Despite an impressive upturn in recycling rates nationwide in the last decade or so, it’s inevitable that landfills will continue to reach capacity, prompting closure, capping, and a move to an alternative site. Such was the case when the Rock Prairie Road Landfill near College Station, Texas, a fixture to the area for more than 30 years, maxed out, shifting disposal to the newly constructed Twin Oaks Landfill. Operated by the Brazos Valley Solid Waste Management Agency (BVSWMA, pronounced buh-vis-ma), Twin Oaks is a state-of-the-art facility that is designed to meet the area’s waste disposal needs for the next 60 years. A decent portion of that overall waste stream is green waste generated from throughout the area, material that was, in the past, stockpiled then processed by a contract grinder. Realizing that doing so meant being at the mercy of someone else’s operation from both a financial and logistical perspective, BVSWMA opted to purchase their own grinder—a Morbark 4600XL—and take back control of the grinding effort. Today the landfill, still in its infancy, is poised to improve upon the green waste recovery effort, explore new markets for the product and lower the costs associated with doing so.
A Look at Twin Oaks
The new site at Twin Oaks is a model of how a landfill can be designed to meet today’s solid waste disposal needs and be a good environmental steward. Situated on 610 acres, the landfill footprint itself is about 220 acres, with the balance providing a buffer zone of protected wetlands and areas which are home to an endangered native orchid species.
“There was a lot of thought put into every aspect of this new facility,” says Howard Stough, Landfill Operations Supervisor. “It’s been laid out in such a way that both commercial and residential customers can utilize convenience areas installed specifically for them. The landfill itself will provide 37 million cubic yards of space for disposal, so the needs of area residents in the 20 county area we serve will be met for some time to come.”
Twin Oaks has also earned the distinction of being the only LEED (Leadership in Energy and Environmental Design) Silver Certified landfill in the nation. Onsite facilities feature white roofs to keep the buildings cool by reducing the “heat island” effect, as well as water-saving fixtures, energy-saving lighting, geothermal heating and cooling, and the use of recycled and local products as construction materials. Even the roadway parking infrastructure of the landfill facility, which uses concrete surfaces that reflect heat, is part of the LEED certification.
Green of a Different Color
Because the area served by the landfill is so vast, green waste volumes can be fairly sizeable in peak times. Stough estimates that they are set up to easily handle the 110,000 cubic yards of brush, trees, stumps, etc., generated annually, material that is the byproduct of land clearing projects, area landscapers and residential trimming/clearing efforts.
“It’s important to keep in mind that BVSWMA also operates a compost site of its own in Bryan, Texas, so a sizeable portion of the incoming green waste heads there as well,” he says. “In addition, several other municipalities in our service area have compost facilities of their own. But we still take in a tremendous amount of material here and, until now, have been contracting with an outside vendor to periodically come in and grind it for us. While that fit the bill in terms of meeting our needs, we found it was not the most ideal setup possible.”
Challenges to that arrangement included costs, convenience and being dependent upon the contract grinder’s schedule. While the vendor could, in effect, grind anytime they were needed, they preferred to wait until the volumes were sizeable enough to warrant bringing their machine out.
“They didn’t like to mobilize unless there was a substantial amount of material to do,” says Stough. “They would come with less on the ground, but we’d pay a hefty price for it. So that meant we had to live with a lot more stockpiled material than we often would have liked. That all came into play when deciding whether or not to purchase our own machine. Obviously, once we ran the numbers, we realized that it made sense for us to make the move.”
Stough and BVSWMA took a good deal of care researching what equipment would best suit their needs, looking into the track records each of the major manufacturers put forth in terms of support and service and, at the end, chose to order a Morbark 4600XL Wood Hog horizontal grinder through equipment dealer Doggett Equipment. Having worked through Doggett for many of their John Deere loader, excavator and articulated dump truck purchases played a huge role in their decision.
“We were really impressed with both the design and the durability of Morbark machines we saw,” he says. “But having worked with Bill Talbott and the crew at Doggett Equipment in the past, we knew we could count on them for support after the sale, and because of the amount of work we see this grinder doing in the long term, we knew how important that would be.”
When Stough references what he envisions for the grinder, he is basing that both on past practices and anticipated needs. He says they have already started moving the unit back and forth between the Twin Oaks site and the Bryan Composting Facility, and have other immediate uses for it at the new site.
“There are a lot of areas here that still need to be cleared in advance of new cell construction,” he says. “To do that, we can do one of two things: haul the material to the grinder or take the machine to the clearing site using a dolly that Moe Tyler our mechanic devised. It was fabricated using the lower frame of an old military vehicle and an upper with the fifth-wheel plate from a regular semi-trailer. We just shackle the dolly to the tooth of an excavator’s bucket and pull it around onsite as needed. It’s really made the unit mobile for us.”
Mindful of Mechanics
While the added convenience of having their own grinder has proven invaluable in terms of planning, there were of course, tradeoffs for that luxury: most notably added fuel and maintenance costs. The that end, Tyler is quick to point out that the 4600XL has been one of the more pleasant surprises he has encountered in his decades of equipment maintenance work.
“The grinder is maintenance-friendly; they must have had mechanics on hand during the design process,” he says. Everything on it is very accessible—all the hydraulic hoses are easy to get to, the chains can be inspected by simply removing a couple of covers, and tensioning the belt is a snap. Other equipment manufacturers—and I mean makers of all equipment not just grinders—could learn a lot from Morbark’s approach.”
Stough agrees that the new grinder minimizes their maintenance headaches and adds that one feature in particular—Morbark’s upward-feed design—has been very impressive.
“Because of that approach, with the mill rotating upward, it is actually lifting the material as it is feeding it in. As a result, a lot of the dirt and debris that is coming along the floor drops out instead of going in and dulling the hammers. That’s really going to benefit us over the life of the machine. In addition, I had an opportunity to see secondary-grind material from both the contract grinder and from another unit we had demoed and the material we are getting is, by far, of a much better quality and consistency—another result, I suspect, of that uplifting grind approach designed in to the unit.”
The end product for the green waste processed at Twin Oaks Landfill is, of course, mulch. What happens to that mulch, however, is driven by need: a portion being diverted for use in the compost operation, the remainder divided up between onsite use and sale to the general public.
“We’ve found the mulch to be useful in many areas onsite, including for erosion control and as base material for our wet weather pad, a rock-base area to which we direct truck traffic in rainy weather,” says Stough. “In that case, we spread out a layer of mulch that trucks can back up onto to get traction and unload—if it gets saturated, we simply replenish it. In addition, we sell quite a bit of the material to residents and landscapers, both here and at the compost site.”
He adds that they have also been approached by some of the area power plants about taking their material for biofuel. In the past, mulch created by the contract grinder—heavily laden with longer pieces—was deemed unsuitable, for fear it would jam their augers. “Now I’m confident that the second-grind material we are getting with this machine would easily pass the specs they need for their boilers,” says Stough.
“There are so many advantages we are finding to bringing the grinding operation in-house,” he says. “We are no longer on the heels of a contract grinder and paying the fees associated with it. It is great to be able to have the flexibility to grind when we start running low on material and need it, instead of having to maintain such a huge stockpile. And we feel we’ve really got an excellent support structure in place between our onsite maintenance crew, the people from Doggett Equipment and Morbark itself. This is a whole new approach for us and, though it’s early in the game, we are excited and feeling really good about our decision.”