Sea change: The engineering challenges of harnessing our oceans to remove CO2

Ocean CO2 removal expert Dr Sifang Chen discusses the challenges of carbon dioxide removal (CDR) and the emerging technologies that could help us harness the power of our sea to fight climate change.
Sade Agard
The ocean is our largest carbon sink, but are the risks worth it?
The ocean is our largest carbon sink, but are the risks worth it?

Philip Thurston/Courtesy of Dr. Sifang Chen 

  • With the capacity to absorb approximately 31 percent of human-created carbon dioxide, the oceans offer a natural solution for reducing greenhouse gas levels.
  • Ocean-based carbon dioxide removal (CDR) approaches (both biological and chemical), are being researched to enhance the ocean's ability to absorb CO2.
  • Implementing these technologies at scale requires addressing challenges and a phased approach.

With carbon dioxide levels continuing to rise in Earth's atmosphere, scientists and engineers worldwide have been tirelessly searching for efficient methods to remove greenhouse gas. Amid these efforts, one natural ecosystem emerges as a potentially critical player: our vast oceans.

Functioning as essentially giant carbon sponges, the oceans have the estimated capacity to absorb approximately 31 percent of the carbon dioxide created by humans when burning fossil fuels (oil, coal, and natural gas).

The oceans already hold more carbon than any other part of Earth's biosphere. They have the potential to contain even more, although this task must be undertaken without causing additional harm to the marine ecosystem.

In this context, a number of ocean-based carbon dioxide removal (CDR) approaches are being studied. Each approach requires additional research and testing, especially to measure their impact on the ocean environment.

To grasp the current landscape in terms of the risks, challenges, and crucial steps necessary to implement ocean CDR technologies to harness the immense power of our oceans as catalysts for global change, Interesting Engineering (IE) interviewed an expert in this domain — Dr Sifang Chen of climate NGO Carbon180

The following Q&A session has been slightly edited for flow.

Could you shed light on some of the types of ocean CDR solutions available?

Ocean carbon removal (CDR) refers to a portfolio of approaches, both biological and chemical, that amplify the ocean's uptake of carbon dioxide. 

By removing CO2 from seawater, these approaches cause the ocean to soak up more CO2 from the atmosphere. 

Ocean CDR methods range anywhere from biological methods like ocean fertilization or macroalgae cultivation that sinks phytoplankton biomass or seaweed to the deep ocean – all the way to chemical solutions like ocean alkalinity enhancement that distributes alkaline minerals in the ocean. 

Sea change: The engineering challenges of harnessing our oceans to remove CO2
Ocean carbon dioxide removal methods

The graphic (above) gives a good visual overview of all types of solutions available. Still, to deploy these solutions at scale tomorrow– we must begin filling current knowledge gaps today.

What are the potential risks associated with large-scale ocean carbon dioxide removal technologies?

There are still foundational scientific knowledge gaps we need to address about ocean CDR. The ocean is a vast and complex system that already plays a natural role in the carbon cycle.

However, if we aggressively develop and deploy ocean CDR, there may be unintended consequences for our ocean ecosystems. This raises important questions about governance and the long-term benefits and risks of ocean carbon removal.

The ocean represents over 95 percent of the Earth's biosphere and is home to 78 percent of animals on the planet. Billions of people live near coastal regions, and millions depend on the ocean for their livelihood. 

Without more research and a phased approach to deployment, ocean CDR may add disturbances to both the marine ecosystem and our coastal communities.

Today, ocean carbon removal faces four significant challenges: insufficient governance, a small knowledge base, underdeveloped monitoring and verification processes, and uncertain environmental and social impacts. 

These four interrelated challenges must be addressed to lower uncertainties around ocean carbon removal and unlock shared opportunities.

So, imagine this – If we do not have controlled field tests and low funding, a lack of research will ultimately impede our understanding of ocean CDR's efficacy and its social/environmental implications. 

If we do not have existing governance and regulations and companies still proceed with deployment, this could potentially aggregate climate injustices in Black, Indigenous, and BIPOC coastal communities that are already historically disadvantaged. 

Without robust and community-vetted accountability to hold developers accountable, we risk contributing to carbon credit schemes that allow continued pollution in historically disadvantaged communities and ecosystems.

However, if we move forward with well-researched, intentional, and phased approaches, we can effectively redress the harms of the past while also generating new benefits.

Is any research being conducted to address the potential risks of carbon dioxide removal technologies? 

To minimize risks from ocean carbon removal, it's crucial to answer questions about the efficacy, safety, and impacts of these technologies. 

While there's some research on modeling the effects of certain carbon removal methods on the ocean, much more must be done to advance our understanding of how ocean carbon removal will impact marine chemistry, marine ecosystems, and coastal communities.

Carbon180 released its first-ever whitepaper on ocean CDR, exploring how policy can help lower existing uncertainties around ocean carbon removal and offering specific recommendations aimed at clarifying efficacy, ecosystem impacts, and necessary regulations and governance.

One of our key recommendations in the paper is to develop and fund targeted research programs to advance scientific understanding and increase the technology readiness levels of ocean carbon removal.

The National Oceanic and Atmospheric Administration (NOAA) is also a nexus for US ocean research. NOAA is equipped with a wealth of knowledge and expertise in ocean biogeochemistry and observation.

Likewise, the Advanced Research Projects Agency–Energy (ARPA-E) has its existing MARINER and direct ocean capture programs in place.

Formalizing frameworks for responsible innovation will also minimize potential harm from ocean carbon removal. The American Geophysical Union (AGU) is working on an ethical framework for climate intervention research, including ocean carbon removal research. The Aspen Institute published a report on guidance to develop a code of conduct for ocean CDR.

But for these frameworks to be effective, appropriate mechanisms for management need to be developed and put into place.

How can the risks be mitigated and managed effectively?

To carry out ocean carbon removal and safeguard the ocean from unintended risks, ocean CDR should proceed with a phased approach:

1. Develop appropriate permitting and oversight mechanisms to allow controlled field trials of ocean carbon removal research projects to take place, with guidelines to ensure open, transparent scientific monitoring of project performance.

2. Improve global governance of ocean carbon removal.

3. Develop and fund targeted research programs to advance scientific understanding and increase the technology readiness levels of ocean carbon removal.

4. Fund the development of key enabling technologies for ocean observation and ocean carbon removal MRV.

5. Establish an interagency group to assess the climate, environmental, and social benefits of ocean carbon removal and align ocean carbon removal with broader climate goals.

6. Create a framework for incorporating environmental and climate justice into ocean carbon removal projects and establish best practices for community engagement and public education.

Overall, in order to avoid damaging the very system we are trying to protect and leverage, it is imperative that we minimize uncertainties around the effectiveness, community, and ecosystem impacts, and governance of ocean carbon removal. 

Only by doing these, can we make informed decisions on the next steps for responsibly developing this field.

Are there any regulations currently in place to ensure the safe implementation of ocean carbon dioxide removal technologies?

Today, policy and governance for ocean carbon removal are lagging behind the pace of innovation. But this does not have to be the case. 

Sea change: The engineering challenges of harnessing our oceans to remove CO2
Effective implementation of CDR technologies will need to take into account potential impacts on coastal communites, marine chemistry and marine ecosystems.

Developing the right frameworks should be an iterative process where regulatory policies are being updated in a timely way and always informed by the best available science. 

As we learn more about the efficacy and impacts of ocean CDR technologies, what constitutes appropriate regulations and guardrails may evolve over time.

Currently, a key governance issue is to clarify permitting around ocean CDR field tests. This will allow researchers to collect vital data about the efficacy, safety, and impact of different ocean CDR methods. In turn, this data will help inform policy designs and governance for the next phase of ocean CDR scale-up.

In the future, if society decides to greenlight deployment, the key governance issues may look quite different.

In our whitepaper, we outline the importance of robust federal policy support to establish governance and regulatory frameworks that allow controlled field trials of ocean CDR projects.

The federal policy will also play a massive role in increasing the technology readiness levels of ocean CDR and advancing the development of key enabling technologies for ocean observation and ocean carbon removal MRV. 

The policy will also ensure that ocean CDR is developed in line with national, state, and local climate action plans and created with a framework for incorporating environmental and climate justice into ocean CDR projects.

All in all, robust policies and regulations can allow the industry to enable timely research and development for ocean CDR. It would also support the development of ocean CDR technologies under a framework of responsible innovation and equitable distribution of benefits.

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