Victoria, Australia, August 26, 2026: A new study has found that floating wetlands planted on wastewater lagoons could significantly reduce greenhouse gas emissions, offering a simple nature based solution to one of the hidden climate challenges of sewage treatment.
Researchers conducted what they describe as the first full scale trial of its kind at an operating wastewater lagoon on Phillip Island, Victoria. Over two years, floating wetland reduced overall greenhouse gas emissions by between 22% and 31% compared with a similar untreated channel.
Wastewater treatment helps clean polluted water, but the process can also generate significant amounts of carbon dioxide, methane and nitrous oxide as microorganisms break down sewage and nutrients. Methane and nitrous oxide are particularly powerful greenhouse gases, making emissions from wastewater treatment an important climate concern.
The research team installed a 330 square metre floating wetland roughly the size of two tennis courts, in one channel of a wastewater lagoon. The platform was planted with three Australian native wetland species: common reed, jointed rush and marsh club rush. A second channel without the floating wetland was used for comparison.
The results showed a substantial fall in emissions. Methane emissions dropped by 32% to 66%, carbon dioxide emissions fell by 24% to 36%, and nitrous oxide emissions declined by around 18%.
The researchers found that the reduction began within four to seven months of installing the floating wetland. Interestingly, significant reductions in nutrient concentrations were not detected until about a year into the study, suggesting that nutrient removal alone may not explain the early fall in greenhouse gas emissions.
Floating wetlands work by placing plants on buoyant platforms allowing their roots to extend into the wastewater. The roots create an environment where plants microorganisms and water interact. Plants can absorb nutrients and pollutants, while microbial communities around the roots help break down organic matter.
Unlike major wastewater infrastructure upgrades, floating wetlands can be installed on existing ponds and lagoons without requiring additional land or extensive reconstruction.
The researchers cautioned that the experiment was carried out at a single site and in two channels rather than across an entire wastewater lagoon. More studies will be needed to determine whether similar emission reductions can be achieved in different wastewater systems and climates.
The environmental footprint of the floating structures themselves will also need consideration, as the system used in the trial included plastic based materials. Future designs using natural or biodegradable materials could potentially make the technology even more sustainable.
Despite these limitations the findings suggest that floating wetlands could become a promising nature based tool for reducing emissions from open wastewater treatment lagoons while also supporting improvements in water quality.
As countries look for new ways to cut methane and other greenhouse gas emissions, the simple idea of putting wetlands on water may offer an unexpected solution to a growing climate challenge.