Best Available Techniques (BAT): the most effective and advanced stage in the development of activities and their methods of operation which indicate the practical suitability of particular techniques for providing in principle the basis for release limitations designed to prevent and, where that is not practicable, generally to reduce releases of chemicals listed in Part I of Annex C and their impact on the environment as a whole. (Source: BRS Conventions).

The best available technology or best available techniques (BAT) is the technology approved by legislators or regulators for meeting output standards for a particular process, such as pollution abatement. Similar terms are best practicable means or best practicable environmental option. BAT is 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. (Source: Wikipedia).