12. Condensable and Liquid Compounds from Biomass and Waste Thermal Degradation

This chapter deals with condensable/liquid compounds produced during biomass and waste thermal degradation processes. These compounds include a huge number of species, mainly organic, but also inorganic. These species may vary according to biomass or waste type, and even more according to process operating conditions, namely temperature, heating rate, reactive gas or pressure. For instance, liquids obtained during torrefaction and their related yields will be strongly different from those obtained during slow pyrolysis, fast pyrolysis or gasification. A general overview is therefore firstly given of the condensable/liquid compounds produced in each of the main thermal processes together with their typical mass yields. Then the emphasis is put on the challenging task of determination of composition in organic and inorganic species. The most common measurement techniques of these condensable/liquid compounds are detailed. For each technique, the principle and a typical experimental procedure are given, as well as the main advantages and drawbacks, notably regarding species detected, accuracy limits and thus suitability with the different thermal processes. Both online analysis methods, and offline methods are considered. In the case of offline analysis, particular attention is paid to the sample collection step, for instance through condensation in staged cooled vessels.