Turning Waste into Gold
BY BAY STEPHENS
Alow roof of clouds obscured Lone Mountain on the gray April day I followed Peter Bedell into a warehouse-like building at the Big Sky Water and Sewer District’s wastewater treatment plant. The smell as we stepped inside struck me. Instead of the nasal assault you’d expect of a place that processes human waste, I was met with an earthy aroma, like a mossy forest after a rain.
Bedell, one of the district’s certified wastewater operators, had started our tour of wastewater processing at the headworks building where raw sewage enters the plant. He then showed me the pair of giant batch reactors that separate the liquids from the solids, followed by the maze of pipes and filters that treat the effluent before pumping it out to a holding pond. But what I was really there for was this: the final stop on the tour, where the solids are alchemized into a fertile resource.
Bedell led me to an 8-foot-tall pile of the end result: compost. To my untrained eye, it looked like dirt—or soil, more precisely, with its dark hue and a texture indicating organic composition rather than mineral.
“That’s the finished product,” he said, scooping up a bare handful. “Smell it.”
Tentatively, I leaned forward and took a whiff. There was no doubt this material was the source of the building’s earthy aroma. Without knowing it, you’d never guess the loamy material Bedell proffered had been human feces mere weeks ago.
WHY COMPOST HUMAN SH*T?
Although composting food waste has become a popular way for folks to participate in the sustainability movement over the past decade in southwest Montana, municipal composting of human excreta in the United States is a far less acknowledged trend.
Regardless of its mainstream invisibility, “biosolids composting,” as those in the wastewater industry call it, is becoming an increasingly attractive alternative to long-used waste disposal methods.
While you simply flush your waste down the toilet and likely don’t think about it again, every wastewater treatment plant in the country must decide what to do with the biosolids that remain after the treatment process.
One option is to truck the municipal sludge to a landfill. But this means a shorter lifespan for the landfill, higher costs for the wastewater district due to tipping fees, and the production of methane, a potent greenhouse gas created when organic matter decomposes without oxygen—not an ideal solution.
Another option for biosolids disposal involves spraying them in slurry form on farm fields to add important nutrients like nitrogen, potassium and phosphorus to the crops. But according to industry expert Steve Diddy, this too is complicated, requiring land on which to apply, costly permits, careful monitoring and a longer growing season than Montana has to offer.
In contrast to landfilling or land applying municipal sludge, composting allows wastewater management facilities to create a sanitized, microbially vibrant and nutrient-rich product they can sell back to their communities.
Suddenly, human feces goes from waste to valuable input. What was previously an untouchable end is now a bountiful beginning. Biosolids composting: a circular economy operating right under our noses.
SPINNING STRAW INTO GOLD
Composting can be as simple as a backyard pile of food scraps and dried leaves, or as high-tech as insulated, temperature monitoring, auto-aerating containers that precisely optimize the environment for beneficial microbes to thrive. With the right balance of inputs and proper moisture, the former method might take a year to create the rich, fertile material that is compost. The latter—which describes Big Sky’s municipal composting system—takes a matter of weeks.
Whether occurring at a simple at-home scale or an industrial one, a few things must be true to qualify the process as composting: bacteria do the work of heating up the mass and breaking it down (killing pathogens); the process takes place in the presence of oxygen; and humans manage it.
“Compost, like agriculture, is a human creation,” writes compost guru Joseph Jenkins in his book, The Humanure Handbook. “You will not find it in nature any more than you will find a corn field.”
Once raw materials are combined, the process involves three phases: mesophilic, thermophilic and curing.
In the mesophilic phase, bacteria that thrive at moderate temperatures begin consuming organic matter, combining carbon and oxygen molecules to form carbon dioxide, water and heat.
As these bacteria munch, they multiply and raise the temperature of the pile to a point where a different class of heat-loving bacteria take over. These thermophilic bacteria continue to break down organic material, upping the temperature as high as 185 degrees Fahrenheit, though usually topping out closer to 158. If held above 140 degrees for three consecutive days, this natural biological activity reduces the number of disease-causing bacteria to undetectable levels, the EPA’s version of zero.
The cooling or curing phase ensues. Beneficial bacteria, protozoa and fungi migrate back into the pile, further decomposing organic matter and eliminating parasites.
If a pile traverses these three phases, the result is a material rich with organic nutrients, beneficial microbial life, desirable agricultural properties and virtually no disease-causing organisms. Thanks to the marvelous labor of these microbes, a fetid heap of waste is transformed into the fertile matter composters call “black gold.”
From enriching soil to saving money to remediating pollution to retaining water, compost offers a host of benefits.
For starters, compost holds a whopping nine to 20 times its weight in water. This means soil amended with compost not only holds more water, but it holds that water for longer, empowering plants with greater drought resistance.
And when tested against synthetic fertilizer, compost was shown to furnish the same or greater vegetable yields than NPK (fertilizer made with nitrogen, phosphorous and potassium). The big difference, though, is that fertilizing soil with compost instead of synthesized fertilizer builds soil year over year, rather than slowly depleting it.
In other words, compost builds resilience into agriculture.
Composting is also one of the most effective ways to bind up or break down contaminants, according to Dr. Sally Brown, a research associate professor at the University of Washington specializing in land remediation and biosolids reuse.
This remedial quality of the process renders composting especially apt for biosolids recycling because more than just human waste goes down the drain. Biosolids contain varying levels of heavy metals, toxic chemicals, and per- and polyfluoroalkyl substances (PFAS). But the alchemy of composting binds up these contaminants in such a way that they are generally less available for humans.
“A lot of the best ways to remediate soils and biosolids is actually through biological activity, so composting,” said Karl Johnson, owner of Yes Compost in Bozeman.
While biosolids composting is quite commonplace, it’s still gaining steam. Livingston, Montana’s water reclamation facility uses the same high- tech, containerized composting system as Big Sky, selling their compost in bulk to residents. In the western reaches of the state, Missoula’s wastewater treatment plant does the same.
The city of Bozeman collaborates with the nearby Logan Landfill so its biosolids are composted at the landfill, then used to cover completed sections. Gallatin Solid Waste District Manager Jim Simon said this effort diverts 15,000 tons of organic matter from the landfill every year by composting biosolids onsite. That’s equivalent to a month’s worth of waste.
Further north in Kalispell, Montana, biosolids have been trucked to Olney, Montana, since 1993, where they’re transformed into Glacier Gold compost, a product sold in at least seven states.
In many cases, biosolids composting kills at least two birds with one stone. In the case of Glacier Gold, the practice allows the logging operation in Olney to put a mountain of sawdust and wood chips to good use, rather than burn it. And Kalispell has saved untold acres of landfill space.
“We’ve taken two problems on this planet and created a positive,” said Joe Warner, a long-time Glacier Gold employee.
Selling their compost in bulk for $25 a cubic yard—about half a pickup-bed load—Big Sky Water and Sewer District has no problem getting rid of it. And those who overcome the initial “ick” factor of using composted biosolids tend to have rave reviews.
Bay Stephens is a former Outlaw staff writer and editor. He currently lives in Colorado where he builds bike trails in the summer, ski patrols in the winter, and nurtures his curiosity with great books, audio and film.