INSIGHT | SUSTAINABILITY
EMBODIED CARBON OF MICROTUNNELLING
Knowledge of embodied carbon in microtunnelling has taken a step forward with research supported by Ward and Burke. Key points of the findings are described by Alexander W. Swallow1
and Brian B. Sheil2 1DPhil Student, University of Oxford 2Associate Professor and RAEng Research fellow, University of Cambridge
The impetus for this article stems from two compelling facts. Firstly, the creation of new water and wastewater infrastructure is essential. Secondly, it is a critical priority to minimise carbon emissions associated with constructing this new infrastructure. Microtunnelling is a trenchless method that will play
a key role in the construction of future pipelines. In microtunnelling, drives commence and terminate in pre- installed shafts. A tunnel boring machine (TBM) carries out excavation, with the tunnel created by a string of pipes jacked behind the machine. Despite the important role trenchless methods play
in creating necessary utility infrastructure, existing published research fails to comprehensively consider all contributors to the embodied carbon. Many of the published studies consider onsite emissions only, neglecting the embodied carbon of materials used.
700 600 500 15.4% 400 300 200 100 0 Tunnels Structure
Above, figure 1: The aggregated embodied carbon for the three case studies, which together comprise a total tunnelled length of 870m and nine shafts
30 | November 2024 Shafts 64.4% 75.9%
21.1% 2.94%
Some studies do consider both onsite emissions and materials (e.g., Piratla et al. 2012; Khan and Tee 2015; Chilana et al. 2016; Kyung et al. 2017; Alsadi and Matthews 2020), however none of these studies focus on microtunnelling. Only two studies specifically considering microtunnelling were identified by the authors (Lu et al. 2020; Matar et al. 2019), both of which fail to give a holistic insight into the embodied carbon of microtunnelling. Working in collaboration with Ward and Burke
Construction Ltd., we set out to address these shortfalls in understanding by analysing the embodied carbon of three recent microtunnelling projects undertaken in the UK.
All three of these projects were undertaken using
reinforced concrete pipes and open-dug caissons for the launch and reception shafts.
On-site emissions Transport to site Materials/manufacturing
20.2%
Embodied carbon (tCO2
e)
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