Can Sinking Plants Fight Climate Change?

Companies developing methods to remove atmospheric carbon dioxide are facing challenges after Microsoft, a major supporter, paused its carbon removal purchases. Microsoft had previously acquired approximately 80% of contracted carbon removal volumes, making its retrenchment a significant blow to the sector.

In a potentially hopeful development, the U.S. EPA granted a research permit in March to Carboniferous, a startup exploring ocean biomass sinking. This technique involves harvesting land plants and sinking them in the ocean to durably store carbon. The company plans to conduct experiments in the anoxic Orca Basin off Louisiana.

While the Intergovernmental Panel on Climate Change deems carbon removal necessary to meet climate goals, ocean biomass sinking faces scrutiny. Concerns include its scalability, with estimated annual storage of 0.1 to 1 gigaton of CO2 annually, falling short of the 7-9 gigatons needed by mid-century. Potential risks to ocean ecosystems, such as methane production and harm to marine life, are also significant.

Other marine carbon removal approaches are also being explored. Rewind is experimenting with burying plant matter in the Black Sea and Mediterranean, while BlueGreen Water Technologies uses hydrogen peroxide to sink harmful algal blooms, which also sequester carbon. Despite the oceans' capacity as a carbon sink, further research is crucial to address the risks associated with these methods.