Fixing the acidity of the oceans and atmosphere towards 350 ppm of CO2 at ground level at some point in the future and the role of Calcium ions and calcium carbonate and carbonate ions in this endeavour.
pH of the ocean surface is approximately 8.05 as of 2009 on average, and varies from place to place due to upwelling ocean currents and downwelling ocean currents due to circulation patterns and local phenomena like el nino and la nina and hurricanes and water spouts.
In general, the pH drops and becomes more acidic with depth and increasing pressure in the ocean.
In general, if no steps are taken for remediation of ocean acidification, the ocean will become more acidic in time due mostly to anthropogenic emissions of CO2 primarily from coal plants, but also from the transportation and oil and gas sectors.
Fixing the acidity in the ocean
Submitted by Richard Belshaw on 26 August 2009 - 5:27pm
The ice bergs are melting at a rapid pace, and ocean circulation patterns may be affected. Seasons will change their norms and average temperatures, and indeed in some places, winter may disappear altogether. This is viewed by some short sighted persons as a good thing and something to positively look forward to.
However, concomittently and concurrently with this phenomenon, is the increasing acidity of the oceans due to carbonic acid in the oceans increasing with increasing CO2 levels in the atmosphere. This will have myriad impacts on the food chain and the web of life on the entire planet.
Indeed, by 2017 , if no steps are taken to reduce CO2 emissions and turn the corner on this problem, the southern ocean will become so acidic that the saturation horizon .... The depth at which calcium carbonate in calcite and aragonite forms dissolves will essentially reach the surface of the southern ocean when the CO2 level is at 450 ppm at sea level, due to upwelling ocean currents carrying much CO2 with them from the depths to the surface; at this point the ocean their will off gas CO2 into the atmosphere in a positive and runaway feedback process that will exacerbate the problem, ie. Make it progressively and exponentially worse. Life forms like plankton and zooplankton and foraminerafa, coccolithospores and shell fish of all kinds including mollusks will dissolve their shells at shallow depths and have virtually no protection from their environment and may disappear altogether, ruining a sensitive ecological system. Already , corals the world over in cold waters and hot waters too, are suffering and dying, and the ecosystems they provide to the ocean and its life, is VERY endangered and precarious.
We need a practical approach to reducing CO2 in the oceans and subsequently the atmosphere if we are to reach the target of 350 ppm to save the arctic and polar bears, and preserve the worlds coral and many marine species.
Many fish will be affected, due to calcium in the water being unavailable for plankton and zooplankton at the basis of the ocean food web and chain. If they are unable to calcify their skeletons, the fish that feed on them will be short of calcium too, and will be unable to effectively form their skeletons, and may perish or be deformed suffering from many diseases associated with this condition. Evolution may not have sufficient time to generate new species that can adapt to such conditions and it may take 100s or several thousand years or more before the return of life to the oceans, or longer. Similarly fish have a narrow band of pH or acidity of sea water in shallow seas where they can effectively fertilize their offspring. Beyond a certain tipping point of acidity in the oceans, a bit different for each species, the fish will die off in huge numbers without being able to procreate and pass on their genes to the next generation, they will not be able to fertilize their eggs below a certain pH or acidity point. This is the true catastrophe of the oceans, and it will occur in the southern oceans first around 2017 if we don’t change the corner on CO2 emissions.
One project that can possibly reduce CO2 in the oceans and suck CO2 out of the atmosphere is to add calcinated water, highly saturated in calcium and magnesium, can react with carbonate and carbonic acid in the water in high concentrations to precipitate out calcium carbonate only to be redissolved at depth or collect on the ocean bottom. At any rate it would increase the calcium carbonate saturation horizon, or the depth at which calcite and aragonite would dissolve, preserving the shallow water shell fish and fish spawning grounds.
Where do we get extra calcium and magnesium from? There are vast stores of calcium carbonate in many locations of the Earth just below the surface or up to 100 m down, indeed the white cliffs of dover symbolize such a cache. A simple parallel system of a combined drill and sea water/calcium carbonate vacuum can be fashioned so that it will suck up calcium carbonate and sea water at a reasonable depth and carry it to the surface. Reducing pressure near the surface of this current from many drills at once, allows it to precipitate more calcium carbonate as it reaches the surface. A fine sieve is required to remove these crystals from the sea water and they can be stored separately to be used later in the process.
In the mean time, the filtered sea water can then be passed through a reverse osmosis system or distillation procedure. Reverse osmosis is cheaper energetically and just as effective. The salts and minerals can be strored in a mound outside in shelter for use at a later stage and represent the ocean chemistry that exists at the drill site at depth. It will be necessary to tap into this reserve later and it can be recycled.
Now the calcium carbonate, calcite and aragonite and magnesian calcite can be added to the reverse osmosised water and can be boiled under medium pressure, the calcium carbonate and magnesium carbonate will dissolve in this water at the right temperature and pressure, and perhaps this should be under high pressure to achieve this. But higher temperatures help. The equations for this are known and can be predicted with precision.
Once dissolved, the boiling water will boil off the CO2 gas, and conversion from bicarbonate and carbonate to CO2 will occur until there is very little carbonate and CO2 left in the double boiler. The double boiler can be heated by magnetic induction and methane, or natural gas, more about this later. The electricity can be supplied by solar panels and wind turbines or perhaps in sunny climes by a magnifying glass focused on the double boiler.
The off gased CO2 can be bubbled through an algae bed and along with the CO2 from the methane and nitrous oxides from burning the methane the CO2 and NOx will be absorbed by the algae bed, also fed fertilizer and minerals, perhaps from the mineral pile mentioned earlier to just the right concentration. These concentrations are either known or will soon be known. The dying and dead algae can be harvested based on beds of a certain age and the life cycle of algae in an artificial environment. The harvested algae can be passed through a pyrolysis cycle, also heated by methane and optical magnified light and electricity. It will form biochar, or biodiesel as the needs be. The biochar can be used to refertilize depleted soils nearby for growing vegetables and crops to raise goats and sheep for nourishment of the staff. It also will absorb CO2 once buried and mixed in with the soil. This is preferable to biodiesel. Though some biodiesel may be needed to operate machinery or for transportation.
The CO2 that is absorbed by the algae will be converted to methane which can be used as a general fuel for a engines or for heating the double boiler or for heating homes or for heating the pyrolysis reaction. Careful design is required to get the right amount of it and the size of the algae beds is critical to this process.
The calcified heated water, once the carbonate has been boiled off, can be used like geothermal energy, and can either be used to heat homes until it cools off, or can be used to generate electricity. This can be fed back into the project. Once cooled, but super saturated in calcium and magnesium, some of the mineral pile can be added in the right proportions to match the ocean surface chemistry over the drilling site.
The separation of minerals may need to be accomplished from this mineral mound and will require energy and sophisticated separation chemistry to isolate and reduce the proportions of minerals to match the sea water surface chemistry.
Lastly, this matched but calcium and magnesium laden sea water can be added back in over the drilling site where it will react with CO2 in the water in carbonate form, and will form calcite and aragonite and magnesian calcite, calcium carbonate and magnesium carbonate. It will precipate, and will collect on the sea floor to complete the cycle, once the saturation horizon drops below the sea floor in that location.
This will act as a natural pump to suck CO2 out of the air, and primarily will increase the alkalinity in the sea water, thus reducing the acidity and raising the pH level to some desired local level like 8.3 or whatever is appropriate for local corals and fish breeding.
If this process is carried out at 10000 to 40000 sites around the globe on an ongoing basis, we can actively reduce the CO2 level in the oceans and decrease their acidity and we can also reduce the CO2 level in the atmosphere in a sustainable and renewable way.
Richard J. Belshaw
AGU, AAAS, ASA, IEEE