Valuable raw materials from olive waste

His aim was clear from the start: “I wanted to find a way to reuse agricultural waste in support of a sustainable circular economy,” says Claudio Reinhard. That’s why, for his Master’s degree in Mechanical Engineering at ETH Zurich, he chose to research the use of biochar in Tunisia. It was there that he learned about Tunisian oliviculture firsthand and saw the huge amounts of waste generated in oil production – to the detriment of the environment: the waste pollutes ground water and soil and releases the greenhouse gas methane. “One bottle of olive oil generates waste equivalent to the amount of four bottles,” Reinhard says. Worldwide, this amounts to some 12 million tonnes of waste consisting of olive peel, pulp, stones and wastewater each year.

Along with the waste, a valuable treasure trove of natural compounds is lost. However, recovering them calls for know-how and suitable technologies – instead of simply incinerating the waste as usual or, in the best case, reusing it for the extraction of pomace oil or in biogas plants.

Reusing olive waste

To develop such a technology, Reinhard teamed up with Laura Nyström, Professor of Food Biochemistry at ETH Zurich. She brought her food knowledge to the table, and he provided the technical expertise. Together, they initiated the Phenoliva research project in 2019, funded by the EU as a European Institute of Innovation and Technology (EIT) project.

“With Phenoliva, we laid the foundation for the spin-off Gaia Tech,” Reinhard says. For three years, he worked with Nyström and other scientists at ETH Zurich to find out what high-quality ingredients and biocomponents can be extracted from olive waste and which processes are particularly suitable for this purpose.

Antioxidants from a biological source

Ultimately, they determined that the most marketable constituent of olive waste is the antioxidants. “Until now, 98 percent of the antioxidants were simply thrown away,” Reinhard says. But they are a valuable natural alternative to synthetic or fossil substances and can, for example, be used to preserve food and animal feed or, in cosmetics, to prevent skin ageing. “This is very important to many end customers, who are critical of synthetic additives.”

There is also the sustainability aspect, which has been at the centre of Reinhard’s research from the start. Reusing olive waste greatly reduces the olive oil industry’s ecological footprint and is an important step towards a circular economy.

Extraction and purification

To extract the antioxidants, the olive waste is first separated into solid and liquid components in a centrifuge. The liquid then passes through an absorber specially developed by the researchers. Like a sponge, this absorbs the antioxidants as a raw extract. The absorber is made of a completely biodegradable material and can be regenerated several times. At the end of its life cycle, it can be used as an agricultural fertiliser.

However, extraction is not the final step in the process. Before the antioxidants can be added to industry products, the extract must be purified and further processed. “The raw extract looks like dark honey and is very bitter,“ Reinhard says. Only after several purification steps to remove the colour and bitter substances can Gaia Tech’s antioxidants be brought to market.