exposed bedrock in the gulf of maine, usa

well, if injecting CO2 supercritical gas into bedrock is loaded with caveats, imagine how much worse it is to inject CO2 gas into the ocean — a living ecosystem teeming with biota (albeit i am not averse to Buddhist teachings and the contemporary Gaeia hypothesis, which contend that all matter has life) …

i’m especially bothered by any anthropogenic perturbations to oceans, largely because my training and schooling as a marine biologist made me shockingly aware of the enormity and extent of issues plaguing marine ecosystems as well as the (often unappreciated) importance that oceans play in global ecosystems …

so what may happen as a result of our attempts to store excess atmospheric CO2 gas in oceans?

the belief is that oceans can serve as “carbon sinks” … however, oceans do not provide ‘permanent’ CO2 storage sites as the CO2 gas eventually escapes from the surface of the ocean and cycles back into the atmosphere …

where does atmospheric CO2 gas go?

i struggle to see any “pros” to this geotechnology, so once again i admit my biases … please enlighten me if you know of any potential advantages this science may confer …

first, let me list the various methods proposed for ocean CO2 storage:

* dissolution –> injecting CO2 gas at depths of 1000+ metres by ship or pipeline … the CO2 gas is expected to dissolve into the water column … this is presently the most commonly used method …

* creating lake deposits –> injecting CO2 gas at depths of 3000+ metres … at this depth, CO2 has a greater density than saline water and therefore would theoretically dissolve into the surrounding water at a slower rate than it would were it injected in a more shallow ocean strata (as in the above example) …

* bicarbonate (HCO3-) formation –> converting CO2 into bicarbonate compounds using limestone … this would theoretically bind the CO2 into a form that would not eventually escape from ocean waters …

* clathrate formation –> binding CO2 into clathrate hydrates, which exist on the ocean floor … alternatively, promoting growth of solid clathrate may also (theoretically) help bind and store CO2 gas over the long(er) term …

* crop residue sequestration –> collecting residues of agricultural crops (e.g., corn stalks, stems from crop grains, etc.) into enormous bales, weighting them accordingly, and depositing them into alluvial fans on the ocean floor … the biomass would become buried within the trenches of the alluvial fans and remain inert while sequestering CO2 for thousands of years …

corn ... recently, a much maligned crop plant that in actual fact has laudably nourished innumerable communities for millenia ...

CONS:

* as i mentioned above, this is not a permanent solution to high atmospheric CO2 levels … if CO2 injected into the marine ecosystems eventually equilibrates with the atmosphere and escapes from ocean waters, i wonder if we could accurately predict the rate at which the CO2 gas will be released … it may eventually create more problems than the global climate change crisis we are currently facing …

* theoretical mathematical models predict that CO2 turn-around in the oceans (i.e., the length of time it will take injected CO2 deep in the oceans to cycle to the surface) is approximately 1600 years … however, stochastic events may affect ocean CO2 circulation in ways we are unable to anticipate … furthermore, this calculation was likely made using current values for the rate at which ocean waters naturally sequester atmospheric CO2 gas … we do not know how the solubility pump and biological pump processes will change with human injected CO2 …

* relatively little is known of ocean cycles and patterns and even less is known about water in the depths of the oceans … these regions are inaccessible for thorough study and we have no concept of how hydrologic processes occur and interact across the vertical ocean column … injecting CO2 very deep in the ocean can have incredibly dire consequences to ocean currents, ocean temperatures, ocean pH, biodiversity, etc. that we can’t even conceive with our presently limited knowledge …

* the majority of marine biota breathe oxygen (O2) gas … injecting CO2 gas will directly affect respiration and literally choke out resident plants and animals …

* a proportion of the injected CO2 gas will react with ocean water to form carbonic acid (H2CO3) … this will decrease ocean pH (i.e., increase acidity) and directly affect the ecosystem cycles, biodiversity, and physiology of all ocean life …

exchange of CO2 gas at the atmosphere-ocean water surface interface ... source: alfred wegener institute for polar and marine research, bremerhaven, germany

* storing CO2 as bicarbonate in the ocean may help to mitigate the acidity problem … however, bicarbonate itself affects ocean pH (it will increase pH and alkalize the waters) and therefore potential ecological implications must be investigated … it may act as a buffer if CO2 gas is injected simultaneously or in proximity … this is also a more costly method, and 1 that remains grossly untested …

* clathrate hydrates have naturally formed on the ocean floor over millenia … basically, a CO2 clathrate hydrate is a molecular ‘cage’ that holds CO2 in the centre of its molecular lattice … the CO2 is not chemically bound to the lattice, but actually ‘imprisoned’ within it … therefore, once this lattice breaks open (e.g., changing ocean temperatures, pH, pressure, etc. — the patterns of which change dramatically with each anthropogenic disturbance), the CO2 gas is released en masse … methane (CH4 gas) clathrate hydrates also exist on the ocean floor and disturbance of these clathrates (and therefore release of CH4 gas) would be even more catastrophic as methane is a much more active and powerful greenhouse gas …

algal bloom in the Barents sea off the coast of norway. august 1 2007. photo source: nasa.

* the idea behind biomass burial into alluvial fans is that atmospheric CO2 gas is naturally fixed via photosynthesis by crop plants … to prevent decomposition of this biomass and release of CO2 back into the atmosphere, the biomass is buried either deep underground or, in this case, deep in the ocean … hypothetically, decomposition of this biomass deep within the oceans would not only eventually release CO2 gas but also inject vast amounts of nutrients into the ocean at an unprecedented rate … potential resulting algal blooms and increased eutrophication of the ocean may eventually choke out marine life and definitely affect biodiversity within the oceans …

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so where does all this negative talk leave us?

i caution to please tread carefully my fellow humans!! … i laud the intellectual brilliance and genius of human inventions, but true intelligence and logic are demonstrated by the careful real-world application of these innovations …

as a member of the general public who has little, if any, leverage within industry, NGOs, or government, i make my voice heard through my lifestyle habits, consumption patterns, and constant investigation into environmental issues …

protect Earth's oceans ... they're the only ones we have ...

protecting marine and freshwater systems starts with water habits you have at home, at work, at school, and elsewhere … extending your efforts to community or political action is a great step forward and i recognize that not everyone is ready for this latter step …

so, i suggest that you commend yourself for the efforts you do make and feel good about any change you make to your lifestyle habits … keep yourself inspired and know that you are contributing in the best way that you are able …

some further reading that may be of interest:

IEA greenhouse gas reference manual. 2005.