Emergy as a function of exergy

This paper aims to clarify some aspects of the discussion between ‘‘emergists’’ and ‘‘exergists’’. First, we address the problem of the differences between energy-based emergy and exergy-based emergy: we show that the two are proportional, having the exergetic equivalent of solar energy as scale factor. In the second part, we show that emergy and transformity can be written as a function of exergy alone, in particular of ‘‘partial’’ efficiencies of the processes involved in a production system, from solar energy to the final product.