New Hope for Old Mine Tailings 1

Of Bark Beetles, Burnt Offerings and Biochar

Played out. It’s a term that can describe an empty mine, or soil so depleted that nothing can grow in it. By the 1940’s, the Hope Mine, near Aspen, was played out in both senses.

The mine was founded in 1911 and reported no production between 1916 and 1920, or in 1929, 1931 or 1934. Although it did produce some silver, Hope never really panned out. It was left squatting in all of its polluted squalor at an elevation of 8,740 feet along the banks of Castle Creek—Aspen’s water source. Tests by the national Forest Service, which by 2003 owned the site, revealed the presence of heavy metals: arsenic, lead and trace amounts of zinc.

The poison hadn’t reached the river, but on a 30-degree slope laden with toxins that prevented plants from taking hold and stabilizing the tailings, catastrophe was just one rainstorm away. Drenching rain could send heavy metals cascading into the creek, shutting down Aspen’s source water for up to two years.

For decades, Hope had been abandoned, one of 23,000 played-out mines that pepper Colorado’s evergreen forests. Along with gray swaths of beetle-killed pine, those toxic orange or gray tailings are among the most prominent eyesores in an otherwise beautiful landscape.

But in 2010, a Carbondale not-for-profit, the Flux Farm Foundation, partnered with the U.S. Forest Service (USFS) and the Aspen Center for Environment Studies (ACES) to conduct a privately funded re-vegetation project that holds hope for abandoned mine tailings and the played-out soils around them.

Flux Farm is a scientific think-tank whose mission is to sustain “the lifestyle, livelihood and ecological future of the West through agricultural innovation.” One of those innovations is the use of “biochar” to improve depleted soils both for agriculture and mine reclamation. Aspen’s Hope Mine—a site belching tailings and contaminated soils—was the first whole mine to undergo reclamation through the use of biochar.

What the heck is biochar?

The concept of biochar has around for centuries. From tribal subsistence farmers to modern-day horticulturalists, growers have long burned fields to improve soil vitality and productivity. With the seasonal conversion of residual organic field matter to carbon, soils flourish; microbes, mycorrhizae, fungi, nutrient availability and moisture retention all increase as carbon is incorporated into the soil.

Biochar is simply that idea on steroids. Large volumes of matter are slowly burned under low-oxygen conditions, in a container, pretty much. In a process called “pyrolysis”, organic matter is dehydrated to become coal. The result is a granulated charcoal product that will retain soil moisture, increase soil biodiversity and bond with heavy metals.

The addition of biochar enables seedlings to establish themselves and thrive on formerly degraded soils. Heavy metals, held in the sponge of biochar, have time to break down naturally before leaching and draining into waterways.

The standard mine reclamation process costs over one million dollars per mine, at minimum. But beginning in October 2010, the USFS, ACES and the Flux Farm Foundation conducted a pilot project on the use of biochar at the Hope Mine for less than 20 percent of that cost.

Thousands of pounds of biochar were mixed with compost and native grass seedlings in different proportions, then spread over 42 test plots around the Hope Mine site. After one year, the 60-year-old wasteland was lush with native grasses. The biochar test plots grew dramatically green in comparison to the untreated gray tailings.

The biochar used at Hope was sourced from beetle-kill pine. Could one forest problem—decaying trees contributing carbon to the atmosphere and posing a fire hazard—be used to address another forest problem: the thousands of toxic mine tailings that scar Colorado’s forests?

While biochar seems new to most of us, it’s a centuries-old idea, and one that has been under intensive ecological study for almost a decade. Scientists believe that biochar is “carbon-negative”, meaning that it sequesters carbon. But that and many other aspects of biochar are not fully understood: How long is it stable in the soil? Does the initial carbon sequestration pan out over the lifecycle of the product? Will business models hold integrity, limiting biochar sources to manures, field wastes and dead trees, or will forests need to be clear-cut to provide fuel?

As with many innovations that seem wonderful at first, it will be interesting to see how biochar plays out. Can burnt offerings and bark beetles become part of the solution for reclaiming played-out mines? Time—and research—will tell.