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.

Effect of Paenibacillus cellulase pretreatment for fiber surface.

Refining is the major process of paper formation. This study focuses on the impact of a specific enzyme (Paenibacillus cellulase) for fibers on the surfaces, the roughness and height of the fibers are also investigated. Effects of enzyme dosages and the mechanical refining action (PFI revolution) on fiber physical properties were also analyzed. The fibers were observed by scanning electron microscopy (SEM), their roughness and height were analyzed by Atomic force microscopy (AFM). Results show that the Paenibacillus cellulase pretreatment increased the drainability of both kinds of pulp at the same level of refining energy. In other words, enzymatic treatment on pulp refining consumed less refining revolutions to reach the same drainability compared to the untreated pulp. Although the viscosity of both kinds of pulp was degraded with the enzymatic treatment, the physical properties of paper had no significantly negative influence on them. The results indicated the treatment with cellulase swelled the fibers in the absence of refining, and there were better fibrillation on the fibers treated with cellulase after refining. Furthermore, the statistical analysis of AFM suggested that both kinds of pulp treated with low cellulase dosage with PFI refining had higher roughness.