Assessing BAT in practice

The fluidised bed incinerator already has semi-dry acid gas abatement which reduces NOX emissions to about 200mg/m3. However, the waste incineration Directive sets this as a maximum limit, necessitating further abatement.

The BREF identifies two options: selective non-catalytic reduction (SNCR) to reduce emissions to 180mg/m³, or selective catalytic reduction (SCR) to achieve a limit of around 63mg/m³. Both techniques increase energy consumption, but this is seen as insignificant in the context of EU-wide CO₂ emissions.

The capital cost is put at €185,000 for SNCR and €1,475,000 for SCR, with annual operating costs of €188,000 and €670,000, respectively.

The SCR option, though more expensive, is more cost-effective, reducing NOX at a cost of €1,938 per tonne compared with €3,424 for SNCR. The BREF goes on to say that these costs are below the average "external cost" of NOX of €4,200 per tonne - suggesting that neither is unreasonable.

On viability, the BREF says that demand for incineration is fairly inelastic because competition in the sector is limited, and the costs of abatement could easily be passed on to customers and would not damage the sector. It sees no case for easing the speed of implementation.

The case study concludes that SCR is the "preferred option". However, the Environment Agency, which submitted the case study, stresses that it is intended for illustrative purposes only.

The case study may be misleading clear-cut - not least because the NO_x emission limit is set by an existing Directive. In most cases, the emission levels to be achieved under IPPC will be indicative and subject to negotiations between operators and regulators.

For cement kilns for instance, the achievable NOx level associated with BAT is 200-500mg/m³ using a combination of primary measures and SNCR. In the UK, where SNCR is not used, average performance is around 900mg/m³.

The Agency recently set a limit of 800mg/m³ for Rugby Cement's Rugby kiln after concluding that SNCR was not BAT in this case. The company is required to achieve 500mg/m³ by August 2005 and hopes to do so by using tyres as fuel (ENDS Report 327, p 9 ).