Oil fractions from the pyrolysis of diverse organic wastes: The different effects of conventional and microwave induced pyrolysis

• MSW, sewage sludge, agroresidues and plastic wastes are pyrolyzed.
• Tars from conventional and microwave induced pyrolysis (MIP) at 800 °C are compared.
• MIP of organic wastes produces fewer oils than conventional pyrolysis.
• MIP of MSW and sewage sludge yields less PAHs than conventional pyrolysis.
• MIP of plastic wastes produces high amounts of benzene-derived compounds.

Several studies have dealt with the microwave-induced pyrolysis of organic residues as an effective technology for maximizing the production of syngas at the expense of the production of oily tars. This liquid fraction is composed of a complex mixture of organic compounds making it difficult to upgrade for use as a biofuel and containing hazardous compounds such as polycyclic aromatic hydrocarbons (PAH). In this study the effect of the type of residue (municipal solid wastes, sewage sludges, plastic wastes and agroresidues) and the heating mechanism on the product distribution within the oil fraction has been investigated by means of GC–MS technique. Two different approaches have been performed: direct GC–MS analysis and methanolysed-oils GC–MS analysis, the later determining the non-volatile compounds. In general, quite different distributions are attained when microwave pyrolysis is conducted, providing lighter compounds. In some cases, such as the plastic-derived oil, microwave pyrolysis lead to a potential source of chemicals such as benzene, toluene and xylenes.