A review on control factors of pyrolysis technology for plants containing heavy metals

The treatment of plants with heavy metals, whether they grow naturally in heavy metal contaminated soil or are used for remediation of heavy metal contaminated soil has attracted increasing attention. Pyrolysis is often used for the disposal of plants with heavy metals because it stabilizes heavy metals effectively and produces biochar. The resulting products of pyrolysis are in the form of solid components (char and ash), liquid components (bio-oil and tar), together with gas components (condensable and non-condensable vapor gas). The metal amount in the char or liquid and gaseous phases can be maximized or minimized via treating a plant feedstock containing heavy metals under different conditions. In addition, the potential risk of biochar produced from plants after pyrolysis becomes a research hotspot in the field of pyrolysis technology of plants containing heavy metals. Herein, we review current literatures that emphasize the influencing factors on the metal content in the biochar, liquid and gaseous phases, as well as the potential risk of biochar.