Carbon Footprinting AMP4 Projects

Black, J. and Rands, J., United Utilities, UK


United Utilities has made a public commitment to reduce its CO2 emissions by 60% by 2050 compared to the 1990 level. The predicting of CO2 and other greenhouse gas emissions for specific projects is still an emerging science for most UK water companies. UU have developed a model to estimate the whole life CO2 footprint associated with capital projects. This paper highlights the carbon footprint results obtained using this model for two major United Utilities AMP4 (Asset Management Period 4) projects at Wastewater Treatment Works (WwTW): Fleetwood WwTW and Northwich WwTW.

For the Northwich WwTW project, the embodied (carbon emissions associated with construction of the
assets) and operational CO2 emissions for two options are compared: a lower energy, gravity flow option
requiring significant excavation, and a higher energy, pumped flow option, with lower construction costs.

The whole life carbon associated with the gravity option is found to be lower, however the additional
costs, including allowance for the shadow price of carbon and risks involved, show the pumped solution
to be preferable.

For the Fleetwood WwTW project, the total embodied CO2 emissions and the net impact on operational
CO2 emissions associated with the project are quantified. A breakdown of the whole life carbon arising
from the project is also carried out to show the contribution from specific process areas such as primary
settlement tanks, raw sludge treatment (de-watering) and odour control. The analysis show that approx.
90% of the embodied carbon is attributable to the new Primary Settlement Tanks, whilst the operational
carbon is evenly split between sludge treatment and odour control. The analysis also shows that over a
30 year life-cycle the operational carbon is by far the main factor, contributing approx. 90% of the whole
life carbon.

Key Words
AMP4, Carbon, Embodied, Emissions, Footprint, Gas, Greenhouse, Operating

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