The Efficient Planet

We’re Spreading What on Our Parks?

How to turn your own waste into top-grade biosolids.

Austin City Limits festivalgoers in the Zilker Park mudpit on Oct. 4, 2009.
Austin City Limits festivalgoers in the Zilker Park mudpit on Oct. 4, 2009

Photo by Megan Wiegand for Slate

The 2009 Austin City Limits Music Festival stank.

It wasn’t the bands that were the problem. Earlier that year, Austin had laid sod in Zilker Park, home of the annual fall festival, after years of dust problems, including one gritty festival infamously known as the “dust bowl.” In keeping with the city’s environmentally friendly ways, Austin used a locally made compost called Dillo Dirt when laying the new grass. But a day of heavy rain and tens of thousands of festivalgoers turned Zilker’s lush lawn into a mud pit. Dads toting Texas-orange camping chairs, hipsters decked out in impractical vintage, and college students in bikinis and rain boots all shared the same traumatized, confused expression as they waded into the chocolate-pudding-like sludge: What is that smell? The park was ripe with the scent of human waste.

The culprit? The Dillo Dirt, a compost whose central component is highly treated human waste, known in waste-management circles as biosolids. In cities across the United States, biosolids are being used to achieve greater civic efficiency while reducing costs. But concerns over regulation and health effects and a general uneasiness with our bowel movements—sterilized or not—are providing fodder for punny poop headlines in newspapers large and small.

Humans have been using their own waste as fertilizer for eons, but many Americans remain squeamish about taking the trend to a Portlandia level of green dedication. Nowadays, when you flush the toilet, your waste flows through a multipart system that ultimately discharges treated water into waterways and has standards for how to deal with the leftovers, known as sewage sludge. Until the mid-20th century, cities often dumped raw or partially treated waste directly into nearby rivers, lakes, or oceans. (The 1972 Clean Water Act eliminated most freshwater dumping, but ocean dumping wasn’t outlawed until 1988.) Cities then faced the dilemma of what to do with the 7.18 million tons of sewage sludge produced annually in the United States.

Some wastewater facilities, usually for cost reasons, dump sludge in landfills or incinerate it. The rest—about 55 percent, according to a study published in 2007—use their biosolids for agriculture, reforestation, or as makeshift Slip ‘N Slides. (That’s up from about 30 to 40 percent in the 1990s.) About 230 U.S. facilities compost biosolids to make products like Austin’s Dillo Dirt, which combines biosolids with lawn clippings, branches, and old Christmas trees; others create a heat-dried pellet fertilizer like the Milwaukee-produced Milorganite. Biosolids have been used in the restoration of metal-laden mined lands—such as near Leadville, Colo., and Bunker Hill, Idaho—to “turn moonscapes into revegetated habitats,” says Greg Kester of the California Association of Sanitation Agencies. According to the Environmental Protection Agency, biosolids are used on less than 1 percent of total U.S. agricultural land, but every state has some application of biosolids to the soil.

Biosolids may sound like just a bunch of crap, but the substance is governed by strict standards. EPA rules, coupled with state and local laws, govern the amount of metals biosolids can contain, where they can be used, treatments for reducing pathogens, and restrictions and monitoring of crops that were planted on biosolids-treated fields. More and more wastewater treatment plants are converting their biosolids into Class A products—the top grade—which have no detectable pathogens and could be used to grow herbs in your garden. Class B biosolids are treated less, may carry detectable pathogens, have more restrictions on their use, and require more stringent management practices. Biosolids can reduce agricultural production costs and reliance on chemical fertilizers, replenish organic matter in soil, and improve soil structure. Biosolids are also being used to produce renewable energy. Many wastewater treatment plants—which can account for one-third of a city’s electric utility bill, according to Ned Beecher of the North East Biosolids and Residuals Association—aim to include biosolids in their push for net-zero energy.

Biosolids vary in stink level—which is largely determined by compounds containing ammonium and sulfur—depending on the treatment process. “Odors can be a real concern,” says Beecher, adding that more facilities are now working to eliminate problems like smell. “If we produce a product that’s going to smell if it rains on it, that’s unacceptable.” Zilker Park had no noticeable waste smell the day before the rain; only after festivalgoers churned up the mud did the stench emerge. (If there’s one advantage to biosolids stinking up a music festival, it’s that it makes a late-day port-a-potty trip slightly more tolerable.)

So why are groups such as the Sierra Club or the Organic Consumers Association raising a stink (sorry) about biosolids? They say that outdated regulation, the potential for illness, and the unknown cocktail of components found in human waste make biosolids a disconcerting trend. And research on the long-term health effects of biosolids and their components appears scarce. A 2009 study of the biosolids produced by 74 publicly owned waste treatment facilities found metals, pharmaceuticals, steroids, hormones, flame retardants, and other chemicals in the samples. “It is not appropriate to speculate on the significance of the results until a proper evaluation has been completed and reviewed,” the EPA said of the study. A 2002 University of Georgia study of 48 individuals found that participants living within 1 kilometer of sites where biosolids were applied to the land suffered from skin rashes and burning of the eyes, throat, and lungs after exposure to winds blowing from the treated fields.

But wastewater treatment experts disagree. “There are literally thousands of ongoing programs where biosolids have been applied routinely for two to three decades, and if there were some significant issues, they would have been raised by now,” Beecher says. Many land-grant universities have ongoing biosolids studies, and an 18-month Virginia study concluded “there does not seem to be strong evidence of serious health risks when biosolids are managed and monitored appropriately.” Another study by the National Research Council, with which Kester was involved, found that there is no documented scientific evidence that EPA biosolids regulations, known as Part 503, have failed to protect public health. In addition, Beecher points out that employees at sewage treatment facilities are at the epicenter of biosolids exposure, and long-term health studies haven’t turned up major health issues. “They’re not paid hazard pay,” he says. “They’re not considered high-risk.”

Though a few Austin festivalgoers reported rashes after slopping around in the park’s Dillo Dirt soup, the only casualties I observed were my flip-flops, shorts, and the formerly white towels in my Austin hotel room. Austin’s health department spokeswoman told the Austin American Statesman nearly two weeks after the festival that there was no evidence that any illnesses had been caused by Dillo Dirt. My two friends and I slushed around shoeless for roughly 10 hours on the muddiest day of the festival, and though the smell may have brought on music festival PTSD (one friend recalls thinking “What the hell died in this park?” and swears that she could taste the smell) we had no rashes or other health issues afterward.

As cities push for greater efficiency and greener policies, biosolids will continue to be a component of that debate. After all, reusing our own waste is the ultimate achievement in efficiency. But we should continue to monitor biosolids’ components and possible health impacts as waste treatment plants simultaneously move to make biosolid products less objectionable and push the limits of their environmental potential. We’re limited only by our supply.