Worm compost bin produces great garden, clear conscience

Birchwood Cafe owner Tracy Singleton (top) says her restaurant recycles 90 percent of its kitchen waste through commercial compost sites or in Birchwood's garden
Alma Guzman

About once a week, I toss whatever food scraps I've collected into a plastic bin in my kitchen, and in less than a month they disappear. That's because the bin contains hundreds of red wriggler worms, which eat the food and convert it to "castings," which is a nice way of saying worm poop. When I open the bin, I often find the worms clumped together like a tangle of thin, pink noodles in the spot where I buried their previous meal. A few times a year, I remove a portion of the vermicompost and use it to supplement garden or houseplant soil, but otherwise I leave the worms alone. (And no, I don't touch them. I dig with a spoon.) The bin doesn't emit any odors or noise. Most visitors to my kitchen wouldn't even know the worms are there.

The creatures' ability to thrive is even more remarkable because I am, admittedly, a neglectful worm mother. In the summertime I leave the bin on the porch, where it certainly gets too hot. I tend to replenish their bedding less frequently than is recommended. More than once I have forgotten to feed the worms before going on vacation. But through it all—aside from a minor fruit-fly infestation that I ruthlessly combated with the vacuum cleaner—we'd maintained a pleasantly symbiotic relationship for about three years.

That is, until the day, a few months back, when I shuffled, bleary-eyed, toward the kitchen and noticed an odd, squiggly pattern on the hardwood floor. Fortunately (I was barefoot), I didn't enter the room before realizing that the squiggles were actually the carcasses of hundreds of dehydrated worms. I hadn't knowingly done anything unusual or neglectful, and yet the worms had somehow become dissatisfied with conditions in the bin. Perhaps their home was too wet, or contained too many citrus peels? (The problem with worms is that they can't tell you there's a problem until they're dead.) They'd expressed their displeasure by embarking on a suicidal exodus in search of dirtier pastures. And I was left with an annelid Jonestown.

WHY WOULD SOMEONE willingly keep hundreds of worms in her kitchen? Because the United States produces more than 30 million tons of organic waste each year, and when that material ends up in either the incinerator or the landfill, it creates far more problems than benefits. When incinerated, water-rich organic material doesn't burn efficiently or provide much in the way of BTUs. Biodegradable waste in landfills (material put down the garbage disposal eventually ends up there, too) will decay slowly, by an anaerobic, or oxygenless, process, and create methane, an extremely potent greenhouse gas. In fact, in the landfill's dark, dry conditions, organic matter is more likely to mummify than decompose. Back in the 1970s, when the anthropology professor William L. Rathje conducted a series of landfill excavation projects, his crew famously unearthed a perfectly recognizable, years-old T-bone steak. It was so well preserved that Rathje remarked, "I swear, if we brushed the dirt off and cooked it, you would eat it." If that doesn't turn you off to the idea of compostable material in landfills, I'm not sure what will.

The most obvious solution to dealing with the 10 pounds or more of compostable material each household generates per week (more than 25 percent of your trash) is to create a backyard compost pile. But not everyone has her own yard or one owned by an understanding landlord. Also, Minnesota winters can slow the decomposition process nearly to a halt, and the food scraps run the risk of attracting animals. Trust me when I tell you that sweeping up a few worm carcasses is nothing compared to trying to exterminate a rat-infested compost pile.

Hence, the worms. My adventure in vermiculture began somewhat accidentally when I received a worm-filled bin as a gift from a well-meaning friend who has several of his own. (When he showed me his worms, I may very well have remarked, "Wow," or, "That's interesting," but I am quite certain I never said anything like, "Those are amazing" or, "I'd love to have my own worms.") In any case, the bin and its contents didn't seem like the sort of thing one could return for store credit, donate to Salvation Army, or regift, and so I became responsible for 500 or so red wrigglers.

My squirm—seriously, that's the term for a group of worms—is tiny compared to the one managed by Ellen Sandbeck, who has been a vermiculture advocate and worm retailer for about 20 years and who operates the website A garden shed in Sandbeck's Duluth-area backyard contains two 150-gallon vermicomposting bins that look like pony-size bathtubs. When I visited, the tubs smelled of dirt, and Sandbeck dug into one of them and pulled out a pair of decomposing blue jeans.


After helping establish hundreds of home and institutional bins in northern Minnesota, Sandbeck has found even large-scale bins to be extremely low-maintenance as long as the worms have the right home, food, and bedding. The only true disaster she's experienced involved a large amount of leftover pizza crusts that went into a school bin and coagulated into a dense ball, which the worms couldn't penetrate. ("It smelled like a corpse," Sandbeck says. "All the teachers were ready to kill me.") On the other hand, one time someone added the head of a deer carcass to one of Sandbeck's bins and the worms consumed it with no trouble at all.

But even as worm and backyard composting becomes more mainstream (both Martha Stewart and Julia Roberts have recently touted vermiculture's virtues), Sandbeck and I are still niche practitioners. For most people to start composting voluntarily, the process needs to be more American—and by that, I mean it needs to be simple, efficient, and a lot less messy. In other words, we need somebody else to do it for us.

In a few small suburban communities in the Twin Cities, haulers are already offering curbside pickup of organic materials just as they do for refuse and recyclables. The city of Minneapolis plans to do the same, and just launched its pilot program in Linden Hills last fall with the help of the neighborhood environmental group, Linden Hills Power & Light.

Each week, participating households park their wheeled green carts beside their black garbage carts and fill them with organic matter—food scraps, coffee grounds, egg shells, and non-recyclable paper products such as tissues and egg cartons—bundled into biodegradable bags. Because commercial-scale compost piles generate higher temperatures than backyard ones, the haulers will also accept meat and bones, plus grease-stained pizza boxes, natural-fiber clothing, and wax-coated packaging from refrigerated and frozen foods. (The inks make a negligible contribution to the compost's overall volume.) Since her family started composting, Felicity Britton, Power & Light's executive director, says they produce just one small plastic shopping bag of trash each week. "People are amazed by how little 'real garbage' they have left," she notes. And she's seen her neighbors adapt quickly to the idea of sorting organics from their trash, just as they would plastic or glass. "Recycling used to be foreign," she says. "Now that's just what we do."

Compared to household organic material, the biodegradable waste produced by commercial kitchens is "low-hanging fruit" for those interested in recovering it, says John Jaimez, Hennepin County's organics recycling specialist. Jaimez says there are currently 60 K-12 schools composting in the county, as well as the University of Minnesota and Augsburg College. Several county facilities, such as adult corrections and medical centers, are participating, along with roughly 50 business cafeterias, including Best Buy's corporate headquarters and many Twin Cities restaurants.

Corner Table, the Craftsman, Galactic Pizza, Common Roots, and the Red Stag, to name a few, are among those recycling their organics through programs offered by Randy's Sanitation and Eureka Recycling. Tracy Singleton, owner of the Birchwood Cafe, estimates that her restaurant now recycles 90 percent of its kitchen waste—the restaurant's compost dumpster is much larger than the one for trash. Singleton says the switch to composting has added extra costs in upgrading to biodegradable bags and takeout containers, but that it dovetails with her restaurant's commitment to serving fresh food from local farmers. "Compost is the bedrock of local food," she says.

The organic matter generated by residential and commercial sources is used by animal farmers who feed it directly to hogs and cows, by livestock processors who use it as an ingredient in their products, and by commercial composters such as RW farms. RW, which operates a site near the Minnesota Landscape Arboretum in Chanhassen, is one of only a few large-scale composters in the Twin Cities that combines towering piles of source-separated organic material with yard waste. The process isn't so different from what happens in backyards, except the piles are turned with bulldozers instead of shovels.

On the day I visited, the site had only a mild, farm-like smell, with the occasional whiff of silage, even though it was 90-some degrees outside. The decomposition process creates its own heat, and to kill off pathogens and weeds, the piles must maintain a temperature of at least 131 degrees for 10 days straight. The piles are turned several times in the three to six months it takes them to become finished compost. At that point, a screening machine sifts out the fluffy black material and sells it to landscapers, nurseries, and farms, completing the biological cycle. (One more important reason not to incinerate organic material or bury it in landfills: Those methods waste a valuable soil-replenishing resource, essential to rebuilding the country's nutrient-rich topsoil, which is being depleted at an alarming rate.) One truckload of RW's compost recently ended up just a few blocks from the Birchwood Cafe, where Tracy Singleton and local landscape designer Kim Knutson are helping to create a food-producing teaching garden at Seward Elementary School.


I RETURNED FROM my composting tour eager to find out when curbside organics pickup would be available in my neighborhood. But Susan Young, Minneapolis's director of solid waste and recycling services, reminded me that the practical side of organics collection hasn't quite caught up to its philosophical ideals. "Those of us who are trash ladies need to worry about carts and people and routes and getting the job done," she says. While Linden Hills residents may be among the city's most enthusiastic and compost-savvy—some started storing compost in the freezer in anticipation of the program's launch—Young notes that a little less than half of the neighborhood's households are signed up for the free pickup service. She plans to launch several more pilot programs in a variety of areas (ECCO's pilot should start later this summer) to figure out how to make the process the most efficient and cost-effective before rolling it out to the entire city, which she hopes to do by 2013.

Commercial composting faces some of the same challenges the recycling industry did when it began in earnest some 30 years ago—so far, only about 3 percent of the state's organics are diverted from the waste stream for refuse. To be economically feasible, composting needs a business model that balances supply and demand: an adequate source of material, systems to collect and process the material, and markets for the finished product. Young says that the limited number of commercial compost processors is a significant limitation. "In the waste business," she remarks, "you can't pick it up if you can't put it down." Young says she hopes that economies of scale and increased business competition will reduce the cost to dump the organic material enough to offset the cost of collection. Jaimez of Hennepin County notes that if, for example, local transportation departments decided to use compost to re-vegetate roadsides after construction projects (compost has proven to reduce erosion better than dirt), it could quickly create a much larger demand.

Jaimez says that state mandates like those that launched recycling programs—setting specific goals and offering financial support or incentives to getting facilities in place—would give organics composting a significant boost. In its last session, the state Legislature did approve a half-million dollars in funds for composting-related grants. Still, it's unlikely, Young says, that Minneapolis will go the way of San Francisco, which operates the country's largest organics recycling program and plans to levy fines on those caught commingling organic matter with trash.

While waiting for curbside organics pickup to become available in my neighborhood, I considered buying an automatic indoor composter like the ones my friends picked up at Target. The appliance, which looks a bit like a desktop computer tower, is filled with food waste, sawdust, and a little baking soda. The machine automatically heats and mixes the material before dumping out finished product in a couple of weeks. The composter does have a few downsides—it's expensive, it consumes a fair amount of electricity, and it generated an unpleasant odor strong enough that my friends moved it outside—but overall, it's pretty slick. Still, I don't think it's right for me. When I opened the lid and peeked inside, I kind of missed the worms. 

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