Risk management and regeneration of brownfields using bioenergy crops

Abstract

The potential of phytoremediation, as a cost-effective in situ alternative to conventional technologies for remediation of contaminated brownfields, has often been pointed out. Yet, phyto-technologies have failed to find widespread adoption in practice. To gain social and commercial acceptance of these technologies, there is a clear requirement of field studies that provide information on success and failures. The aim of this study was to investigate benefits and potential risks with phyto-stabilisation on brownfields using bioenergy-crops. Two field trials with willow (Salix Klara and Salix Inger) were set up aiming for phyto-stabilisation on metal-contaminated sites. By the use of a tiered risk assessment approach, the cultivation’s effect on ecological risks in different environmental compartments, such as soil, porewater and up-take to biota (including potential risks for wild grazers), was investigated before the cultivation was started and during following three growth seasons. Growth assessments were also made to evaluate the biomass’ potential revenue. The risks to the soil fauna proved to be unchanged or declining. The uptake in the plants was, as aimed for, low to moderate, and the growth rate depended on the soil texture rather than the contamination level of the sites. The low uptake indicated a negligible risk for wild grazers. The field trials were accomplished using no, or low, amounts of amendments, minimum soil interventions, no, or very simple, weeding control and conducted at sites with low annual temperature. Despite harsh conditions, the biomass production was high enough to potentially provide revenue. This study shows that cultivation of brownfields using phytostabilising willow clones can reduce the ecological risks, improve the soil quality of the site and provide revenue if the biomass is sold for e.g. bioenergy production. By choosing phytostabilisation willow clones, potential risks associated with phytoextraction of metals, such as biomass combustion and food chain transfer of metals, were eliminated. Consequently, using bioenergy crops for phytostabilisation on brownfields can contribute to preserve and improve ecosystem services, create economic regeneration of these areas and at the same time be a sustainable risk management option.