Harnessing the power of the oceans to fight the climate crisis
Photo: Guss B on Unsplash
Earth Day is a time to celebrate the awe-inspiring wonders of this planet – a place full of biodiversity hotspots, from lush rainforests to scenic mountain ranges, home to rich endemic species. These pristine and ecologically unique landscapes are increasingly threatened by human-made stressors such as greenhouse gas emissions, which contribute to the adverse effects of climate change on people and the planet.
Tackling the climate crisis requires a multifaceted approach. We know we need to quickly and significantly reduce greenhouse gas emissions, including through a just transition to a renewable energy economy. We also need to better prepare for the impacts of climate change that are already happening or are expected in the future. In recent years, climate litigation has increasingly been used to pressure governments and others to reduce emissions and invest in adaptation measures (see Sabin Center climate litigation databases here). International agreements, such as the Paris Agreement, and national laws in the United States. and elsewhere, have also played an important role in driving change.
Although progress is being made, much remains to be done. The IPCC said that in addition to reducing emissions, it will also likely be necessary to extract greenhouse gases from the atmosphere to mitigate climate change. THE Sabin Center for Climate Change Lawa subsidiary of Columbia Climate Schoolexplored various ways to achieve this, including ““blue carbon” approaches. Blue carbon is carbon sequestered by ocean and coastal ecosystems. In this article, we will focus specifically on the removal and sequestration of carbon dioxide of ocean origin, also known as “ocean CDR”.
The ocean covers 70% of the Earth’s surface and is a major carbon sink. Through natural processes, the ocean has absorbed about 25% of human-produced carbon dioxide emissions to date, and could absorb even more in the future. The uptake of carbon dioxide by the ocean occurs both through biological processes – for example, via carbon sinks such as phytoplankton and whales — as well as non-biological ones.
Ocean techniques for carbon dioxide removal
An illustration of several ocean techniques for removing carbon dioxide. Artwork: Rita Erven/GEOMAR
The Sabin Center for Climate Change Law has published a series of four white papers exploring the legal issues associated with a range of strategies for removing carbon dioxide from the oceans, which are outlined below. These white papers, authored by Romany Webb, Korey Silverman-Roati and Michael Gerrard, provide the most comprehensive analysis of the legal aspects of ocean CDR. These same authors have also published a book on “Ocean Carbon Dioxide Removal for Climate Mitigation: The Legal Framework” this week. For the purposes of this article, we will provide a general overview of these techniques, as well as the potential benefits and risks associated with them.
- Artificial upwelling and downwelling: This technique involves using vertical pipes to bring nutrient-rich water up from the depths to the surface, where it could stimulate the growth of phytoplankton. Phytoplankton would absorb CO2 during photosynthesis, then pipes would send the carbon-rich water from the surface to the depths.
- Algae cultivation (also known as seaweed farming): This method involves growing or cultivating algae, also known as macroalgae, which convert dissolved carbon dioxide into organic carbon during its growth through photosynthesis. The algae can then be harvested (for example, for use as bioenergy or for low-carbon products such as algae-based packaging materials) or sunk in the deep ocean for carbon sequestration. How long can biomass be sequestered? It depends on various factors, including the location of the sinking. Biomass could potentially be sequestered for over 500 years if it sank below 1,000 meters in some parts of the ocean, but the duration would be considerably less if the biomass were sunk in shallower waters. Environmental co-benefits include lower levels of ocean acidification, among others.
- Ocean Fertilization (also known as microalgae cultivation): In this technique, iron, nitrogen, or phosphorus is released to the ocean surface to stimulate phytoplankton growth. The hope is that the phytoplankton will absorb the carbon dioxide and then die and sink, transporting the carbon they contain to the deep ocean or seafloor sediments for long-term storage. Some scientists believe the benefits could include an increase in the growth rate of fish populations due to improved phytoplankton productivity, while others fear it could lead to harmful algal blooms or it only diverts nutrients from other places.
- Improved ocean alkalinity (also known as enhanced weathering): This method involves adding crushed limestone or other alkaline rocks to ocean water. The addition triggers a series of chemical reactions that allow the ocean to absorb additional CO2 from the atmosphere. The materials needed for this method would be mined on land and then spread on beaches or added to seawater via pipelines or ships. This method has the potential to dramatically accelerate natural mineral weathering processes, which absorb CO2 but normally take thousands of years. Like growing algae, this can also lead to a decrease in ocean acidification. Potential risks include increased levels of toxic metals and other minerals with largely unknown effects on biodiversity.
The laws of the ocean
Determining how and where these techniques for removing carbon dioxide from the oceans would work best, what risks they pose, and how best to ensure protection of the ocean environment is the subject of ongoing research. Most of the techniques have yet to be tested on a large scale and require much more research before it can be decided if and how they could be used to fight climate change.
Although there are international and national laws governing ocean activities, such as the United Nations Convention on the Law of the Sea and the London Convention and Protocol, there remains a need to develop strong legal frameworks specifically tailored to research on the removal of carbon dioxide from the oceans.
With this in mind, the Sabin Center developed and recently published model legislation to advance safe and responsible ocean CDR research in the United States. According to a recent opinion piece authored by Korey Silverman-Roati and Romany Webb, the purpose of this model legislation is to facilitate safe and responsible ocean CDR research, including by “establishing a single federal agency licensing authority, designating preferred areas for CDR ocean research with simplified permits, as while calling for a balance between climate goals and environmental risks.
When developing CDR ocean research projects in the United States, high priority should be given to involving Native American tribes, states, and the public in these decision-making processes. If you want to learn more about the importance of this model legislation, join this online seminar hosted by Ocean Visions and featuring Sabin Center Deputy Director Romany Webb.
The broader question regarding these ocean-based carbon dioxide removal techniques, particularly those that use labor and cost-intensive technologies, is: can these approaches bring a significant contribution to the fight against climate change? And do the economic, social and environmental benefits and risks posed by these activities justify their use? Until we have more definitive answers to these questions, we must not lose sight of collective action to drastically reduce existing emissions.
Can we avoid the worst impacts of climate change? It depends on how quickly we act. Our Earth needs us to step up climate action now.
