According to WPB, researchers at Chiang Mai University in Thailand have developed and implemented an innovative road construction system that incorporates recycled plastic and biochar into asphalt pavement and road base materials. In an announcement published on November 2, 2026, the university confirmed that a 3.5-kilometer road project in Chiang Mai had used 108 metric tons of biochar and 4 tons of recycled plastic, achieving an estimated reduction of approximately 90 tons of carbon dioxide equivalent (CO₂e) compared with conventional road construction.
The project was implemented on Ton Yang Na Road in Saraphi District, Chiang Mai Province, covering approximately 28,000 square meters. Unlike technologies that remain at the laboratory testing stage, the materials have already been incorporated into a road construction project, providing an opportunity to evaluate their performance under actual operating conditions. The development forms part of a broader research initiative aimed at reducing construction-related emissions while improving the use of agricultural and plastic waste.
The technology combines two main components: porous asphalt concrete incorporating recycled plastic and biochar, and an innovative road base known as Smart and Green Road Base. The approach is designed to improve pavement performance while reducing reliance on newly manufactured materials, lowering construction-related resource consumption, and creating opportunities for carbon storage within road structures.
Biochar is a carbon-rich material produced by heating biomass under limited oxygen conditions through a process known as pyrolysis. This process converts agricultural residues into a relatively stable solid material that can retain carbon over extended periods. Incorporating biochar into road construction offers a potential alternative to open burning of agricultural waste while allowing some of its carbon content to remain stored within construction materials.
Recycled plastic serves a different engineering function. When incorporated into asphalt mixtures, suitable plastic materials can improve resistance to permanent deformation and contribute to the mechanical performance of the pavement. The researchers combined recycled plastic with conventional AC 60/70 asphalt cement and biochar to develop porous asphalt mixtures intended to offer an alternative to more expensive polymer-modified asphalt formulations.
The use of conventional AC 60/70 is an important distinction. This project does not eliminate petroleum-derived bitumen from the asphalt mixture. Instead, it seeks to improve the performance and environmental characteristics of a bitumen-based pavement by incorporating recycled materials and reducing dependence on more costly modifying agents.
The porous asphalt layer contains interconnected voids that allow rainwater to pass through the pavement surface. This drainage capability can reduce surface water accumulation and improve road safety during wet conditions. However, porous asphalt also requires an effective binder system to maintain aggregate cohesion and resist damage caused by traffic loading and environmental exposure.
To address these performance requirements, the research team developed a formulation combining recycled plastic, biochar, and conventional asphalt binder. The approach aims to achieve suitable mechanical performance while reducing reliance on expensive polymer-modified binders. Its effectiveness across different traffic conditions and service periods remains a subject of continuing evaluation.
The second major component, Smart and Green Road Base, is based on Controlled Low-Strength Material (CLSM), a flowable construction material that can harden without the conventional mechanical compaction required for many road base applications. The system is designed to reduce construction steps, heavy equipment requirements, and cement consumption. Incorporating biochar also creates an opportunity to retain carbon within the pavement's supporting layers.
The researchers have additionally developed a root-watering system using bio-permeable concrete containing biochar. The material is designed to allow water to reach tree roots while maintaining sufficient strength to support surface loads. The system is intended for roadside environments where protecting existing trees and maintaining pavement performance are both important considerations.
One of the project's most significant results concerns its estimated environmental performance. A life-cycle assessment covering material sourcing through the completion of construction indicated that the 3.5-kilometer road project could reduce greenhouse gas emissions by approximately 90 metric tons of CO₂e compared with conventional construction methods.
The reported reduction reflects the defined assessment period, from raw material procurement to construction. It should not be interpreted as a verified reduction covering the road's entire service life, including future maintenance, repairs, and end-of-life treatment. The long-term environmental benefits will depend partly on pavement durability and maintenance requirements.
The research has also been applied to other infrastructure projects at Chiang Mai University. A parking area covering approximately 5,000 square meters at the university's UNISERV facility incorporated 83.7 tons of biochar and 1 ton of recycled plastic, demonstrating the use of similar materials in a different construction environment.
Another application involved a parking area of approximately 750 square meters and a 469-meter internal road at the university's Faculty of Engineering. This project used 1.3 tons of NEWTLAC, a recycled polymer powder developed from waste polyethylene terephthalate (PET) bottles. The material quantity was equivalent to approximately 18,909 recycled plastic bottles. This application is separate from the 3.5-kilometer Ton Yang Na Road project.
For the bitumen industry, the development is particularly relevant because it demonstrates how recycled materials can be integrated into conventional asphalt systems without necessarily replacing petroleum-based binders. The use of recycled plastic alongside AC 60/70 could influence future approaches to binder modification, particularly in markets where the cost of polymer-modified asphalt is a significant factor in pavement construction.
The environmental implications are also important for road authorities and infrastructure developers seeking to reduce construction-related emissions. Combining biochar, recycled polymers, porous asphalt, and alternative road base materials offers several potential avenues for improving resource efficiency within a single infrastructure system.
The next stage of the research will focus on monitoring pavement performance, service life, and maintenance costs under different road and traffic conditions. These evaluations will be essential for determining whether the materials can deliver consistent engineering performance and environmental benefits over extended periods of use.
The Chiang Mai project demonstrates a practical application of recycled plastic and biochar in road construction, supported by a quantified assessment of emissions during the construction phase. Its significance lies in combining waste-derived materials with conventional bitumen technology and innovative road base design. Continued field monitoring will help determine the potential for broader adoption in Thailand and other asphalt markets.
By WPB
Thailand Sustainable Roads, Chiang Mai University, Recycled Plastic Asphalt, Biochar Asphalt, Green Road Construction, Low-Carbon Asphalt, Asphalt AC 60/70, Porous Asphalt Concrete, Smart and Green Road Base, Carbon Emissions Reduction, CO2e Road Construction, Biochar Carbon Storage, Waste Plastic Recycling, Polymer Modified Asphalt, Asphalt Pavement Technology, Sustainable Bitumen, Road Construction Innovation, Pavement Durability, Circular Economy
