AGROMINE

Soils and wastes contaminated with heavy metals are prone to create major problems because of their toxicity and their management is generally expensive. But this drawback can be turn into advantage if these solid matrices contain compounds of industrial interest. However, metal concentrations are generally too low for conventional mining and metallurgical recovery. Hence, new extraction and processing technologies must be developed to ensure production of strategic metals, while preserving soil functions, and improving soil and waste quality by decreasing their toxicity. These processes would provide a range of economic, social and environmental values from materials and lands of initial low value. AGROMINE is the conception of agro-metallurgical production chains based on the culture of hyperaccumulator plants on contaminated matrices (soils, wastes) or naturally rich in metals (ultramafic soils) to produce high value metal compounds. These chains are developed for nickel (Ni) and cobalt (Co), metals of high strategic importance. They are based on a previous work devoted to the synthesis process of ammonium and nickel sulfate double salt hexahydrate (ANSH) from the biomass of Alyssum murale. They combine agromining (or phytomining) and hydrometallurgy. • Agromining is an alternative treatment for contaminated soils and wastes, and an application of phytotechnologies to exploit secondary resources. On soils naturally rich in metals it generates incomes for farmers or managers and metal removal improves soil (or matrix) quality. Here the main innovation is the production of hyperaccumulator plants on constructed agrosystems. • Hydrometallurgy produces metals with a niche strategy, seeking forms of Ni and Co of strong industrial interest. Focus is put here on Ni and Co carboxylates, which is completely innovative, but attention will still be given on Ni and Co salts for surface treatment. The AGROMINE project involves 4 research teams of Nancy (LRGP and CRPG, LIEC, LSE of Labex Ressources 21) and two SMEs (Soléo Services and Microhumus), which have a long collaboration history. It also has strong connections with joint activities between Labex Ressources 21 and ERAMET, a major French nickel mining company. ERAMET has expressed its interest for the project by providing a support letter. The consortium maintains regular contacts with the main international actors of phytomining: Albania (UAT), Québec (INRS-ETE), China (SYSU), Australia (CMLR-UQ) and the United States (USDA). Work is organized in 1 management task and 5 scientific tasks, including: 1. Characterization of matrices, including soils, sediments and sludge: new agrosystems containing metal contaminated matrices will be designed, characterized and prepared to grow hyperaccumulators; 2. Selection of hyperaccumulators and control of metal bioavailability to identify the best Ni and/or Co hyperaccumulators for each environmental condition and metal recovery; 3. Implementation of agromining at platform scale with constructed agrosystems; 4. Hydrometallurgy for metal recovery from biomass and production of high-value compounds, based on our experience on the patented synthesis of a Ni salt (ANSH), and focus on the preparation of Co salts and Ni and Co carboxylates; 5. Life Cycle Assessment and economic evaluation of the agromining chain as well as its transfer to the end-users. AGROMINE is intended to produce economic and social value from low value material and land. It is not planned to supplant conventional mining technologies. Contrary to popular belief, our field data have shown that this process makes profit: agromining on 4 000 ha producing 200 kg Ni ha-1 converted in ANSH would give an economic benefit of c.a. € 6.15 million per year. The results obtained in AGROMINE would be of great importance for the two SMEs and for the ECONICK start-up, which is currently in an incubating process in Nancy.