California county processing more material with its tub grinder, finding new markets for wood chips

By Gregg Hennigan, features writer

How does recycling in Calaveras County, California, in 2016 compare with recycling in 1989 when the county’s Rock Creek Solid Waste Facility opened? A quarter century ago, recycling wasn’t on the radar of most residents in this Northern California county. Recycling at the landfill was essentially: back a truck up to the drop-off area and dump the material. Now, more than half the county’s waste is recycled. Many more types of items are accepted. More importantly, the landfill sorts the material to increase its recycling effectiveness.  

Of the facility’s 200 acres, 61 are permitted for waste treatment. The county’s diversion rate is 65 percent, with 6,000 tons of material diverted from the landfill in 2015. That’s a good number for a rural county of just 44,500 residents, but the goal is to reach 75 percent in 2017 through the use of a variety of diversion programs.

“With the diversion programs that we’ve started, our recycling has grown exponentially,” says Nathan Powers, an engineering tech at the Rock Creek Landfill. “It has been phenomenal.”

The landfill diversion efforts include a permanent household hazardous waste facility. At the end of last year, the county joined a statewide program to recycle mattresses and box springs. It also accepts electronic waste, carpet, rugs, mixed recyclables, and construction and demolition debris.

The county also recycles wood and yard waste. Powers identifies this program as the one most affected by state regulations that are shaping the California recycling and organics industry. New state rules will take effect over the next few years requiring the diversion of food and yard waste from landfills in an effort to reduce methane emissions.

News Markets for Wood Chips

Calaveras County already has a head start on the regulations with its wood and yard waste recycling program. Traditionally, much of the green material has been ground to create wood grindings to be used as alternative daily cover (ADC) at the landfill. The county accepts an average of 25,000-cubic-yards per year. Nevertheless, the state says that beginning in 2020, green material used as ADC will not count as diversion in a local jurisdiction’s recycling requirements. To get a head start on these new regulations, Calaveras County is already finding new markets for its wood chips.

One of the ways is their contract with a local biomass power plant that burns the wood chips to produce power. Another outlet is a startup company that does erosion control by taking some of the county’s wood chips to fill its wattles, those python shaped, fence-like devices used for water runoff prevention on sloping hillsides.

Interestingly, the county itself is using chips as ground cover to promote grass growth and help stabilize the soil in areas damaged by a large wildfire known as the Butte Fire that broke out in September 2015. “This is the first major fire that we’ve had since we’ve started the green waste program,” Powers says. “We’re looking into how well this works. Then, the advancement with the wattles has been huge for us. We didn’t know we could do that.”

New Grinder Doubles Productivity

The landfill’s tub grinder has played a key role in the advancement of the green waste program. When the county’s program started in the mid 1990s, it contracted out its grinding. In 2009, the county bought its own grinder to reduce that expense. AT the time, they purchased a horizontal grinder, however they found out over time that the brand and model it chose couldn’t keep up with the demand.

After doing additional research, in November 2015, the county purchased a Vermeer TG5000 tub grinder. Since then, the county’s productivity has nearly doubled using the new grinder. The previous machine took about 50 minutes to process 90-cubic-yards of material. That has been cut to about 30 minutes with the TG5000. That’s important for a taxpayer funded facility.

“We’re cutting costs on our man hours and on our fuel,” Powers says. “The trucking time was the biggest expense that was hurting us. Because it would take 50 minutes to fill a truck with ground material, you’re paying for that truck to sit there. But if you can fill a truck in 30 minutes, you just saved 20 minutes of idle time. And you can turn more trucks in a day.”

The grinder is in operation approximately six hours a day Tuesday through Saturday, largely at the Rock Creek Solid Waste Facility. The landfill serves only Calaveras County residents and property owners. Most of them bring material to the landfill themselves, although some contract with permitted haulers for curbside service.

The county also has two satellite locations for collecting yard waste, both located on winding mountain roads. Landfill staff also liked the mobility of the TG5000. Powers says it was important to have a unit that could easily be moved.

Sorting Process

At the landfill, each load is weighed and goes through a quick visual inspection. If it’s all brush and no contaminants, it goes straight to the facility’s holding area and eventually is run through the tub grinder. Mixed material is sent to another area and goes through a negative sort, a process where workers separate material that is not to go through the grinder. A loader outfitted with a grapple grabs and loads the wood waste into the TG5000 from a large bin.

Powers says switching to a negative sort early last decade led to a big improvement at the Rock Creek Solid Waste Facility. “Using a negative sort process, we catch chunks of steel, concrete, rocks, rebar, T-posts. Now, the grinder operator is more confident about the sorted raw material.”

Screens and Specs

Given the different uses of its wood chips, the county must use a variety of screens on its tub grinder.

The biomass plant’s specifications call for material that is 6-inches long and not too fine. For that, the landfill uses a 4×6-inch screen. They also use the 4×6-inch screen for their ADC.

For erosion control, a finer material is needed so that it’s easier to fit in the wattles. That process calls for a 4×4-inch screen.

The county recently purchased 2-inch screens to produce the ground cover material for the Butte Fire reclamation sites. With the smaller chips they hope to make hillside application easier by blowing them onto the hillsides with a mulch blower. Calaveras County has everything from flat terrain to rolling hills to mountains.

Changing screens so often can be a hassle, but Powers says it’s simpler on the TG5000 than other grinders he’s used because the screen is held in place by gravity within the frame. With no bolts they can quickly be changed out. “It’s unbelievable,” he says. “It’s so easy. We’re up and running in 25 minutes.”

Powers offers readers an important tip before buying a grinder of their own. He said facilities should be fully aware of the material specifications of their customers, not just their own needs. “If you find out exactly what they’re looking for and you get those screens to match their demand, then from day one you’re grinding, putting the wood chips in trucks, hauling it out and there’s no problem.” For more information on Vermeer recycling equipment visit www.vermeer.com .