Fate of Trace Elements during the Combustion of Phytoremediation Wood

Abstract

We investigated the fate of trace elements (TE) in poplar wood on the conversion of biomass to heat in a 0.2 MW combustion unit equipped with a fabric filter. The phytoremediation wood was harvested from a TE-contaminated agricultural site planted with a high-density poplar stand. The combustion technology used in the present experiment allows for an efficient separation of the various ash fractions. The combustion process concentrates Cu, Cr, and Ni in the bottom ash, heat exchanger ash, and cyclone ash fractions. Therefore, the impact of the fabric filter is negligible for these elements. Conversely, Cd, Pb, and Zn are significantly recovered in the emission fraction in the absence of the fabric filter above the emission limits. The use of a fabric filter will allow the concentration of these three TEs in the ashes collected below the filter, thus complying with all regulatory thresholds, i.e., those from the large combustion plant EU directive. Because the TE concentrations in the different fractions differed significantly, it is recommended that these fractions be treated separately, especially when recycling of ashes from phytoremediation wood through application in agriculture is envisaged.

Effect of mycorrhizal inoculation on metal accumulation by poplar leaves at phytomanaged sites

“…As poplars accumulate lower amounts of PTEs in wood than in leaves, we assume that Cd concentrations in wood are 1.2 to 2-fold lower than in leaves, and Zn concentrations, 4 to 10-fold lower considering similar foliar concentrations and moderately contaminated soils (Laureysens et al, 2004;Madejón et al, 2004;Migeon et al, 2009). In comparison with reference values obtained from a non-contaminated area (Chalot et al, 2012), Cd and Zn estimated concentrations in the wood of the present poplars may be in excess by the end of the first rotation. Valorization options (torrefaction, pyrolysis) of noninoculated 7-year-old Skado poplars were investigated at a Zn and Cd contaminated site in Northern France .…”

“…The last few years, phytotechnologies have progressively shifted to phytomanagement, a concept which included the valorization of the plant biomass produced on contaminated sites, to generate economic revenue (Evangelou and Deram, 2014). Although some valorization options have been deeply investigated and provided opportunities for such biomass Chalot et al, 2012;Delplanque et al, 2013) phytomanagement is still scarcely applied in European countries and suffer from lack of field experiment feedbacks (Cundy et al, 2013).…”

“…In addition, this strategy is based on the selection of the less accumulating cultivars to avoid or limit the transfer of the contaminants in the food chain and in the end-products after wood conversion process . Short rotation coppice (SRC) of inoculated poplars for bioenergy production in metal contaminated lands has been proposed as a phytomanagement strategy that may control environmental impacts and increase economic opportunities (Chalot et al, 2012).…”

Genotypic variations in the dynamics of metal concentrations in poplar leaves: A field study with a perspective on phytoremediation

“…Poplar harvestable parts correspond to the wood which can be safely and profitably used for energy production (Chalot et al, 2012). However, the highest metal concentrations are usually observed in leaves, and the lowest in wood (Dominguez et al, 2008;Laureysens et al, 2004;Migeon et al, 2009;Unterbrunner et al, 2007).…”

Bioenergy grown on contaminated land – a sustainable bioenergy contributor?

“…In addition, the biomass produced can be economically valorized for example in the form of bioenergy [31,[53][54][55].…”