Burn ban spawns a composting facility

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Courtesy of BioCycle Magazine

Situated on the leeward side of Washington’s Cascade Mountains, Kittitas County has a relatively small population of 39,000 and a correspondingly small amount of green waste collected on an annual basis. When faced with a decision to make about its green waste, the county’s Solid Waste Department bucked tradition by replacing a contract grinding service with the purchase of an electric grinder. It has been generating its own high quality compost for over four years. About 2,000 tons/year of green waste are handled by the county facility located in Ellensburg.

“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.”

Going Electric

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.”

The 3800 Wood Hog is powered by a trio of electric motors: a 100-HP unit to power the hydraulics and two 300-HP main drives. Though a dedicated electrical line and transformer had to be run to power the grinder, the savings have been steady and significant since start-up more than four years ago, Johnson adds. “We are averaging utility costs for the grinder at about $1,700/month, which is a fraction of what we would be paying for fuel and upkeep, given the recent fluctuations in the price of diesel. However, the savings run much further than just fuel. Maintenance on the electric is also a fraction of what it would be otherwise.”

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.”

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