English to French Tech/Engineering Environment & Ecology Waste gasification

This expression appears in a report on waste gasification. It is a particular type of gasifier, developed by a Finnish company. I have found the expression "staged gasification", which can be translated by "gazéification étagée". The process implies various stages. But I have not found any equivalent for the whole expression in any database (IATE, etc.).

Could it be something to to with the gasifier being of a technologically advanced type (which seems logical).

NB : In the original text, the expression is mentioned between quotation marks, as opposed to "conventional gasifiers".
Many thanks in advance for your help !