Seattleites at the kitchen sink this week will have a new place to put the remains of a meal. As mandatory disposal of food waste in a receptacle separate from the trash becomes routine, the compost bucket -- as it takes not only coffee grounds and carrot trimmings but used chicken bones and cheese rinds -- is assuming a role coequal with the trash bag and recycling bin.
It's a big change at home. But at Cedar Grove Composting Co., it's no big deal.
The state's largest remanufacturer of yard, wood, dairy, and other waste already gets the table leavings from commercial tenants in Seattle and King County. The added material -- or feedstock, to use the preferred term for the state's largest manufacturer of compost -- won't make too much of a difference.
And while backyard composters have long known to omit meat, dairy, and other such items from their piles for fear of rot and rodents, Cedar Grove's massive composting plants -- one in Maple Valley, the other, which this reporter visited last week, between Everett and Marysville -- use a method that will turn the nastiest bison bone into sweet black tilth in eight weeks flat.
"I know we're going to get more bones and things like that, but for the most part it'll still be vegetative material," says Susan Thoman, the marketing and business development director for Cedar Grove, an eight-decade-old private company that started out as a garbage hauler.
"Home composters know that meat and dairy is bad, but the real difference here is that this is a major composting plant," she says. "We've always been able to do it under our permit."
"Temperatures get very high in our system, about 170-175 degrees Fahrenheit, says Thoman. "If you had an open system, a lot of them can only get to about 130. A meat bone is mostly protein and a twig is mostly sugars; this process will break down the meat bone first."
Cedar Grove began taking green waste in 1989 in their Maple Valley plant, then expanded from dead leaves and grass clippings to pre-consumer green trash, like unsold heads of lettuce from grocery stores. In 2000, the company undertook some pilot projects "that ultimately determined that this particular technology was the best" -- a system, says Thoman, that uses the signature northwest fabric, Gore-Tex.
The feedstock, which on any given day may include tree limbs, unsold plants from commercial nurseries, food, wood pallets, and cardboard boxes that can't be recycled, is dropped off by garbage truck and ground into four-inch or smaller pieces; it passes under a powerful magnet, which vacuums up stray bits of metal. The conveyer belt sends the feedstock more than 100 yards into the composting yard, then up a ramp.
"The kids that come -- we do bus tours -- the kids call it the compost escalator. I think that's the best name it's ever been given," says Thoman.
At the head of the ramp, the compost is dumped into the center of a yard, where it will be piled into one of 32 quonset hut sized heaps, then covered with a large Gore-Tex cover. Two probes inserted through holes in the top of the fabric measure the oxygen levels and the temperature inside. The yeoman's work is done by billions of microbes that love oxygen, carbon, and nitrogen; under their Gore-Tex protection, which keeps moisture out while letting air pass through, they heat the pile past the temperatures mandated by the county health department for prepared pork, beef, or poultry.
To keep oxygen plentiful, cast iron treads underneath the heaps blow air up through small holes, billowing the fabric out like a blimp. Any water that leaches out of the heap is stored and sprayed back in during summertime to keep it moist.
The high temperatures kill dandelion seedheads and foodborne pathogens alike -- and render the material ready for commercial sale. Thoman says Cedar Grove is the largest composting facility in the world using GORE brand equipment.
I dig my arm into one towering heap of nearly finished compost. At elbow's depth, it's nearly too hot to rest one's hand in.
"Isn't that cool?" says Thoman. "We call it enhanced biology."