If there is nickel in the soil, alyssum plants can collect it in recoverable amounts. The plants are cut and baled like hay, then burned to make a nickel-rich ash (up to 30% Ni) suitable for further processing. It's time to learn a new word: phytomining.
For three years Toronto's Inco Ltd. and Viridian Resources LLC of Houston have been testing plots near Port Colborne, Ont., where the plume of a former base metal refinery elevated nickel levels in the soil. The alyssum they planted is carefully bred and selected from naturally occurring varieties. The plants contain up to 2% Ni if they are harvested just before going to seed. They are incinerated in an existing furnace on the property, with the added benefit of potential power generation from the waste heat.
Inco claims that phytomining could be used in Indonesia in an estimated 50- to 100-year operation. In the top 50 cm of soil there, the natural nickel content is about 0.5%. The U.S. Department of Agriculture has estimated that the economics of nickel recovery far outweigh the money that could be made by farming the land.
The mechanics of phytomining can be found at various web sites by entering "phytomining" or "phytoremediation" in your favourite search engine. Or check out the USDA's economic estimate at www.ars.usda.gov/is/pr/2002/020109.htm