Common kitchen baking soda, sodium bicarbonate, has many versatile uses throughout the home. It is currently mined at some expense for sale, however it has also been able to be formed from industry exhaust along with hydrogen and chloride.
The initial cost to add the collecting device to smoke stacks would be an investment however selling the hydrogen and chloride could offset cost and baking soda is fairly inexpensive but might also be able to be sold. The amount of baking soda that would be sequestered from all the potential smoke stacks would be far more than the current market for household baking soda however even if it couldn't be sold there would be advantages over the current smoke exhaust cleaning systems.
Currently carbon dioxide is collected from power plant smoke stack/flue exhaust in a liquid form which then might leak from what ever is stored in and reach the atmosphere or ground water anyway. Solid crystalline baking soda could be stored as a solid and might even be able to be used within construction if large quantities were produced.
For more details and some ideas for how baking soda can be useful throughout the home or garage (can help soak up oil spills from a concrete floor) see: Can baking soda save the environment? by Julia Layton, HowStuffWorks. How much sodium bicarbonate might be produced per power plant using the new technology? "A single large coal-, gas- or oil-fired power plant produces more than 300,000 tons of CO2 in a year. Pass that CO2 through SkyMine, and you've got yourself more than 600,000 tons of baking soda. And there are more than 10,000 of those power plants in the United States [source: EIA]." "As opposed to liquids and gases, solids are a cinch to store. Baking soda is stable. Used as coal-mine filler or dumped in landfills, it's not going to pollute the soil or leak into the air." HowStuffWorks.
In many areas sand for construction purposes is in short supply, if excess sodium bicarbonate was available it might also be useful within the construction industry for some purposes.
For a thorough description of the current use of sodium bicarbonate in a variety of industries see: Sodium Bicarbonate, Chemical Economics Handbook, (4).
Baking soda is alkaline and can be used to adjust the pH/acidity of a substance. Within the fishing industry it is used as an anesthetic to calm fish during transport. (1, 2, 3) Adding it directly to an overly acidic ocean however would just be adding more carbon dioxide to the ocean. Anesthetizing fish for more humane transport is humane, anesthetizing the ocean is not.
So converting global warming gases into sodium bicarbonate seems much better than allowing it to reach the atmosphere or ocean.
Other chemicals that have been considered for use in the ocean:
Is there any other mineral oxides that might help re-oxygenate the ocean without anesthetizing fish, or causing unwanted algal blooms? Lime is also alkaline and can reduce acidity and neutralize carbon dioxide (CO2) in ocean water, the negative to the idea is availability of lime. The production of lime, "calcium hydroxide (Ca(OH)2)" causes some carbon dioxide to be produced. (6) So the SkyMine smoke exhaust technology, HowStuffWorks, might help with that, or lime might not be the best idea available.
Iron oxide has also been discussed as a way to increase growth in the ocean - the negative might be too much growth of algal blooms leading to decomposition and lack of oxygen, and the experimental trials have shown it increases dimethyl sulfide in the atmosphere which can have a cooling effect on the atmosphere (7) but do we want more dimethyl sulfide in the atmosphere? Other concerns regarding the idea of increasing phytoplankton growth with the addition of iron to ocean waters include the increased production of other global warming gases, "nitrous oxide and methane, two greenhouse gases [source: Haiken]" and "chemicals called methyl halides, which erode the ozone layer." (7) From Wikipedia: "Most coastal waters are replete with iron and adding more has no useful effect." Increased fertilization occurs naturally with upwelling from deeper layers of ocean water (8), so the upwelling tube idea in the previous post would also be a way to increase iron and other nutrients without needing to add anything extra to the ocean.
Magnesium hydroxide is also alkaline and is used in the treatment of water and wastewater. (9) Magnesium would be expensive to add to the ocean in bulk, but ocean health produces jobs and food when fish supplies are numerous. The ocean plankton also produce a significant percentage of our atmospheric oxygen, so a healthy ocean means healthy air for all of us who breath oxygen, unlike the sulfur loving bacteria who don't need it and don't produce it.
The series: 1. Oceans need oxygen, 2. Oxygenating the ocean's dead zone, 3. Non-traditional windmills can increase efficiency, 4. Upwelling tubes, hurricanes, and mussels. 5. Baking Soda to the rescue! - Yes really. 6. Supplementing the Ocean, 7. Mussels - Delicious and Sustainable. 8. The big picture of climate change is bigger than businesses may consider. 9. Inventions Occur in Stages. 10. Stacked Horizontal Turbines. The series in one document, minimal images, on Google-docs: (Oxygenating the Ocean).
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Tülay Altun, Ramazan Bilgin, Durali Danabaş Effects of Sodium Bicarbonate on Anaesthesia of Common Carp (Cyprinus carpio L., 1758) Juveniles, Turkish Journal of Fisheries and Aquatic Sciences 9: 29-31 (2009) https://www.dropbox.com/s/8m86qp0adpuggcf/pdf_725.pdf?dl=0
Dr. Lydia A. Brown, Anaesthesia for fish, PHARMAQ Ltd, VIETFISH Vol 8 Issue 2 MAR/APR 2011, https://www.dropbox.com/s/3ienl00ypphlnij/2011_aquaculture_anasthesia_lydia.pdf?dl=0
Kelvin Chai, What is the purpose of adding sodium bicarbonate (baking soda) into clean water prepared for live fish transportation? (pdf links, 1 & 2, provided by Salah Mahdi Najim, University of Basrah) https://www.researchgate.net/post/What_is_the_purpose_of_adding_sodium_bicarbonate_baking_soda_into_clean_water_prepared_for_live_fish_transportation
Sodium Bicarbonate, Chemical Economics Handbook, (CEH), IHS Markit, https://ihsmarkit.com/products/sodium-bicarbonate-chemical-economics-handbook.html
Julia Layton, Can baking soda save the environment?, HowStuffWorks, https://science.howstuffworks.com/environmental/green-science/baking-soda-save-environment.htm.
Maria Trimarchi, How could adding lime to seawater cut atmospheric CO2? HowStuffWorks, https://science.howstuffworks.com/environmental/green-science/lime-seawater1.htm
Jennifer Horton, How can adding iron to the oceans slow global warming? HowStuffWorks, https://science.howstuffworks.com/environmental/green-science/iron-sulfate-slow-global-warming.htm
Iron Fertilization, Wikipedia, https://en.wikipedia.org/wiki/Iron_fertilization
Wastewater and Water Management, Martin Marietta Magnesia Specialities, LLC, https://magnesiaspecialties.com/category/wastewater-and-water-treatment/