Why Biochar Might Eventually Replace Peat Moss

Posted by Brian Sparks|February 18, 2018

Peat moss is a major component of potting mixes, but according to an article in Industrial Crops and Products posted on the University of Illinois news page, harvest of the material is becoming unsustainable. Not only is peat being removed faster than it can re-form, its use in potting mixes contributes to the release of carbon dioxide into the atmosphere.

“Peat bogs naturally store carbon. When peat moss is harvested, there’s a transfer of a global carbon sink into a net source. Within a couple growing seasons, most of the peat moss from the potting mix is either mineralized by microbes or thrown out and decomposed. Either way, carbon dioxide is released,” says Andrew Margenot, Assistant Professor in the Department of Crop Sciences at the University of California, Davis.

In a recent study, Margenot and colleagues from the university investigated biochar as an alternative to peat moss in potting mix. Similar to charcoal, biochar is produced through a process called pyrolysis, or heating to high temperatures in the absence of oxygen. And like charcoal, it can be derived from virtually any organic substance.

“In our study, we used one made from softwoods from selective logging. But biochars can be made from corn stover, switchgrass, and lots of other organic waste products,” Margenot says. “Biochar could even be made from a greenhouse operation’s own waste, if there are trimmings from plants or old peat moss.”

Margenot emphasizes that “biochar” refers to a very broad class of material that can vary greatly in its properties depending on the pyrolysis temperature and the feedstock used.