Heini Elomaa, Lotta Rintala, Mari Lundström
Chlorination was applied widely in gold processing throughout the 1800s as vat and barrel leaching,
with chlorine gas acting as an oxidant. In the early 1900s, hydrometallurgical gold process technology
changed from chlorination to cyanidation, which replaced chlorination as the predominant gold leaching
process due to technical and financial advantages. The challenges in the chlorination process were
related to the highly corrosive leaching chemicals and associated high reagent consumption. In the
past, new gold extraction technologies have not been evaluated by their environmental footprint, but
rather by the financial, technological and operational advantages. In order to determine the associated
ecological impact and sustainability, new transformative technologies need to be evaluated from the
environmental footprint point of view prior commercialization. In this study, the environmental indicator
category chosen for evaluation was global warming potential (GWP) and the other impact categories,
such as human toxicity potential and acidification were left out of the scope. The global warming
potentials (GWP) were determined both for the historical chlorination process and for a state-ofart
cyanidation process by modelling with HSC Chemistry 8.0 HSC-Sim module combined with life
cycle analysis by GaBi 6.0. This analysis provides a baseline scenario for comparison, which can be
used to support the future life cycle assessment research for development stage gold processes. The
combination of HSC-Sim and GaBi was shown to be an efficient way for the investigation of the environmental
footprint of the historical and current gold processes. The GWP of the cyanidation process
was 455 kg CO2 equivalent and the GWP of chlorination process was 10500 kg CO2 equivalent.
The main emission source in cyanidation was found to be electricity, whereas in chlorination the main
emissions originated from the chlorine gas, although, it is worth noting that environmental impacts are
not defined for all chemical products in the GaBi database. Additionally, some compromises had to be
made when the LCA Equivalents were applied to the process streams modelled in HSC-Sim. The
corresponding or most appropriate LCA Equivalents were defined from the HSC/GaBi database and
the LCA group was defined for all the inputs and outputs within the scope of the process.