Abstract:

Life-cycle assessments comparing secondary critical mineral recovery, from electronic waste and industrial effluent, against virgin extraction are increasingly cited to justify recycling incentives and carbon-linked market access under regulations such as the European Union Critical Raw Materials Act and Battery Regulation. This paper argues that much of the reported carbon advantage of secondary recovery is an artifact of discretionary system-boundary and allocation choices rather than a stable process-level result. Reviewing published inventory data for gold recovery from waste electrical and electronic equipment and chromium recovery from tannery and electroplating wastewater, we show that the same underlying recovery chemistry yields carbon footprints spanning two to three orders of magnitude depending on whether a cut-off, avoided-burden, or Circular Footprint Formula allocation is applied. Reported secondary gold values range from approximately 40 to 57,900 kg CO2 equivalent per kilogram against a virgin benchmark near 30,000; chromium recovery via microbial fuel cell shows a saving of up to 97% under avoided-burden accounting that falls to 61.8% once allocated credits are withdrawn, with the pre-credit process itself a net emitter. We further show that avoided-burden accounting assumes near-complete displacement of virgin production, an assumption the empirical industrial-ecology literature does not support for analogous metals. We propose a minimum disclosure checklist, comprising allocation method, feedstock burden treatment, displacement assumption, and functional unit, for any carbon claim submitted in support of secondary critical mineral recovery under emerging regulatory frameworks, grounded in the requirements of ISO 14044, ISO 14067, and ISO 14064-3.

Keywords:

life cycle assessment, system boundary, allocation method, critical minerals, circular economy, carbon footprint, gold recovery, chromium recovery, avoided-burden allocation, ISO 14044.

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