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10.4 Characteristics and Quantity of Ashes and
Residues from the WTE

The EIA report states that the total quantity of ash generated is 90,000tonnes/year44. This includes bottom ash, fly ash and residues from the air pollution control system. However the quantities and characteristics of the different wastes are not stated except that mention is made that45:

• Bottom ash will comprise of the bulk of the ash volume and is composed of mineral oxides and non-volatile metals;
• Fly ash consist of fine particles from flue gas, spent activated carbon and residual lime from air pollution control system and incorporates trace concentrations of heavy metals and organic contaminants;
• Their toxicity or non toxicity will be determined at operational stage of the proposed WTE Plant.

The above statements from the EIA report seem to minimise the fact that the fly ash and residue wastes from a MSW incinerator are considered as hazardous in many countries as these wastes contain dioxins and furans, heavy metals and other pollutants. The hazardous nature of these wastes has been demonstrated and reported extensively in the literature.

Again, this is a situation where the EIA report should have used reported data in the literature and develop various scenarios for an appropriate impact assessment and subsequent identification of mitigation measures in conformity to the risk assessments.

It can be argued that if by using state of the art air pollution system emissions control is better, then the resulting ashes are likely to contain higher concentrations.

Carl Bro provides a clear range of characteristics for the various by products from
MSW incineration and their data is reproduced below.

Table 10.4.1: Characteristics of Bottom Ash, Fly ash and FGT Residues from a Dry/Semi-dry Control System
and a Wet Control System46

The data of Carl Bro indeed show a far different scenario whereby the various by products of waste incineration are highly contaminated to the extent that they raise doubts on the validity of the assumptions made in the EIA report.

The high range of concentrations of heavy metals and PCDD/PCDF observed in the bottom ash, fly ash and residues of the air pollution control systems in particular establish the hazardous character of these by products of MSW incineration.

With regard to the level of distribution of dioxins and furans (PCDD/PCDF) in the various by products of MSW incineration, recent studies tend to confirm that the concern on the presence of dioxins in all by products of waste incineration.

Giuglano et al (2002)47 carried out a Dioxin mass balance on an MSW WTE Plant of 400tonnes/day with a state of the art flue gas treatment consisting of air bag filters, a two stage wet scrubbing system and a SCR for reduction of NOx and Dioxins and Furans (PCDD/PCDF). The PCDD/PCDF masses in the various components of the incineration by products are given in Table 10.4.2.

Table 10.4.2: PCDD/PCDF masses in MSW Incineration
By products48

Giuglano et al concluded that the concentrations of PCDD/PCDF in the various by products of MSW incineration plant raise considerable concern on the capacity of MSW incineration plant even when equipped with state of the art technology, to conform to PCDD/PCDF strict emission standards. They concluded that the decontamination of the incinerator by products will be necessary.

The European Union Dioxin Inventory presents the following incinerator-related waste generation rates:

• Fly ash: 30-38 kg/tonne of waste burnt, Bottom ash: 300 kg/tonne of waste burned. Fly ash 9000-11400tonnes per year and 90000tonnes per year Carl Bro estimates that the fly ash and air pollution control residues at about 5% of the input MSW (i.e. around 50kg/tonnes of waste burnt whereas the bottom ash is around 15% of the waste input (150kg/tonne of waste) but does not provide any indications on generation rate of the boiler fly ash.

Hence on the basis of the data from the Dioxin Inventory, one can estimate that over the projected 25 year life span of the WTE Plant about 225,000-285,000 tonnes of highly toxic fly ash and 2,250,000 tonnes of bottom ash will be produced. All of these ashes will be contaminated with heavy metals, POPs, dioxins among others.

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44 EIA report section 6.3.2 p6-3.
45 EIA report section 6.3.2 p6-3
46 Source: Carl Bro (2005)
47 Giuglano M., Cernuschi S., Grosso M., Miglio R., and Aloigi E., 2002. PCDD/F mass balance in flue gas cleaning units of a MSW incineration plant. Chemosphere 46,1321-1328.
47 Source: Giuglano et al (2002)
48 EIA report p7-15, Table 7.6b

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