Island Composts Aggressively

By Tara Hansen, Technical Writer, Two Rivers Marketing, Des Moines, IA | September 28, 2010

Transporting a 56,000-pound grinder to the island was no small task. A special barge was used to transport the grinder and tractor across Lake Michigan.

When it comes to recycling wood waste on Mackinac Island, MI, the city's public works director admits that he's trying to accomplish a very normal feat in a very abnormal place.

Mackinac Island, nestled in the straits of Mackinac where the Upper and Lower Peninsulas of Michigan meet, is a national historic landmark and is special in the fact that motor vehicles, excluding emergency vehicles, have been prohibited on the island since the 1920s. The beautiful island, which is surrounded by Lake Huron, is largely known as a tourism destination, boasting old Victorian charm from its carriage tours to its fudge, music and lilac festivals.

Because the most common modes of transportation are horse, bicycle and foot, the island poses special challenges when it comes time for the public works department to grind its construction debris twice a year.

"We compost aggressively. We recycle aggressively," says Bruce Zimmerman, who has been Mackinac Island's public works director for the past 16 years. "Day in and day out we defer a little less than 55 percent of solid waste from our landfill."

The city began grinding wood waste in 1992 when it was forced to close its landfill and evaluate other ways to dispose of solid waste. Today, Zimmerman says he and his staff of five employees collect construction debris throughout the year, separating that which can be ground up and reused in their compost process.

"We are a compost facility, and for landfill materials, we are nothing more than a transfer station," Zimmerman said. "We separate anything that is non-wood material because the debris comes to us in a mixed fashion from the construction site."

Typically, Zimmerman and his crews grind the debris at least once or twice a year. Due to the infrequency that they grind wood waste, Zimmerman says it's most cost-effective for his department to lease a grinder for one or two days and have it transported onto the island to complete the job. This year, Zimmerman contacted Vermeer — Wisconsin Inc. to help them tackle an especially large wood-waste pile measuring 600 to 700 cubic yards. The dealer leased Zimmerman and his crews a Vermeer HG6000 horizontal grinder.

Selecting the machine was the easy part. Getting it on the island required quite a bit of planning. Because of the island's ban of motorized vehicles, Zimmerman took special measures to bring the grinder onto the island. "We brought the machine on early in the morning and transported it off the island late at night under the cloak of darkness," he said. "Mackinac Island is a magical place. We have to preserve its history because that's what we sell."

Once stationed at the compost facility, the HG6000 horizontal grinder processed nearly 700 cubic yards of wood waste. Zimmerman's crew used a front-end loader with a 4-cubic-yard bucket to feed the wood debris into the grinder and haul away the finished product.

By grinding the wood waste, the city sees a 50-percent volume reduction. After the wood waste goes through the HG6000 horizontal grinder, most of it is distributed throughout the compost windrows while a portion of the wood chips are sold to buyers who use them for walking paths and landscaping. "When the time comes and as the recipe calls for it, we'll add the wood chips to our raw compost," Zimmerman said.

Once the compost has been turned, watered, cooked, and is ready to sell, the city uses a 1-inch screen on its screening machine to fluff the final product.

"It's all about volume reduction," says Zimmerman of leasing the HG6000 horizontal grinder. "If I have a pile of construction debris that has to be disposed of, I would much rather deal with 300 cubic yards than 600 cubic yards.

"The Vermeer — Wisconsin dealer was very impressive. Those guys took very good care of us. Anybody can build a gizmo to do something, but when they said they were going to do something, they did it," he added.

Feature provided by Vermeer Corporation, Pella, IA.