Oyster shells might look like just restaurant garbage, but they could soon be used to develop future cars.

German researchers have created a non-toxic magnesium foam from only natural marine raw materials.

The Helmholtz-Zentrum Hereon team developed a process that eliminates toxic additives by using ground oyster shell powder (a massive byproduct of the food industry) as a blowing agent.

It offers a highly sustainable, ultra-lightweight material with a broad range of industrial applications in automotive manufacturing.

Eco-friendly manufacturing

Every year, the global food industry generates millions of tons of oyster shells. Most end up in landfills. Some are dumped carelessly back into local waters.

Now, researchers are finally finding ways to rescue this abundant waste product.

Oyster shells are naturally rich in calcium carbonate — otherwise known as limestone. At first, these shells were ground into a fine powder and then mixed into a molten magnesium-calcium alloy. This way, researchers unlocked a simple chemical reaction.

At high temperatures, the shell powder decomposes. It releases carbon dioxide gas. This gas creates tiny, uniform bubbles throughout the thick, liquid metal.

Once the mixture cools and hardens, the resulting material is a highly uniform, porous metal foam. The CO2 is trapped safely inside the pores. The result is a material that is light, durable, and completely non-toxic.

Interestingly, the blowing agent is derived from oyster shells discarded by the seafood industry, and the magnesium and calcium are sourced as natural byproducts of seawater desalination. 

This marine origin enables an end-of-life solution: if returned to the sea, the material safely and completely dissolves back into the water, leaving no toxic footprint. It was also verified by researchers in laboratory testing using artificial seawater.

“At the end of its life, the material could be returned to the ocean. It would simply dissolve in the water,” said Dr. Hajo Dieringa, a materials scientist at Hereon and co-author of the study.

Use in cars

Furthermore, materials scientists partnered with researchers at the Hereon Institute of Coastal Environmental Chemistry to ensure the magnesium foam’s safety within the marine ecosystem. 

Environmental analyses confirmed that returning the foam to the ocean would not release any toxic heavy metals or harmful impurities derived from the raw ingredients. 

Although ocean disposal remains a completely safe and viable option, the primary goal for a real-world closed-loop recycling system is to melt the foam down so it can be endlessly reused as a fresh magnesium alloy.

The automotive industry is currently turning to lightweight design to make vehicles lighter and extend the battery range of electric vehicles. This new magnesium foam is a dream come true for aerospace and automotive engineers.

The unique porous structure of this magnesium foam endows the material with exceptional mechanical properties, combining high formability with high energy absorption. 

When subjected to stress, the sponge-like matrix allows the material to deform predictably and absorb vast amounts of kinetic energy rather than snap. 

This makes it an ideal candidate for manufacturing ultra-lightweight components specifically engineered to dampen severe vibrations or cushion heavy impacts, such as vehicular crumple zones designed to protect passengers during a collision.

Future uses for the foam extend to aviation, shipbuilding, and body armor—industries where ultra-low weight and superior energy absorption are non-negotiable.

The findings were published in the journal Discover Materials.