"There's Metals in Them Thar Plants!"

By Don Comis
June 22, 2000

Miners might have been better off farming plants rather than digging pits for high-grade ores.

U.S. Department of Agriculture agronomist Rufus L. Chaney and colleagues in USDA's Agricultural Research Service, at the University of Maryland, and in England have patented a way to use plants to "phyto-mine" nickel, cobalt and other metals.

Phyto-mining, or biomining, is the use of plants to extract valuable heavy-metal minerals from soils.

One of the plants being used is alpine pennycress, a wild perennial herb found on zinc- and nickel- rich soils in many countries. It--or a high-yielding commercial crop like canola that had pennycress genes incorporated into it--would be harvested and burned. Then the phyto-miners would process these ashes and recover the valuable metals for sale.

Ashes of pennycress grown on a high-zinc soil in Pennsylvania yielded 30 to 40 percent zinc, the equivalent of high-grade ore. Electricity generated by the burning could partially offset costs.

Ironically, early prospectors in Europe used weeds such as alpine pennycress as indicator plants to find metal ore. These plants thrive on soils with high heavy-metal content, taking up metals through their roots and storing them in their leaves to protect themselves from chewing insects and plant diseases.

USDA has signed a cooperative research and development agreement with Viridian Resources, LLC, a technology company based in Houston, Texas. It involves Chaney and colleagues associated with the patent as well as a scientist at Oregon State University. An article about the research appears in the June issue of Agricultural Research magazine and on the web.

Scientific contact: Rufus L. Chaney, ARS Environmental Chemistry Laboratory, Beltsville, Md., phone (301) 504-8324, fax (301) 504-5048, rchaney@asrr.arsusda.gov.