Roles of Heavy Metals during Pyrolysis and Gasification of Metal-Contaminated Waste Biomass: A Review

Abstract

The presence of contaminates (i.e., heavy metals) in biomass through various sources (industrial activities and municipal solid waste) from its growth to end use has become a nuisance. Over the past years, biofuel production from metal-contaminated waste biomasses (MCWBs) has attracted more attention on account of the potential roles in addressing both energy and environmental concerns. This review considers the migration and transfer behaviors of heavy metals into various output streams, including solid products (i.e., biochar), tar and syngas from MCWBs, i.e., contaminated energy crops, plants, industrial wastes, and municipal solid waste, and using thermochemical processes (gasification and pyrolysis). In addition, the authors also shed light on the transfer mechanisms of heavy metals (however, the availability of the literature on the transfer mechanisms of heavy metals during thermal process is very limited) and usability of products (bio-oil, biochar, and syngas), including a comparison of gasification and pyrolysis processes in regard to the conversion of MCWBs into bioenergy. In the end, technoeconomic assessments and future perspectives are presented. This review will be helpful to promote future research and may aid in the scale-up of the current practices to visualize MCWBs as potential opportunities instead of nuisances.

Fluidized bed gasification of biomass from plant-assisted bioremediation: Fate of contaminants

“…In the present analysis, Cd and Ni are almost completely captured by the cyclone filter, and their content is negligible in the fugitive ashes. This result agrees only partially with a recent review about the assessment of HM during gasification process [43] in which it is shown how Cd and Ni have opposite behaviours: the first is easily transported away by the syngas, while the second tends to accumulate mainly in the bottom ash. In the case studied the olivine has influenced the emission of Ni, but the cyclone has represented an effective system of abatement for the fractions in which both Ni and Cd have concentrated.…”

Microbial–Plant Collaborative Remediation of Cd-Contaminated Wastewater and Soil in the Surrounding Area of Nuclear Power Plants and Risk Assessment

“…A 10 g soil sample was selected from the area polluted by cadmium emitted by the nuclear plant, and was put into a conical flask with 90 mL sterilized liquid beef extract peptone with glass beads under a sterile environment. The obtained conical flask was placed into a shaker and shaken to obtain a uniformly mixed soil-liquid sample [8,9]. During the process, the shaking table speed and temperature were set to 150 rmp and 37 • C, and oscillated continuously for 12 h. The uniformly mixed soil-liquid sample was applied on different agar culture media, with 4 replicates set for each group.…”

“…Al-Afify et al analyzed water, sediment and two naturally growing plant samples collected seasonally from eight sites to investigate the level of heavy metal contamination in the Nile River. The results showed that cadmium and nickel contributed 80% and 10%, respectively, to the ecological risk assessment [8]. Fayuan W's team proposed the inoculation of soil with Mycorrhizal Fungi (AMF) for the purpose of heavy metal phytoremediation in response to heavy metal contamination in sweet sorghum.…”

Potential for Thermo-Chemical Conversion of Solid Waste in Canada to Fuel, Heat, and Electricity

“…The most abundant heavy metals are calcium and silicon in food, paper, wood, yard and garden waste, railway ties, and biosolids [31]. These contaminants arise from the fertilization and pest control of crops as well as from the processing of materials and are harmful to the ecosystem [88]. In unmanaged landfills, there is the possibility for these metals to enter the food chain through the water system and/or soil.…”