mulch coloring products have evolved into sophisticated, electronically controlled equipment capable of producing considerable volumes of mulch in thousands of different colors. Dan Brandon, marketing manager for Morbark, Inc., makers of wood and green waste recycling equipment said, “Colored mulch is an excellent opportunity for wood recyclers and traditional landscape contractors to add some real value to what had traditionally been a commodity product. By coloring mulch, the retail-selling price can sometimes be two to three times greater than uncolored, raw grind. That kind of incentive brings a lot of people into the market and affords manufacturers the opportunity to develop some great products to meet the need,” he said.

Morbark is among the leading manufacturers of tub grinders capable of producing large quantities of colored mulch from wood waste of all kinds.

Liquid, powder or foam
Applying pigment to mulch can be accomplished by any one of three principal means - a liquid spray; a dry pigment coloring, or by a pressurized foam process. All three methods require supplies of water and electricity to apply the pigment onto the recycled wood, and each has its unique considerations.

The mulch coloring system in most widespread use is the liquid based spray. Liquid based systems blend concentrated colorants with water. The blend is then sprayed onto ground mulch either inside of (in the case of Rotochopper), or upon exiting the grinding chamber of a wood recycler. Liquids allow operators the primary advantage of ease of use. For most people, liquids are easy to handle, they can be metered effectively and flow easily through the variety of available spray nozzles onto the ground mulch. In addition, liquid based coloring systems provide good adhesion of the pigment to the wood fiber. An attractive feature of liquid based systems is their adaptability to a wide variety of wood recyclers. That can be important for recyclers already equipped with grinders, especially if more than one brand or type of machine may be in use.

Liquid based mulch colorants require some time to dry before the finished product can be bagged or applied. The length of time required depends on several factors. Mike Chase, corporate counsel for Amerimulch, Inc. of Independence, Ohio said, “The moisture content of the mulch itself determines how much water is necessary, which in turn determines how much drying time is needed. The surface layer dries very quickly, but deep in a pile of treated mulch, it could stay wet for several days,” he said. Known for their thorough mixing capabilities, Amerimulch is a leading producer of liquid-based mulch coloring systems.

An alternative to the liquid based systems is a relatively new process using dry powdered pigments. Bandit Industries, Inc. of Remus, Michigan has been marketing their version of the dry process colorant system, known as the “Color Critter,” for more than a year. Paul Farmwald, a primary developer of the system, describes how the process works. “The Color Critter is an accessory designed to work with any of the Beast recyclers from Bandit. It consists of a metering tube with five discharge ports. The port opening is electronically controlled by a formula that reflects infeed conveyor speed, a constant material depth and the desired weight of colorant per yard to be dispersed,” he said. Mr. Farmwald operates Big Chipper, Inc. of Grand Rapids, Michigan.

An auger conveys dry color granules to the ports. The auger speed is set to keep the colorant dispersing tube full of granules at all times. That ensures a consistent discharge of dry colorant and an even application to the mulch. Any excess colorant is captured and returned to the dispersing tube holding hopper. The main storage hopper was designed to hold more than 2,000 pounds of colorant granules. Gravity delivers the dry granules from the storage hopper into the auger feed hopper.

The system uses two sets of water spray nozzles, one to discharge water ahead of the colorant port and the second after the colorant port. Dry colorant systems use only about 20% of the water required by liquid based processes. A common garden hose supplies all the water needed.

The Color Critter system straddles the infeed conveyor and attaches to the Beast’s infeed conveyor using guideposts. The unit is placed on the infeed conveyor with a loader or forklift. Requiring just a single 110-volt plug-in, the unit was designed to be simple to operate. If there is no electricity available, or if the Beast is moved around the yard while coloring, it can be powered by a generator as well.

Pressurized foam based mulch coloring systems may be the most complex. Doug Logan, vice president of manufacturing for Toms River, New Jersey based Wizard Technologies, Inc., makers of foam-based mulch colorant systems, described their model P-60. “It’s a portable, self contained diesel-powered unit with two separate hydraulic pumping systems on board. The first system pumps a specially prepared blend of colorant, surfactants and bonding agents from either a 55 gallon drum or 275 gallon tote into the water stream of the unit. The second hydraulic system pressurizes the mix in a high pressure hose and directs it out through a specially designed manifold,” he explained. “The pressurized solution creates a foam as it passes through the manifold. A bulk water supply, such as a well or tanker is commonly used for higher volumes of mulch production. But even a garden hose will provide enough water for very small volumes,” he added.

Foam based systems produce even, uniform color coverage and require considerably less water, and less drying time for the finished mulch product. In addition, there is little chance of unused drainage leaking out onto the ground.

Over the past 10 years, colored mulch has come a long way, and regardless of how colorant is applied, its popularity continues to grow. Estimates are that wood waste recyclers will consume more than 50,000,000 lbs. of mulch colorant this year alone. Due to repeat business opportunities, colored mulch is a viable market for recycled wood waste with a promising future. It’s a process that rewards everyone involved – recyclers, landscaping contractors and property owners alike.