Factors influencing the GHG emission consequences of industrial excess heat usage in district heating systems

The potential to increase usage of industrial excess heat is considered to be substantial and an important measure to reach targets of increased energy efficiency and decreased greenhouse gas (GHG) emissions. This paper shows and discusses factors that influence the global GHG emissions consequences of using industrial excess heat in district heating systems. The factors include emissions allocated to the industrial excess heat itself, competing technologies in the district heating system, how emissions related to biomass usage are handled and how different systems are set up and compared. Unavoidable excess heat is defined as excess heat that cannot contribute to decreased usage of primary energy resources in the industrial process. From the examples included in this paper, it can be concluded that if a resource perspective is adopted, it is always preferable to use unavoidable industrial excess heat instead of alternative district heating production from natural gas or biomass-based combined heat and power plants or heat only boilers from a GHG emission perspective