Engineers seek marine areas with reduced oxygen levels as potential sites for carbon sequestration.
The idea of battling climate change by sinking plant scraps into the ocean has been a topic of discussion among scientists and entrepreneurs. A recent gathering in Bucharest explored this concept, but the current status of this method specifically in the Black Sea and Gulf of Mexico is unclear.
While some companies are developing marine carbon capture technologies, such as Calcarea's system that chemically sequesters CO2, direct sinking of organic biomass in ocean basins is not a mainstream climate solution.
The Black Sea, known for its anoxic depths devoid of oxygen and saturated with hydrogen sulphide, has attracted interest due to its potential to slow the decomposition of organic carbon and preserve it for longer periods. However, large-scale sinking of biomass could disrupt marine ecosystems, cause oxygen depletion, release methane, and increase nutrient loading, resulting in unintended negative effects like harmful algal blooms or dead zones.
Similarly, the Gulf of Mexico experiences seasonal hypoxia, and sinking plant scraps could worsen these conditions if not carefully managed.
Recent developments in this area include applications for permits. Rewind, a company planning to drop crop waste 2 kilometres into the Black Sea, has applied for a permit for a 100-tonne trial in Romania. Carboniferous, another company looking to sink agricultural waste, has targeted the Orca Basin in the Gulf of Mexico for a trial depositing 20 tonnes of biomass.
Critics argue that the crop residues could be better used to return nutrients to soils on land. The microbiomes in the Black Sea are thought to be vulnerable to catastrophic events such as the sinking of biomass, according to some researchers.
The Intergovernmental Panel on Climate Change concluded in 2022 that carbon dioxide removal is "unavoidable" for achieving net-zero CO2 or GHG emissions. However, the effectiveness of methods like biomass sinking under a full life cycle analysis is questioned, and more research and regulatory evaluation are likely needed before such strategies could be adopted widely.
The ocean absorbs about 90% of the excess heat produced by human activities, but the long-term impacts of sinking plant scraps for carbon sequestration are still uncertain. As the debate continues, it is essential to consider the potential risks and benefits carefully and approach this innovative solution with a precautionary approach.
[1] Calcarea, the company developing the CO2 capture technology, has not been involved in sinking organic biomass in ocean basins. [2] Puro.earth, a company looking at certifying carbon directly captured from the air and stored in the ocean, unveiled its methodology for carbon removal via "ocean storage of biomass" in January. However, concerns have been raised about the 1,000-year time frame for locking up carbon and the suggested monitoring period of only 15 years after deposition. [3] James Kerry, of the marine conservation NGO OceanCare, has called for a precautionary approach to all marine carbon dioxide removal efforts.
- Battling climate change through sinking plant scraps in the ocean, like the proposed trials in the Black Sea by Rewind and in the Gulf of Mexico by Carboniferous, has raised concerns among environmental scientists due to potential disruptions of marine ecosystems, oxygen depletion, methane release, and increased nutrient loading.
- The use of carbon dioxide removal strategies, such as biomass sinking, is considered necessary for achieving net-zero CO2 or GHG emissions according to the Intergovernmental Panel on Climate Change, but its effectiveness under a full life cycle analysis and long-term impacts are still uncertain.
- Companies developing marine carbon capture technologies, like Calcarea, are focusing on methods other than direct sinking of organic biomass, such as chemically sequestering CO2.
- The topic of marine carbon capture and storage is veiled in controversy, with marine conservation NGOs like OceanCare advocating for a precautionary approach to all efforts involving ocean carbon dioxide removal, such as the proposed biomass sinking trials in the Black Sea and Gulf of Mexico.
