Archive for September, 2013


Just add limestone. Molten salt reactors could process limestone and dolomite into a substance that would help neutralize ocean acid, says Alex Cannara.

Ask anyone to identify the consequences of CO2 emissions, and the answer that most people who are not climate change skeptics will give is “global warming.”

It’s a good reply. Rising concentration of atmospheric CO2 is heating up the planet to temperatures that could have broad, catastrophic climate consequences by 2050.

But while global warming rightly receives plenty of attention, there’s another ongoing and lesser known CO2 scourge that could be even more disastrous: ocean acidification.

Simply put, up to half of the world’s man-made CO2 emissions land in the ocean, where it forms carbonic acid which will eventually wreak havoc if not stopped according to the United Nations-backed Ocean Acidification Network and other groups.

Scientists say that the oceans’ average acidity managed to remain constant for 300 million years until the Industrial Revolution came along. Over the last two centuries, it has increased by about 30 percent. In technical terms, the pH level has dropped from an average of around 8.2 to 8.1.

The ocean is not acidic per se, but on the 0-to-14 pH scale where anything over 7 is “alkaline” and under 7 is “acidic”, the needle has moved dangerously down. pH measurement is one of those logarithmic things like the Richter scale where progressions are much bigger than their numbers outwardly suggest, so a 0.1 drop in pH indicates a signifiant move toward acidity. If any of you humans suffer a 0.1 drop in blood pH, for instance, hold on for a seizure or a coma.


A more acidic ocean threatens the existence of anything in the waters that has a shell or a skeleton. Translation: let the acidification continue, and before long, oops, there goes the fish, crustaceans, molluscs, coral and more. As oceanic CO2 levels rise and form carbonic acid with a “CO3” molecule (H2CO3), it will increasingly deprive marine creatures of the carbonates – CO3 – that they need to combine with calcium to build strong bones and shells.

Ocean acidification is even undermining certain plankton, the foundation of the ocean’s food chain. So the carbonic acid that’s not directly weakening the bigger creatures could eventually starve them.

Exactly how long this pH decline can continue before real trouble starts is a matter of debate, but some experts believe that if we don’t raise the pH, we’ll hit a tipping point before 2050 and as early as 2035, when the ocean will lose its ability to recycle carbon into living creatures.

As the U.S. National Oceanic and Atmospheric Administration (NOAA) notes:

“Fundamental physiological processes such as respiration, calcification (shell/skeleton building), photosynthesis, and reproduction have been shown to respond to the magnitude of changes in CO2 concentrations in seawater, along with the resultant changes in pH and carbonate ion concentrations that are expected over the next century.

“This change is more rapid than any change documented over the last 300 million years, so organisms that have evolved tolerance to a certain range of conditions may encounter increasingly stressful, or even lethal, conditions in the coming decades.”

The implications of that are staggering. NOAA points out that over a billion people in the world rely on the ocean as their primary source of food protein. Then there’s the hit to the global fishing industry, which employs hundreds of millions of people.

Alex Cannara Ocean Slide

Acid attack. A slide from Alex Cannara’s presentation shows that carbonic acid could cause “big trouble” for sea life as soon as 2035.

What can be done?

Alex Cannara is glad we asked.

Dr. Cannara, an engineering and environmental consultant based in Menlo Park, Calif., says that molten salt reactors (MSRs) can come to the rescue in a multi-pronged assault on acidification.

As regular readers of this blog will know, MSRs are small nuclear reactors that use liquid fuel and operate at much higher temperatures than today’s solid-fuel reactors, over which they offer operational, safety and economic advantages. As such, they have huge potential as CO2-free energy generators for the future (nuclear reactors do not emit CO2 during electricity and heat production; their lifecycle entails some CO2 emissions during stages including manufacturing and mining).


Just like MSRs could be a key weapon in the fight against CO2-induced global warming, the same CO2 reduction would help reverse the toxic build-up in the world’s seawaters, notes Cannara, speaking at the recent Thorium Energy Alliance Conference in Chicago (some MSR developers believe the reactors would work best using thorium rather than uranium).

That’s good, but you could say that the reduction in CO2 emissions is just a warm-up act to a direct MSR-based scheme (a substantial warm up act that is – a bit like Santana opening for the Rolling Stones, which they used to do).

In Cannara’s vision, heat from MSRs could process limestone and dolomite (both are carbonate minerals) into a residue that, when dumped in seawaters, would raise the pH level. As Cannara explained in a letter to anti-global warming campaigner and former U.S vice president Al Gore earlier this year:

“One path is to process billions of tons of dolomite/dolostone (calcium-magnesium carbonate) so that it can be distributed in seas to neutralize the carbonic acid created by our emitted, then dissolved, CO2 and thus to precipitate that carbon as new seafloor carbonates. Similarly, calcium oxide (quicklime) can be used — again derived from limestone and similar rock.”

The process mimics the production of cement, in which fossil-fuel fired kilns heat limestone (calcium carbonate) and break it down into quicklime that blends into a “clinker” that becomes cement.

“Basically, you’re doing a cement plant that’s not making cement,” Cannara told me when I spoke with him after the Chicago conference. “You don’t ship it for cement, you ship it for the ocean. It would suck carbonic acid from the water – it’s just like putting a Tums in your stomach. It neutralizes some of the acid.” (Tums is an over-the-counter indigestion tablet).

It’s a grand vision, but it comes with a few major challenges. As Cannara acknowledges, it will require an immense amount of ground-up rock to make a difference, requiring a sizeable fleet of MSRs. “We would be talking about doubling the amount of processing that’s done for cement,” he said.


On the technical side, I also wonder if MSRs can operate at a hot enough temperature. Even at, say, 800 or 900 degrees C, which MSR developers are targeting, an MSR would still be short of the 1,450 degrees C of today’s cement kilns.

That aside, in a virtuous circle, once MSRs are enlisted for grinding limestone and dolomite in the fight against ocean acidification, they could also go to work replacing CO2-spewing fossil fuels as a heat source for cement production. As Cannara noted when I spoke with him, “You could make cement without combusting things.”

There’s more to this MSR campaign too: Cannara notes that in the MSR process, CO2 that naturally breaks off from the limestone and dolomite could be captured and combined with hydrogen to form synthetic fuels. Where would the hydrogen come from? It would be extracted from water in a process that would be powered, again, by an MSR. As an added benefit, the water’s oxygen would be released into the air.

But the focus of Cannara’s plan is to reverse the decline in ocean pH.

“We have to neutralize at least everything that’s currently being emitted, and that’s a lot of carbon,” says Cannara. “The problem is so immense. It’s non-linear. It’s a true tipping point problem, because once you turn off the ocean’s natural recycling of carbon to the life forms that live in the ocean, you’re not going to get that back. What you’ve done is a massive extinction. We need massive amounts of clean power through MSRs, not only to eliminate combustion power, but also to deal with the issue of how to ameliorate the ocean chemistry problem.”

In other words, now’s the time to recruit MSRs in the environmental fight against catastrophic CO2 emissions on all fronts – land, air and sea.

Photo of Alex Cannara presenting in Chicago is from Mark Halper. Slide is from Alex Cannara.

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