Carbon footprint assessment of maintenance and rehabilitation techniques for sewer systems

The research study presented in this paper sets out to improve our understanding of the environmental impacts associated with the maintenance and rehabilitation of conventional gravity sewer systems and, through this, support decision-making processes in sewer system management. The objects assessed are open trench replacement, trenchless renovation, open trench and trenchless spot repair, inspection, and hydraulic cleaning of sewer pipes. Carbon footprint assessment was carried out according to the ISO14067:2018 standard. The life cycle stages considered included raw material extraction, manufacturing processes, maintenance/rehabilitation, and the transportation of materials. The functional unit was defined as: ‘A gravity sewer section with a length of 45 metres and a diameter of 200 to 1500 mm operating in normal conditions over a period of 100 years in the Netherlands’. A sensitivity analysis was included to assess how the results vary as a consequence of changes in the input dimensions. The findings of this study suggest that the main opportunities for reducing the environmental impacts of conventional, open trench pipe replacement lie in the choice of the pipe material and the design of the asphalt pavement that requires reinstatement. Adopting trenchless sewer rehabilitation technologies can significantly reduce the environmental burdens of sewer system rehabilitation.