Dioxin Emissions From Incineration Processes: Role of Feedstock Constituents

It has been suggested that a reduction of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) emissions can be based on an overall strategy of lowering the chlorine content of the municipal solid waste (MSW) by separating chlorinated plastics, e.g. PVC, and if necessary, sodium chloride, from the refuse. This suggestion originates from one of the proposed theories for the occurence of PCDDs and PCDFs in municipal incinerators which hypothesizes that these trace organic compounds are formed from unrelated materials under specific conditions (de novo synthesis). This paper will review the theoretical basis of this formation hypothesis and examine experimental data from recent studies, e.g., Environment Canada study at Prince Edward Island (PEl), New York State Energy Research and Development Authority (NYSERDA) coordinated study at Pittsfield, Massachusetts, as well as an earlier laboratory study by Karasek. Data from these studies indicate that there is no correlation between PCDD/PCDF emissions and refuse chlorine content. It is concluded that the separation of PVC and other plastics from refuse will not significantly reduce PCDD/PCDF emissions. This can be achieved most effectively by promoting good combustion through proper incinerator design and operating conditions, and employing state-of-the-art air pollution control systems.