Why it Works

If we take mature forest biomass and bury it in a repository, we can arrest the decomposition process. Then as the forest regrows, it will continue to capture more carbon. The result? Less CO2 in the atmosphere and more sequestered. The decomposition of biomass can be arrested by storing it in a dry condition, or in a submersed condition. If you’ve ever seen the show Swamp Loggers, logs and trees submerged in water can be retrieved over a hundred years later with little show of decomposition. Maintained in the right conditions, wood can be preserved nearly indefinitely. Recently, a well-preserved 40,000-year-old log was unearthed in New Zealand*.

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AVOIDING METHANOGENESIS

The effectiveness of any biomass repository in mitigating the greenhouse effect relies upon avoiding methanogenesis, the process by which microbes known as archaea convert biological materials into methane*. Methane, sometimes referred to as swamp gas, is a more potent greenhouse gas than CO2.

Methanogenesis can be inhibited in several ways. One is the addition of compounds known as methane inhibitors**. Another is the use of probiotics that alter the ratio of archaea to other microbes. A third is oxygenation, as methanogenesis occurs in anaerobic environments*. Research also suggests that the presence of tannins**** inhibits methanogenesis. Methane emissions can also be avoided by using biosolids as a cap material***, which allows other bacteria to convert methane into less harmful CO2. Or, methane can be captured and used for the production of energy*****, which nonetheless results in some level of CO2 emissions. The solution to controlling methanogenesis and emissions at the Mid Coast Carbon Repository will likely involve using several of these methods, in concert. For example, the circulation of oxygenated water, or the addition of ozone, plus a careful measurement of water chemistry and selective use of methanogenesis inhibitors, as well as a capture system.

*https://en.wikipedia.org/wiki/Methanogen **https://www.sciencedirect.com/science/article/pii/S0160412019307135 23 *** https://link.springer.com/chapter/10.1007/978-1-4613-0405-0_9 ****https://www.mdpi.com/2076-2615/9/11/856/pdf#:~:text=Tannins%20may%20also%20play%20a,%2C%20subunit%2C%20MW%20and%20dose. ***** https://www.americanprogress.org/issues/green/news/2014/04/16/88084/next-steps-to-reduce-methane-emissions-from-landfills/