Indicative assessment of the feasibility of Ni and Au phytomining in Australia

Phytomining involves the extraction of metals from solid and liquid substrates using specially selected hyperaccumulating plants. Phytomining is commercially motivated, the objective being to produce a viable metal yield, at production costs low enough to compete with traditional mining techniques, e.g. heap leaching. In this work we assess the technical feasibility of nickel and gold phytomining in Australia by identifying possible sites, plant species most suited to these regions and methods of recovering the metals from the plants once sequestered. We then investigate the economic viability using published technical and financial models. In the near term, phytomining appears most viable where there are comparatively high metal concentrations around existing mines and mineral processing plants, e.g. near tailings dams or smelters, and in recovering metals from low grade ores considered unprofitable using conventional techniques. Phytomining has the added advantage of improving the quality of the land following completion of the operation. The indicative profitability for a Ni phytomine in Australia is predicted to be ∼11,500 AU$/ha/harvest, using the hyperaccumulator Berkheya coddii on nickel rich serpentine soils and with energy generation from the harvested biomass. For Au, a profit of ∼26,000 AU$/ha/harvest is predicted using induced accumulation (with thiocyanate) with a crop of Brassica juncea coupled with energy generation from the harvested biomass. In both cases, profitability is most sensitive to the metal price and the extractable metal content.