From Fertilizer Waste to Magnet Metals: Rainbow and Mosaic Bet Big on Brazil

• Rainbow Rare Earths and Mosaic announced a positive Economic Assessment for Brazil's Uberaba project, which aims to extract 1,971 tonnes of NdPr oxide annually from phosphogypsum fertilizer waste—without opening a new mine—with production targeted for 2030.
• The project shows eye-catching economics with a post-tax NPV of $916 million, 45% IRR, and $279 million initial capital cost, placing it in the lower quartile of the global rare earth cost curve, though it remains early-stage without JORC-compliant resources.
• Uberaba represents a broader industry shift toward recovering critical minerals from industrial waste streams rather than traditional mining, potentially reducing capital intensity and development timelines while supplementing Western rare earth supply chains.

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Rainbow Rare Earths and U.S. fertilizer giant Mosaic say their Uberaba project in Brazil could become a major new rare earth supply source—without opening a mine. The companies announced a positive Economic Assessment (EA) and a Joint Project Development Agreement to move the project into prefeasibility studies. If successful, the partners plan to build a processing facility capable of treating about 2.7 million tonnes of phosphogypsum per year, producing roughly 1,971 tonnes of NdPr oxide and 659 tonnes of a SEG+ rare-earth product.

Production is targeted for 2030, assuming studies, permitting, financing, and execution proceed as planned.

For readers trying to understand the significance: Uberaba is not a conventional rare earth mine. It is a plan to extract rare earths from a fertilizer waste stream already produced at Mosaic’s phosphate operation.

The Rainbow Model: Rare Earths Without the Mine

Rainbow’s strategy is unusual in the rare earth sector.

Rather than developing new mining projects, the company focuses on secondary sources—specifically phosphogypsum, a byproduct of phosphoric acid production in the fertilizer industry.

At Uberaba, the feedstock comes from Mosaic’s existing phosphate complex in Minas Gerais, where phosphogypsum residues are already generated as a byproduct of fertilizer production.

The proposed process uses Rainbow’s proprietary hydrometallurgical flowsheet, derived from its Phalaborwa project in South Africa, to extract rare earths from this material. According to the company, the recovered products would include:

• NdPr oxide (critical for permanent magnets)
• SEG+ concentrate containing samarium, europium, gadolinium, and valuable heavy rare earths such as dysprosium and terbium

Because phosphate mining already occurs, Rainbow argues that its model avoids some of the highest costs and permitting barriers faced by traditional rare-earth projects.

Eye-Catching Economics—But Still Early

The Economic Assessment released alongside the announcement paints a striking picture.

Using Argus rare earth prices from March 2026, the study estimates:

• Post-tax NPV10: $916 million
• Post-taxIRR: 45%
• Annual EBITDA: $217 million
• Payback: 1.7 years
• Initial capital cost: $279 million

Those numbers place the project firmly in the lower quartile of the global rare earth cost curve, according to Rainbow. But investors should read the fine print carefully.

The EA is not a JORC-compliant resource study, and the project remains based on grade estimates from phosphogypsum sampling rather than a formal mineral resource.

In other words, the economics are promising—but far from bankable.

Why the Supply Chain Is Watching

What makes Uberaba important is not simply another rare earth project announcement.

It reflects a broader shift toward recovering critical minerals from industrial waste streams—tailings, residues, and byproducts—rather than relying solely on new mines.

If successful, projects like Uberaba could:

• Reduce capital intensity
• Shorten development timelines
• Supplement Western rare earth supply chains

But they are unlikely to replace traditional mining.

For now, the rare earth world will watch closely as Rainbow attempts to prove its “rare earths from waste” model at a commercial scale. If it works, it could become one of the more interesting innovations in the global rare earth supply chain.