Best available technology

Best available technology (or just BAT) is a term applied with regulations on limiting pollutant discharges with regard to the abatement strategy. Similar terms are best available techniques, best practicable means or best practicable environmental option. The term constitutes a moving target on practices, since developing societal values and advancing techniques may change what is currently regarded as "reasonably achievable", "best practicable" and "best available".

A literal understanding will connect it with a "spare no expense" doctrine which prescribes the acquisition of the best state of the art technology available, without regard for traditional cost-benefit analysis. In practical use, the cost aspect is also taken into account. [See also discussions on the topic of the precautionary principle which, along with considerations of best available technologies and cost-benefit analyses, is also involved in discussions leading to formulation of environmental policies and regulations (or opposition to same).]

"But no person shall be subject to the foregoing penalties for any act done in the exercise of any right to which he is by law entitled, if he prove to the satisfaction of the court, before whom he is tried, that he has used the best practicable means, within a reasonable cost, to render harmless the liquid or solid matter so permitted to flow or to be put into waters."

Best practicable means was used for the first time in UK national primary legislation in section 5 of the Salmon Fishery Act 1861 and another early use was found in the Alkali Act Amendment Act 1874, but before that appeared in the Leeds Act of 1848.

The BAT concept was first time used in the 1992 OSPAR Convention for the protection of the marine environment of the North-East Atlantic for all types of industrial installations.

Some doctrine deem it already acquired the status of customary law.

In the United States, BAT or similar terminology is used in the Clean Air Act and Clean Water Act.

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