New way to resurface roads with zero carbon impact and no carbon offset trialled in Cardiff


Pengam Road in Splott, Cardiff, has been resurfaced using a new pioneering technique to ensure that the materials used have a negative carbon impact.

An 877m² section of Pengam Road has been resurfaced using a surface course mix containing slag steel aggregate and Biochar, incorporating and imbedding the equivalent weight of naturalized carbon into the surfacing, with a saving of over of 4.5 tonnes of emitted carbon.

The key ingredient to this is Biochar, which is a by-product of waste treatment technology,Pyrolysis. All organic material (wood, food, compost, sewage) degrades naturally, eventually releasing all of its carbon into the atmosphere.  Pyrolysis uses heat treatment at 500 and 600 Degrees Celsius without oxygen which captures the Biogas, Syngas and Biochar of organic matter. The resulting Biochar has a high stable carbon element, which in turn is incorporated into the new surfacing material to give the negative carbon impact.

Working closely with our contractor Miles Macadam, the council is trialling this unique material and variations of design, as the more biochar that is added to the mix, the lower the carbon impact of the materials that are used. If enough Biochar is added to the product, the impact of other items involved in the process, such as transporting the materials, could also become carbon neutral by default.  Again, if this system is used in all road resurfacing works, it would result in significant carbon savings across the city and nationally.

Cllr Dan De'Ath, Cabinet Member for Strategic Planning and Transport said: "The council is continuing our journey to reduce the carbon impact of council services, and this is an excellent example of how we can reduce the carbon impact of resurfacing our roads.  Climate change is the biggest threat facing our planet and steps must be taken to reduce the amount of carbon produced in our everyday lives. The reduction of carbon in the petrochemical industry, which includes road resurfacing, is quite an achievement and we are now looking on how to reduce the carbon impact further, so we can resurface roads with zero carbon impact and without a need for carbon offsetting."

Charlie Clarke, Managing Director of Miles Macadam said:"Miles Macadam is delighted to be able to trial these new materials and grateful for the opportunity that Cardiff Council have given us. Together we will create a blueprint for the road surfacing and construction industry and greatly assist the drive towards climate change".