By Emily Vidovich. Emily has a background in environmental journalism and sustainability and is a member of the George Washington University Class of 2019.

Since the day in 1988 when a NASA scientist testified to the U.S. Senate about the certainty of anthropogenic climate change, the global response to the climate crisis can be represented by various points on a Venn diagram of denial, indifference, and insufficient action. Only over the past few years has the impetus to address the crisis begun to match the severity of the challenge. Currently, 38 countries—including the member states of the European Union and the United Kingdom as well as New Zealand and Japan—have declared a climate emergency, encouraging their governments to take comprehensive action as they would with any other state of emergency. 

Treating climate change as an emergency is a critical step in the response, because lackluster effort over the preceding three decades and slow movement towards fulfilling the commitments of the Paris Agreement mean that it is time to enter triage mode—it is no longer enough to stop emitting greenhouse gases, we must also draw down past emissions.

Reabsorbing past emissions from the atmosphere is known as carbon sequestration, and it has become a necessary component of the climate response. According to the Center for Climate and Energy Solutions, “More than half of the models cited in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report required carbon capture for a goal of staying within 2 degrees Celsius of warming from pre-industrial days.” To limit global warming to 1.5 degrees Celsius, one trillion tons of carbon dioxide (CO2) emissions must be removed from the atmosphere this century. 

The ocean is our planet’s largest carbon reservoir, capable of containing a larger quantity of carbon than the biosphere and the atmosphere combined. Natural oceanic carbon capture occurs through photosynthesis and chemical reactions. Scientists have started to harness these natural processes to create effective carbon sequestration technology. At the Ocean Visions Summit, held virtually in May of this year, experts discussed two key developments in oceanic carbon sequestration technology—algae farming and artificial ocean alkalinization.

Through the process of photosynthesis, algae captures and stores carbon. When algae is grown in bioreactors that use artificial intelligence to optimize growing conditions, it can remove carbon from the atmosphere 400 times more effectively than a tree. Algal carbon sequestration is particularly promising because it results in value-added products—algae can be used as a food source for humans as well as nourish livestock in both land-based farming and aquaculture. It can also be incorporated into products such as cosmetics and pharmaceuticals, and be converted into biofuels that produce 50 to 70 percent less life cycle CO2 emissions than fossil fuels. Due to its effectiveness and co-benefits, scaling up algae farming will be critical to the climate response over the coming decades.

Artificial ocean alkalinization increases the ocean’s ability to absorb carbon by adding alkaline substances, such as naturally occurring minerals or artificially produced lime, to the ocean. This can be done by spreading small particles of alkaline substances over the open ocean or depositing alkaline sand and pebbles onto the coastline or coastal seabeds. As the Center for Carbon Removal Law & Policy at American University explains, “adding alkalinity to the ocean removes CO2 from the atmosphere through a series of reactions that convert dissolved CO2 into stable bicarbonate and carbonate molecules, which in turn causes the ocean to absorb more CO2 from the air to restore equilibrium.”

Adding alkaline sand and rocks to the coast would increase the ocean’s pH, and as such make it able to capture more carbon from the atmosphere. Photo by Matt Bango on StockSnap.

This strategy has the significant co-benefit of counteracting ocean acidification, which is the decrease of the ocean’s pH as seawater absorbs the CO2 emitted from burning fossil fuels. The ocean has become 30 percent more acidic since the beginning of the industrial revolution, negatively impacting marine ecosystems and shell-building organisms. Artificial alkalinization would increase the ocean’s pH, restoring balance to the seawater. However, this methodology is a recent development, and it is not yet clear if there are harmful side effects on ocean ecosystems when the alkaline sediments are deposited. 

More research is required to determine if ocean alkalinization is a practicable strategy for large-scale sequestration. Fortunately, support for research into oceanic carbon sequestration technologies is gaining momentum. According to the Natural Resources Defense Council, CO2 removal technology research has recently received bipartisan support in congress through the Ocean Based Climate Solutions Act, the Sea Fuels Act, and the Carbon Capture Prize Act, underscoring that the federal government understands that ocean policy and climate policy must be approached jointly. 

Between the ocean’s natural carbon sequestering abilities and the development of sequestering technologies, there remains room for optimism that we will be able to sequester the amount of CO2 necessary to prevent the worst effects of climate change.

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