Key to speeding up carbon sequestration in the ocean discovered

Scientists at Caltech and USC have discovered a way to speed up the slow part of the chemical reaction that ultimately helps the earth to safely lock away, or sequester, carbon dioxide into the ocean. Simply adding a common enzyme to the mix, the researchers have found, can make that rate-limiting part of the process go 500 times faster.

On paper, the reaction is fairly straightforward: Water plus carbon dioxide plus calcium carbonate equals dissolved calcium and bicarbonate ions in water. In practice, it is complex. “Somehow, calcium carbonate decides to spontaneously slice itself in half. But what is the actual chemical path that reaction takes?” Adkins says.

Studying the process with a secondary ion mass spectrometer (which analyzes the surface of a solid by bombarding it with a beam of ions) and a cavity ringdown spectrometer (which analyzes the 13C/12C ratio in solution), Subhas discovered that the slow part of the reaction is the conversion of carbon dioxide and water to carbonic acid.

“This reaction has been overlooked,” Subhas says. “The slow step is making and breaking carbon-oxygen bonds. They don’t like to break; they’re stable forms.”

Armed with this knowledge, the team added the enzyme carbonic anhydrase — which helps maintain the pH balance of blood in humans and other animals — and were able to speed up the reaction by orders of magnitude.

Key to speeding up carbon sequestration discovered | EurekAlert! Science News

That makes me wonder about the chemical limitation of carbon sequestration in soils.

Leaf particles cause nitrous oxide hotspots in large pore soils

“The leaf particles act as tiny sponges in soil, soaking up water from large pores to create a micro-habitat perfect for the bacteria that produce nitrous oxide.”

Not as much N2O is produced in areas where smaller pores are present. Small pores, such as in clay soils, hold water more tightly so that it can’t be soaked up by the leaf particles. Without additional moisture, the bacteria aren’t able to produce as much nitrous oxide. Small pores also make it harder for the gas produced to leave the soil before being consumed by other bacteria.

Every time you till, what are you creating? Large pores.

Decomposing leaves are a surprising source of greenhouse gases | MSUToday | Michigan State University

Why microbes sometimes fail to break down organic carbon in soils

A new study has found that:

In oxygen-starved places such as marshes and in floodplains, microorganisms do not equally break down all of the available organic matter. Instead, carbon compounds that do not provide enough energy to be worthwhile for microorganisms to degrade end up accumulating. This passed-over carbon, however, does not necessarily stay locked away below ground in the long run. Being water soluble, the carbon can seep into nearby oxygen-rich waterways, where microbes readily consume it.

Tests found that, in contrast to the layers where oxygen was available, leftover carbon compounds in the sediment samples where sulfur had been used for respiration instead of oxygen were mostly of the sort that requires more energy to degrade than would be liberated through the degradation itself. Making these carbon compounds of no use, then, to growing microbes, and had remained within the deeper sediment layers.

Shunned by microbes, organic carbon can resist breakdown in underground environments, Stanford scientists say | Stanford School of Earth, Energy & Environmental Sciences

New nitrogen cycle pathway bypasses the greenhouse gas N2O

Nitrous Oxiden_bypass_900

Nitrous oxide is 300 times more effective at trapping heat than carbon dioxide and 10 times more effective than methane. Nitrous oxide also moves into the stratosphere and destroys ozone. Now a new pathway in the nitrogen cycle has been discovered that avoids nitrous oxide production.

Virginia Institute of Marine Science – Researchers discover greenhouse bypass for nitrogen