Can I choose between best available technology as defined by IPPC and the permit alternative?

The purpose of a trading scheme is to give flexibility concerning emission reductions. Installations combine in-house abatement and purchasing credits to optimize costs and achieve compliance. Best available technology is a reference to establish best-in-class and set the environmental standards per industrial sector. ‘Emission limit values parameters, or equivalent technical measures should be based on the best available techniques, without prescribing the use of one particular technique or technology and taking into consideration the technical characteristics (..) its geographical location and local environmental conditions’ (96/61/EC, §17)

In general, trading schemes tend to discourage compliance only through purchasing reduction credits and there often has to be some minimum in-house abatement. Beyond this point, which differs from one scheme to another, flexibility is given to achieve compliance.