Do you ever wonder where your poop goes when you flush the toilet? If you live in Boise, it ends up somewhere a little out of the ordinary. It goes to a place called 20 Mile South Farm, so named because it's 20 miles south of Boise.
“Everybody who flushes the toilet contributes to this fertilizer right here,” Says Ben Nydegger, Boise's biosolids program manager.
Biosolids is the industry term for the stuff he’s standing next to. It’s a dark-brown pile about three-feet-tall and roughly twice the area of an Olympic swimming pool.
When Nydegger went to college to study environmental health and biology more than a dozen years ago, he says he didn’t expect to end up working with poop. And as a city kid, he didn’t expect to work on a farm either.
Standing next to the giant pile, I’m struck by two things: It doesn’t smell bad, more earthy than anything else. And there are fewer flies buzzing around than in my kitchen when I leave the back door open. Nydegger says most of what smells bad, or attracts pests, get removed in the treatment process.
From waste to fertilizer
Wastewater from homes and businesses goes to Boise’s two treatment plants. After treatment, the liquid goes into the Boise River. The solid stuff goes through a process that includes heat and bacteria-eating microbes that leaves the waste nearly pathogen free. Then, up to five 30-ton loads are trucked from the treatment plants to the farm each day.
The city used to take this stuff to area farmers and spread it on their fields for them. But it was a logistical challenge, and tightening federal regulations were making it even harder.
A city spokesman says in the early 1990s land was dirt cheap, so in 1994 Boise bought a farm. It’s nearly 4,300 acres, or about 2.5 miles by 3.5 miles.
City employees spread the biosolids on the fields a few time a year, usually before planting crops like corn, alfalfa and wheat. Until it's needed, the biosolids are stored in several piles like the one Nydegger stands next to.
He explains the stuff sits in the sun all summer and develops a crust. I give the pile a kick and a ripple spreads through it a few feet before dissipating. It makes me think of Jell-O with Corn Flakes on top.
“This is excellent fertilizer, works great with our crops,” he says. “It provides organic matter to the soil, helps to build the soil, helps to retain more moisture.”
Those crops are mostly sold to big dairies as cattle feed. But the wheat is for people to eat.
“Could be made into bread or cereal. Could be anything,” Nydegger says.
The pros and cons of fertilizing with human waste
The Environmental Protection Agency (EPA) strongly endorses using biosolids as fertilizer. The agency says about half of the biosolids produced in the U.S. get used as fertilizer. In Idaho, the EPA says it’s a little higher, about 60 percent.
Private farms or farm cooperatives can get permits to store and use biosolids as needed. Some cities use the waste for grass in parks. Some process the waste to such a high degree it's considered completely pathogen free and can be sold for home garden use. In Idaho, Coeur d'Alene markets a product called "Coeur d'Green."
If University of Washington researcher Sally Brown had her way, all biosolids would be used as fertilizer. She says biosolids are better environmentally, in nearly every way, compared to the synthetic fertilizers commonly used in agriculture, and biosolids are just as effective.
“What we eat comes from the soil,” Brown says. “And we eat all this food giving very, very little back to the soil. When you use biosolids as a soil amendment, it adds carbon, which helps your soil’s structure, you get nitrogen, phosphorus all the nutrients, the same way our food provides the nutrients we have to give those nutrients back to the soil."
Don’t start singing "The Circle of Life" just yet. Some environmental groups, most notably the Sierra Club, oppose using biosolids, also known as sludge, for fertilizer. They’re concerned that things like the drugs we take will end up back in our food.
Studies show that some medications and other household chemicals do survive the treatment process and can end up in soil spread with biosolids. But no hard evidence shows that plants take them up.
The ick factor
Brown thinks much of the opposition to using biosolids as fertilizer is because cities, wastewater managers and scientists haven’t done a good job educating the public. Even people who would not think twice about cow manure get squeamish about the idea of using the human equivalent.
“Everybody knows that you get sick from poop,” Brown says. “You have to wash your hands after you go to the bathroom, that’s instilled from early childhood. And people have that association of the poop, where it came from.”
Brown says untreated waste is dangerous. But she says modern treatment methods are so good that diseases associated with human waste have been completely eliminated from the United States and the rest of the developed world.
Other ways to dispose of human waste
Besides use as fertilizer, the only legal options for getting rid of biosolids are incineration or putting the treated waste in landfills.
“Burning biosolids or landfilling biosolids is like throwing away a perfectly good steak,” Brown says.
Those options not only waste a valuable resource, Brown says they create their own environmental problems.
Burning releases greenhouse gasses and takes huge amounts of energy because biosolids have so much water. When biosolids are concentrated in landfills they also produce greenhouse gases that don’t occur when spread on the ground.
No cities in Idaho use incineration but many put biosolids in landfills. Brown says that’s because in Idaho doing so is really cheap.
“So that’s a strong incentive to just make the biosolids go away. And there currently is very little incentive to use them beneficially,” Brown says.
Many southern Idaho cities landfill their biosolids, including Nampa, Meridian and Eagle, so do most south central Idaho counties including Blaine County.
Meridian has a five-year plan to begin using some of its biosolids for fertilizer. Nampa used to give its biosolids to farmers but stopped for the same reasons Boise bought the farm. Nampa waste managers decided it was easier and cheaper to put it in a landfill.
Boise's biosolids-to-farm program is rare
There’s a huge farm in Colorado owned by a wastewater utility that serves nearly 60 communities, including Denver. Los Angeles sends its biosolids to a city-owned farm but it contracts out operations. In Boise, all dozen or so farm workers are city employees.
“We do everything from the tillage practices, to the planting to the harvesting,” Ben Nydegger, Boise's biosolids program manager says.
Perhaps the system that most resembles Boise's operation, is a farm owned and operated by Kansas City. But it’s about a third the size of Boise’s, serving a city that's more than twice the population, meaning Kansas City also burns a lot of its waste.
Boise’s farm is not cheap to run. It costs about $3 million a year. But when commodity prices are good, it turns a profit. It’s made money the last four years and that profit goes to reduce the costs at the processing plant.
Like other big farms in Idaho 20 Mile South has to spend a lot on electricity to pump water from the ground and onto the crops. It has a lot of expensive machines. But it saves about $200,000 a year on fertilizer.
In fact, instead of fertilizer existing for a farm, this farm exists for fertilizer.
“We produce about 28,000 tons [of biosolids] a year,” Nydegger says. “That’s job security.”
Find reporter Adam Cotterell on Twitter @cotterelladam
Copyright 2014 Boise State Public Radio