Wastewater process cleans up C02

The new treatment method, known as Microbial Electrolytic Carbon Capture (MECC), purifies wastewater with an electrochemical reaction that absorbs more CO2 than it releases.

According to the University researchers, MECC uses the natural conductivity of saline wastewater as the basis of an electrochemical reaction that absorbs CO2 from both the water and the air. 

The results should be viewed as a proof-of-concept with promising implications for a wide range of industries

Professor Zhiyong Jason Ren

This turns CO2 into stable mineral carbonates and bicarbonates that can be used as a chemical buffer in the wastewater treatment cycle.

The reaction also yields excess hydrogen gas, which could be stored and harnessed as energy in a fuel cell, the researchers said.

Current wastewater treatment methods produce CO2 emissions through both the burning of fossil fuels to power the machinery, and the decomposition of organic material within the wastewater itself.  Deployment of treatment technologies also consumes high amounts of grid energy.

“This energy-positive, carbon-negative method could potentially contain huge benefits for a number of emission-heavy industries,” said Zhiyong Jason Ren, an associate professor of civil, environmental, and architectural engineering at CU-Boulder.

This is because carbon capture technologies are both energy-intensive and logistically demanding in terms of transportation and storage requirements.

Many wastewater treatment plants are located on coastlines, which also raises the possibility that MECC implementations could provide CO2 and ocean acidity mitigation.

However, further research is needed to “determine the optimal MECC system design and assess the potential for scalability,” said Ren.

“The results should be viewed as a proof-of-concept with promising implications for a wide range of industries.”

Results of the study have been published in Environmental Science and Technology.