Life cycle assessment of agromining chain highlights role of erosion control and bioenergy

Vivian Houzelot,Jérémy Rodrigues,Baptiste Laubie,Marie-Noëlle Pons,Jean-Louis Morel,Guillaume Echevarria,Marie-Odile Simonnot,Florent Ferrari

doi:10.1016/j.jclepro.2016.08.110

Abstract

Agromining is the recovery of valuable heavy metals from soils with high metal concentrations, using hyperaccumulator plants, to produce value added products. It allows the exploitation of low-grade ores for which conventional mining techniques are too expensive and detrimental to the environment. It is also a means for the restoration of closed mines and heavy metal contaminated soils. On lands of low fertility and high concentration in metals, e.g. serpentine soils in the Balkans, it can provide income sources for the local farmers and improve soil fertility and resistance to erosion.We presented here the Life Cycle Assessment of an agromining supply chain. This chain included i) the recovery of nickel from serpentine soils in the Balkans with cropped hyperaccumulator Alyssum murale, and ii) the production of ammonium nickel sulfate hexahydrate (ANSH) from the resulting ashes using hydrometallurgical processes. Results showed that if not controlled by anti-erosion practices, soil loss at farm scale is responsible for significant impacts, especially on human and environmental health, due to the high heavy metal content of soil particles. However, agromining has a similar impact as normal agricultural practices implemented on the territory. It may be used as cover crop instead of leaving bare soils. Its impact would therefore be beneficial. Heat recovery from biomass combustion avoids significant impact, depending on the energy source it may replace. Proper combustion fume filtration and fly ash recovery reduce risks on human health and maximize metal recovery. Byproducts derived from the process may return to the field to compensate nutrient uptake by crops and improve soil fertility. In conclusion, LCA demonstrated that the whole agromining chain offers the opportunity to promote new agricultural practices and preserve valuable resources. Improvements of the industrial processes are however necessary to increase Ni recovery, purity and added value of final products.

Highlights

Agromining is the recovery and subsequent purification of strategic metals from soils with hyperaccumulating plants (Morel and Mollier, 2013)
A process was designed to extract Ni from A. murale, and synthesize salts of Ammonium Nickel Sulfate Hexahydrate (ANSH), that crystallize at low temperature (Barbaroux et al, 2012; Mercier et al, 2012)
This study is the first attempt to assess the sustainability of agromining using Life Cycle Assessment (LCA)

Summary

Introduction

Agromining is the recovery and subsequent purification of strategic metals from soils with hyperaccumulating plants (Morel and Mollier, 2013). Agromining may be compatible with the production of other crops with the phytoextraction of metals, and allow a much quicker post-mining reconversion of the land (van der Ent et al, 2015). It could suitably complete conventional mining and depollution processes, respectively on low-grade ores and heavy metal-contaminated soils. Agromining of Ni from serpentine soils using the HA A. murale was conducted with success in Oregon and Albania (Li et al, 2003; Bani et al, 2007) This Brassicacea is found in the Balkan Peninsula, and has an average bioaccumulation ratio of 2.9 for Nickel (Ni) (Shallari et al, 1998). It has been recently improved to high levels of purity (Zhang, 2014)

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Conclusion