The city of Basel is set to use a novel type of CO2-negative asphalt on local roads and pavements. The material is designed to absorb more carbon dioxide than it takes to produce, and drivers will soon be able to see the first carbon-negative roads right in the heart of the city in the suburb of St. Alban.

CO2 absorbent asphalt made with 50 percent recycled material

According to Blick, the CO2 absorbent asphalt is made by mixing regular asphalt with around 50 percent recycled materials and then 2 to 3 percent of biochar. The biochar, which is biomass cooked in a high-temperature, low-oxygen environment, gives the asphalt its negative-emission qualities due to being classed as a "carbon sink" - meaning it absorbs more CO2 than it emits.

In a statement, the Basel Construction and Transport Department described the plans as a "milestone for climate-friendly road construction". Green Liberal Party councillor for Basel, Esther Keller, told a media conference on Tuesday that the asphalt had been developed in Switzerland thanks to work by the government, the Civil Engineering Office and the Basel Industrial Works (IWB) in cooperation with the ViaTec Basel AG institute.

New carbon-capturing roads have slightly higher production costs

During the press conference, officials also addressed the costs associated with the new material. Officials explained that biochar-treated roads will cost slightly more than standard road coverings, mainly due to the more complex mixing process involved in making the carbon-negative asphalt.

The Basel Industrial Works obtains biochar from trees that are periodically cut down throughout the canton, as well as from Christmas trees that are not used. The material has already been used for many years in gardening to improve compost and soil quality, as well as in the production of cement.