Climate change has been hotly debated (pun intended) in recent years, gaining prominence in the political and public arenas, especially as America and other Western nations have grown more socially and environmentally conscious. Although many people refer to the infamous 97% consensus statistic, claiming that 97% of climate scientists believe climate change is real, there is a huge debate among scientists, policy-makers, and the American public who have added their own spin on the statistic, further confusing the validity of the claim and increasing partisan divide over the issue.
Regardless of one’s position on the credibility of this statistic, one fact remains clear – there is no unanimous scientific or legislative agreement on what should be done about climate trends such as increased CO2 greenhouse gases, elevated global temperatures, or ocean acidification. In this past year, the newly-elected Democratic Congresswoman, Alexandria Ocasio-Cortez released a controversial plan to combat carbon dioxide emissions in the United States in her Green New Deal. Although both parties killed the bill, the question remains: how can we combat climate change and reverse worrying CO2 trends?
Historically, greenhouse gas production has increased dramatically after the industrial revolution in the early 1900s. Carbon dioxide, a prominent greenhouse gas is released through activities such as deforestation, burning of fossil fuels, and natural disasters like volcanic eruptions. Below are two graphs showcasing the rise in CO2 levels since 1960 and in the past five years.
More and more scientists and policy makers are calling for efforts to mitigate our carbon dioxide production now that our atmospheric CO2 has surpassed over 400 ppm (parts per million). However, even if we stop producing carbon dioxide tomorrow, the current levels of CO2 in the atmosphere will continue to harm our planet by increasing Earth’s temperature through a concept called the greenhouse effect. Not only do we need to execute initiatives to decrease our rates of CO2 production, but also devise solutions to reduce the total amount of CO2 already present in our atmosphere.
One such idea is to store CO2 either underground or in the ocean. According to the International Energy Agency (IEA), several projects are already storing millions of tons of CO2 underground. Due to the success of these projects, the IEA has high confidence in the ability to store large quantities of CO2 underground safely and securely. However, the total storage capacity for hydrocarbon reservoirs is 800 gigatons of CO2 (GtCO2) – a method that could handle just shy of 20 years worth of emissions at our current levels. With the ocean covering more than 70 percent of the planet and approximately three-quarters of it having a depth greater than 3,000 meters (the required depth where CO2 storage becomes effective), 20 years can be extended to nearly 250 of storage at our current rate. This is nearly 13 times the storage potential of current reservoirs. By storing CO2 emissions in deep regions of the ocean, we can buy more time with our carbon budget to avoid maximum concentrations, irreparable damage, and avoid the worst of climate change.
...20 years can be extended to nearly 250 of storage at our current rate. This is nearly 13 times the storage potential of current reservoirs.
How does ocean storage work?
Ocean storage of CO2 depends on its phase (solid v. liquid or gas) as well as the depth at which it is released. In general, pressure increases and temperature decreases the farther you descend in the ocean (think of the insulated dry suits and highly pressurized equipment scuba divers must use to protect themselves from harsh ocean conditions). Just like any molecule, CO2 can change its phase based on pressure and temperature conditions. Between the ocean surface and 500 meters below, CO2 would exist in gaseous form, whereas those same molecules at a depth between 500 and 2,700 meters would be in liquid form. However, because the density of gaseous and liquid CO2 is less than liquid water, it would rise back to the surface. To correctly store CO2, we would need to compress the molecule into its solid form.
At depths greater than 3,000 meters, not only would the CO2 be compressed into solid form, but the weight of the water would cause the CO2 to sink to the seafloor as solid carbon dioxide or as a hydrate. Once at the bottom of the sea floor, the CO2 would form pools, trapped in place by its own density, looking similar to the Brine lakes shown in this photo.
There are three proposed methods that can be used to release carbon dioxide into the ocean at the proper depth. The first would be from a pipe that runs from the shore to the desired ocean depth. This pipe would receive a stream of CO2 from an intermediary storage facility on the coast. Another method is by dispersing the CO2 into the ocean from a ship where a long hose or pipe towed behind the vessel would release the CO2 stored on it. The last method would use a stationary vessel or platform to inject CO2 to a fixed location at or near the ocean bottom. All three methods would release the carbon dioxide into the ocean at the proper depth in the correct phase. Although the fixed location is considered the most popular design, it is currently not as feasible as the moving ship method since it would take a lot of resources, funding, and time to build.
Critiques of the plan
Although the theories and experimental data for this plan checks out, there are a number of concerns. The biggest concern is the acidification of the ocean where gaseous CO2 reacts with ocean water to form carbonic acid (H2CO3) that dissociates into H+ and HCO2-. This increase in hydrogen ions have resulted in a more acidic ocean by 30%. A drastic change to the ocean’s pH can significantly devastate marine ecosystems as well as our own health since animals and humans alike are very sensitive to acidic conditions. As a result, the idea garners a huge negative backlash from the public, especially from coastal cities and fisherman fearing the carbon dioxide will continue to destroy wildlife and fishing business.
In other words, to test this idea on a large scale, the public would need to be convinced of its safety, and measures would need to be taken to counteract any acidification effects. Independently, work has been done to decrease the current rise in ocean acidity, including the use of iron fertilization as a buffer to mitigate the acidic effects. While further research needs to be conducted to determine the practicality of storing large quantities of carbon dioxide in the ocean, the public must first be made aware about this opportunity and its low risk towards people’s health, the environment, and marine life.
Ultimately, we are running out of time before permanent damage is done to our environment. Unprecedented CO2 levels in our atmosphere has made WALL-E’s version of Earth in the Pixar movie seem that much more plausible, but because we are refusing to create solutions, there will be no WALL-E or luxury spaceship to save us. Storing our CO2 emissions is not the solution, but a way to extend our time to find alternative energy sources and ways to save our environment.