Asphalt made with recycled vegetable oil and olive oil by-products is being trialled in Spain, according to local media reported by Olive Oil Times.

Authorities in Castile and León were planning to pave a 40m section of heavily-used motorway connecting the community’s two largest cities – Valladolid and Segovia – with the experimental asphalt, the 10 August report said. Another 40m section of the highway would be paved with conventional asphalt.

The experimental asphalt is made with a mixture of semi-hot bitumen – a by-product of the petroleum refining process – by-products from the olive oil refining process and recycled vegetable oil, according to the report.

For every 1,000 litres of semi-hot bitumen, the new manufacturing process required 300 litres of olive oil refining by-product and 400 litres of recycled vegetable oil, the report said.

The plan was to compare the performance of the two sections, with officials hopeful that the experimental asphalt would be at least as durable as the traditional formulation, Olive Oil Times wrote.

Previous research had indicated that asphalt made with by-products from olive oil production could be more resilient than traditional asphalt, the report said.

For example, a 2021 study conducted by California’s Olive Oil Commission found that adding olive pomace to asphalt binder increased the paving material’s resilience to cracking and other forms of weathering.

According to local authorities in Castile and León, as the experimental asphalt can be produced at temperatures 400C cooler than traditional asphalts, this would reduce the amount of energy required to manufacture and reduce greenhouse gas (GHG) emissions.

In addition, officials said the experimental asphalt formulation could improve working conditions as it emitted less smoke and odour while being poured compared to conventional asphalt.

Researchers in Spain had been looking for ways to create value from the waste created during olive oil production since 2020, the report said.

According to Spanish non-profit research institute Ainia, 80% of the biomass of olives transformed into oil is converted into waste products.

Removal and treatment of these products were a significant cost for mills but could also provide an extra revenue stream, Olive Oil Times wrote.