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In less than a month, six dead people became dirt, according to results presented yesterday (February 16) at the American Association for the Advancement of Science meeting in Seattle. The trial, run by Seattle-based company Recompose, the first-ever human composting company, set out to test the effectiveness of its technique and ensure that the resulting soil product met Environmental Protection Agency safety standards for heavy metals and other contaminants.

Last year, Washington became the first state to legalize this practice of human composting. Katrina Spade, Recompose’s founder and chief executive officer, tells the BBC that compared with cremation or traditional burial, the process of composting a body—or “natural organic reduction,” as Recompose calls it—can avoid the atmospheric release of nearly one-and-a-half tons of carbon and therefore is a motivating factor for people concerned about climate change. Compared with traditional burial, composting avoids the risk that formaldehyde and other embalming agents will leach into groundwater and eliminates the land space needed for coffins.

Composting “is a fabulous option,” University of Tennessee environmental microbiologist Jennifer DeBruyn, who did not participate in the research, tells Science News. The approach has long been used to process animal carcasses, she notes. “The idea of applying it to humans, to me, as an ecologist and someone who has worked in composting, it just makes perfect sense, honestly.”

Recompose’s recipe includes woodchips, alfalfa, and straw grass. A body is placed in a closed vessel with these materials and rotated slowly to encourage microbial breakdown of the tissues. In a month’s time, the composted material—a couple cubic yards of bone-riddled soil that meets EPA safety standards—is made available to relatives, who can spread it in their garden or use it to plant a tree.

Lynne Carpenter-Boggs, a soil scientist at Washington State University in Pullman who led the small trial of six volunteers, found that the bodies got warm during the composting process—stabilizing at around 55 °C (131 °F) for some time. “We are certain that there has been a destruction of the vast majority of [disease-causing organisms] and pharmaceuticals because of the high temperatures that we reached,” she tells the BBC.

DeBruyn adds to Science News that the heat generated during composting also helps destroy pathogens. Prions, however, are not killed by heat, Carpenter-Boggs adds, meaning that composting “wouldn’t be allowed for people who have diagnosed Creutzfeldt-Jakob disease,” she tells Science News.

Washington’s new law to add compositing as an acceptable means of human remains disposal goes into effect in May. Recompose plans to open for business soon. Colorado is currently considering legislation to legalize human composting, according to the BBC.

“It’s an interesting concept,” Edward Bixby, the president of the California-based Green Burial Council, tells The Guardian. “I’m curious to see how well it’s received.”

Jef Akst is managing editor of The Scientist. Email her at jakst@the-scientist.com.