The long road to developing agromining/phytomining

The concept of phytomining is a natural extension of botanical prospecting and the study of metal biochemistry and biogeography of metal hyperaccumulator plants. Some elements may be phyto-extracted to remediate soils, but the recovered biomass would have little economic value (Cd, As, etc.) and disposal of the biomass would be a cost. A few elements may have sufficient economic value in phytomining biomass to support commercial practice (Ni, Co, Au). The development of phytomining requires (1) selection of high-biomass hyperaccumulator plant species; (2) evaluation of genetic diversity and breeding of improved strains with higher yields of the phytoextracted element; (3) development of agronomic practices to maximize economic return; and (4) development of methods to recover the phytomined element from the plant biomass. Plant species and methods for phytomining of soil Ni have been demonstrated for several species and locations (temperate and tropical climates). Production of Ni metal in an electric arc furnace smelter, and of Ni(NH4) 2SO4 using a hydrometallurgical method, have been demonstrated. Full commercial phytomining of Ni is beginning in Albania using Alyssum murale, and major trials in Malaysia are underway using Phyllanthus securinegioides. Variable prices of commodity metals add confusion to the development of commercial phytomining

Agronomy of ‘Metal Crops’ Used in Agromining

Agromining involves growing selected hyperaccumulator plant species ('metal crops') on low-grade ore bodies or mineralized (ultramafic) soils, or anthropogenic metal rich materials (e.g. contaminated soils, mine spoils, industrial sludge), prior to biomass harvesting and incineration to recover valuable metals or salts. This chapter begins with an introduction that explains the concepts of phytomining and agromining. We then acknowledge the role of agronomy in enhancing metal yield of 'metal crops,' with emphasis on Ni. Highlighted in the selection of sites section is the issue of potential agromining substrates, and the role of metal phytoavailability in economic agromining. We present criteria for selecting potential 'metal crops' and possible regions where these species are most suited for successful agromining operations. We then discuss thoroughly the soil and plant management practices that have been proposed to increase biomass and metal yield of 'metal crops.' Also reported is progress of the tropical agronomic trials. Finally, we provide a conclusion and present an outlook on the agronomy of 'metal crops' used in agromining

Agromining from Secondary Resources: Recovery of Nickel and Other Valuable Elements from Waste Materials

International audienceIndustrial activities produce a variety of metal-rich waste, which are often classified as hazardous due to high concentrations of metals such as Ni, Zn, Cu, Cr, Pb and Cd. Metals recycling from waste materials is still limited, especially from those waste types characterized by complex matrices and multi-metal contamination, with large amounts of metal-rich waste materials being discharged into the environment. Although several pathways of metal recovery from waste have been developed, landfilling often remains the most convenient alternative in terms of costs. In recent years, a new approach to metals recycling from waste materials has been investigated: agromining with hyperaccumulator plants on waste-derived substrates. Hyperaccumulator plants can isolate specific metals from multi-metal waste matrices and bioconcentrate target metals in their biomass. Specific characteristics of industrial waste might limit plant establishment and uptake of target metals; thus, the addition of amendments is required prior to plant cultivations as well as the construction of waste-derived artificial substrates. Research conducted to date has shown limited effectiveness of agromining when applied on certain metal-rich industrial waste materials, while promising results were obtained from other types of waste. Upscaling trials are currently underway to demonstrate the applicability of waste agromining for metals recycling within waste generation industrial facilities

Using AFLP genome scanning to explore serpentine adaptation and nickel hyperaccumulation in Alyssum serpyllifolium

Background and aims Alyssum section Odontarrhena is the largest single clade of Ni-hyperaccumulator plants, most of which are endemic to ultramafic (serpentine) soils. Alyssum serpyllifolium is a facultative hyperaccumulator able to grow both on limestone-derived and ultramafic soils. Analysis of different populations of this species with contrasting phenotypes could allow the identification of genes involved in Ni-hyperaccumulation and serpentine tolerance.Methods A glasshouse pot experiment on compost-amended ultramafic soil was carried out with three ultramafic (U) and two non-ultramafic (NU) populations of A. serpyllifolium. The leaf ionome was determined by elemental analysis and used as a proxy for serpentine adaptation. A Ni-hyperaccumulating phenotype was estimated from leaf Ni concentrations. Cultured plants were genotyped using Amplified Fragment Length Polymorphism (AFLP) markers. Outlier analysis and regressions of leaf ionome over band distribution were applied to detect markers potentially involved in Ni-hyperaccumulation and serpentine tolerance.Results As well as U populations, some plants from NU populations were found to be able to hyperaccumulate Ni in leaves to concentrations exceeding 0.1% (w/w). U populations had a higher Ca/Mg leaf ratio than NU populations, mainly due to Mg exclusion. 374 AFLP markers were amplified and a potential adaptive value was identified in 34 of those markers.Conclusions Phenotype regression analyses were found to be more powerful than outlier analyses and indicated that regulation of foliar concentrations of Ni, Ca, Mg and P are the main factors involved in serpentine adaptation. More research is needed in order to resolve the ancestral or recently -evolved nature of Ni-hyperaccumulation.Strategic metal resources of the 21st centuryAgreenSkills