Emission factors are the core of the Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs. They are derived from measured data, preferentially from well-documented results taking into account technology, process characteristics and operating practices. Expert judgment is applied to aggregate results obtained for processes with similar characteristics into one emission factor representing "order of magnitude" release estimates.
Definition of emission factor
An 'emission factor' is a value for the quantity of PCDD/PCDF, expressed as toxic equivalent (TEQ), released from a source to each release vector per unit of activity (e.g., μg TEQ per ton of material produced, per ton of fuel burned, etc.) that have been assigned for each class within the source categories. Most emission factors have been derived for PCDD/PCDF; where possible, for the other unintentional POPs - PCB, HCB, PeCBz - mass concentrations has been assigned as appropriate.
UNEP has implemented several measurement projects to develop scientifically sound emission factors for open burning of waste and biomass with active participation of developing countries and under their national and local conditions. The results should assist the Parties to the Stockholm Convention in preparing their action plans under article 5 of the Convention, in their national reporting and their national implementation plans (NIPs). The project also give some recommendations on implementation of best environmental practices to reduce formation and release of dioxins and furans and to reduce exposure of people living close to sites with such practices. Finally, the data generated in these projects contributed to the database of 'default emission factors' contained in the PCDD/PCDF Toolkit.
Open Burning of Waste
A multi-national project including research institutions from China, Mexico, Sweden, and United States was initiated by the Chemicals Branch to study the formation and release of unintentional persistent organic pollutants (POPs) from open burning of waste in developing countries. The objectives of the project were to characterize waste compositions in developing countries according to situations where such open burning might occur, to undertake controlled burn experiments to study different waste compositions with respect to their potential for formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) to develop field sampling equipment capable to take smoke samples from open burn sites in the field, and to determine emission factors for use in the UNEP Dioxin Toolkit. The project did not only provide validated emission factors for polychlorinated dibenzo-para-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) for the updating and review process for the UNEP Standardized Toolkit to Identify and Quantify Releases of PCDD/PCDF, it also included an enhanced methodology for the determination of the national activity to determine which types of waste are burned in the open and describe the conditions thereof.
Waste composition characterization was undertaken in Mexico and China according to national statistic schemes and fractions assigned. Fractions were characterized into cardboard and other papers (diapers, napkins), dust, multilayer beverage container, fibers, metals, ceramic, wood, demolition waste, plastics, garden waste, food waste, textile, glass, shoes, batteries, electronics, and others. The project included experiments in hurn huts and field burning experiments. For the burn hut experiments, waste from China and Mexico, representative of urban to rural sites, were shipped to the US-EPA site in Research Triangle Park, NC (RTP) and to Umeå University, Sweden, for combustion testing. A total of 26 burns were undertaken in the Umeå (n=14) and the RTP (n=12) burn huts.
For the field sampling experiments, a new high-volume ambient air sampler mounted on a movable 6 m-long boom was developed and used in the field samplings in Mexico and China. In total, 20 field burns were undertaken. The results are summarized in the report below and several scientific publications.
Scientific papers (subscription needed):
- Lundin et al. (2013): The effects of developing countries nations' municipal waste composition on PCDD/PCDF emissions from open burning - Atmospheric Environment 79, 433-441
- Solorzano-Ochoa et al. (2012): Open burning of household waste: Effect of experimental condition on combustion quality and emission of PCDD, PCDF and PCB - Chemosphere 87, 1003–1008
- Zhang et al. (2011) Emissions of unintentional persistent organic pollutants from open burning of municipal solid waste from developing countries - May 2011
