Here's a world record you perhaps missed: The planet's largest collection of Gore- (as in Gore-Tex) covered mulch piles is decomposing near...

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Here’s a world record you perhaps missed: The planet’s largest collection of Gore- (as in Gore-Tex) covered mulch piles is decomposing near the shores of Steamboat Slough, in the Snohomish River delta.

Spring is the busiest time of year for Cedar Grove Composting, which in 2004 began operating on Smith Island at the northern tip of Everett.

Tons of grass clippings and dead leaves dredged from garden beds are getting mixed into the company’s year-round food-scrap offerings from restaurants and groceries, providing a fresh feast for the microbes that turn the mush into organic garden mulch.

Jerry Bartlett, the company’s co-owner and vice president, leads trivia-packed tours of the 26-acre operation, replete with science and vocabulary lessons as he explains how the Gore Cover material creates self-regulating biospheres within each 10-foot-high, 450-ton heap.

Ciscoe Morris, host of “Gardening with Ciscoe” on 710 KIRO, loves the place.

“I’m really kind of in awe about how they do it. It’s amazing that they put a Gore-Tex jacket on the compost piles, so it breathes and stays moist,” he said. “They’ve really got it down to a science like I’ve never seen.”

The Everett site is among 175 worldwide using the Gore Cover technology, which first appeared in Germany in 1993. Israel held the title to “world’s biggest” for years, producing 130,000 tons per year. Now Everett tops that with a 164,000-ton yearly output.

A steady influx of garbage-company big-rigs and industrial trucks dump their loads into a “negative-air” building, which sucks all the smells into a biofilter — layers of compost and wood — where microbes eat the odors.

Workers keep an eye on the balance of high-nitrogen matter — food scraps and grass — with high-carbon woody matter such as tree branches, broken pallets and lumber ends.

The moisture content is kept at around 60 percent, and every once on a while a front-loader adds a batch of “inoculants” — microbe-loaded mulch scraps — to the mix.

Next, the combined raw matter is mixed in a grinder, screened and then passed beneath a huge magnet, which salvages two to three tons per week of mangled nails, forks, champagne caps, horseshoes and garden clippers.

“Their collection of stuff is the coolest thing. They should make a museum,” said Morris, who sometimes hosts his radio show on the site. “I think half of it is my tools.”

The material spends its first 28 days in 32 long, narrow heaps, each secured beneath a Gore Cover tarp. The actual Gore Cover material is a fragile white substance, tucked between an inner white layer and a tougher fabric exterior. Underground trenches running the length of each pile feed fan-blown oxygen into the material, while also providing drainage for excess moisture.

Pairs of probes — blue for oxygen, red for temperature — measure conditions within the biospheres. The company wants to encourage aerobic microbes, not the stinky anaerobic type that produces greenhouse gases, so the fans kick on if oxygen levels fall below 8 percent. The oxygen-loving microbes produce heat while they eat, keeping phase-one temperatures at about 175 degrees.

Next the mulch is moved into 16 covered, second-phase piles, where after two weeks it’s again moved, this time into uncovered rows for two more weeks. Then it gets added to a 35-foot-tall mulch mountain, which holds the equivalent of 1,000 tractor-trailer loads.

A final sifting removes more stray items that end up in people’s yard-waste toters — dog toys, action figures, golf balls, shredded plastic bags — as well as the biggest compost chunks, which get recycled back as inoculants.

Then the mulch is bagged and sold under the company’s name in stores such as Lowe’s and Home Depot.

The Everett Shorelines Coalition and other environmental groups are fans of the operation, which includes a one-mile paved trail along Steamboat Slough.

“It’s a net earth-friendly process, where you take stuff we can’t just leave in our backyards and turn it into something useful,” said coalition President Peggy Toepel.

Diane Brooks: 425-745-7802 or dbrooks@seattletimes.com