HMIP eases up on emission rules for incinerators

Incinerator operators have heaved a sigh of relief following the publication of the latest batch of process guidance notes by HM Inspectorate of Pollution (HMIP). The guidance, though stricter than the previous rules, takes a softer line than HMIP had proposed in its initial drafts. But the respite is likely to be short-lived as the notes are overtaken by the EC's draft Directive on hazardous waste incineration.

The 11 new guidance notes (see ENDS Report 208, p 32, for availability ) cover the waste disposal and recycling industry. This will be the second sector to come under integrated pollution control (IPC) after the fuel and power industry.

Operators of existing plants will have to apply for IPC authorisations between 1 August and 31 October. The deadline for upgrading to the standards set for new plant is 1 December 1996.

  • Chemical waste incineration. Inevitably, the most controversial process is incineration. The first draft of the guidance note for chemical waste incinerators followed the draft EC Directive's requirements closely.

    The EC proposal explicitly sets out to be technology-forcing (ENDS Report 208, pp 36-7 ). Tight emission limits and a proposed ban on discharges of flue gas scrubbing liquor from new plants have nettled UK operators. Les Baker of ReChem International claims that the limits are "barely achievable".

    HMIP was persuaded by incinerator operators to tone down the requirements proposed in its draft guidance. The main emission limits set out in the final note are shown in the table alongside the standards in force under the old "best practicable means" regime. The different reference conditions for the BPM 11 limits tend to make them even less strict than they may at first appear.

    There appear to be two main reasons behind HMIP's move away from the EC proposals. Firstly, if the UK adopted them lock, stock and barrel its negotiating stance on the draft would be compromised. The guidance note can be viewed as setting out the UK's bargaining position.

    Secondly, there is a philosophical difference between the draft Directive and IPC. The former sets out the "state of the art" in incineration - whereas HMIP is obliged by law to ensure that the "best available techniques not entailing excessive cost" (BATNEEC) are used. It views the EC proposals as being incompatible with "NEEC", and also feels that the requirement to prevent scrubber discharges will not be the best practicable environmental option (BPEO) in all cases.

    ReChem and Cleanaway claim that they are already in compliance with most of the guidance note's requirements. ReChem's Pontypool incinerator is currently failing to meet the particulate limit, but the company says that its third electrostatic precipitator will solve the problem (ENDS Report 208, p 14 ).

    Environmentalists may be worried about the balance that HMIP has struck between "BAT" and "NEEC". The UK's position contrasts with that of Germany and the Netherlands, where legislation already in place is in some instances stricter than the draft Directive.

    In-house chemical waste incineration is also covered by the guidance note. At present only a few companies such as Fine Organics, Glaxochem and Shell Chemicals have in-house incinerators to handle a variety of waste streams. But several dozen other firms incinerate wastes in bolt-on units dedicated to a particular process stream. Although the guidance note does not apply directly to these processes, HMIP is likely to look for similar standards of operation.

    Fine Organics operates two incinerators at its Seal Sands site. The company claims to have no problems with dioxin emissions, but says that the limits for SO2 and NOx will prove hard to meet when sulphurous or nitrogenous wastes are being burned. HMIP has said that it regards low NOx emissions as an indication of efficient combustion - but Fine Organics points out that this does not take account of the starting composition of the waste.

    The process description in the guidance has been extended to include "the destruction of waste explosives or pyrotechnics by burning". This will have important implications for the Ministry of Defence's planned ammunition incinerator in Warwickshire (ENDS Report 208, pp 14-15 ).

  • Incineration of sewage sludge and clinical waste.
    In the longer term, the regulation of these processes will depend on the final shape of the EC incineration Directive. It will not be clear until next year whether these wastes will be classed as "hazardous" and therefore come within its scope.

    Again, while the first drafts of HMIP's guidance notes for both waste types followed the EC proposal closely, the finished versions are much less stringent. The limits for releases to air are similar to those for chemical waste incinerators, although the standards for hydrogen chloride and sulphur dioxide are less demanding.

    Several of the operating requirements for clinical waste incinerators are stricter than those for chemical and sewage wastes. For instance, the temperature of the combustion gases must be raised to over 1000° C for at least two seconds after the last injection of air. For incinerators burning non-halogenated chemical waste the minimum temperature required is only 850° C.

    But HMIP expects only new clinical waste incinerators to be fitted with a secondary combustion chamber. This contrasts with a recommendation in a report by consultants Cremer & Warner, commissioned last year by HMIP, which said that such plants "must be equipped with a secondary combustion chamber."

    Despite this, HMIP's requirements are likely to accelerate the trend towards incineration of clinical waste on a regional basis in large units. Only a few incinerators currently burn more than one tonne of clinical waste per hour and thus come under IPC. Some 700 smaller units are subject to local authority air pollution control. Although these have been set less stringent emission limits, many are unlikely to comply and will close down in the near future.

    Sewage sludge incineration is being widely touted as the best alternative to sea dumping, which is to end in 1998. Only Yorkshire Water and Severn Trent Water incinerate large amounts at present, but all the water companies are assessing the implications of the UK and EC rules for new plants.

    Yorkshire Water has been operating two sludge incinerators at Esholt, Bradford, and Blackburn Meadows, Sheffield, since the late 1980s. A third at Calder Valley will be commissioned this year, and planning permission has just been obtained for a fourth at Knostrop, near Leeds.

    Yorkshire Water believes that HMIP's guidance note "will not cause too many headaches". The company says it already complies with the guide value for dioxins. Its main worries are over the limits for heavy metals, notably cadmium and mercury, and it may have to tighten up on trade effluent consents in order to reduce metal inputs to its sewage works.

    Severn Trent Water's Coleshill incinerator in Birmingham is some way short of the limits for new plant. But the company is to replace it with a larger 45,000 tonnes per year unit. It is also building a new incinerator near Stourbridge.

  • Incineration of municipal waste. An unusual feature of this guidance note is that it is the first to set wide-ranging limits on releases of prescribed substances to water. All the existing IPC guidance notes have contained discharge limits only for cadmium and mercury.

    Municipal incinerators were chosen as the test bed because HMIP felt that its expertise is particularly strong in this area. Spot and seven-day average flow-weighted limits have been set for 15 substances and their compounds. Several of these are pesticides which are unlikely to occur in incinerator effluent.

    The air emission limits for refuse incinerators follow those prescribed for chemical waste incinerators, although the standards for particulates (30mg/m3), hydrogen chloride (30mg/m3) and sulphur dioxide (300mg/m3) are slacker. However, they are considerably tighter than limits prescribed by two 1989 EC Directives on new and existing municipal incinerators. Most existing plants are having difficulty reaching even these lower limits.

    All existing plants will also have to comply immediately with a particulate limit of 100mg/m3. For many units this will require extensive and urgent modifications.

  • Making solid fuel from waste. Only those processes which involve the use of heat are covered by the note. HMIP's principal concern is to control odours from the drying process. The note recommends the use of alkaline sodium hypochlorite scrubbers, biological techniques or an afterburner operating at over 850° C to handle the problem.

  • Distillation of organic solvents and waste oil. These notes set a relatively high emission limit of 50mg/m3 for volatile organic compounds (VOCs). Earlier this year, HMIP proposed that the VOC limit for organic chemical processes should be 20mg/m3 (ENDS Report 207, pp 17-20 ). But it has taken the view that solvent recovery processes, because they involve boiling organic liquids, have an intrinsically high emission of VOCs.

    There appears to be a potential loophole in the regulation of waste oil recovery. Only those processes which involve distillation fall under IPC - yet the Chemical Recovery Association says that only a handful of its 34 member companies distil the waste. Most oil recoverers simply warm the oil to break up emulsions and then separate it from the sludge and aqueous layer.

    However, HMIP has warned that the burning of solid distillation residues and sludges on site will be covered by the chemical waste incineration guidance note unless the waste's composition can be shown to be compatible with the requirements for waste oil burning.

  • Regeneration of ion exchange resins. This note covers only the regeneration of resins in centralised units, of which there are few in the UK. Regeneration of resins in situ will be treated as part of the parent process and will come under the relevant guidance note.

    One of the major uses of ion exchange resins is in the treatment of potable water, but the guidance note says that this may fall within the exceptions set out in IPC regulations. The requirement is that the concentration of prescribed substances in a discharge to controlled waters should not exceed the background concentration.

    HMIP's principal concern with these processes is over releases to water, but no release limits are specified in the guidance. Where resins are contaminated with heavy metals or prescribed organic compounds, the note says that "a better option" may be to dispose of it at a merchant incinerator or other waste disposal facility.

    Otherwise, the main requirement is that wastes are segregated into compatible streams in order to facilitate recycling.

  • Regeneration of activated carbon. The air emission limits for the thermal regeneration of carbon closely follow those for chemical waste incineration. An afterburner chamber with a gas temperature of at least 850° C is required for new plant.

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