Packaged in beer

The typical airy structure of aerogel (Electron microscopy, colored) Image: Empa
The typical airy structure of aerogel (Electron microscopy, colored) Image: Empa
Researchers have extracted nanocellulose from a waste product of beer brewing and processed it into an aerogel. The high-quality biodegradable material could be used in food packaging.

It all starts with the mash: the mixture of malt and water, which is stirred and gently heated for several hours. The resulting liquid is known as the wort, and eventually, several processing steps later, as beer. The remaining malt - known as brewer’s spent grain - has a much less glamorous path ahead of it. It usually ends up as animal feed or on the compost heap.

Researchers from Empa’s Cellulose and Wood Materials laboratory, led by Gustav Nyström, are looking for ways to valorize this residue. They have developed a process to produce high-quality nanocellulose from brewery waste - a versatile biodegradable raw material that can be processed, for example, into packaging materials or fiber-reinforced polymers. The researchers published their findings in the journal ACS Sustainable Chemistry & Engineering.

To explore the potential of nanocellulose from brewer’s spent grain in greater detail, the researchers varied the individual pretreatment and processing steps in order to test their effects on the final product. For example, the quality of the nanocellulose fibers was improved by bleaching and oxidation of the starting material. Different freezing processes can be used to control the size and orientation of the pores in the aerogel, which in turn influences its insulating and mechanical properties.

Grain instead of wood
"We aimed to keep the whole process as simple as possible," says Siqueira. After all, having a convincing product is not enough to gain traction in the real world - it should also be as simple and inexpensive to manufacture as possible. That’s another reason the researchers are interested in extracting raw materials from waste products. "Compared to the agricultural residues, wood is a more expensive source of cellulose and it already has so many applications," Siqueira explains. In further research projects, the scientists are therefore investigating even more residues from the food industry and from forestry. And although Nadia Ahmadi Heidari has already returned to Isfahan, the Empa team is planning another publication together with the young researcher, in which they will describe aerogels from brewer’s spent grain in more detail.