The authorities in Barcelona are testing an idea that could change the way roads are built. The idea is to add charcoal from olive pits and pine biomass to asphalt. Such a material should not only reduce the carbon footprint of road construction, but also turn part of the pavement into long-term CO2 storage.
The project is part of the municipal program “Street of the 21st Century”, which is being developed by the Barcelona City Council, the BIT Habitat Foundation and BIMSA. The main material is biochar – a stable vegetable charcoal produced by pyrolysis, i.e. the remains of olives are heated without oxygen, which prevents the carbon from quickly returning to the atmosphere when rotting or burning.
In conventional asphalt, the bituminous binder is mixed with mineral aggregates – sand, gravel and crushed stone. In the new mixture, some of these components have been replaced with vegetable charcoal. The logic is simple – the olive tree absorbs CO2 during growth, part of the carbon remains in the seeds, and after processing into biochar, it can be “locked” under the road surface for decades.
According to the project participants, the technology can reduce CO2 emissions associated with the production of asphalt layers by up to 76% compared to traditional methods. This is not unimportant – each street, highway, parking lot or cycle path requires thousands of tons of materials, and road construction rarely falls into the spotlight of the environmental agenda.
The first laboratory tests, carried out with the participation of the Political University of Catalonia and the design companies, turned out to be not only environmentally friendly, but also technically encouraging. Asphalt with biochar, according to preliminary data, is no worse than conventional asphalt and may be better in a number of parameters – higher moisture resistance, lower risk of cracking, more stable behavior at extreme temperatures. For cities with frequent heat waves, this is no longer a question of image, but of the service life of the road.
However, it remains to be seen how the new material performs in reality, since laboratory tests are no substitute for years of traffic by buses, trucks, cars, rain, heat, temperature changes and repairs to utility networks. That is why Barcelona will start real tests from September on several city sites. In 2027, the coating will be constantly monitored to see how it ages, withstands traffic, reacts to water and overheating in the summer.
Before mass use, the exact proportion of biochar in the mixture must be chosen, compatibility with current laying techniques must be checked and it must be understood whether the new asphalt will become more expensive to maintain. So far, this is not a ready-made replacement for conventional asphalt, but an experiment with good engineering logic.
Illustrative photo: pexels-hamid-eshafah-245702689-17503894
