The ‘carbon footprint’ of sewer pipes: risks of inconsistency

Abstract

The sewerage industry needs to understand and reduce embodied carbon dioxide emissions associated with its assets in order to contribute to the national carbon dioxide reduction agenda. There are at least six recognised methodologies for calculating so-called ‘carbon footprints’ of construction products and tens of standard-based or ad hoc calculators. With the increase in information from different sources, the use of different methodologies and the absence of representative data and data collection methods, there is a risk that inappropriate data, results or methods are used to justify crucial decisions in the sewerage sector. This paper presents an assessment of the problem and its impact on the reliability of embodied carbon dioxide emissions data for large diameter (≥225 mm) sewer pipes. Fifteen scenarios are developed based on a number of methodological rules and assumptions associated with data accuracy, functional unit, technology and geographic coverage. A significant variance, reaching over 50%, is found between widely accepted carbon footprint values for concrete and plastic sewer pipes and values based on alternative scenarios. Guidance is then offered on how secondary data should be handled and what methodological questions should be addressed prior to data use.