Life cycle assessment of heavy metal contaminated sites: phytoremediation and soil excavation.

Phytoextraction by native Taiwanese chenopod (Chenopodium formosanum Koidz.) and Napier grass (Pennisetum purpureum) for heavy metals such as chromium (Cr), nickel (Ni), and copper (Cu) was reported first. Maximum bioconcentration factors of Cu and Cr were 8.8 and 12.5 by Taiwanese chenopod. Napier grass cultivar Taishi No.4 plants demonstrated higher survivals than that of Taiwanese chenopod, under heavy metal stress in soils. All heavy metal accumulation and biomass data were employed, as well as historical engineering data were collected for conventional excavation-and-refill remediation of two sites. Life cycle assessment (LCA) was conducted for comparing environmental performances of phytoextraction and conventional remediation for two contaminated sites. Assuming one-year growth, three harvests were done and biomass was collected and sent to the nearest municipal incinerators, phytoextraction by both plants demonstrated superior environmental performances than conventional methods for contaminated site remediation. High quantities of fuels to haul the soils of conventional methods mainly contributed to the greenhouse gas emission. Phytoextraction has the most advantages for sites with lesser extents of pollution and time restraints. Environmental performances of phytoremediation were even better if energy recovered from biomass incineration is counted. Novelty statement Phytoextraction by native Taiwanese chenopod and Napier grass was firstly reported. Life cycle assessment was conducted for comparing the phytoextraction and conventional remediation. Phytoextraction demonstrated superior environmental performances. Energy reutilization of biomass recovered made phytoremediation more sustainable.