Eggshell waste can yield rare earth elements needed for green energy

A collaborative team of researchers has made a groundbreaking discovery with the potential to have a significant impact on the sustainable recovery of rare earth elements (REEs), which are increasingly in demand for use in green energy technologies. The team found that humble eggshell waste can regenerate REES from water, offering a new, environmentally friendly method for their extraction.

Scientists from Trinity College Dublin’s School of Natural Sciences and iCRAG, the Irish Research Center in Applied Geosciences, have just published their findings in the journal. ACS Omega.

REEs, which are essential for technologies used in, for example, electric cars and wind turbines, are increasingly in demand but relatively scarce. As a result, scientists must find new ways to extract them from the environment – ​​and sustainably, with current methods often harmful.

Here, researchers discovered that the calcium carbonate (calcite) in eggshells can effectively absorb and separate these valuable REEs from water.

The researchers placed eggshells in REE-containing solutions at various temperatures from a comfortable 25°C to a scorching 205°C and for varying periods of time up to three months. They found that elements can enter eggshells by diffusion along the boundaries of calcite and the organic matrix, and at higher temperatures rare earths form new minerals on the surface of the eggshells.

At 90°C, the eggshell surface helped restore formations of a rare earth compound called cozoite. As things warmed up, the eggshells underwent a complete transformation, with the calcite shells dissolving and being replaced by a polycrystalline cozoite. And at the highest temperature of 205°C, this mineral gradually transformed into bastnasite, a stable rare earth carbonate used in industry to extract REEs for technological applications.

This innovative method suggests that waste eggshells could be reused as a cheap, environmentally friendly material to help meet the growing demand for REES, as eggshells capture different rare earths in their structure over time.

Lead author Dr. Remi Rateau says: “This study presents a potential innovative use of waste material that not only offers a sustainable solution to the problem of recovery of rare earth elements, but is also in line with the principles of circular economy and waste recovery.”

Principal investigator, prof. Juan Diego Rodriguez-Blanco, highlighted the broader implications of the findings, adding: “By turning eggshell waste into a valuable resource for the recovery of rare earths, we are solving critical environmental problems associated with traditional mining methods and contributing to the development of greener technologies.”