Harmonization of LCA Methodologies for Metals
From 2012 to 2014, IMOA participated in an industry wide effort to review current LCA practices and experience, and develop new guidance on how to adopt a more harmonized approach to LCI and Life Cycle Impact Assessment (LCIA) methodologies within the metals and minerals industry. The exercise was carried out to provide metals and minerals industry groups, life cycle database providers, and LCA practitioners the guidance necessary to take a consistent approach to metal LCA studies, which can enable comparisons of results across different studies, help establish credibility for LCA databases, and ensure consistent messaging within the industry. The resulting guidance document with its accompanying FAQ, covers four areas:
- System boundaries;
- Dealing with coproducts;
- Life Cycle Impact Assessment (LCIA) category choices; and
- End of life recycling.
Including all life cycle stages in a study’s system boundaries is generally important for any LCA. The Guidance document states that the system boundaries should include end-of-life disposal and recycling and, whenever possible, the product use phase. For an LCA on a Mo-containing product, the use phase – and a well-defined functional unit – should always be included, especially when the LCA is comparing a Mo containing product to an alternative. By accounting for the function and performance of the product, the Mo containing product will be able to take credit for its properties for any given application. Note: much of the LCI/LCA work that IMOA and other metals associations has done has been cradle-to-gate (partial) life cycles, with the expectation that the high quality production data sets will be used by LCA practitioners or companies to produce full cradle-to-grave LCAs of metal-containing products.
The Guidance document’s stance on dealing with co-products is that no one allocation choice should be used for all coproducts. Instead, the practitioner should consider the type and properties of co-products being produced. The guidance document is not prescr"+"iptive; it presents all sorts of allocation options and offers recommendations (plus rationale) on what the metal industry associations believe to be best practice for their industry.
The guidance document provides recommended LCIA categories for practitioners to use (i.e., ones that are well-established and scientifically-defensible), and it points out ones that are less established and/or have deficiencies which could compromise the confidence of those categories’ results. The Mo LCIs do not include LCIA, but LCAs utilizing the Mo LCI data will invariably include LCIA. LCA practitioners and users of LCA studies are encouraged to read this section in the Guidance document to understand why some impact categories are acceptable while others should be “used with caution”.
Recycling at end of life is not as applicable to Mo, although recycling does happen indirectly when stainless steel is recovered and recycled. The Mo in the steel is not recovered from the stainless steel. Rather, it keeps its inherent qualities with the recycled steel, and along with other added alloys, enforces the steel with the properties needed for the next use. Those performing LCAs of stainless steels and other Mo-containing products that are recovered and recycled at end of life are encouraged to follow the recycling methodology described in the Guidance. Since it is a "living document" the metals industry will revise it as current topics evolve, or expand upon it in the future to include other topics as appropriate.