GeoEngineering the Oceans
I’m part of a discussion group that is largely composed of scientists whose main concern is the vast damage that our society continues to wreak upon the environment. One of the benefits I derive from this is the ability to read conversations on a range of important issues, like the one I’ve reproduced below on ocean acidification:
Rudy writes: You may not have seen this paper. It’s the best written of any I’ve seen so far about basalt, water & CO2 reactions.
I gather from it that simply dumping finely ground raw basalt into the ocean might be the simplest way to readjust its pH. The reason for this is that it’s a “basic” rock whose water dissolution scavenges up hydronium ion converting CO2 to bicarbonate and bicarbonate to insoluble carbonate minerals formed from the Ca/Mg in both the water and leached from that rock.
In my opinion it’s apt to be more practical than lime making/dispersal because it’s …
1) cheaper – less energy would be required to grind rock than to both grind and calcine it
2) cheaper – the CO2 would simply settle out as a carbonate-mineral mud at the bottom of the ocean – it would not have to be separated from a calciner’s off gas, transported to a suitable place & then injected into the earth
3) less environmental impactful – dumping lime into water is apt to kill anything in it because lime is a very strong base & its hydration rapidly generates heat – basalt “dust” would react slowly & fish, etc. would have plenty of time to get away from dump zones
Proving/demonstrating this one way or the other should not be difficult – maybe even DOE could to do it.
Alex writes: We have years, not decades, to get going with protecting ocean pH. For Apollo 13, we proudly agreed “failure is not an option”. Where are such folks today?
Limestone is certainly plentiful enough to be able to come up with ~70 gigatons (to get ~35Gt of lime) in a year. This is a dozen or so cubic miles.
There’s far more basalt in the world than needed — a modest island near Iceland is estimated to be able to hold all the CO2 we emit and convert it back to carbonate, because basalt was already baked free of CO2 in volcanoes.
No question that gaseous CCS is a false god.
Blooms of non-calcifying organisms accomplish nothing, since when they die they get digested by oceanic bacteria and CO2 & methane are released.
The effort requires ~10,000 electrically-heated ‘cement’ plants delivering lime to the ~1 million commercial ocean transits each year–35,000 tons average each transit–marine biologists in control.
Singapore handles ~350,000,000 tons in containers alone in a year.
We’re at the edge of possibility because we’ve pussy-footed around for so long. But, if we begin both addressing ocean pH and reducing combustion power, the need to do all the above liming gradually decreases, and we start nibbling into the past 200 years of emissions, as they dissolve.
So the question for us all is simple — sit back and watch, or do something? Our descendants are watching from the future. Would they rather have sea food, whales, polar bears… and continued 1gt of natural CO2 sequestration, or not?
Steven Chu told me at a 2012 meeting that “we don’t want to mess with the oceans”. He and some others seem to miss that we already have.
Interesting concept.
I’ll have to do far more study to determine where I stand on it… but I will state that considering the impact to local ecology for dumping of any given basic material into the oceans is not really necessary. Just dump the dust – whether it be basalt or lime – into the middle of the Pacific or Atlantic oceans.
The conveyor currents should serve to gradually disperse the higher-Ph water, and the areas that are considerably far away from land already have very little life anyway… The diffusion of the too-contaminated water would begin to impact the most vulnerable life at the maximum extent of the diffusion, and the lack of food would direct the higher life forms elsewhere before they get into a concentration that would harm them.
(Obviously, a marine biologist would tell me that I’m unaware of half a billion considerations… but since I’m unaware of them, I don’t see anything that’s a non-starter with lime).
For me – as is the case with all geo-engineering ideas – the issue is cost. A ton of lime, in today’s market, is ~$30/ton. If we need 35 Gt/year, then before considering the cost of pulverizing it into fine powder, we’d need $1 trillion dollars/year.
For basalt, it looks like that is closer to $300/ton (again before pulverizing into fine powder and shipping/dispersing)… and the discussion above seems to indicate that a greater tonnage of basalt would be needed than lime – due to the fact that basalt is less basic.
So in my mind we’d need to, as a global society, determine whether we are willing to spend >$1 trillion/year in dumping finely powdered lime into the center of the Pacific and Atlantic oceans.
The issue here is cost effectiveness: If it costs us ~$1 trillion/year to sequester the portion of GHG’s absorbed by the ocean every year, we would then still face ~2 ppm/year increase in atmospheric concentrations, and we would still face all of the other known problems of AGW.
If, however, we were to spend $1 trillion/year on renewable and nuclear energy (that’s at least an order of magnitude more than the entire world currently spends on renewables), and we were to concentrate our efforts towards lower-hanging fruit (which is not what we’re doing now)…
We should be able to mitigate some ~5% of our emissions/year – at least at first.. and we should be able to be net carbon neutral within a generation, or at least within 40 years.
During that time, if we instituted carbon recycling technologies, we could plausibly slip towards negative net emissions.
Between the increased freshwater volume from ice melt and the reduction in the rate of acidification, the ocean might well find a balance without us dumping billions of tons of lime into it… AND we’d have reversed the gradual buildup of GHG’s in the atmosphere.
It seems the latter option is the better use of $1 trillion/year.
Olivine Basalt is able to absorb around 1.4 tons of CO2 per ton (assuming 25 billion tons of the stuff is enough to absorb all anthropogenic CO2)
Hard coal emits 2.86 tons of CO2 per ton burned.
On this basis you would need to mine and crush to powder around 2 tons of pristine unbroken olivine basalt per ton of coal mined to absorb the emissions from the coal. (heavily fractured basalt may have absorbed significant amounts of CO2 already)
Note that in the UK, Basalt gravel sells retail for around £88 per ton. Even assuming that fine basalt sand could be produced at a quarter of this price, you would still be looking at £44 or around $66 to produce enough crushed basalt to absorb the CO2 from the burning of 1 ton of coal with unknown environmental consequences from dumping this much basalt powder
Technically possible? Probably
A viable solution? I very much doubt it.
Gary,
Clearly you found a better price of basalt than I did – it might have been the nature of the googling, and it might have been the difference between prices in England and the prices in SE America.
Regardless, we both came to the same conclusion: It seems highly unlikely that this would be a good use of funds.
🙂