New research shows green wastewater infrastructure could significantly reduce emissions

Switching to green wastewater infrastructure could save a staggering $15.6bn and just under 30 million tonnes of CO2-equivalent emissions over 40 years.

The comprehensive findings from Colorado State University were highlighted in a paper in Nature Communications Earth and Environment in a first-of-its-kind study.

It explores the potential economic trade-offs of switching to green infrastructure and technology solutions that go beyond existing grey-water treatment practices.

Built off data collected at over 22,000 facilities, the report provides comprehensive baseline metrics and explores the relationship among emissions, costs and water treatment capabilities for utility operators and decision-makers.

Developing potential solutions for green wastewater infrastructure

Braden Limb, the paper's first author and a PhD student in the Department of Systems Engineering, explained: "These findings draw a line in the sand that shows the potential for adopting green wastewater approaches in this space—both in terms of money saved and total emissions reduced.

"It is a starting point to understand what routes are available to us now and how financing strategies can elevate water quality treatment from a somewhat local issue into something that is addressed globally through market incentives."

Findings centre around both point-source green wastewater treatment and non-point sources of water pollution.

Traditional point-source water treatment facilities such as sewage plants remove problem nutrients like nitrogen and phosphorus before releasing water back into circulation.

This grey infrastructure system is monitored by the Environmental Protection Agency.

However, regulation standards may tighten in the future, and facilities would need more power and more emissions to reach newly allowable thresholds.

Identifying sources of freshwater contamination

Existing facilities already account for 2% of all energy use in the US and 45 million tonnes of CO2 emissions.

Another significant source of freshwater contamination in the US comes from non-point sources, such as fertiliser runoff from agriculture entering rivers. Other non-point sources of pollution can come from wildfires—aided by climate change—or urban development, for example.

Limb said that rather than building more grey infrastructure treatment facilities to address those increasing sources, the paper explores green wastewater approaches financed through carbon markets that can tackle both types simultaneously.

He said: "There could be a switch to green wastewater solutions, such as constructing wetlands or reforestation instead of building yet another treatment facility.

"Those options could sequester over 4.2 million carbon dioxide emissions per year over a 40-year time horizon and have other complementary benefits we should be aiming for, such as cheaper overall costs."

What is carbon financing and could it be a potential solution?

Carbon financing is a mechanism aimed at mitigating climate change by incentivising activities that reduce emissions or sequester them from the atmosphere.

Companies voluntarily buy 'credits' on an open market that represent a reduction or removal of carbon from the atmosphere, which can be accomplished in various ways.

These credit offsets the institution's emissions from operations as it aims to reach sustainability goals.

These trades incentivise the development of sustainable activities and can also provide a source of fresh money to further develop or scale up new approaches, such as green wastewater facilities.

While there are similar financing markets for water, the problem is initially more localised than it is for air quality and carbon. That dynamic has limited the value of water market trades in the past.

The paper suggests that these existing markets could be improved and that the carbon markets could also be leveraged to change some of the financial incentives farmers have around water treatment and impacts from their activity.

The researchers found that using the markets could generate $679m annually in revenue, representing an opportunity to further motivate green infrastructure solutions within water quality trading programmes to meet regulated standards.

Mechanical Engineering Professor Jason Quinn, who worked on the study, said the findings have some limitations but that this was an important first step to model both the problem and opportunity available now.

He concluded: "This is the first time we are considering air and water quality simultaneously - water is local, and carbon is global.

"But by bringing these market mechanisms together we can capitalise on a window of opportunity to accelerate the improvement of America's rivers as we transition to a renewable energy and restored watershed future."