There is a global interest in the application of thermochemical processing of sewage sludge resulting in numerous technologies entering the wastewater market. Currently, pyrolysis is one of the technologies with the most experience utilizing 100% sewage sludge as a feedstock. Autothermal pyrolysis, in which sufficient air is introduced to drive the endothermic reactions of pyrolysis, overcomes the scaling problems associated with conventional pyrolysis and allows pyrolysis to be scaled up in size for applications at large facilities. For example, one unit capable of treating 150 - 225 dry-tonnes/day. The subject of this presentation will be the energy and mass balance of the complete autothermal pyrolysis process including: drying, pyrolysis, combustion and recovery of the thermal energy. Although pyrolysis extracts additional energy for the sludge, the drying step often requires more energy than is typically recovered from the thermochemical process. The primary parameter for an accurate energy balance is the enthalpy for pyrolysis, which is the energy required to drive the pyrolysis reactions for a given sludge, and it varies each sludge. Additionally, characteristics of both the feedstock and products will be discussed, including elemental analysis. This presentation will highlight the importance of an accurate energy balance and mass balance in evaluating pyrolysis.