Feeding metals to microbes could reduce greenhouse gases, says study

According to researchers, providing copper for microbes to feed off can reduce the release of the greenhouse gas nitrous oxide.

All microbes need metals in their diet to help ‘digest’ their food, through which they gain energy and release the harmless by-product of nitrogen.

But scientists from Washington University in St. Louis have discovered not enough copper is present in the aquatic environments these microbes live in.

This means they can’t complete the ‘digestive’ process, known as denitrification, causing them to release 50% of nitrous oxide emissions.

While previous studies have highlighted the importance if copper for denitrification, this study has investigated levels of copper in wetlands and riverbeds.

‘Material in a beaker is not the same as material in the environment,’ said Daniel Giammar, Professor of Environmental Engineering at the McKelvey School of Engineering. ‘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.’

Giammar, alongside PhD student Neha Sharma and senior scientist Elaine Flynn, tested whether adding copper to these ecosystems would affect the release of nitrous oxide.

They found that the nitrous oxide was converted into different things, but none of them were harmful greenhouse gases.

‘If we put a bit of metals into the natural systems, it might mitigate the release of N2O,’ said Sharma, highlighting the importance of the research. ‘Currently, models that are predicting the release of gases from various systems do not account for these factors.

‘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.’

Sharma collaborated on another study published in May with PhD student Zixuan Wang and professor of energy, environmental and chemical engineering Zhen ‘Jason’ He.

They analysed the behaviours of four different metals, found in wetland soils and stream sediments from the Savannah River Site, to see if their availability changed when the metals were underwater compared to when they were exposed to air.

While they expected the metals to act similarly, each metal has a different reaction in similar situations.

‘This means the bioavailability of certain metals changes with seasons,’ Sharma said. ‘It just highlights the extreme complexity of natural systems.’

Photo by Elaine Flynn