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Phytotechnology with Biomass Production
and endangered species, support of pollinating insects), and enhancement of
carbon storage in soils. Apart from these positive ecological and environmental effects, Kidd et al. (2018) critically discuss also possible negative effects of
phytomining on biodiversity (introduction of exotic species, behavioral consequences for pollinators by metal contents of flowers), soil CO 2 emissions as
dependent on agricultural management, depletion of natural resources (e.g.,
water in case of irrigation), and the natural environment (land use and land
use change), and emphasize the need for more research on descriptors and
indicators, assessment methods, and cause-and-effect chain models on ecosystem services (Bouma & van Beukering, 2015; Kumar, 2010).
4.6 Options for Commercial Application of Phytomining
Although phytomining has a number of technological, economic, and environmental advantages, among others due to limitations as discussed in
Section 4.2 (limited soil volume explored by plant rooting systems, adverse
site conditions, low bioavailability of target elements), there is limited experience with field experiments (see Section 4.3) and technological applications.
The most well-known and popular application of phytoremediation is the
use of Alyssum murale for extracting Ni from ultramafic soils at the shores of
Lake Ohrid in Albania, e.g., by the French company Econick (2018), based on
long-term research on improving phytomining efficiency, e.g., by fertilization, weed control, and planting techniques (Bani et al., 2015). Ni recovered
by hyperaccumulator plants can be processed, e.g., via hydrometallurgical
technologies which have already been developed up to pilot scale for the production of Ni salts (ammonium and nickel sulfate hexahydrate, nickel sulfate,
nickel acetate, etc. (Simonnot et al., 2016).
Already 10 years earlier, Haverkamp et al. (2007) suggested to synthesize
metal nanoparticles by plants for catalytic purposes. Harumain et al. (2017)
tested the suitability of plant species from various growth forms (mustard,
miscanthus, willow) to extract palladium (Pd) from mine-sourced tailings.
Although the accumulation of Pd was still below the target for commercially
available 3% Pd-on-carbon catalysts, authors emphasize the strong potential
for supplementary Pd supply by phytomining and positive environmental
effects due to re-vegetation of tailings and other areas contaminated by mining activities and the restoration of their ecosystem functions.
The potential of both woody (e.g., Populus tremula) and nonwoody
(e.g., Phragmites australis and Phalaris arundinacea) plant species for extracting
valuable elements such as germanium and REEs from a dump field has also
been demonstrated by Midula et al. (2017). An alternative source for conservation of primary resources by phytoextraction was suggested by Rosenkranz et
al. (2017): waste incineration bottom ash. “Exotic” elements investigated so far