The civil engineering department of Basel has developed a road surface that can bind more carbon dioxide (CO2) than it emits during production. By adding plant charcoal to the pavement, the city could store an additional 450 tons of CO2 per year. This innovative approach to road construction is considered a milestone in climate-friendly infrastructure. The cost of using plant charcoal in paving is only slightly higher than standard methods, making it an economically viable solution. The goal is to use this technology extensively in future road renovations. Source: (Die Zeit 08.08.2023…)
We’ve asked Prof. Dr. Reto Knutti for his assessment on “Green Asphalt”.
The answer
That’s right.
Vegetable carbon is produced by the pyrolysis of biomass. The resulting often powdery charcoal material has many exciting properties, e.g. as a filter material, and can be used in concrete and other (building) materials, but also for soil improvement in agriculture. Empa is developing, for example, insulation materials made from plant carbon.
It is interesting to note that plant carbon represents a permanent solid storage form of CO2, and thus, along with sequestration in the soil (Climeworks), one of the most promising methods for CO2 removal from the atmosphere. A large part of the carbon of the biomass bound in photosynthesis is thus permanently bound.
Biochar is the lightweight black residue, made of carbon and ashes, remaining after the pyrolysis of biomass, and is a form of charcoal. Biochar is defined by the International Biochar Initiative as “the solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment”.[1]
In principle, the technology of production of plant carbon is known, its use in agriculture is already the case today. So potential CO2 is already listed that today.
Technologies: The most important NET approaches (in German…)
Materials and construction materials are mostly under development, where costs and certification are the challenges. It is quite possible that asphalt is already ready for the market. Besides the vegetable carbon, the fact that half of the material is recycled asphalt helps, of course. However, asphalt alone won’t solve the climate problem because we simply don’t need that much asphalt. If it were used in concrete on a large scale, that would be a much bigger contribution.
The question is why this asphalt is not used everywhere….
Maybe the material is not available in large quantities.
But the main reason is probably simply the price. This is also true for recycled concrete and other ecologically better materials: they are more expensive. And in the construction industry, calculations are hard, and very few investors are willing to pay more just because it helps the environment. Exceptions are people who build for themselves and are convinced and want to make a contribution, and like here the public sector, where with the new procurement law also sustainability criteria can/must be taken into account.
Translated with www.DeepL.com/Translator (free version)
