This presentation explores the macromolecular composition of various sewage sludges and its influence on pyrolysis behaviour. Five sludges—primary, secondary, blended raw, post-thermal hydrolysis process (THP), and digested—were selected from two UK wastewater treatment plants (WTP). Sludge macromolecular content was analysed once in each season during a year; thermogravimetric analysis (TGA) was used to produce pyrolysis “fingerprints”. The five types of sludge from one site were tested in a laboratory-scale pyrolysis rig at the intermediate pyrolysis regime (500˚C -700˚C, around 20 min retention for complete pyrolysis) and under batch mode. Deconvolution and multivariate analysis were tested as promising methods to establish links between sludge macromolecular content and the TGA results of pyrolysis “fingerprints”. Thermodynamic analysis of pyrolysis kinetics revealed that different macromolecules have varying entropy changes during decomposition. Digested sludge feedstock resulted in the most stable pyrolysis behaviour with respect to the organic decomposition “fingerprints” during the year. Secondary sludge exhibited distinct characteristics in pyrolysis outputs—particularly biochar characteristics and volatile element release—as temperatures varied. While raw sludge yielded higher total calorific outputs, digested sludge demonstrated greater energy conversion efficiency. The presentation will discuss the data from the analysis of biochar and pyrolysis gas quality and quantity.