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Select Committee on Environment, Food and Rural Affairs Minutes of Evidence


SUPPLEMENTARY MEMORANDUM SUBMITTED BY THE ENVIRONMENT AGENCY

IMPLEMENTING THE HAZARDOUS WASTE INCINERATION DIRECTIVE (HWID) ON CEMENT AND LIME KILNS BURNING SUBSTITUTE LIQUID FUELS (SLF)

THE CEMENT-MAKING PROCESS

  1.  For approximately twenty years cement kilns have used coal and/or petroleum coke to generate the heat needed to convert a mixture of limestone and shale to clinker, the precursor to cement. Lime is manufactured in a similar way except that shale is not used in the raw material feed.

  2.  In terms of concentration and/or volume, both the fuels and the raw materials contain significant levels of sulphur, chlorine and metals, which are either trapped in the clinker or are converted to pollutants such as sulphur dioxide, oxides of carbon and nitrogen, dioxins and hydrogen chloride. The process also results in the release of large volumes of carbon dioxide as calcium carbonate changes to calcium oxide (a process known as calcination).

  3.  Over the last five to 10 years operators have sought to reduce their fuel costs by replacing the conventional coal and/or petroleum mix with substitute fuels. The Agency has taken the decision that the substitute fuels that have been used to date are waste, with some being classified as hazardous waste. As a consequence of this decision cement companies burning hazardous liquid waste must comply with the requirements of the HWID.

REQUIREMENTS OF THE HWID

  4.  The HWID was adopted in 1994 and introduced into UK law in 1998 through a Secretary of State's Direction and Regulations. These required processes burning hazardous waste to comply fully with the Directive's requirements by 30 June 2000.

  5.  The Direction required the Agency to vary all Part A Integrated Pollution Control (IPC) [1]authorisations for processes burning hazardous waste to include conditions by 30 June 2000 that satisfy the Directive's requirements.

  6.  By the end of June 2000 the Agency had varied all the authorisations for cement kilns burning hazardous waste in accordance with the requirements of the HWID. This has ensured that the Agency's regulation of hazardous waste burning in cement kilns is in accordance with the minimum standards set by EU legislation.

METHOD ADOPTED FOR APPLYING EMISSION LIMITS

  7.  In applying the HWID to cement plants burning hazardous waste, the Agency imposes the same emission limits on the flue gas generated by hazardous waste as it would if the waste was burned in a dedicated hazardous waste incinerator. Emissions from a cement or lime kiln burning hazardous waste would be apportioned between those emissions arising from the burning of hazardous waste and those arising from the combustion of conventional fuel: the HWID limits apply to the former, and the latter are regulated in accordance with Best Available Techniques Not Entailing Excessive Cost (BATNEEC). The method of doing this is prescribed by Annex II of the HWID.

  8.  The HWID provides for limits to be based on a "mixing" or "pro-rating" formula. For cement and lime kilns the emission limit values set out in the HWID were applied to the volume of flue gas generated by the hazardous waste fraction and the existing cement plant limits were applied to the remainder of the gas. This ensures that the emission limit values in the HWID are applied to the gas generated by hazardous waste burning irrespective of the type of combustion unit. The rules for calculating the final emission limit values are complex.

  9.  Cement and lime kilns have a residence time for the gases which is estimated to be around six seconds and a gas temperature of at least 1500ºC. This compares with the HWID's requirements of two seconds and 1100ºC as a minimum for halogenated hazardous waste, eg wastes containing 1 per cent chlorine. This should result in a very high level of destruction of organic components in the hazardous waste. The atmosphere in the kilns is highly alkaline, resulting in the absorption of acid gases. The solids levels in SLF are low, and most would be incorporated into clinker or would be captured by the air pollution control equipment. Similarly, metals are also likely to be captured in the same way.

COMBUSTION PRODUCTS OF CEMENT AND LIME KILNS

    (a)  Gases generated by a cement or lime kiln burning SLF arise from four principal sources:

    (b)  Breakdown of carbonates to release carbon dioxide—the bulk of the gas comes from this source (a process known as calcination);

    (c)  Combustion of the traditional fossil fuel—coal and/or petroleum coke;

    (d)  Combustion of SLF; and

    (e)  Combustion of non-hazardous waste such as tyres.

CEMENT AND LIME KILNS CURRENTLY BURNING SLF

Region
Operator
Type
1999 usage
(tonnes)
2000 usage
(tonnes)
Anglian
Castle Cement Ketton
Cement
11047
10017
Anglian
Rugby Cement Barrington
Cement
26646
23531
NW
Castle Cement Clitheroe
Cement
39228
15830
Midlands
Lafarge Whitwell
Lime
237
9601
NE
Lafarge Thrislington
Lime
9611
10455


WHAT CAN GO INTO SLF FOR CEMENT AND LIME KILNS?

  10.  The Agency's policy on what material can and cannot be incorporated into SLF is set out in two documents:

  11.  The Environment Agency's response to the House of Commons Environment Committee Report on the Environmental Impact of Cement Manufacturing (June 1997); and

  12.  The Substitute Fuels Protocol for use on cement and lime kilns (August 1999).

  13.  The first document is "high level" and sets out in a general manner the policy of the Agency when it regulates substitute fuels on kilns. It requires the exclusion of certain materials from SLF and commits the Agency to defining a specification for substitute fuels.

  14.  The policy outlined above was translated into practical guidance in August 1999 by the Substitute Fuels Protocol which requires that substitute fuel must conform to a specification agreed with the Agency. No substitute fuels to which the following substances have been deliberately added should be subject to trial-burning:

    —  PCBs;

    —  PCP;

    —  radioactive material or radioactive waste;

    —  pharmaceuticals;

    —  pesticides;

    —  biocides;

    —  explosives; and

    —  iodine compounds.

  15.  Although each case must be considered on its merits, trials of substitute fuel containing the following substances should not be permitted:

  16.  radioactive material or radioactive waste (as defined in sections 1 and 2 respectively of the Radioactive Substances Act 1993); and

  17.  explosives, including: propellants, cartridges, or bombs, or explosive material extracted from them or explosive-contaminated material from their manufacture or decommissioning.

  18.  Inspectors should seek to avoid the blending of waste streams into substitute fuel which do not contribute to its performance as a fuel. In addition, for SLF, solids content should generally be less than 20 per cent. Operators should propose a specification for substitute fuel to be burned in the trials and this should cover at least the following parameters:

    —  calorific value (gross);

    —  moisture content;

    —  content of individual halogens;

    —  sulphur content;

    —  heavy metals content (as defined in IPC Process Guidance Note S2 5.01);

    —  suspended solids content (for SLF); and

    —  ash content.

  19.  If the Agency is satisfied with the outcome of trial-burning of SLF, the authorisation that is eventually granted will contain, as a minimum, a specification for SLF which:

  20.  sets maximum concentrations of the parameters listed above (except CV where a minimum value will be set); and

  21.  lists the type of waste that may be incorporated into the SLF and its associated six digit identification code from the EU's Hazardous Waste List.


1   IPC processes are those designated for regulation by the Environment Agency through Regulations made under Part I of the Environmental Protection Act 1990. Back


 
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Prepared 26 July 2002