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CHAPTER 5. TECHNICAL REQUIREMENTS OF THE REGULATIONS

5.1 Permit Conditions for Waste Incineration Installations

Where an application for a permit or variation to comply with the Regulations has been made, SEPA will include conditions in the permit or variation that give effect to the technical requirements of the Waste Incineration Directive. SEPA is required to do so by virtue of directions which the Scottish Executive has given it. The relevant requirements are set out in the Schedule to the directions.

The directions impose stringent requirements on incineration and co-incineration plants falling within the scope of the regulations. These requirements cover types of wastes permitted at the plant, their delivery and reception, combustion furnaces, abatement plant, residue handling, monitoring equipment and emission limit values. All these requirements have to be included in the permit.

As well as ensuring SEPA implements the mandatory requirements of the Waste Incineration Directive, the directions to SEPA include two minor additional provisions:

• SEPA is required to set measurement requirements for "dioxin-like PCBs and PAHs". This is in addition to requirements in Article 11(2)(c); and
• SEPA is required to authorise the appropriate exemptions for NOx that are provided by Annex V of the Waste Incineration Directive.

Previous directions giving effect to Municipal Waste Incineration Directive and the Hazardous Waste Incineration Directive are dis-applied on a progressive basis as the EPA direction is given effect.

5.2 Process Requirements: permitted waste and their delivery and reception

The type of furnace chosen and the type/size of abatement plant will be influenced by the waste to be burned (e.g. its calorific value, heterogeneity, moisture etc.).

An explicit list of the categories of waste permitted at the plant should be included in the permit.

The total waste incineration/co-incineration capacity of the plant should be specified. Note that the Directive defines capacity as "the sum of the incineration capacities of the furnaces of which an incineration plant is composed, as specified by the constructor and confirmed by the operator, with due account being taken, in particular, of the calorific value of the waste, expressed as the quantity of waste incinerated per hour".

Any sampling and measurements relevant to the permitted waste should be included in the permit.

Where the permitted waste is a hazardous waste, SEPA will also specify the quantities of different categories of permitted wastes, their minimum and maximum mass flows, their lowest and highest calorific value, and their maximum content of pollutants e.g. PCB, PCP, chlorine, fluorine, sulphur and heavy metals.

Article 5 of the Directive requires that operators must take all necessary precautions concerning the delivery and reception of waste in order to prevent or to limit as far as practicable negative effects on the environment, in particular the pollution of air, soil, surface water and groundwater as well as odours and noise.

Operators should obtain documentary and analytical details of hazardous waste prior to its acceptance in order to comply with any specified restrictions on types that may be accepted. For hazardous waste, operators are also required to check statutory documents (consignment notes); take representative samples, unless inappropriate, e.g. for infectious clinical waste, to verify the waste type and retain samples for at least one month after incineration.

5.3 Operating Conditions

The Directive specifies a number of requirements on the operations of incinerators and co-incinerators. These include combustion gas temperatures, gas residence time, the TOC content of residues, conditions when waste feed should be stopped, and energy recovery from the plant. It also allows some derogation from these requirements under some conditions. The above requirements are discussed in more detail in the following sections.

Residues - TOC/ LOI Content of slag and bottom ashes

Article 6.1 requires that all incineration processes must be operated in such a way that Total Organic Carbon ( TOC) or Loss on Ignition ( LOI) content of the slag and bottom ashes will not be higher than 3% or 5% respectively. This requirement does not apply to fly ash or air pollution control ( APC) residues.

Article 6.4 of the Directive appears to allow derogation from the above requirement, but allowing higher levels of TOC than specified would conflict with the requirements of Article 6.4 which states that any derogations should not result in higher content of organic pollutants. The Scottish Executive is, therefore, of the view that SEPA cannot give any derogation for TOC/ LOI.

For gasification and pyrolysis plants this limit applies to the slag etc after the gasification / pyrolysis stage as well as the final stage.

Any dusty wastes shall be handled on-site such that they do not give rise to fugitive dust releases to the environment by using BAT. Bottom ash and APC residues should not be mixed together.

The Directive also requires that appropriate physical and chemical testing, including the pollution potential of the residues is carried out prior to determining their disposal or recycling routes.

Operating conditions - Combustion Requirements: Temperature/Time Requirements

All incinerators and co-incinerators burning waste must be designed, equipped, built and operated in such a way that the gas resulting from the process is raised to a temperature of 850 ^oC for 2 seconds. In the case of hazardous waste with more than 1% of halogenated organic substances, expressed as chlorine, the temperature must be raised to 1100 ^oC for 2 seconds. Operators whose plants cannot operate at temperatures at or above 1100 ^oC will, therefore, have to demonstrate that they will not incinerate hazardous wastes with chlorine content of more than 1%.

The temperature has to be raised in a controlled and homogenous fashion. To satisfy this, operators will need to demonstrate that cold spots in the chamber or channelling in the gas flow have been avoided. New plant, or plant undergoing a substantial change in operation, shall demonstrate this by using computerised flow dynamics ( CFD). Existing plants shall demonstrate this by CFD or actual measurements. CFD should be followed by actual measurements on all plants once operational in order to demonstrate that the CFD model was accurate.

The Directive also requires that the above temperatures are achieved under the most unfavourable conditions. This is taken to mean the most unfavourable operating conditions i.e. at the edge of the operational process design envelope and requires operators to understand their waste stream and its impact upon their plant.

The combustion requirements must be met at all times when waste is being burned. This therefore effectively excludes the use of any waste (no matter how clean) as a start-up fuel because the minimum temperature requirements will not be met (but see section below on Derogation from Operational Parameters).

Start-up fuels used in the auxiliary burners must not cause higher emissions than those arising from the burning of gas oil, liquefied gas or natural gas. For practical purposes this may be determined by comparison of fuel specification with gas oil, and may usually be limited to the pollutants listed in Annex V for release to air, unless the fuel contains a particular substance of concern.

Waste feed interlocks are required to prevent waste from being fed to the incinerator/co-incinerator when the required temperature conditions are not reached either at start up or during operation.

Derogation from Operational Parameters

Article 6(4) of the Directive allows for certain conditional derogation from operational parameters for certain categories of waste or for certain thermal processes provided other requirements of the Directive are met. This means that it is not a universal derogation for all wastes and for all plants.

It is expected that all new plants would have been designed to meet the requirements of the Directive and would not need this derogation. It is likely that older plants may not achieve the required residence time. The operators will need to apply for derogation with a full justification. In addition to the older plants, the most likely candidates for this derogation are gas turbines and gas engines burning gas from waste gasification and waste pyrolysis.

Operating conditions - Energy Recovery

Article 6(6) requires that any heat generated by the incineration or the co-incineration process shall be recovered as far as practicable. It will, therefore, be necessary for all operators of incineration plants to demonstrate that this condition has been met or explain why it is not possible to recover energy.

Additional Operating conditions

Article 6(5) requires that exhaust gas stack heights are calculated in such away that significant ground level concentrations of pollutants are avoided and that relevant Community air quality standards are met.

Article 6(6) requires that infectious clinical waste should be fed straight into the furnace without first being mixed with other categories of waste and without direct handling.

The Directive also requires that the management of the incineration or co-incineration plant shall be in the hands of a natural person who is competent to manage the plant. Natural person means a real person rather than a company.

5.4 Air Emission Limit Values for Incinerators

Emission Limit Values for Incinerators

Article 7(1) requires all incinerators to be designed and operated, as a minimum, to meet the ELVs set out in Annex V of the Directive.

Until 1 January 2007, an emission limit value for NO _x does not apply to plants only incinerating hazardous waste. However, SEPA will also need to take account of BATNEEC/ BAT considerations in deciding any limit.

The Directive allows for the derogation of NO _x emission limit values until 2008 or 2010 depending on the size of the existing incineration plant. Note that these exemptions do not apply to co-incineration plants. The Scottish Executive has given a direction to SEPA requiring these derogations to be used.

Heavy Metals

These average values cover gaseous and the vapour forms of the relevant heavy metal emissions as well as their compounds and molecules associated with particulate material.

Dioxins

The Directive requires dioxins to be reported using the I-TEQreporting convention. In addition the World Health Organisation toxicity equivalence factors ( WHO- TEF) values for both dioxins and dioxin-like PCBs should be specified for monitoring and reporting purposes.

SEPA will, therefore, set dioxin emission limits using on I-TEF (1990) values but with additional monitoring/reporting requirements for dioxins and dioxin-like PCBs using WHO- TEF (1997/98) factors.

Equivalence factors for dibenzo-p-dioxins, dibenzofurans and dioxin-like PCBs

For the determination of the total concentration, the mass concentrations of each congener should be multiplied by the following equivalence factors before summing:

Other non-specified ELVs

Article 7(5) of the Directive allows Member States to set emission limits for other pollutants especially polycyclic aromatic hydrocarbons ( PAHs). There is lack of monitoring data on the release of PAHs from incinerators on which to base such limits or even to decide if a limit is required. The directions to SEPA require monitoring conditions to be included in permits but not to set a limit. Once sufficient data is available, a decision can be made on the future of this requirement.

Air Emission Limit Values for co-incinerators

Article 7(2) requires that co-incineration plant shall be designed, equipped, built and operated in such a way that the emission limit values determined according to or set out in Annex II of the Directive are not exceeded in the exhaust gas.

However, Annex V ELVs will apply to co-incineration plant in certain circumstances, e.g. when burning mixed municipal waste.

Determination of air emission limit values for the co-incineration of waste.

For this, Annex II of the Directive generally applies a mixing rule based on the principle that, in a mixed fuel/waste firing situation, the flue gases generated by the waste meet the ELVs given in Annex V of the Directive. However, in some particular cases, e.g. cement plants, no mixing rule is applied.

If in a co-incineration plant more than 40% of the resulting heat release comes from hazardous waste, the ELVs set out in Annex V shall apply.

Burning of waste in cement plants is not subject to a mixing rule. Limits have been set which must be complied with if the plant burns waste.

Annex V limits for heavy metals and dioxins also apply in full to all co-incineration plants without pro rata.

Where Annex II does not specify a total emission limit for a pollutant, it must be calculated by using the mixing rule. For example, Annex II does not specify a limit for heavy metals for lime plants. In this case a pro rata limit will apply.

5.5 Water Emission Limit Values

The Directive requires that the waste water from the cleaning of exhaust gases discharged from an incineration or co-incineration plant shall be subject to a permit granted by SEPA. It further requires that discharges to the aquatic environment of waste water resulting from the cleaning of exhaust gases shall be limited as far as practicable, at least in accordance with the emission limit values set in Annex IV.

There are also some more general requirements in respect of the design and operation of the plant to prevent unauthorised and accidental release of polluting substances into soil, surface water or ground water. This applies to all potential sources of pollution on the site, not just to the releases from air pollution control equipment. The Directive specifically states that storage capacity shall be provided for contaminated rainwater run-off from the site or for contaminated water arising from "spillage or fire fighting operations."

5.6 Monitoring Requirements for Incinerators and Co- Incinerators

The aim of the Directive is to prevent or to limit negative effects on the environment and the risks to human health. It achieves this by setting stringent operational conditions and technical requirements and through setting emission limit values for waste incineration and co-incineration plants. The Directive requires that:

• the permit can only be granted if the applicant shows that the proposed measurement techniques for emissions to air will comply with the requirements of the Directive;
• the permit specifies the sampling and measurement procedures to satisfy the obligations imposed;
• measurement requirements are laid down in the permit or in the conditions attached to the permit issued by SEPA;
• measurement equipment should be installed meaning thereby that temporary equipment is not acceptable (on long term basis);
• the location of the sampling or measurement points must be laid down by SEPA; and
• the calibration of continuous monitoring equipment and the periodic measurements of the emissions into the air and water must be carried out representatively and according to CEN standards. If CEN standards are not available, ISO standards, national/international standards which can provide data of equivalent scientific quality must be used.

Monitoring of Process / Operational Parameters

Some of the process/operational parameters, e.g. TOC/ LOI, that should be monitored are discussed earlier. The Directive also requires continuous measurements of the following process operation parameters:

• temperature near the inner wall or at another representative point of the combustion chamber as authorised by the regulators;
• concentration of oxygen;
• pressure;
• temperature; and
• water vapour content of the exhaust gas. The continuous measurement of water vapour is not required if the sampled flue gas is dried before the emissions are analysed.

Monitoring of Releases to Air

NO _x (provided that emission limit values are set - see Annex V in WID), total dust, TOC, HCl, HF and SO ₂ should be monitored continuously. Regulators may also set frequencies for the monitoring of NH ₃ and N ₂O.

Operators should take at least two measurements per year of heavy metals, dioxins and furans, dioxin-like PCBs and PAHs but there should be one measurement at least every three months for the first 12 months of operation. These are the minimum frequencies for periodic measurements. However, SEPA may ask for more frequent sampling and analysis, and certain derogations are allowed by the Directive.

Compliance

It is essential that all results are recorded, processed and presented in a fashion that allows a transparent verification of compliance with the operating conditions and emission limit values specified in the permit.

The Directive requires that if the measurements taken show that the emission limit values for air or water have been exceeded, SEPA should be informed without delay.

5.7 Links to other Directives

The tighter requirements in the regulations will contribute to:

• Improvements in air quality under the Air Quality Daughter Directives; and
• The targets in the National Emissions Ceiling Directive

There is also a link to the Large Combustion Plant Directive ( LCPD). If a plant falling under the LCPD is also burning waste then the overall emission limit values ( ELV) will be based on the ratio of:

• The ELV in accordance with the LCPD for the non-waste portion of fuel; and
• The ELV in accordance with the Directive for the waste materials burnt.

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