For the past 20 years, the European context has been policy-driven by several directives to reduce pollution, one of the most important for industries being the industrial emissions directive (IED). The IED's objective is to minimise pollution from various industrial sources throughout the European Union. One means of attaining the objective is to implement techniques which have at least the same performance as reference techniques called best available techniques (BAT) given at European level. The study of existing methodologies on performance assessment of proven or emerging techniques has made it apparent that there are none taking into account the 12 criteria proposed by the Annex III of the IED to evaluate technique performances. Even if innovative techniques are not considered by the IED, support to (public or private) researchers in their development in terms of assessment methodology must be proposed. This is what we present in this article. The methodology based on a tree-structured information system (objectives, criteria, indicators) and a qualitative assessment of indicators (environmental, technical, economic and social) is an initial approach to an innovative technique assessment method considering BAT on laboratory or industrial scales. In an aim to adapt the criteria and indicators to a specific process, assessment methodologies must be adaptable. Our method allows for choosing indicators to comply perfectly with the process studied. Only the first level of the tree is fixed. The other branches could be adapted to the case studied. Performance assessment is based on a five-level scale coupled with a simple multi-criteria analysis (MCA) method. Three different applications (sludge valorisation, urban wastewater treatment, soil remediation) were carried out to validate the methodology, two of them are presented. Applications of this methodology show its usefulness in the validation of techniques for specific process and local application of the BAT concept and the performance assessment regarding BAT definition. It can then be used to detect innovative and emerging techniques to be proposed for the reviewing of the European BREF documents.