Epsilon Archive for Student Projects

Abstract

EasyMining Sweden AB, a subsidiary to Ragn-Sells AB, has developed a new process for
treatment of fly ash from municipal solid waste incineration called Ash2Salt, which enables
recycling of salts; sodium chloride, potassium chloride, calcium chloride and ammonium
sulphate. To compare this new process with some of today’s fly ash treatment processes
available for Swedish and European fly ash a life cycle assessment (LCA) was performed. The
functional unit used for the comparison was “treatment or disposal of 1 ton of fly ash” and the
environmental impact was compared through four different categories: climate change (kg CO2-
eq), depletion of abiotic resources (kg Sb-eq), ecotoxicity (CTUe) and human toxicity (CTUh).
The results showed that the Ash2Salt process had the lowest environmental impact considering
all the studied environmental impact categories, which mainly depends on the assumption that
the salts recycled from fly ash replaces conventionally produced salts. The treatment process
with the highest environmental impact was the process of stabilising and refilling old salt mines
in Germany, mainly because of the long distances of transport.

Further on, the environmental impact from recycling the salts from fly ash using the Ash2Salt
method was compared to conventional salt production processes. The functional unit used for
the comparison was “production of 1 kg of salt”. Economic allocation was assessed between
the salts from the Ash2Salt process. The results showed that for two of the impact categories
(climate change and depletion of abiotic resources) the salts recycled from fly ash had lower
environmental impact than the conventional production processes, but for both toxicity
categories potassium chloride and ammonium sulphate had higher environmental impact than
the conventional production processes. The reason for this mainly depends on the chosen
principle of allocation and the fact that the production of ammonium sulphate in the Ash2Salt
process demands more inputs than the other salts in the process.