Modeling combined heat and power plants in Life Cycle Assessment: a comparison among different approaches to deal with multifunctionality

In the energy sector, the issue of what fraction of fuel consumed by an energy conversion plant should be allocated among several products, such as electricity and heat is still open. In this work, procedures used to deal with this aspect in attributional Life Cycle Assessment studies were reviewed. In particular, the authors analyzed three approaches of allocation and eight methods as follows, relationships beyond the system boundaries (three methods), physical relationships (two methods), and other relationships (three methods), all of them in compliance with ISO 14044. In order to test the methods proposed to manage multifunctionality, a real combined heat and power plant installed in a dairy placed in Lombardy Region (Northern Italy) was analyzed. According to this analysis, the separate productions reference method, under relationships beyond the system boundaries approach, seems to be the most appropriate.