Anthropocene Magazine · Climate & nature

Floating Wetlands Reduce Greenhouse Gas Emissions from Wastewater

A study found that floating wetlands, made of native plants on buoyant structures, can significantly decrease greenhouse gas emissions from wastewater treatment lagoons.

Wastewater treatment contributes to 1.6% of global greenhouse gas emissions, a figure expected to rise with economic development. Researchers tested the effectiveness of floating wetlands, where plants like reeds are grown on artificial structures with roots in the water, on a large wastewater lagoon in Australia.

Over two years, the floating wetlands reduced carbon dioxide emissions by up to 36%, methane by up to 66%, and nitrous oxide by up to 18%. Overall greenhouse gas emissions decreased by up to 31% compared to an untreated area.

A surprising finding was the rapid decline in greenhouse gas emissions, occurring within four to seven months, even before significant nutrient reduction was observed.

The exact mechanisms behind this emission reduction are not yet fully understood, but researchers suspect interactions between plant roots, microbial communities, and gas production/consumption are involved.

Challenges remain, including managing plant trimming, which can cause methane spikes. The harvested plant material also needs a method for long-term carbon storage, such as conversion to biochar, to ensure a net climate benefit.

The research team plans to investigate the application of floating wetlands to farm ponds, which also experience significant nutrient inputs and greenhouse gas emissions.

This study suggests floating wetlands could be a viable climate solution for various aquatic systems.

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