The cumulative exergy demand is made up from all incoming streams. Exergy is then either attributed to the products stream, the waste stream (external exergy loss), thermal outlets, or internal exergy destruction. Figure outlines that only a small fraction of exergy is incorporated in the products here, and that most exergy is introduced to the process by methane combustion, rather than the biomass source. We will discuss reasons and hotspots for the limited exergy performance of the process in the following sections. precipitator. Note that the ethanol stream reflects fresh solvent required after taking into account solvent recycling which is not shown.