The Excerpt: Can We Give the Ocean an Antacid to Combat Climate Change?
Introduction
In a special episode of "The Excerpt" podcast, released on March 6, 2025, Dana Taylor delves into the intriguing possibility of mitigating climate change through a method known as ocean alkalinity enhancement. This approach, likened to giving the ocean an antacid, involves altering the ocean’s chemistry to increase its capacity to absorb carbon dioxide from the atmosphere. While researchers have been exploring this concept for several years, it has only recently begun to move from theory to tangible reality. The podcast features Jaime Palter, an associate professor of oceanography at the University of Rhode Island, who provides valuable insights into the science, potential, and challenges associated with this innovative climate intervention strategy.
The Science of Ocean Alkalinity Enhancement
The podcast begins by establishing the fundamental role of the ocean as a natural carbon sink. Palter explains that the ocean inherently absorbs carbon dioxide from the atmosphere, striving to maintain equilibrium with atmospheric carbon dioxide concentrations. This natural process has allowed the ocean to absorb approximately 25% of human-caused emissions. Ocean alkalinity enhancement aims to accelerate this natural absorption rate by manipulating the chemistry of the surface ocean. By increasing the ocean’s alkalinity, its capacity to absorb and store carbon dioxide is enhanced beyond its natural capabilities.
Ocean Alkalinity Enhancement vs. Carbon Capture and Storage
A key distinction is drawn between ocean alkalinity enhancement and carbon capture and storage (CCS). Traditional CCS methods involve capturing carbon dioxide emissions from point sources like power plants or cement factories and storing it underground. While CCS prevents carbon dioxide from entering the atmosphere in the first place, it does not actively remove existing carbon dioxide. Ocean alkalinity enhancement, on the other hand, targets carbon dioxide already present in the atmosphere, effectively reversing the effects of emissions. The ocean stores the absorbed carbon dioxide as bicarbonate or carbonate, forms of salt already abundant in the ocean. Palter highlights that the ocean’s natural background state already holds 50 times more carbon than the atmosphere, primarily in the form of bicarbonate and carbonate. Therefore, even a small increase in the ocean’s carbon storage capacity can have a significant impact on atmospheric carbon dioxide levels.
Potential Impacts on Marine Ecosystems
A crucial consideration is the potential impact of ocean alkalinity enhancement on marine ecosystems, particularly sensitive environments like coral reefs. Palter emphasizes that this is an ongoing area of research and that the oceanographic community is deeply invested in ensuring the safety of this intervention. Concerns arise from the fact that the ocean is already undergoing acidification due to the absorption of carbon dioxide, which can be detrimental to marine life. However, increasing alkalinity is the opposite of acidification and could potentially reverse some of these harmful effects. By increasing the ocean’s ability to absorb carbon dioxide, the goal is to return it to a chemical equilibrium closer to its original state.
Scientists are employing rigorous testing methods to assess the potential ecological impacts. Mesocosm experiments, involving mid-scale tanks filled with natural seawater and its inhabitants, are used to observe the effects of adding varying doses of alkaline substances. These experiments allow researchers to carefully monitor the biological responses and identify any potential harms. The results are being published transparently, and so far, studies suggest that pure alkalinity is linked to minimal biological harm. Some alkaline sources may be less suitable than others, underscoring the importance of careful selection and testing.
Challenges and Risks of Large-Scale Implementation
Palter acknowledges the inherent risks of providing a false sense of security. She emphasizes that ocean alkalinity enhancement, or any carbon dioxide removal approach, can only be effective if emissions are drastically reduced. Currently, humans emit approximately 40 billion tons of carbon dioxide annually, a figure far exceeding the capacity of any removal process. Therefore, reducing emissions by 50-80% is crucial for carbon dioxide removal technologies to make a meaningful difference.
The potential harm to the ocean at a large scale is a primary concern. Extensive research efforts are underway to evaluate the potential ecological consequences with complete transparency. Initial findings suggest that harm can be avoided if the right alkalinity sources are used without disrupting biological systems.
Logistical challenges also exist in distributing alkaline substances throughout the ocean. Current deployment efforts are at a research scale, limited to small-scale field trials. One innovative approach involves using pure magnesium hydroxide in the cooling waters of a power plant, leveraging existing infrastructure and social acceptance. Scaling up this approach could involve utilizing cooling waters from numerous power plants or wastewater from sewage treatment facilities, targeting areas that are already subject to human manipulation.
Economic Considerations
Palter notes that the costs associated with ocean alkalinity enhancement appear competitive with, or even lower than, other carbon removal solutions like direct air capture (DAC). DAC is incredibly energy-intensive, requiring significant resources to power the machinery that extracts carbon dioxide from the atmosphere. In contrast, the primary costs of ocean alkalinity enhancement lie in sourcing alkaline materials and ensuring their dissolution in the ocean, potentially making it a more affordable option.
Community Concerns and Scientific Responses
Public perception and acceptance are crucial factors in the viability of ocean alkalinity enhancement. Many view the ocean as a pristine environment and are concerned about any intervention that could potentially disrupt its delicate balance. Scientists are addressing these concerns by proceeding cautiously and prioritizing controlled experiments, starting in laboratories and then progressing to mesocosms and small-scale field trials. Transparency and open communication are essential in building trust and ensuring that stakeholders are informed about the potential risks and benefits.
Future Directions
Research and development efforts are proceeding along multiple pathways simultaneously. Biologists are continuing to conduct mesocosm tests to assess biological safety, while a handful of field trials are underway to evaluate the effectiveness of deploying alkalinity sources in real-world conditions. The long-term goal is to scale up the technology to a level that can have a meaningful impact on the climate. However, it remains uncertain when widespread application of ocean alkalinity enhancement might become a reality.
Alternative Technologies
When asked about other promising carbon removal technologies, Palter identifies enhanced rock weathering as a potential alternative, this involves reacting alkaline substances with CO2 and creating stable bicarbonates, as a viable approach. Both ocean alkalinity enhancement and enhanced rock weathering share the same fundamental principle: removing carbon dioxide from the atmosphere through a chemical reaction with an alkaline substance, creating stable bicarbonate and carbonate that can be stored for thousands of years. While other carbon removal ideas exist, Palter believes these two approaches are the most promising due to their scalability, cost-effectiveness, and potential safety.
Conclusion
Ocean alkalinity enhancement presents a novel and potentially promising strategy for mitigating climate change. While challenges and risks remain, ongoing research and development efforts are focused on ensuring the safety, effectiveness, and scalability of this technology. Transparency, open communication, and community engagement will be critical in determining whether this approach can play a significant role in addressing the global climate crisis. The conversation around climate change solutions necessitates exploring innovative approaches like ocean alkalinity enhancement, acknowledging both their potential and the necessary precautions to safeguard the environment.
