Abstract

Germanium is increasingly important for high-tech applications, yet its supply chain is vulnerable, with production limited to a few countries. Although prior research has explored alternative techniques for extracting and recovering germanium, the literature lacks comparative life-cycle evidence that quantifies their environmental burdens and translates findings into actionable (policy) recommendations. This paper presents a cradle-to-gate life-cycle assessment that compares the environmental burdens of producing 1 kg of single-crystal germanium from coal fly ash via chlorinated distillation (CD) and solvent extraction (SX). Under the study's assumptions, CD has lower potential impacts in 15 of 19 impact categories, while both routes show similar stratospheric ozone depletion potential. For SX, transportation (of fly ash and GeO2) and kerosene consumption each contribute 28–35% of the global warming, terrestrial acidification, and particulate matter formation impacts, while water leaching accounts for 67% of water consumption, and kerosene contributes 53% of cumulative energy demand. For CD, electricity consumption dominates (>50%) most impact categories, except terrestrial acidification, which is dominated (>50%) by chlorine gas used in GeCl4 purification. For SX, the most significant impact-reduction strategies are increasing organic-phase reuse (>95%), eliminating fresh kerosene input (or substituting lower-impact diluents), and up-concentrating germanium in the fly ash. For CD, cleaner production should prioritize the use of low-carbon electricity, integrating waste heat into acid-regeneration operations, and exploring chlorine substitutes in GeCl4 fractional distillation. These results show that policies seeking to advance new Ge process routes should first evaluate environmental burdens. Also, new process routes should be efficient and reduce waste.

Department(s)

Mining Engineering

Second Department

Materials Science and Engineering

Publication Status

Full Text Access

Comments

Office of Energy Efficiency and Renewable Energy, Grant SC-24-600

Keywords and Phrases

Chlorinated distillation; Cleaner production; Coal fly ash; Critical minerals; Germanium; Life cycle assessment; Solvent extraction

International Standard Serial Number (ISSN)

1879-1786; 0959-6526

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 Elsevier, All rights reserved.

Publication Date

08 Jul 2026

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