Harmonization of LCA methodologies for the metal and mining industry

Abstract

Purpose The metal and mining industry routinely conducts life cycle assessment studies to monitor and document the potential environmental impacts of their products. These studies are typically conducted independently by the various commodity associations. To facilitate alignment of these methodologies, a working group comprised of interested industry organizations and their representatives was formed to propose uniform recommendations for key methodological choices. Methods Existing methodologies used by the participating associations were reviewed to identify areas of alignment as well as areas which could benefit from discussions and alignment. Recommendations for selected topics were then developed through a series of moderated discussions among the participating organizations throughout 2012 and 2013. Efforts were taken in the creation of the document to ensure alignment with the international standards ISO 14040 (2006) and ISO 14044 (2006). Four methodology issues were chosen to be addressed with respect to industry alignment: system boundary, recycling allocation, co-product allocation, and impact assessment categories. Results and discussion Recommendations for system boundary conclude that boundaries should include end-of-life disposal and recycling and, whenever possible, the product use phase, particularly for material and product comparison. For co-product allocation methods, the recommendations were based on the type of co-products being produced and included a range of options to guide practitioners' decisions. It was recommended for recycling allocation that practitioners use the avoided burden methodology. Lastly, for the life cycle impact assessment stage, it was recommended that life cycle assessments (LCAs) on metal and mining products should report the following impact categories: global warming potential, acidification potential, eutrophication potential, photochemical oxidant creation potential, and ozone depletion potential. It was recommended that inclusion of other impact categories will be periodically re-evaluated by the metal industry. Further, the recommendation is that, while impact categories included are limited to the five above, all life cycle inventory (LCI) datasets themselves should contain accurate and comprehensive inventory data, given reasonable accessibility and data collection cost constraints. Conclusions Methodological alignment for LCA studies in the metal and mining industry will lead to improved consistency and applicability of the LCA data and results. Specifically, these recommendations improve the consistency of decisions regarding system boundary, recycling allocation, co-product allocation, and impact assessment categories. Further research is suggested to improve the specificity of certain recommendations (e.g., allocation), as well as expand the scope of the harmonization efforts to include other methodological decisions.

A global life cycle assessment for primary zinc production

“…In accordance with the recommendations of the Harmonization of LCA methodologies for metals (Santero and Hendry 2016), the set of impact assessment categories for this project include global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical ozone creation potential (POCP), and ozone depletion potential (ODP). In addition, the primary energy demand (PED) inventory metric was characterized.…”

“…Toxicity, land use change, and water scarcity are also excluded, in line with the recommendations of the harmonization document that these impacts not be reported for metal LCAs (Santero and Hendry 2016). Finally, water consumption is excluded due to the lack of data provided on water outputs, as discussed in Sect.…”

“…Additionally, this co-product allocation approach is preferred for base metals (such as zinc), based on recommendations made in the Harmonization of LCA methodologies for metals (Santero and Hendry 2016), because it reflects the underlying principle that the metal content of the coproducts is the useful product that creates a market for these materials. Zinc content allocation ensures that the final zinccontaining products have an accurate value for quantity of zinc extracted from the Earth's crust, which would enable proper reporting of environmental indicators related to resource extraction.…”

“…Consistent with the 2009 study, this study uses system expansion to credit the production of sulfuric acid. This is the preferred approach provided in the Harmonization of LCA methodologies for metals for non-metal co-products within metal production systems, allowing for consistency with LCAs conducted on other metals (Santero and Hendry 2016). Only the portion of the acid not used within the smelting facility was credited.…”

“…If specific materials were reported and known by the company to be recycled, a system expansion approach was used to credit the creation of the recyclable product. The Harmonization of LCA methodologies for metals article recommends the use of system expansion for coproducts with alternative production routes, as is the case with steel and lubricants (Santero and Hendry 2016). End-of-life scrap is first balanced out with the manufacturing phase to account for any open scrap inputs into production.…”