BioCycle July 2007, Vol. 48, No. 7, p. 30
Competition for drier wood sources for boiler fuel has led to increasing use of ground green waste and processed C&D wood streams to make colored mulches.

THIS time of year, many landscapes pop out brightly – not just from the blooming flowers, but from the decorative mulches around homes, shopping centers and office buildings. What started as a niche market for mulch producers many years ago has become a thriving seasonal product throughout North America. “We are still seeing growth rates of 20 percent annually in the number of companies producing colored mulch,” says Kriem Michel, National Sales Manager for T.H. Glennon Co., Inc., a colorant manufacturer. “Initially, growth rates were 100 to 200 percent annually, and then it slowed down to 50 percent.” Michel tracks about 900 colored mulch producers in her database.
Along with the growth in the number of producers is expansion of the types of wood being colorized. When BioCycle first started covering mulch colorization about 10 years ago, it was felt that ground pallets were the best option because the wood was dry and could absorb colorant more easily than greener woods. Today, according to manufacturers of colorizer equipment and colorants, there is widespread use of ground green waste being colorized. “We have quite a few customers coloring green waste and mixing it with construction and demolition wood fiber,” says Matt Cox of Amerimulch, a colorant and colorizer company. “In the past, green waste was a ‘no-no.’ But if it is ground and dried properly, and blended with a drier wood, it can be used to make darker colored mulches such as brown and black.”
Jerry Morey of Bandit, which manufactures the Color Critter II equipment as well as a full line of wood chippers, also sees significantly more green waste being colorized. “The product we’re seeing a lot of is colored pine mulch,” says Morey. “It tends to hold its color better than mulch made out of pallets. Also, because pallets are dry and lighter and more buoyant, they have a tendency to blow, or to float in heavy rains. We’ve found the ground and colored pallets don’t stay down as well as mulch made out of green materials.”
Colorization also is being used by producers of double or triple ground hardwood mulch, who typically age the wood chips to achieve a darker color. “During times of peak demand, they will add color to give the mulch a rich, dark brown look,” adds Morey. “This cuts down on the time it normally takes to get a double ground hardwood mulch to that color.”
DEGREES OF INVESTMENT
There appears to be two general tiers of investment in colored mulch production equipment. The lower cost option is to purchase an attachment that sprays colorant onto ground chips. The more significant investment is a dedicated mulch colorizer. “It all comes down to the number of yards being colored,” says Kent Rotert, Marketing Manager for Colorbiotics, a division of Becker Underwood. “For less yardage, e.g., when running some loads of chips with color and some without, a $6,000 color pump may be adequate. But with higher production, a producer may want a more secure system with consistent product each time.” Colorbiotics manufactures three types of colorizers: the Infusion, a colorant pump; Second Harvester, a multistage mixing and colorizing system; and the Sahara Series, a water efficient pump and metering system.
Rotochopper, Inc. pioneered the concept of grinding and colorizing “in one pass,” and obtained the patent on the technology. The patented liquid colorant system can be installed on any of the company’s grinders, e.g., the 266 horizontal grinder capable of processing and colorizing 400 cubic yards (cy)/hour of bark (150 cy/hour of pallets). “We have always emphasized the importance of producing the ideal particle size for the local market,” says Vince Hundt of Rotochopper. “Consumers are not just looking at the color, but the texture as well. Our liquid colorant and water are put directly into the grinding chamber – a high energy environment that does a very thorough job of dispersing and injecting colorant into the wood.”
The company’s CP118 mobile grinder/colorizer is popular with tree care companies, he adds. The unit has a 5-yard hopper and an infeed rate of up to 70 cy/hour. “Tree care and landscaping companies can take a tree down in a yard, chip and color the mulch, and use it at that home or business for landscaping,” says Hundt. “This unit is ideal for companies that don’t have a mulch yard or composting site as they can supply mulch as well as produce it.”
In addition to Colorbiotics, other companies interviewed for this article with colorant pumps or spray units include T.H. Glennon Co., Inc., Bandit Industries, Concept Products Corporation and Amerimulch. T.H. Glennon, well known for its colorants, sells the Mulch Color Jet that can be adapted to tub, horizontal and stationary grinders. Models range in capacity from 100 cy to 450 cy/hour, with water usage ranging from 15 to 60 gallons/minute. “The Mulch Color Jet weighs 150 pounds and sprays color into the top of the grinder during the second grind,” says Kriem Michel. “It costs less than $10,000 and has been on the market for a number of years.”
Bandit Industries’ latest model is the Color Critter II, an attachment for several of Bandit’s Beast Recycler models. It attaches to the infeed conveyor of the chipper during the final grind of material. The system uses granular pigments with a minimal amount of water. “The flow of colorant is based on the speed of the infeed conveyor,” says Jerry Morey of Bandit. “It is electronically controlled and tied into the computer system on the Beast. So as the machine slows down, the amount of colorant being discharged slows done. If the machine stops, the colorant flow stops.” One improvement on the newest model is that the ports are self-cleaning. “That makes the machine run more efficiently and reduces the amount of colorant used,” he adds.
Concept Products Corporation markets the M60 Colorizer, with a production rate of 25 cy to 200 cy/hour. The spray manifold on the unit can be mounted on any type of grinding equipment. The M60 has a pressurized delivery system with interchangeable brass nozzles. “There is an electric speed controller for the dye, and a gate valve for adjusting the flow of water and dye output,” says David Wilson of Concept Products. “That is adjusted depending on the quantity of chips being processed.” The unit weighs 250 pounds and can be operated remotely.
SCREEN-COLORANT “MARRIAGE”
One of the newest innovations in the mulch colorization market grew out of a joint marketing venture between Amerimulch and Wildcat Mfg. Co., Inc. At BioCycle’s West Coast Conference in April, the two companies introduced a Wildcat trommel equipped with Amerimulch’s colorizing spray bars and colorant. “We are the only company that has a unit that can screen and color in one step,” says Tim O’Hara of Wildcat. “We are using Amerimulch’s pump and metering system and their controls. Together, we designed a spray bar that is mounted inside the trommel drum. Custom-made UV resistant tarps go over the screen panels. Depending on the amount of feedstock screening that needs to be done, we can cover one, several or all of the panels on the trommel. Color and water lines are coupled to the spray bar and the mulch is colored as it tumbles in the drum. At this point, we are making the colorizing system available with our Cougar 626 trommel, which is 26-feet long and 6-feet in diameter.”
A grinder can feed directly into the hopper of the trommel. Fines are screened out in the first section, with colorant added in the next section. “Fines tend to soak up a lot of the dye,” adds O’Hara. “Removing the fines means less colorant and less water are used.” Matt Cox of Amerimulch notes that all the screen panels can be tarped to colorize mulches without a lot of fines. “If they are already prescreened, you can use the full length of the trommel and color up to 250 cy/hour of mulch. But when there are fibers loaded with fines, a tarp can be removed and the colorant manifold shut off, and then that material can be screened prior to colorization.”
Cox explains that removing fines from the mulch prior to colorizing not only saves on dye and water costs, but also on freight charges. “The objective is to properly size the fiber while minimizing the percentage of fines – a half-inch or less particle size. When we took the Model 626 trommel equipped with the spray bars on the road as a demonstration unit, we averaged 220 cy/hour, 25 percent of half-inch fines removed, and 100 percent coverage of the finished mulch. On the East Coast, base fiber [processed chips] weights are exceeding 650 lbs/yard. A 25 percent reduction of fines reduces the weight of each yard by 162.5 lbs, which can be significant.”
Introduction of the screen-colorizing “combo” is timely, he feels, as consumer demand has increased for a finer mulch product. “Until three or four years ago, the typical particle size was up to 4-inches, typically the size of a boiler fuel. Now the market has matured and we are getting down to smaller and smaller particle sizes. Some customers find the finer mulch visibly nicer as it lays around the plants better.”
In addition to its joint venture with Wildcat, Amerimulch markets three freestanding color injection units that can be adapted to any type of grinding equipment. The units range in capacity from 100 cy to over 400 cy/hour. “For every piece of equipment, a sales technician will engineer a spray manifold to match the particular grinding unit,” says Cox. The company also has a series of Color Mills that feature a dual paddle-shaft mixing design. Processed mulch is fed into the colorizers, which range in capacity from 50 cy to 250 cy of mulch per hour.
COLORANT OPTIONS, PRODUCT TRENDS
There is a wide assortment of colors and forms of colorant – liquid, granular and powder – available. Where shipping is involved, some colored mulch producers are opting for the powdered colorants because of the reduced weight. “They are getting more popular because of freight costs,” says Michel of T.H. Glennon. “However powders are difficult to dispense in a grinder. I’m aware of a company that developed a machine that sprinkles powder on the infeed belt as the wood goes into a horizontal grinder.”
Bandit, which does not produce its own colorant line, sees advantages to the granular product. “We find it covers and penetrates the wood very well, while using a limited amount of water,” says Morey. “Another consideration for companies that bag colored mulch is the moisture content of the material going into the bags. A granular colorant may be preferable in that instance.”
Colors available include various shades of red and brown (including burgundy and cocoa), black, yellow, gold, cypress and orange. Kent Rotert of Colorbiotics points out that with more mulch producers using a range of wood sources for colorized mulch, the key is to match the colorant with the type of wood being used. “We have multiple colors within our lines because of the varying wood sources,” he says. “A darker wood needs a more aggressive colorant with more tint shade to match the desired end result. For example, a dark wood can be colored a dark red or black. Lighter woods need a less aggressive colorant, so there are multiple shades that can be used.”
Companies also have introduced colorants that provide mold and fungus protection. “We have an additive that protects the dry colorant film from discoloration caused by microbial attack,” says Michel. “That builds in color longevity, so mulch makers can stockpile large amounts of mulch and not worry about fading.”
Amerimulch recently introduced the Heartland Enriched Colorant line that has been chemically formulated to improve bonding to the wood fiber. Notes the company’s literature: “Our liquid colorant formulation includes special humectants, color enhancers and adhesion promoters to enhance freeze-thaw stability and improve colorant performance.” Cox says that the Heartland Ultra is designed for green wood fiber, overcoming the “drowning out” effect that can occur with that wood source.
Michel of T.H. Glennon says that the price of colorants has decreased over the past few years, primarily due to an increasingly competitive marketplace. “I remember when colorant was $3/lb,” she says. “Now the average price is $.70/lb. When I started out in this industry, there were one or two companies making colorant. Now there are about 12. And because the cost has come down, mulch producers can use more color in order to have their products looking better than their competitors!”
The increasing popularity of colored mulch has led to growing demand for bagged product. “The fastest growing market in the colored mulch sector is bagged mulch, due to the big box stores,” says Rotert. “They are getting more and more aggressive into carrying mulch, and they are not going to sell bulk product. A drier colored mulch product is preferable for bagging. First, shipping is based on load weight and you can get more pallets of drier bagged product onto a truck than a wet product. Second, there are runoff issues if bags of wetter colored mulch get punctured, especially if they are stored outside.” – N.G.