PVC incineration and dioxins
When an organic substance is incinerated in the presence of chlorinated compounds, dioxins can be unintentionally generated due to incomplete combustion, whatever the incinerated substance may be. For example, dioxins occur from natural phenomena such as volcanic activities and forest fires.
General information on dioxins nature, formation, human exposure, health and environmental impacts can be found here.
Incineration and control measures
Through complete combustion, PVC can be broken down into water, carbon dioxide and hydrogen chloride (HCl). However, complete combustion is rarely feasible in reality, and dioxins can be unintentionally generated as by-products according to incineration conditions.
The European Union Commission published a Green Paper in July 2000 on the Environmental Issues of PVC. The Commission states that: “It has been suggested that the reduction of the chlorine content in the waste can contribute to the reduction of dioxin formation, even though the actual mechanism is not fully understood. The influence on the reduction is also expected to be a second or third order relationship. It is most likely that the main incineration parameters, such as the temperature and the oxygen concentration, have a major influence on the dioxin formation. The Green Paper states further that “at the current levels of chlorine in municipal waste, there does not seem to be a direct quantitative relationship between chlorine content and dioxin formation”. These views are based on many in-depth studies carried out in various parts of the world.
J. Vehlow (Forschungszentrum Karlsruhe Technik und Umwelt Institut für Technische Chemie) investigated the behavior of a large range of chlorinated products in the feed of municipal solid waste incinerators. His conclusion was: “The increased Cl and Br levels (in the feed) caused no significant increase of the concentration of PCDDs or PCDFs in the raw gas”. These findings are in line with many studies concerning the possible impact of PVC materials in the feed of municipal waste incinerators.
The most extensive study was performed in the United States, where the impact of the waste feed chlorine content on PCDDs and PCDFs emissions was analysed on 155 facilities. The conclusion was: “The hypothesis that the amount or type of chlorine in the waste feed to combustion units is directly related to PCDDs/PCDFs concentrations measured at the combustion outlet is not supported by the preponderance of the data examined during this study”.
A study included chlorine feed concentrations from less than 0.1% to 80%20 (1900 test results, 169 facilities, MSWI, HWI, Hazardous Waste Incinerators, Hazardous Waste Fired Boilers, Cement Kilns, Biomass Combustors, Laboratory, Bench-, Pilot-Scale Combustors). The study showed no statistically significant relationship between chlorine input and PCDD/F stack concentration.
A study later performed at the University of Umeå showed that the chlorine source and level are unimportant for formation of chlorinated organic pollutants.
Regulations relevant for dioxins
Relevant EU regulations are spread over several health and environmental Directives. However, on the 24th October 2001 the European Commission adopted a Communication on a Community Strategy for dioxins, furans and PCBs, aiming to reduce the presence of dioxins and PCBs in the environment and as well as to reduce the presence of dioxins and PCBs in feed and food. The conclusions were adopted on 12 December 2001 by the Environment Council.
The main regulations in place in the EU include:
- Industrial emissions in general are regulated by Directive 2010/75 “on industrial emissions (integrated pollution prevention and control)”
- Directive 2000/76/EC “on the incineration of waste” sets a 0.1 ng/m3 TEQ limit on dioxin + furan emissions in the exhaust gas from all incineration and co-incineration plants, except those treating only vegetable waste but including cement kilns co-incinerating waste. The maximum concentration of dioxins and furans in waste water is 0.3 ng/l.
- Decision 2000/479/EC “on the implementation of a European Pollutant Emission Register (EPER) requires the public reporting of dioxin emissions to air and water from all major industrial sites.
- Council Regulation (EC) 2375/2001 sets maximum levels for dioxin contaminants in foodstuffs.
- Recommendation 2002/201/EC sets action limits and target levels in various foodstuffs and animal feed.
Dioxin levels in the environment
Data for the Dioxin Inventory reports (Stage I 1997 and stage II 2001) were published by the North Rhine-Westphalia State Environment. The studies were carried out on behalf of the European Commission. They reflect the emission situation of the period 1993 to 1995. Stage I estimated that an annual PCDD/F air emission of 6500 g I-TEQ per year is released to air by all known sources in the 17 countries considered. Much less is known about PCDD/F emissions through waste water and process residues/wastes. Some of the reviewed national documents contain emission estimates which amount to a total of 3500 g I-TEQ per year for residues and about 20 g I-TEQ per year for waste water. Stage II came up with a revised total emission to air of 3715 – 6415 g/year for 1995, of which 2823 – 4110 g/year from industrial sources (including waste incineration).
Quaß et al (2000) attempted to provide estimates of PCDD/F emissions to air, land and water for the reference period 1993- 1995 in the 15 EU member states, Norway and Switzerland. Estimated emissions to air were 5,728 g I-TEQ/year with municipal solid waste incinerators (MSWI) the predominant source at 1,437 g I-TEQ/yr, followed by sintering plants at 1,010g I-TEQ/yr.
In the EU, industrial emissions of dioxins peaked in the 1980s and active abatement policy has now reduced emissions from the European industry by up to 90%. In the same period reduction of dioxin emissions from domestic sources has been much lower and consequently domestic sources now account for more than one third of total dioxin emissions. This fraction can be as high as 70% in some regions . Between 1990 and 2007 industrial emissions of newly formed dioxins, furans and PCBs were reduced in the European Union by 80% . In Japan, total dioxin emissions to air and water decreased from about 8 kg TEQ in 1997 to about 1 kg in 2002 and about 300 g in 2007 (Dioxins (Government of Japan, 2009).
Dioxin emissions in VCM manufacturing facilitiesThe ethylene dichloride (EDC) purification section is one of the emission sources for which standards for the quality of discharged water are applicable under the OSPAR Decision 98/4. This Decision sets a limit of 1 μg TEQ per tonne oxychlorination capacity in waste water, after final treatment, for all EDC/VCM plants, from January 1st 2006. The Best Available Technique Reference (BREF) for Large Volume Organic Chemicals (LVOC) adopted in December 2017 sets a limit of 0.3 µg TEQ per tonne of EDC produced by oxychlorination.
Information about dioxin emissions can be extracted from the (publicly available) eco-profiles of VCM. The latest figures were collected in 2014, based on the average 2013 performance of all plants of ECVM member companies . These figures are “cradle to gate” and hence include also dioxins generated during chlorine production. Nevertheless, the figures are low, i.e. 0.07 ng TEQ/kg VCM produced emitted to air, and 0.03 ng TEQ/kg VCM produced emitted to water. Based on a VCM production of 6 million t, the yearly total emission related to VCM production (including its chlorine supply) was therefore around 0.6 g/year TEQ in 2013.