Ocean acidification is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. Seawater is slightly basic (meaning pH is over 7), and ocean acidification involves a shift towards pH-neutral conditions rather than a transition to acidic conditions (pH less than 7). An estimated 30–40% of the carbon dioxide from human activity released into the atmosphere dissolves into oceans, rivers and lakes.
Between 1751 and 1996, surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14, representing an increase of almost 30% in H+ ion concentration in the world’s oceans. In the 15-year period 1995–2010 alone, acidity has increased 6 percent in the upper 100 meters of the Pacific Ocean from Hawaii to Alaska.
At the current rate, 70% of North Atlantic cold-water corals will be living in corrosive waters by 2050-60.
A study conducted by the Woods Hole Oceanographic Institution in January 2018 showed that the skeletal growth of corals under acidified conditions is primarily affected by a reduced capacity to build dense exoskeletons, rather than affecting the linear extension of the exoskeleton. Using Global Climate Models, they show that the density of some species of corals could be reduced by over 20% by the end of this century.
Acidification Remediation – With a Lot of Lime
900 Gigawatts of nuclear power could be used to offset ocean acidification. A different alternative is iron fertilization of the ocean but this article will just focus on Dr. Cannara’s remediation plan.
Dr. Alex Cannara says that molten salt reactors could be used to crush dolomite and limestone rock, making a residue that would reverse ocean acidification.
Duplicate natural processes…
a) Reverse ancient seafloor carbonate formation via heating dolomite/limestone from land deposits, just as subduction & heating in magma accomplishes.
b) Capture freed CO2.
c) Return residue of Ca/Mg oxides (lime) to oceans. d) Dissociate CO2 and H2O via catalytic heating, releasing Oxygen to air and capturing C & H2, and/or, sequester unusable CO2 to geologic storage.
e) Process split C & H2 into desired hydrocarbons for…
1) Carbon-neutral fuels;
2) Industrial feedstocks;
3) Benign C-H compounds for geologic storage – in old wells/mines, etc
Remediation – The Numbers
• Processing limestone/dolomite to lime (>1GJ/ton)
• Lime transport to ocean (rail 0.085kWHr/ton-mile + ship
• CO2 cracking (assume electrochemical reduction of at least 505 kJ/mole ~1.5GJ/ton)
• H2O cracking — @2000C, or electrolysis @850C 225 GJ/ton H2 (64% efficient incl electricity gen)
• C-H compound reforming (use H2O cracking heat)
– Fuels (for critical uses – aircraft, etc.)
– Feedstocks (petroleum/gas/coal substitutes)
– For geologic sequestration (waxes – C25+)
• Assume remediate 10% of yearly CO2 emissions = 3Gt
– (3×10^9 (1 + 1.5)x10^9 ) x 2.8×10-7 = 700TWHrs + H2O cracking
– less than 90, 1GWe non-emitting powerplants + H2O cracking energy