Marsh wetland at Argonne National Laboratory.

Metal for microbes: Copper reduces wetland microbes’ greenhouse gas emissions

Cows have come under attack for the global warming effect of methane in their flatulence. But some scientists are looking at the significance of microbes’ gas emissions. 

Feeding metals to aquatic microbes could prevent emissions of the harmful greenhouse gas nitrous oxide following the microbes’ digestion process, according to Washington University in St. Louis researchers.

About half of nitrous oxide, the third most potent greenhouse gas, comes from microbes in aquatic environments.

From lab to real life

Previous studies have concluded that metals, especially copper, help microbes “digest” food. Microbes naturally emit the harmless gas nitrogen during normal digestion. But if copper isn’t available during the digestion process, the microbes instead emit the greenhouse gas nitrous oxide. 

The WUSTL research team advanced previous lab work and determined that not enough copper exists in some of the microbes’ aquatic environments to support denitrification. It is called the first study to show the connection between wetlands’ natural copper content and microbes’ real-life nitrous oxide production.

“Material in a beaker is not the same as material in the environment,” Daniel Giammar, environmental engineering professor, said in a news release.

“A big part of our approach was to take real materials from real environmental systems and bring them to the lab and look at them in controlled ways.”

The scientists collected microbes from riverbeds and wetlands with the help of three national laboratories, including Illinois’ Argonne National Laboratory, and analyzed how much copper was in the ecosystems. They determined it wasn’t enough for the microbes to complete denitrification.

Mitigating metal deficiency

The team manually added copper to see if it would affect the microbes’ release of nitrous oxide, and it did. With the added copper, all the nitrous oxide was converted and not released as a greenhouse gas.

The results suggest that adding some metals to aquatic ecosystems could reduce the amount of nitrous oxide released into the atmosphere. The finding could also aid other climate scientists’ research. For example, the WUSTL researchers suggest that incorporating more real-world complexities into climate models and predictions could yield more useful results.

“Currently, models that are predicting the release of gases from various systems do not account for these factors,” said Neha Sharma, a Ph.D. student. “They know factors like food availability or temperature might affect greenhouse gas release, but they don’t include the effect of metals on this aspect of greenhouse gases.”