Is Composting the Key to a Carbon-Free Minneapolis?

minneapolis composting
Compostable food waste. Photo by TJ Turner.

On a cold winter morning, Anne Ludvik bounds up the snow-covered hill that separates the food scraps from the yard waste at the Rosemount composting site where she oversees business development. Steam rises from the rows of decaying organic matter, and an American flag flaps in the icy wind. “That’s there because we’re patriots, of course,” says Ludvik, “but also so the front-end loader operators who move the piles always know which way the wind is blowing.” As if on cue, a gunshot sounds in the distance. No composting facility can afford to offend its neighbors’ nostrils—especially when that neighbor is a shooting range.

In the field of waste management, this is what cutting edge looks like. Minnesota has been a leader in the sector since it opened the Hennepin Energy Recovery Center (known by its acronym, “HERC,” or, more colloquially, “the trash burner”) 26 years ago, when waste-to-energy plants were hard to find outside of progressive European cities. Today, HERC, which is located in what has become Minneapolis’ trendy North Loop neighborhood, burns about 40 percent of Hennepin County’s trash and produces enough energy to light and power 25,000 homes.

Photo courtesy of Hennepin County Environment and Energy.

The city’s next frontier in transforming waste into a valuable commodity is recycling the organic material that comprises a whopping 40 percent of Minneapolis’ residents’ garbage. The process keeps compostable materials out of landfills (where biodegradable substances increase emissions of methane, a greenhouse gas more potent than carbon dioxide) and incinerators (where the organic material’s high water content reduces burning efficiency). The resulting nutrient-rich compost not only sequesters carbon and improves plant growth, but it reduces reliance on chemical pesticides and fertilizers, and helps prevent nutrient runoff and erosion. 

Minnesota is in third place nationally (just behind California and Washington) in the number of cities, Wayzata and St. Louis Park among them, offering composting to residents. And the new Minneapolis program has emerged as a key step for the city to achieve its vision of being carbon-neutral by 2030—an audacious goal that would put it among the ranks of Oslo and Stockholm in terms of environmental sustainability. The first phase of Minneapolis’ curbside organics recycling rolled out to about a quarter of the city’s residents last August, and that number will jump to roughly a third as more households receive their bins this spring. 

If the program reaches its goal of 40 percent participation, nearly 8,000 tons of organic material will be diverted from HERC, and the city stands to save $80,000 per year in disposal fees. When organics recycling was piloted in eco-conscious Linden Hills beginning in 2008, the participation rate topped 50 percent; but getting public buy-in across broader Minneapolis—where the recent move to (relatively simple) single-sort recycling didn’t nudge total recycling rates up quite enough to meet projections—may be challenging, especially considering the more complicated nature, and perceived ick factor, of separating compostable discards.

With single-sort recycling (Minneapolis’ current system of collecting paper, glass, and metals in one bin), the city gave everyone a cart, with the option of opting out. The organics program, however, is opt-in so people are committed to understanding how to do it before they start filling their bins. “People don’t necessarily know what ‘organics’ even means,” says David Herberholz, the city’s director of solid waste and recycling. “It requires a lot of education, because if we have contamination, it doesn’t work.”

Kellie Kish, Minneapolis’ recycling coordinator, carries around a big rolling tote of trash—in her car, on the bus—always ready to demonstrate what is compostable and what is not. In 2015, Kish and other city staff attended more than 100 neighborhood and community events to provide educational materials on the organics recycling program and explain what goes in the bins, what doesn’t, and why.  

The difference is often easy to miss. Waxy butcher wrap, ice cream containers, disposable silverware that’s “made from plants,” some plastic-lined cardboard restaurant to-go containers—all may appear compostable at first glance, but aren’t. Even some disposable cups and plates labeled “biodegradable” don’t cut it; they break down into microplastics that contaminate the soil. 

“The most common contaminant we pull out of our compost piles is plastic,” says Ludvik, though other notable examples of materials that have been fished out include a tombstone, a chain-link fence, a soccer ball, and dead cats (apparently the compost piles serve as something of a siren song to Rosemount’s feral cat population). 

The situation—at least for plastics—should improve by April 2017, when a city ordinance requiring restaurants, grocery store delis, and food trucks to use recyclable, compostable, or reusable packaging for food or drinks goes into full effect. Until then, “Assume it’s plastic if it’s not marked compostable,” says Kish.

“Kish has fielded queries including one from a woman who wanted to know if she could compost her husband’s toenail clippings (yes, and ew)”

But the list of things that can go into the organics recycling bin is impressive: used pizza boxes, tissues, meat, bones, dairy, paper towels, cotton balls, and q-tips among them. When in doubt, call the city; Kish has fielded queries including one from a woman who wanted to know if she could compost her husband’s toenail clippings (yes, and ew), another from a resident who wondered if she could compost the down from an old quilt (nope: chemicals), and several looking for a useful resting place for their deceased family pet (no dead animals, alas—feral cats notwithstanding).

Even when only the proper materials make it to the composting site, the process must be carefully managed. At the Rosemount site, yard waste and food waste are mixed in specific ratios in an agricultural mixer, and the mixture is laid in rows over a pad of gravel on top of impervious clay that prevents any toxins from leaching into the ground as the material breaks down. Each row is underlaid with an aeration pipe and fan that keeps the piles aerobic, preventing the need for turning them, which can stir up odors that have gotten other, less well-managed composting sites shut down.

Once the rows are laid, they reach temperatures around 170 degrees and cook for four to six months, the aerobic bacteria munching on organic compounds and turning the whole pile into nutrient-dense compost. (The rows are checked frequently to make sure their internal temperatures don’t become too volatile. Combustion is always a possibility, so it’s fortunate that one of the Rosemount staffers also happens to be a firefighter.) The finished product is then sold to customers ranging from residential gardeners and contractors to MNDOT and large corporations, which might scoop up thousands of yards of material when building a new facility

The city evaluated a number of different collection methods and decided that a household pickup system, with mandatory payment ($4 a month per residence) but voluntary participation, would lead to the widest buy-in and ensure that local composting facilities could accommodate the results.

Composting makes financial sense, despite the fact that the city of Minneapolis pays commercial compost sites to take the material, and the sites retain the profits from selling the finished product. But the city saves money by taking organics to a compost site because it would otherwise take the material to HERC, which has slightly higher disposal fees. As with the recycling program, organics collection is largely a fixed cost: Trucks drive the same number of streets and alleys regardless of how many households on each route participate. The more households participate, and the greater their degree of commitment (Minneapolis’ pilot program recovered a rate of 177 pounds per household serviced per year, but other cities have averaged up to 700 pounds), the more the city stands to save in disposal fees (and the more opportunity commercial composters have for profit). 

Composting Facility. photo courtesy of the Mulch Store.

Right now, there’s little immediately obvious personal benefit to residents, besides the potential for removing enough organic material to be able to downsize to a smaller trash bin and save $3/month. (The city hopes to soon give those participating in the program access to the resulting compost.) But instead of making participation mandatory, as in San Francisco and Seattle, where residents who put organics in their trash bins may receive fines, Minneapolis is banking on community buy in. 

Kish is accustomed to using a variety of tactics to sway recycling skeptics. “Whether it be the ‘it’s the right thing to do to save resources for your kids’ or the ‘you can save money’ message, it’s all about identifying those motivations for participation and making them clearly understood,” she says. The city’s immigrant populations pose a particular challenge, for reasons ranging from language barriers to cultural skepticism of governmental programs. “In many other countries, people aren’t used to having a relationship with the local government and receiving assistance from them,” says Kish.

As the composting program rolls out, participation will likely follow the variation by neighborhood currently seen with single-sort recycling, where parts of southwest Minneapolis collect nearly twice the poundage per residence as the north side. So the city is partnering with access and outreach coordinators to target immigrant groups including East Africans and Latinos, and all the program’s instructional materials are translated into three languages. 

With the addition of organics, the city hopes to be recycling and composting more than half its waste by 2020. “The official participation goal of the program is 40 percent of Minneapolis residents,” says Herberholz, “but we’d really like to see 100 percent. We pick up garbage weekly in Minneapolis but pick up recycling every other week. Other cities in the country switch that because the garbage is inert and doesn’t smell.”