In traditional asphalt, bitumen is used as a binder. It binds the gravel in the asphalt mixture together and gives strength. However, bitumen is a crude oil product that is becoming increasingly scarce. The quality of bitumen available is also declining. The road construction industry is therefore looking for an alternative, such as lignin. This biobased binding agent is common in plants and is available as a residual stream from paper and bioethanol production, among others.
Substantial CO2 savings
A key advantage of lignin is its ability to sequester carbon for longer periods of time. As a result, less CO2 is released into the atmosphere. New calculations show that biobased asphalt in which 50% of fossil bitumen is replaced by lignin contributes to avoiding 85 to 170 kilotonnes (kt) of CO2 equivalent per year in 2050, based on 550 kt CO2 eq per year emitted by the current asphalt sector in the Netherlands. With 100% bitumen replacement, the savings are expected to be doubled. This leads to about 30-60% reduction in total CO2 emissions for the current Dutch asphalt sector.
Extending these numbers to the European market, with 11 million tonnes of bitumen use in asphalt per year, a CO2 emission reduction of up to 12,000 kt CO2 eq per year can be achieved. On a global scale (90 million tonnes of bitumen per year), even savings of up to 102,000 kt CO2 eq per year can be achieved.
As such, this development makes a significant contribution to achieving European and global climate goals. The European Union’s ambition is to reduce CO2 emissions by 55% by 2030, compared to 1990.
At various locations in the Netherlands, more than 30 demonstration roads have already been laid for testing lignin-containing asphalt, as part of the CHAPLIN project involving the entire asphalt value chain: from raw material suppliers via knowledge institutes and governments to road builders and road authorities. So far, up to half of the bitumen on roads has been replaced with lignin. Construction of the first demo roads with 100% biobased raw materials in the top layer is expected to start later this year or in 2024.
Image: Ronny Benjamins Bedrijfsfotografie/Avantium