WSP Limited received funding of $141,000 (excluding GST) to carry out laboratory trials of solvents to extract bitumen from end-of-life chipseal.
This project was in response to one of Hoe ki angitū, the NZTA Innovation Fund’s round one challenges: Accelerating the use of recycled materials and sustainable practices.
The objective of this project was to determine whether it would be feasible to extract bitumen from end-of-life chipseal using biodegradable solvents produced from renewable materials. The chip seal road network in New Zealand holds over an estimated one million tonnes of bitumen and many millions of tonnes of good quality aggregate which could be recycled back into road surfacings. This would enable a reduction in the use of new bitumen, which is an imported and a non-renewable resource, and a reduction in the need for new aggregate.
The project involved evaluating different biomass derived solvents and selecting three for further testing. The extraction efficiency of these different solvents was tested on new and aged bitumen and compared to known high-performing petrochemical solvents.
Two of the solvents performed adequately with unaged bitumen, but poorly with aged bitumen. One of the solvents performed at a level equivalent to the best petrochemical derived solvents, including with aged bitumen. This makes it a promising candidate for further investigation into the practical feasibility of use at scale.
The next steps are to obtain more information about the range of physical properties and chemical compositions of aged bitumen, and to understand how the recovered bitumen could best be used. Additional information is also needed about the quantity and location of end-of-life chipseal. A basic plant-concept design for a large bitumen recovery process would need to be developed, alongside a high-level study to understand the economic and environmental impacts of such a process.
Note – due to commercial sensitivities the specific biosolvents used are unable to be identified, and only the executive summary is available for this project. WSP can be contacted directly to discuss further details of this project.
View the executive summary here:
| Sharp, M. (2023). Recycling Chip Seal Road Surfacings [PDF, 118 KB]. Executive summary. Project Number: 5-2132.00. WSP New Zealand Limited. |
