Phytoremediation for Heavy Metal‐contaminated Soils Combined With Bioenergy Production

Abstract

In June 2007, a project started in Flanders (Belgium) in which we will apply phytoremediation to clean soils that are diffusely polluted with heavy metals. Uptake ranges of heavy metals by rape seed, maize and wheat will be enhanced by increasing the bioavailability of these heavy metals by the addition of biodegradable physico‐chemical agents and by stimulating the heavy‐metal uptake capacity of the microbial community in and around the plant. In addition, the harvested biomass crops will be converted into bioenergy by using different energy‐recovery‐techniques. The energy and heavy metal mass balances will be compared for four different energy‐recovery techniques (anaerobic digestion, incineration, gasification and production of biodiesel). The overall information obtained will result in an economic evaluation of the use of phytoremediation combined with bioenergy production for the remediation of sites which are diffusely polluted with heavy metals. In the present review we will first explain the most important research steps investigated in our phytoremediation project. Secondly, an overview of literature discussing the phytoremediation capacity of rape seed to clean soils that are contaminated with heavy metals and the possibilities to produce biodiesel from this (heavy metal polluted) rape seed will be discussed in more detail.

Successes and limitations of phytotechnologies at field scale: outcomes, assessment and outlook from COST Action 859

“…Studies on biosolids over a decade after their initial application show that measuring soluble TE contents, notably those of Pb and Cu, is not enough to predict beneficial changes in plant biomass and microbial activity . The direct financial returns of (aided) phytostabilisation can arise from wood chips for energy co-generation with pyrolysis or thermal oxidation, paper, fibres, biofuel, hydrogen, timber and utility poles, essential oils and forage crops (Van Ginneken et al 2007;Schröder et al 2008a, b;Thewys and Kuppens 2008;Vangronsveld et al 2009). …”

“…The removal rate for winter rapeseed at Balen (42 g Cd per hectare per year) means that it would take 257 years to reduce total soil Cd from 5 to 2 mg Cd per kilogram, showing the influence of cultural practice, cultivar and year ). The addition of biodegradable physicochemical agents and the stimulation of metal uptake capacity of the microbial community in and around the plant have been shown to increase metal bioavailability and metal uptake by rapeseed, maize and wheat (Van Ginneken et al 2007). For sunflower, Cd removal ranges between 4 and 85 g Cd per hectare per year depending on plant material, contamination source and soil type.…”

“…oilseeds and willows), fibre and fragranceproducing plants can be used to recover valuable products (Meers et al 2008;Schröder et al 2008a, b;Nehnevajova et al 2009;Witters et al 2009; see Table 1). Some species such as Brassica juncea (Indian mustard), Brassica rapa (field mustard) and Brassica napus (rapeseed) can grow rapidly with high biomass production even in low and moderately polluted soils (Van Ginneken et al 2007). The shoot BCF and TF generally exceed 1 for Cd and Zn (Table 3).…”

“…Investigations must focus on the long-term possible synergy between energy crop production and contaminant phytoextraction from soil and groundwater. At the Lommel site, harvested biomass crops are converted into bioenergy using four energy recovery techniques, and the energy and element mass balance have been compared (Van Ginneken et al 2007). The valorisation of contaminated biomass may affect the process (Thewys and Kuppens 2008;Vangronsveld et al 2009).…”

Heavy metal accumulation in soils and grains, and health risks associated with use of treated municipal wastewater in subsurface drip irrigation

“…Crop type on the other hand did significantly affect concentrations of Cu, Cd, Pb, and Ni in wheat seeds being significantly higher than in those of corn (p<0.01), whereas Zn and Cr concentrations were larger in corn (p<0.01). This could be ascribed to the plant-specific ability to absorb trace elements from soil (Van Ginneken et al 2007;Wang et al 2009;Bieby Voijant et al 2011). The maximum permissible limit of Pb, Cd, Cu, Zn, Cr, and Ni are respectively 0.2, 0.1, 20, 50, 1, and 0.04 mg kg −1 dry seed based on a dry weight (US-EPA 2012).…”