Chiang Mai University, through Professor Dr. Peerapong Jitsangiam of the Multidisciplinary Research Institute, has developed innovative road pavement and base materials using plastic waste and biochar. The innovation transforms waste into valuable construction materials while enhancing engineering performance, reducing resource consumption, and lowering greenhouse gas emissions. A pilot project on Ton Yang Na Road in Saraphi District, Chiang Mai, has demonstrated an estimated reduction of approximately 90 tonnes of carbon dioxide equivalent (CO?e) compared with conventional road construction.
The innovation integrates agricultural biomass and plastic waste into sustainable road construction. It comprises two key components: porous asphalt concrete incorporating plastic waste and biochar, and Smart and Green Road Base, designed to simplify construction and incorporate a root watering system to support roadside trees.
Biochar is produced from biomass through pyrolysis, a process that heats materials under limited oxygen conditions, allowing stable carbon to remain in solid form. When incorporated into road materials, it offers potential for carbon storage while providing an alternative to open burning of agricultural waste. Meanwhile, recycled plastic can enhance asphalt properties, increase resistance to rutting, and reduce the use of virgin materials.
The porous asphalt concrete features interconnected voids that allow water to drain through the pavement, helping reduce surface water accumulation and improve road safety. The research team has developed a formulation combining recycled plastic with standard AC 60/70 asphalt cement and biochar to improve performance while reducing reliance on costly polymer-modified asphalt (PMA).
The Smart and Green Road Base builds on Controlled Low-Strength Material (CLSM), which flows and hardens without conventional mechanical compaction. Its application can reduce cement consumption, heavy machinery use, construction steps, energy consumption, and carbon emissions. Incorporating biochar also offers potential for carbon storage within the road base.
The team has also developed a Root Watering System using bio-permeable concrete mixed with biochar. This allows water to reach tree roots while supporting surface loads and promoting root growth beneath pavements. Installation requires site surveys to minimize disturbance to existing root systems.
Applications and Environmental Impact
The innovations have been implemented in several projects:
Ton Yang Na Road, Saraphi District, Chiang Mai: Approximately 28,000 sq. m. over 3.5 km, using 108 tonnes of biochar and 4 tonnes of plastic waste. Life-cycle assessment from material sourcing through construction indicates approximately 90 tonnes CO?e lower emissions than conventional road construction.
UNISERV parking area, Chiang Mai University: Approximately 5,000 sq. m., incorporating 83.7 tonnes of biochar and 1 tonne of plastic waste.
Faculty of Engineering, CMU: A parking area of approximately 750 sq. m. and an internal road spanning 469 m, incorporating 1.3 tonnes of NEWTLAC, equivalent to 18,909 recycled PET bottles. NEWTLAC is a polymer powder developed by Kao Industrial (Thailand) Co., Ltd. from recycled PET bottles for asphalt road construction.
This innovation demonstrates how waste materials can be transformed into valuable engineering resources while supporting sustainable infrastructure and environmental protection. Future research will focus on monitoring performance, service life, and maintenance costs to assess suitability for different road conditions and traffic demands.