You are here

Learning How to Release the Smallest Amount of Greenhouse Gas While Storing the Most Carbon in the Delta

April 2014

For Gavin McNicol, a Ph.D. candidate at UC Berkeley who is supported by the Sea Grant Delta Science Fellows Program, research means sloshing around in the Delta’s muddy waters, enduring some rather noxious fumes, and studying the formation of bubbles.

Actually, he’s doing research in some restored wetlands on Sherman Island (muddy waters) on the natural formation of methane and carbon dioxide (noxious fumes) and how methane releases itself when reaching very high concentrations (bubbles).

Ultimately, the 25-year-old Scottish native hopes the research will lead to ways of controlling the amount of methane emitted into the air because it is a potent greenhouse gas, while at the same time maximizing the sequestration of carbon molecules from the atmosphere into the Delta’s peat soil. Balancing these natural reactions could allow the Delta to become self-sustaining in the developing carbon reduction marketplace.

“[Conventional wisdom] had soils under flooded conditions in the wetlands producing a certain ratio of methane to carbon dioxide,” said McNicol. “[Our research found] the chemistry of the water and the availability of carbon can influence that ratio, which suggests that certain management of the water chemistry and certain features of wetland structure might play a role in lowering methane emissions from these systems.”

McNicol’s research began in the spring of last year with the collection of soil samples from three different wetland areas that varied in land use history and soil types. His discoveries not only piqued his interest, it also accelerated his movement forward.

“We saw there was a lot of variability [in the soil samples],” said McNicol. “This challenged the idea that wetland soils are just black boxes of methane production – and we thought it was worth trying to understand what drives those differences.”

Another aspect of his study is learning how methane is produced in the first place. This includes researching the ebullition (bubbling up) of the greenhouse gas. This process of the gas boiling up to the surface is what creates the bubbling effect as the soluble methane is rapidly transported from the wetland sediments and released into the atmosphere.

“When methane is produced in large quantities in the sediment it has a tendency to form bubbles because the gas is under very high pressure,” said McNicol. “When you get the right conditions (the end result) is often a very sudden and a very high concentration of methane, which can potentially add up to quite a lot of methane being released over a short period.”

One goal of his research is to learn the relative amount of methane being released during an ebullition event and what regulates the timing of those events. He believes the answers will allow him to restrict the ebullition process so that smaller amounts of the greenhouse gas are generated and released into the atmosphere.

“In these flooded wetland systems we have methane being released by diffusion, and being released from the plants themselves,” said McNicol. “Understanding the trade-offs from having either more open water cover or more vegetation cover will allow us to ultimately better regulate methane release.”

McNicol will provide his findings in a paper he expects will eventually be published in a peer-reviewed journal. The material he hopes will allow decision-makers to make more informed choices about the types of habitat restoration projects to pursue.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)