Researchers at Colorado State University (CSU) have found that switching from waste greywater treatment facilities to green solutions, such as wetlands, could save $15.6bn and 29.8 million tonnes of CO2-equivalent emissions per year.

A grey infrastructure system includes water treatment facilities such as sewage plants, which remove problem nutrients before releasing water back into circulation. These facilities require substantial power to run and, as such, release emissions into the atmosphere.

According to researchers at CSU, existing facilities already account for 2% of all energy use in the US and 45 million tonnes of CO2 emissions.

Grey infrastructure treatment facilities also address other forms of freshwater contamination, such as fertiliser run-off from agriculture entering rivers, pollution from wildfires or urban development.

Rather than building more grey infrastructure treatment facilities to address these increasing sources, a research team at CSU has explored the potential...