Jürgen Schmid, Andrea Elser and Renate Ströbel, ABAG-itm Mathew Crowe, EPA, Ireland,

"Dangerous substances in waste",

European Environment Agency, Technical report No 38, February 2000

 

(for complete report see EEA web site at: http://www.eea.eu.int/

the report is availabe in Portable Document Format - pdf)

 

Heavy metals

Heavy metals can be grouped into various classes, each with its specific issues. Metals such as Cd, Cr, Hg and Pb are highly toxic. Cu, Pt and Ni tend to be less toxic but they are potent catalysts and contribute to a complex organic chemistry in the flue gases of combustion plants. In particular, they can contribute to the post- formation of dioxins in the flue gases. The volatility of heavy metals is influenced by the conditions of incineration and they may tend to escape through the smoke stack. In order to avoid adverse effects on human health and the environment, the best option, other than removal from the feedstock, is to decrease their bioavailability by ensuring that they are in a form that is neither breathable nor leachable. [5]

 

Incineration of solid waste contributes significantly to the overall global emission of heavy metals, as illustrated in Table 2.5:

 

Metal	Atmosphere emissions from waste incineration
	1000 tonnes / year	As % of total emissions
Antimony	0.67	19.0
Arsenic	0.31	3.0
Cadmium	0.75	9.0
Chromium	0.84	2.0
Copper	1.58	4.0
Lead	2.37	20.7
Manganese	8.26	21.0
Mercury	1.16	32.0
Nickel	0.35	0.6
Selenium	0.11	11.0
Tin	0.81	15.0
Vanadium	1.15	1.0
Zinc	5.90	4.0

 

Table 2. 5: World- wide atmospheric emissions of trace metals from waste incineration [6]

 

[4] Laurent Bontoux, European Commission - Joint Research Centre. Institute for Prospective Technological Studies. The Incineration of Waste in Europe: Issues and Perspectives

 

[5] Laurent Bontoux, European Commission - Joint Research Centre. Institute for Prospective Technological Studies. The Incineration of Waste in Europe: Issues and Perspectives

 

[6] D. Stanners, P. Bourdeau: Europe’s Environment. The Dobris Assessment. European Environment Agency, Copenhagen, 1995.

 

 

[pages 28 - 29]

 

Fly ashes and residues from gas cleaning

With incineration temperatures above 800 °C, a high percentage of metals will be gasified. Thus, metals are transferred to the gas phase and partly condense before entering the gas cleaning unit. The condensed metals are mostly adsorbed on the surface of small fly ash particles. The fly ash tends to concentrate metals. The remaining vaporised metals are transported to the gas cleaning unit and washed out.

 

	Contents mg/kg
Substances	Slags	Fly Ash	Residues from Gas Cleaning
Cd	<0,5 - 10	50 - 1000	300 - 500
Tl	<2	0 - 50	0 - 2
Hg	<0,05 - 5	2 - 30	10 - 30
As	0,5 - 50	10 - 100	40 - 100
Co	15 - 35	30 - 100	5 - 20
Cr	50 - 1000	50 - 2000	50 - 200
Cu	500 - 1500	300 - 5000	500 - 1500
Ni	25 - 100	100 - 400	30 - 100
Pb	100 - 3500	1000 - 12000	4000 - 10000
Sb	20 - 200	300 - 1000	300 - 1000
Sn	100 - 250	500 - 3000	-
Zn	500 - 2500	5000 - 40000	20000 - 30000

 

Table 3. 8: MSW- Incineration, heavy metal concentration [25] (MSW: municipal solid waste)

 

Organic substances are partly destroyed during incineration, but new toxic substances can be formed. Dioxins and furanes are the most important dangerous organic substances. Other organic substances like PCB and PAH may also be released. These organic compounds are also preferably adsorbed by the fly ash and washed out in the gas cleaning unit. Thus the concentration of organic compounds in the fly ash and the residues are significantly higher than in the slags, as illustrated in Table 3.9.

 

Substances	Slags	Fly Ash	Residues from Gas Cleaning
PCDD/F	4 - 25 ngTE/kg	100 - 10000 ngTE/kg	100 - 10000 ngTE/kg

 

Table 3. 9:  MSW- Incineration, typical dioxin and furan concentrations [26] (MSW: municipal solid waste)

 

Quenching and gas scrubbing processes produce high amounts of waste water containing metals. These waste waters are subject to physical/ chemical treatment to reduce the metal concentration. This treatment results in high salt concentrations (e. g. NaCl) in the treated effluents that are released to surface water.

 

 

[25] T. Leclaire: Behandlung und Verwertung von HMV- Rückständen, Gerhard Mercator- Universitat- GH Duisburg; 1998

 

 

Recent estimates suggest that incineration in the EU may account for emissions of more than 16 tonnes per year of cadmium, 46 tonnes per year of chromium, 36 tonnes per year of mercury and over 300 tonnes per year of lead [9]. For cadmium and mercury in particular, incineration is a major contributor to overall emissions and is estimated to account for 8% of all cadmium emissions and 16% of all mercury emissions.

 

[9] The European Atmospheric Emission Inventory of Heavy Metals and Persistent Organic Pollutants for 1990, Umweltbundesamt, Germany, 1997.

 

The incineration of non-hazardous wastes has been identified as the largest known source of emissions of dioxins and furans to air in Europe [19]. Emissions to air from the incineration of clinical and municipal wastes are put at approximately 2300 g I-TE/y (based on 1993-1995). Some reductions in emissions of dioxins and furans from non-hazardous waste incineration in the Community have already been achieved through the implementation of the 1989 Directives on municipal waste incineration and national measures. These measures are expected to lead to reduced emissions of dioxins and furans for a few more years and emissions from all non-hazardous waste incineration can be projected to amount approximately to 1200 g I-TE/y by the year 2000.

 

[19] Identification of Relevant Industrial Sources of Dioxins and Furans in Europe, Landesumweltamt Nordrhein-Westfalen, 1997.

 

In 14 countries a total of 533 incineration plants are reported in operation (nearly 280 of them in France). There is a very high degree of variation in the size of the plants. In addition to these, 239 incineration plants for hazardous waste are reported in operation.

 

Information on the capacity of the incineration plants is incomplete and data are often several years old. Furthermore several countries have not been able to supply data at all. By combining information on capacity where accessible, with supplementary information on amounts of waste incinerated the total incineration capacity for non-hazardous waste within the EEA is estimated to be about 33 million tonnes (NRC’s, 1998b; OECD, 1997a).

 

The total amount of municipal waste generated in EEA member countries in 1995 was about 191 million tonnes. In other words incineration capacity is only available for about 17 % of the total amount of municipal waste arising.

 

Dioxins (PCDD/PCDF) emission

 

 

Dioxin and Furan Inventories. National and Regional Emissions of PCDD/PCDF, UNEP Chemicals, May 1999.