Download and use the calculation tool via this link: Carbon Footprint Calculation Tool for Wastewater Treatment Plants
Wastewater treatment is highlighted in the United Nations’ Intergovernmental Panel on Climate Change (IPCC) guidelines for national greenhouse gas inventories due to its emissions of methane (CH4) and nitrous oxide (N2O) and because of its high energy- and chemical use. A first step to decrease the carbon footprint from wastewater treatment plants is to increase the knowledge about the climate impact of individual wastewater treatment plants and which processes are dominating. Comparisons between plants can thereafter be done and strategies to improve the carbon footprint can be created.
This project has created a user friendly tool to improve the possibility for wastewater treatment plants to calculate their carbon footprint by themselves and thereafter set goals to decrease the climate impact of the treatment plant. The results are presented in tons of carbon dioxide equivalents and are related to a number of different functional units, for example per influent kg nitrogen (kg CO2e/kg Ntot-influent). Today there are no obvious consensus about which unit is preferred, therefore several units are listed in the calculation tool.
A number of sensitivity analyses made it possible to discuss the effect of the assumptions in the calculation tool. These show that assumptions regarding nitrous oxide and methane emissions from the biological processes at the wastewater treatment plant and in the recipient can have a large impact on the carbon footprint. Assumptions about how the electricity used at the plant is produced also effects the result a lot.
A limitation in the calculation tool is that the user only can choose between a certain number of alternatives for the handling of products and by-products that are created at the plants. The options that are included in the tool are meant to reflect the handling at most of the Swedish wastewater treatment plants. Not all of the chemicals used at wastewater treatment plants are represented in the calculation tool either, however the user have the opportunity to add emission factors for chemicals used at the specific plant.
More information about the project can be found here