Research gives clues to CO2 trapping underground

CO2 is an environmentally important gas that plays a crucial role in climate change.

It is a compound that is also present in the depth of the Earth but very little information about it is available. What happens to CO2 in the Earth’s mantle? Could it be eventually hosted underground? A new publication in Nature Communications unveils some key findings.

Carbon dioxide is a widespread simple molecule in the Universe. In spite of its simplicity, it has a very complex phase diagram, forming both amorphous and crystalline phases above the pressure of 40 GPa. In the depths of the Earth, CO2 does not appear as we know it in everyday life. Instead of being a gas consisting of molecules, it has a polymeric solid form that structurally resembles quartz (a main mineral of sand) due to the pressure it sustains, which is a million times bigger than that at the surface of the Earth.

Researchers have been long studying what happens to carbonates at high temperature and high pressure, the same conditions as deep inside the Earth. Until now, the majority of experiments had shown that CO2 decomposes, with the formation of diamond and oxygen. These studies were all focused on CO2 at the upper mantle, with a 70 GPa of pressure and 1800-2800 Kelvin of temperature.

>Read more on the European Synchrotron (ESRF) website

Picture: Mohamed Mezouar, scientist in charge of ID27, on the beamline.
Credit: S. Candé. 

One size does not fit all when exploring how carbon in soil affects the climate

Scientists from Stanford University are opening a window into soil organic carbon, a critical component of the global carbon cycle and climate change.

“We have to know what kind of carbon is in soil in order to understand where the carbon comes from and where it will go,” said Hsiao-Tieh Hsu, a PhD student in chemistry at Stanford University and a member of a Kate Maher’s research group.

The natural fluxes of soil organic carbon, the exchange of carbon moving from vegetation to the soil and recycled by microorganisms before being stabilized in the soil or returned to the atmosphere, is 10 to 20 times higher than human emissions. Even the smallest change in the flux of soil organic carbon would have a huge impact on the climate.

Soil organic carbon occurs naturally and is part of the carbon cycle. Through photosynthesis, plants absorb carbon dioxide from the atmosphere. As plants and their roots decompose, they deposit organic carbon in the soil. Microorganisms, decomposing animals, animal feces and minerals also contribute to the organic carbon in the soil. In turn, plants and microorganisms “eat” that carbon, which is an essential nutrient.

All of this results in different “flavours” or compounds within the soil, say Hsu and Maher, who is also a faculty member of the Stanford Center for Carbon Storage.

>Read more on the Canadian Light Source website

Image: Members of the research team at the East River, Colorado, field site (left to right): Hsiao-Tieh Hsu; Grace Rainaldi, Stanford undergraduate; Corey Lawrence, research geologist at United States Geological Survey; Kate Maher; Matthew Winnick, Stanford postdoctoral fellow.
Credit: Kate Maher.