Calculating the Carbon Footprint of Wastewater Treatment Plants
Hunt, P., Earth Tech Engineering Limited, UK
(free)
The carbon reduction commitment (CRC) coming into force in 2010 (applicable to all businesses which use greater than 6,000 MWh electricity) aims to cut emissions through a cap and trade auction of allowances.
It will place companies in a league table of reduction performance. The Water Industry will be the largest
sector in the league table and it is predicted that water companies are likely to appear at the bottom of
this league table.
The UK water industry is responsible for annual emissions of about 5 x106
tonnes of greenhouse gas (GHG, as CO2 equivalents, CO2e) which is rising every year, according to statistics published by Water UK. Ofwat are encouraging utilities to mitigate their carbon footprint by requiring companies to undertake carbon accounting of their AMP5 activities for direct, indirect and embedded emissions. This is influencing utilities on long term strategic planning, investment decisions, operations, asset serviceability and maintenance. A number of companies have in place Carbon Management Programmes that provide strategies for measuring monitoring and mitigating GHG emissions.
This paper aims to look at the carbon costs for waste water treatment facilities from construction through to demolition. Various recognised designs for a 75,000 P.E. wastewater plants have been developed and compared. The carbon footprint has been calculated for each. The designs are either biological methods or a mixture of biological and chemical processes to achieve nutrient removal.
To enable a critical assessment and comparison of the carbon footprint of the various treatment
techniques an attempt to determine as accurately as possible the carbon emissions for materials used in
the construction and running of these wastewater treatment facilities is made via a purposely constructed model. The information used in this model is drawn from a number of sources ranging from publicly available databases through to specifically commissioned research.
In measuring Carbon footprint there is a need to use industry recognised standards in both the
measurement and the methodology. Specific to the water industry is the UKWIR Carbon accounting
methodology. This has been produced on behalf of the water utilities in collaboration with the Carbon
Trust and Water UK and provides a standardised approach for estimating individual water company GHG emissions. Its outputs are provided in broad accordance with key data sources and guidance’s such as the DEFRA guidelines and the Kyoto protocol. This model enables ‘whole life carbon’ accounting for –
investment selection and a framework for estimating and costing carbon emissions including cost-benefit analysis (CBA), which is required for planning in PR09. Where there are gaps in the data or methodologies it is important that good engineering practices are used to overcome this. It is recognised that at the current time the weak area of carbon foot printing is for chemicals and M&E equipment CO2e, used in water and wastewater treatment. EarthTech is sponsoring research in Universities to overcome this gap for use in PR09.
