Barcelona wants to say goodbye to traditional asphalt and thinks it knows how: with olives

Neither transport nor heating: there is something in cities that generates an enormous amount of carbon dioxide and that usually goes unnoticed. Cities as a whole are responsible for between 67% and 72% of global CO₂ emissions in 2020, according to the IPCCand within them there is a culprit that almost no one points out: the asphalt.

Manufacturing traditional asphalt is a process that uses a lot of energy and requires petroleum derivatives (bitumen), aggregates and calcareous filler, a combo with a high carbon footprint. Barcelona has decided attack the problem replacing these materials with agricultural waste that normally goes to the trash.

For example, the olive pit.

Asphalt made of olives. It is called Biochar and allows reduce 75% of the final carbon dioxide emissions associated with the manufacture of asphalt. As? Using charcoal obtained from olive pits and pine remains to replace the calcareous filler of the conventional asphalt mixture. In addition, initial tests have recorded improvements against water, fewer cracks and better response to temperature changes.

Biochar is not something new, in fact it has been used for soils for decades, but its application for urban pavements is. Developed by the company Carboliva together with ELSAN, AMSA and the UPC, it is the winning solution of the urban challenge “The street section of the 21st century”, promoted by Barcelona City Council together with BIT Habitat and the Barcelona Provincial Council. The other selected proposal is RePavimenta and it goes another way: it uses recycled construction components in the aggregates, promising to reduce the carbon dioxide emissions of the process by half.

Biochar, made from olive pits and pine remains. Carboliva

Why is it important. Because the construction and infrastructure sector represents approximately 13% of global greenhouse gas emissions, according to IPCC data. On the other hand, the budget allocation for urban pavement maintenance is one of the largest precisely due to its deterioration, so reducing emissions by 75% implies a gesture with an enormous impact and even more so doing it with a material that on paper withstands use better.

That one of the raw materials is the olive makes it more relevant, since the Spanish state is a world power: Spain is the largest producer of olive oil in the world, with more than 1.42 million tons in the 24/25 campaign, according to the International Olive Council. This means that there is a huge amount of olive pits available. That is, the waste of one becomes raw material for the other: a kind of symbiosis in a circular economy.

Context. Global warming on the one hand (which has a special impact in the cities and their asphalt) and European regulatory pressure are accelerating municipalities to reconsider their construction materials. The European Directive on Energy Efficiency in Buildings and the Construction Products Regulation that the EU is updating require environmental product declarations, which penalizes materials with a high carbon footprint and rewards alternatives such as biochar. In the call there were six proposals that had to present new solutions on the market and it is not the first time: already in 2022 Barcelona launched a call to renew the traditional Barcelona panot.

How are they going to do it?. The deadlines for R&D&i and prototypes will be open until September of this year. Afterwards, pilot tests will begin in real works in Barcelona with the help of BIMSA and there will be a subsequent 12-month follow-up to check resistance, duration and possibility of extension. The winning projects will receive 90,000 euros, which according to Barcelona City Council covers around 80% of the total cost of design, testing and monitoring. The first streets with this asphalt will begin to be installed in 2027.

Yes, but. The results in the laboratory are tremendously promising, but tests are one thing and reality in real conditions is another, with the dynamic load of traffic, urban pollutants, the climate or clearly improvable maintenance. In fact, already there are studies on the use of biochar in bituminous mixtures that show different results depending on variables depending on the typethe pyrolysis temperature or the substitution percentage.

A relevant question if substitution materializes is what the biochar supply chain will look like at scale in terms of quantities and costs. The European Environment Agency warns that innovations based on biowaste face logistical challenges due to geographical dispersion and limited supplies.

In Xataka | Spanish roads have a problem in 2026: repairing a kilometer of asphalt is more expensive than ever

In Xataka | We invented asphalt for a simple reason: at the beginning of the 20th century, European roads were a dust hell.

Cover | Logan Armstrong and John Cameron