Research & Consulting

Sustainable Chemistry and Materials from Copper Tailings: A Prospective LCA

2022

Lead author — prospective LCA & process modelling

Research case study

Open-access prospective LCA of four chemical and material recovery routes for sulfidic copper tailings, saving 25–930 kg CO2-eq per tonne when all co-products are used.

About this study.

As lead author, I built the process-based life cycle models for four copper-tailings reprocessing routes at a Portuguese mine site and compared them with direct landfilling. The routes run a sequence of chemical operations: desulfurization and magnetic flotation, microwave roasting and leaching, then ion flotation and precipitation to recover copper and zinc, producing CSA cement, ceramic tiles, geopolymer binders and sulfuric acid. In the open-access paper (Resources, Conservation & Recycling 186, 106567, 2022), the prospective LCA scales those processes up and pairs them with projected energy systems. It puts the savings at 25–930 kg CO2-eq per tonne of treated tailings, and they only appear when every co-product is used.

Selected figures.

Figures from the published work behind this study. Select any figure to open it full size.

System boundary diagram showing route A (flocculation and flotation producing CSA cement, ceramic tile, metals and sulfuric acid), route B (microwave roasting and leaching, ion flotation and precipitation, geopolymer production) and the direct-landfilling reference. — System boundaries: route A recovers building materials only (flocculation and flotation), route B adds chemical extraction and metal recovery (microwave roasting and leaching, ion flotation and precipitation), compared with direct landfilling.Adrianto, L. R., & Pfister, S. (2022). Prospective environmental assessment of reprocessing and valorization alternatives for sulfidic copper tailings. Resources, Conservation & Recycling 186, 106567. Open access under CC BY 4.0.

Four stacked bar panels comparing routes A-1, A-2, B-1 and B-2 for climate change, cumulative energy demand, freshwater ecotoxicity and particulate matter, including credits from displaced materials and avoided landfilling. — Net impacts of treating one tonne of tailings per route, including credits from displaced materials and avoided landfilling: climate change (a), cumulative energy demand (b), freshwater ecotoxicity (c) and particulate matter (d).Adrianto, L. R., & Pfister, S. (2022). Prospective environmental assessment of reprocessing and valorization alternatives for sulfidic copper tailings. Resources, Conservation & Recycling 186, 106567. Open access under CC BY 4.0.

Bar chart of all four routes against virgin material impacts for climate change, fossil depletion, metal depletion, particulate matter, cumulative energy demand, ecotoxicity, human toxicity and a ReCiPe single score, with best-case and worst-case whiskers. — Reprocessing impacts relative to virgin production with best-case (lower range) and worst-case (upper range) whiskers; red dots mark cases exceeding the 100% threshold, notably ceramic-heavy routes A-1 and B-1.Adrianto, L. R., & Pfister, S. (2022). Prospective environmental assessment of reprocessing and valorization alternatives for sulfidic copper tailings. Resources, Conservation & Recycling 186, 106567. Open access under CC BY 4.0.

Bar chart showing relative changes in environmental impacts across all routes when the electricity mix, the substitution ratio, or both are modified, with markers for base, full substitution with the 2030 mix, and adjusted substitution with 2015 and 2030 mixes. — Sensitivity to the electricity mix, the substitution ratio, and both combined. Decarbonized electricity improves every route; lower-quality secondary products raise impacts by around 14% on average.Adrianto, L. R., & Pfister, S. (2022). Prospective environmental assessment of reprocessing and valorization alternatives for sulfidic copper tailings. Resources, Conservation & Recycling 186, 106567. Open access under CC BY 4.0.

Discussion.

Reprocessing only helps when the co-products find a use. On base-case assumptions, the routes stay below the impacts of virgin production in 28 of 32 indicators, but none avoids shifting the burden somewhere else, and the credits that make a route viable disappear when secondary metals or building materials have no market.

The ceramic-heavy routes (A-1, B-1) use more energy and emit more greenhouse gases than the virgin materials they displace, because of firing and electricity demand. The metal-recovery routes (B-1, B-2) cut material depletion and toxicity indicators by more than 90% against primary production in the best cases. That split is the trade-off the study quantifies.

Four changes push the results in the right direction: lower-impact chemicals such as alkali activators in place of sodium hydroxide, treatment on site to avoid transport, better-quality secondary products, and decarbonized electricity, where the 2030 grid mix alone cuts impacts by about 11%. Even then, tailings valorization cannot reach the 1.5 °C pathway on its own; demand-side measures and material efficiency still matter. The same process-based, prospective method applies to other chemical product systems, including specialty chemicals and pharmaceutical manufacturing, where early-stage processes must be assessed before scale-up.

More work.

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