Kittitas County, Washington opted to switch from contract services to its own yard trimmings composting operation four years ago.
BioCycle December 2012, Vol. 53, No. 12, p. 35
“Originally, we would get the material at our site — mostly self-hauled as it is today, but also from a number of commercial accounts — and have a contract grinder come in periodically to grind the material for us,” says Patti Johnson, director of Kittitas County’s solid waste programs. “We did that for a number of years until some changes occurred which forced us to rethink our whole approach to green waste.”
One of the changes to which Johnson refers was a Washington State Department of Ecology ban prohibiting residents from burning green waste in urban growth areas. The bans, largely put in place to minimize the detrimental health effects of burning upon area residents, were also instrumental in getting government agencies to be proactive in seeking alternatives to burning. “As a result of those actions, we started researching different ways to handle and process the green waste we take in,” Johnson recalls. “Composting seemed a real, viable alternative, and, armed with a grant from the Department of Ecology, we were able to begin working in that direction.”
While neither Johnson nor Matt Peebles, the county’s landfill operations manager, knew exactly which grinder to buy, they knew from past experience which type was not a good fit for their needs. “The contractor we had been using relied upon a huge tub grinder, which, while it would grind almost anything we put in there — including stumps and large logs — had a tendency to throw debris a pretty good distance,” she says. “I’ve had metal stakes and other material thrown from that tub grinder hit the roof of my office. We could not have that continue as we grew the green waste program, so we needed a different approach.”
While doing research into which grinder would best suit their needs, Johnson looked at all possibilities. That prompted a bit of “out of the box” thinking with regard to how the grinder should even be powered. Because they are situated in the Kittitas Valley, which has an almost constant downdraft from the adjacent Cascades, wind farms are a huge, and ever-growing, presence.
“We have wind farms all around our landfill and, in fact, have leased some of our landfill property to have turbines installed,” says Johnson. “So we felt an electric grinder would be more environmentally friendly. In addition, because of all the available wind and hydropower, electricity in the Pacific Northwest is fairly inexpensive. Going that route just seemed to make sense for us. We placed the grinder proposal out for bid, reviewed the bids and, based on what we got, chose an electric Morbark 3800 Wood Hog.”
Peebles concurs, saying that much of the work generally associated with diesel engines is eliminated with the electric unit. “Running a diesel unit, you are always worried about the radiator, oil changes, new piston rings, and so on. In the four years we’ve had the electric grinder, we’ve had no issues with the motors at all, and we’ve only had to replace a belt and a couple of bearings on the discharge conveyor. What’s also important is that I am able to do most of the maintenance on the unit myself. If we had to tear down a diesel engine, that definitely wouldn’t be the case.”
Making A Product
While some of the material at the site comes from city curbside collection, the overwhelming majority is self-hauled to the site by Kittitas County residents. It is run through the grinder, discharged onto the pad, scooped up using a John Deere tractor and placed in piles in preparation for windrow turning. “We really don’t track the tonnages we put through the grinder,” says Peebles. “However, we usually like to stockpile between 50 to 80 tons of material before grinding it once a week. The longest I’ve ever had to grind at one time was just over three hours. With that in mind, I’d say we are averaging better than 20 tons/hour.”
For the latter part of the season, when the volume of tree waste goes down and the incoming stream is mostly grass clippings, the solid waste department keeps a pile of land clearing debris on hand to grind up and act as a bulking agent when added to the mix. Windrowing is done with a Midwest Bio-Systems turner pulled by the tractor.
Windrows are turned every three days for 15 days in order to meet pathogen reduction requirements. Because Kittitas County is located on the eastern side of the Cascade Mountains, the climate is actually quite dry — much different from the steady rain commonly associated with its neighbors in the western part of the state. Therefore, moisture has to be added with each turning. In addition to the green waste, the county is also permitted to accept manure from local farmers.
“The composting site is essentially designed to be a one-man operation,” says Johnson. “So Matt is able to control the grinder from within the excavator he uses to feed it, then use the tractor to create the piles, turn them and move it aside for sale to the public. The only part of the operation we don’t do ourselves is screening the compost. We contract out that part of the operation.”
Peebles adds that strict quality control procedures, from monitoring and inspecting material prior to grinding, to temperature and moisture control in the composting process itself, help ensure there are no complaints about the nature of the county’s product. Temperatures are checked regularly using a ReoTemp probe.
To maximize both efficiency and economy in its operation, the Solid Waste department leases the excavator. Doing so has provided a number of benefits. “We are not a year-round operation, so in late fall, we turn in our excavator and get a new one again come spring,” says Johnson. “That not only ensures that the machine will be in great working order, it also keeps our operational costs down. There’s little point in owning a machine that will sit idle for six months out of the year. Leasing is a great option for us.”
Johnson is very satisfied with Kittitas County’s decision to start its own composting operation. “Based on what we’ve seen these last four years, I feel good that we’ve met the burn ban challenge with a really creative, environmentally positive solution and, in the process, ensured that our area residents will always have a nice supply of compost to meet their needs.”
Larry Trojak is with Trojak Communications in Ham Lake, Minnesota.