Biosolids, Recycling and Storage Solutions: The Dyno Dirt Story

The Dyno Dirt program in Denton, Texas, creates high-value compost, soil and mulch products that have generated millions in revenue.
Biosolids, Recycling and Storage Solutions: The Dyno Dirt Story
Pecan Creek Dyno Dirt team members include, front row, from left: Monica Benavides, administrative assistant; Gayla Wright, manager; Janice Ross, customer service representative; and Calvin Patterson, heavy-equipment operator; middle row: Kevin Marshall and Brian Rushing, heavy-equipment operators; and Darrell Baker, field service supervisor; back row: Billy Downey, crew leader.

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It’s a common problem: Too much biosolids volume, not enough storage space, and landfill costs becoming prohibitive.

The team in Denton, Texas, 30 miles north of Dallas, solved the problem with an innovative biosolids recycling program that produces compost, soil blend and a variety of mulches. Besides biosolids from the city’s wastewater treatment plant, the composting operation diverts yard waste and clean construction lumber from the landfill.

The program is branded Dyno Dirt and, according to Gayla Wright, beneficial reuse manager, the name doesn’t refer to prehistoric creatures or comic book heroes: “It’s taken from the city slogan, Dynamic Denton. We thought the name would tie in with the slogan and be memorable, as well.”

It has worked, but not just because of the name. Early in the development of the Dyno Dirt products, Denton’s beneficial reuse staff listened to customers and came up with a range of products to meet their needs:

  • Dyno Dirt, a nutrient-rich compost made from biosolids and ground yard waste
  • Dyno Soil, a mixture of compost with sandy soil
  • Dyno Landscape Mulch, containing 20 percent Dyno Dirt and 80 percent wood chips
  • Dyno Lite composted yard waste
  • Dyno Double Grind, a wood mulch made from recycled construction lumber
  • Dyno Deco-Colored Mulch, a variety of mulches made from construction lumber and available in brick red, brown, black and cedar

Ample experience

Area residents and professionals have used Dyno Dirt products since 1997 for applications including landscape planting and mulching, lawn establishment and maintenance, flower gardens, nursery crop and greenhouse production, and turf and sod production. The products meet all requirements of the Texas Commission on Environmental Quality (TCEQ) for uncontrolled use as a soil conditioner and organic fertilizer.

Wright started at the treatment plant as an administrative assistant in 1992 and was involved in the development of the Dyno product line right from the start. Back then, the biosolids were land-injected and the brush and lumber were landfilled. “We would eventually need to purchase more land for biosolids injection, and the wet weather made it difficult to land-inject in the fields,” Wright says.

Research on other ways to manage the biosolids and yard waste began in 1991. The city staff investigated a number of processes and performed some demonstration projects to evaluate their feasibility. The staff chose composting to create a beneficial product. “In 1994 we started giving the compost away to city departments, and in 1997 we began marketing the compost to the public,” Wright says.

Quality process

At the 21 mgd (design) Pecan Creek Water Reclamation Plant, biosolids are anaerobically digested, thickened with polymer, dewatered to cake on a belt press and pumped into a holding bin. Front-end loaders empty the bin and transport the biosolids to an on-site composting area. Wright estimates biosolids production at 3,500 dry tons per year.

The city solid-waste department collects residential yard wastes at curbside; residents and landscapers can also bring clean brush and lumber to Denton’s compost facility. The wood waste is ground by an outside contractor and used in a variety of recycled products. McCloskey screens are used for both compost and mulch.

The Dyno Dirt compost process follows TCEQ and EPA regulations. The ground wood material is first placed in windrows 400 feet long, 18 feet wide and 5 feet tall. An operator then makes a concave V-shape down the middle of each row. Biosolids are then picked up with the loader (Volvo) and placed in the V of the windrow at three parts wood to one part biosolids, then covered with the ground material. The biosolids provide the moisture and nitrogen needed to create the heating process.

After the windrow is complete, the operator turns the row once using an 18-foot Scarab International windrow turner. One-half cubic yard of Harvest Quest inoculant (Ecoverse) is added to each end of the windrow, and then the entire windrow is capped using unscreened compost. The inoculant works its way into the pile and reduces the frequency with which the pile must be turned.

Temperatures are taken the next morning throughout the windrow. When the temperature reaches 131 degrees F (55 degrees C), the pathogen-reduction process has begun. The windrow stays at or above that temperature for 28 days and is turned once more after that. If needed, moisture is added using a water truck.

After the windrow completes the 28-day cycle, the material is hauled to a curing area where it sits in a static pile until it is ready to be passed through a 3/8-inch screener and turned into marketable products.

Seven full-time employees staff the reuse facility: Darrell Baker, field service supervisor; Billy Downey, crew leader; Brian Rushing, Kevin Marshall and Calvin Patterson, heavy-equipment operators; Janice Ross, customer service representative; and Monica Benavides, administrative assistant.

It’s about marketing

Homeowners and other customers can pick up Dyno Dirt and the other materials at Denton’s Beneficial Reuse Compost Facility from 7 a.m. to 3 p.m., Tuesday through Saturday. Dyno Dirt costs $25 per cubic yard (quantity discounts are available). The material is also sold in 1-cubic-foot bags at a local farm store and a building products outlet.

It’s one thing to make useful products out of biosolids; it’s another to successfully get them out the door. The answer is marketing. Wright pulls out all the stops. Dyno Dirt is featured in advertising and news coverage in the local media, in brochures, and even in commercials at the local movie theater and cable TV outlets.

Social media buffs learn about Dyno Dirt on YouTube. Promotional items such as trowels, T-shirts, pens and pencils promote the products. Wright and her staff exhibit Dyno products at festivals and events. Each year, special mailings go out to groups like the Texas Nursery and Landscape Association. Property owners receive Dyno Dirt flyers in their electric bills.

It’s a far cry from the beginning, when Dyno Dirt was promoted by word-of-mouth from satisfied customers. But partnerships with customer groups are still an important part of the “sell.” Wright lists the local solid-waste department, parks and recreation departments, watershed protection groups, and environmental and community beautification organizations as special people her staff interacts with regularly.

Lessons learned

With more than 20 years’ experience making and marketing biosolids products, Denton has learned a lot. Many lessons have to do with the compost curing piles and temperatures. “Back in the day, we didn’t have as much room as we have now, and the compost curing piles were piled up too high,” says Wright. “That caused them to on occasion catch fire.”

Now the rule is to limit the height of the piles and to keep breaks in the piles so that operators can get to them easily if need be. Every Friday, workers take the temperature of the piles and try to identify any hot spots.

Denton has learned a thing or two about odors, as well. In February 2015, the beneficial reuse facility staff began using the Harvest Quest inoculant, which reduces turning and potential odor emissions. Piles are turned twice in 28 days, versus five times in 15 days before the inoculant was used.

“Quality control is crucial,” Wright says. “Removing plastics and other contaminants from the yard waste is essential in creating a clean product.”

That brings up a point Wright makes over and over: “Listen to your customers. They will tell you what they want and whether there is a problem. We listen to them.”

Diversity in the customer base is another lesson. In a webinar sponsored by the Water Environment Federation a few months ago, Wright listed her many customer groups: homeowners, landscape contractors, commercial nurseries, home builders and developers, commercial gardens, the local school district, the Texas Department of Transportation, city departments such as parks and recreation, garden clubs, and other municipalities.

Bottom line

The Dyno Dirt program has generated significant revenue. “In our first year, we netted $19,000,” Wright says. “Since inception, we’ve had over $6 million in sales.”

In 2013-14, she reports over 43,000 cubic yards of marketable products were produced from biosolids and yard waste. While the production and sales statistics are impressive, Wright is just as proud of the amount of material recycled: “Over the past 18 years, we’ve diverted over 1.1 million cubic yards of waste materials from the landfill.”

Pretty dynamic.


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