Introduction

The question of whether discarded dead trees can be used as a method for carbon sequestration by burying them in the ocean is a topic of growing interest. This method, often proposed to offset carbon emissions, has raised questions about its effectiveness and environmental impact. In this article, we will explore whether dead trees placed in the ocean can truly sequester carbon or if the released carbon might still enter the atmosphere and the ocean.

Dead Trees in the Ocean

Dead trees, when deposited into the ocean, will typically float due to the natural buoyancy of wood. As they float, these tree parts are exposed to the oxygen in the air. There are two primary outcomes for these floating tree parts:

Degradation by Aerobic Bacteria

Aerobic bacteria present in the air might break down the wood. This process leads to the production of carbon dioxide (CO2), contributing to atmospheric carbon levels. Consequently, the carbon stored in the dead trees is not sequestered but rather released back into the environment.

Shipping to Beaches

Another scenario is that the floating tree parts might be carried by the ocean currents and eventually end up on a beach. Here, if the tree parts are not removed, they might be referred to as “driftwood” and may even be installed as a work of art. In such cases, the wood is still exposed to air and the sun, accelerating its decomposition and carbon release.

Decay and Carbon Sequestration

The key factor in whether the carbon in dead trees remains sequestered or is released back into the environment is the fate of the wood. When trees are not exposed to oxygen, they can remain sequestered in sediment for a longer period. However, if the wood comes into contact with air, the process of decay and the subsequent release of carbon become inevitable.

Case Study: Pacific Northwest

Observations from the Pacific Northwest provide insights into the long-term retention of carbon in wood. Centuries-old trees that were part of logging operations are still found in muddy areas at low tide. These trees are sequestered as long as they do not rot at the surface. Once decomposition sets in, the carbon-rich wood begins to release CO2 into the environment.

Effectiveness of Ocean Sequestration

The idea of sequestering carbon by burying dead trees in the ocean is inherently limited by the nature of wood. Only a small portion of the carbon in the trees would end up sequestered. The vast majority of wood, once exposed to air, floats and decomposes, either releasing CO2 back into the atmosphere or washing up on beaches as flotsam.

Carbon Sequestration through Shellfish

One unique pathway for carbon sequestration involves carbon from trees ending up in the shells of shellfish via the formation of mineral carbonates. However, this process is highly inefficient and results in a vanishingly small percentage of the overall carbon stored in the trees.

Alternative Approaches

Given the limitations of ocean sequestration, alternative methods for carbon sequestration through discarded biomass should be explored. For instance, using biomass in bioenergy with carbon capture and storage (BECCS) could provide a more sustainable and effective method to reduce atmospheric CO2 levels.

Conclusion

In conclusion, while the idea of sequestering carbon by burying dead trees in the ocean sounds promising, the reality is more complex. The carbon in these trees is far more likely to be released back into the environment through the processes of decomposition and oxidation. Therefore, alternative strategies such as bioenergy with carbon capture and storage offer a more effective and sustainable approach to carbon sequestration.