Nitrous oxide emissions and carbon intensity
This tool helps visualize and compare Scope 1 and Scope 2 greenhouse gas (GHG) emissions from a wastewater treatment plant (WWTP).
What are Scope 1 and Scope 2 emissions?
Scope 1 emissions are direct emissions from the treatment process.
In WWTPs, this mainly refers to nitrous oxide (N₂O) produced during nitrogen removal (e.g., nitrification and denitrification).Scope 2 emissions are indirect emissions from electricity use.
These depend on how carbon-intensive the electricity grid is in your country or region.
What is carbon intensity of electricity?
Carbon intensity refers to the amount of CO₂ emitted per unit of electricity generated, usually expressed in grams of CO₂ per kilowatt-hour (g CO₂/kWh).
This varies widely depending on your electricity source:
Low in countries with renewable or nuclear-heavy grids (e.g., Norway, France)
High where coal or gas dominates (e.g., Poland, parts of the U.S.)
Realtime carbon intensity is available here: https://app.electricitymaps.com/map/72h/hourly
This tool allows you to evaluate and compare greenhouse gas (GHG) emissions at the process unit level by visualizing the combined impact of:
Nitrous oxide (N₂O) emissions resulting from biological nitrogen removal
Electricity consumption for aeration, which depends on oxygen demand and aeration efficiency
For a given process unit, it estimates:
Direct N₂O emissions (Scope 1) based on a user-defined emission factor (e.g., % of N removed converted to N₂O-N)
Indirect emissions (Scope 2) from electricity used to supply the oxygen needed, depending on:
O₂ demand per kg N removed (process efficiency)
Standard Aeration Efficiency (SAE) in kg O₂/KWh
Carbon intensity of the local electricity grid