Push-pull Ocean Pump to remove CO2

[David B. Benson]

Emergency 20-year Drawdown of Excess CO2 via Push-Pull Ocean Pumps
climatecolab.org/web/guest/plans/-/plans/contestId/20/planId/1303629
Mr. Calvin's proposal appears to me to be quite good. However, I may have overlooked something as it appears perhaps too good to be true.

Comments, please.

[Roger Clifton]

His analysis reads very attractively, using numbers at almost every turn. However the numbers are skimpy when it comes to quantifying the amount in $/kg of extra biological productivity his pumped-up waters produce, then are (supposedly 100%) pumped back down.

Pumped down where? He seems to have a rather naive view of the water layers below the thermocline. His concept seems to be simply that we should pump carbon-laden water down to just below the modern bottom of the mixing layer. The mixing layer is the depth through which modern waves stir the ocean surface. He neglects the ocean currents that must eventually take the carbon-rich layers to places where they will return back to the surface. He neglects too, the likelihood of an imminent world of storms, where previously un-heard of waves stir the horror story back to the surface again in the sort of burp of carbon dioxide and methane that he sought to avoid.

The physical thing repeatedly missing from his proposal is the timescale. That carbon has to stay down there for thousands of years until the weathering of rock begins to catch up with the backlog. But as far as our credularity is concerned, the serious error is political, that he proposes that the project begin while emissions purport to taper off.

Sadly, I imagine that the fossil fuel lobby would be happy to fund his word-painting while his dream distracts those of us who might otherwise demand that all emissions cease entirely.

[David B. Benson]

I don't think the push will last long. The surface water is warmer than the water below the mixed layer. A parcel of pushed surface water will tend to rise towards the mixed layer, being less dense.

[hank]

I swapped mail with him about this while the linked page was still open, before they closed it. I don't know if the material is still available. He was clear about the uncertainties, and I think the main problem was no obvious way for anyone to Make Money Fast by doing this. I like the idea a lot better than the other emergency approaches (sulfating the atmosphere, 'depressurizing' methane).

My guess is this sort of pump would boost plankton blooms dramatically, as cold nutrient-rich upwellings do naturally -- and that it might attract a lot of filter feeders, with other benefits to follow.

As to how deep to push, and temperature management -- draw cold water up through a large pipe down to depth X; send water back down through a small pipe inside the large one that goes deeper. Get heat exchange, and drop the return water well below the intake letting it cool down en route by contact with the pipe -- as he says it'd stay down for a thousand years or so.

Remembering, it's an emergency proposal for when people finally wise up and we need a fast patch that does little harm. Unlike, say, sulfating the atmosphere or tapping and burning lots of methane ....

I'd have liked to see his idea worked on further, and suspect it will keep attracting attention.
Calvin has been around writing and thinking and worth reading for a long time, on many subjects.

[Roger Clifton]

David B Benson did raise a rather interesting point: The surface water is warmer than the water below the mixed layer. The thermal coefficient of expansion of water is 0.000214 /K, so a 1 m² pipe of 1 km length containing 10° colder water will have an pressure deficit of 2.14 tonnes. Considering that your (well, I mean "his") pipe will have to have net zero buoyancy, how are you going to stop it collapsing? Perhaps there is an engineering solution for that one, including the energy required to endlessly pump against 2 t backpressure.

Rather more challenging is a chemical problem. The concentration of minerals at depth has arisen because it has been delivered there by faecal matter drifting down from the surface. How are you going to bring the minerals up while leaving the biological oxygen demand behind? There is after all, a risk that the scheme creates a methane burp of impact greater than the CO2 withdrawal intended.

Yes, you may well create an algal bloom. But considering that the emerging water is at least initially devoid of oxygen, the rise of a food chain based on zooplankton will be at least initially suppressed, though jellyfish might thrive. Perhaps it will give rise to a sea chocka with jellyfish, the only vertebrate in sight being the occasional turtle pigging out on the bonanza. In the absence of animals large enough to create "faecal pellets" of sufficiently high descent rate, it would seem that you have to physically pump it all back down again (if you can collect it), and again, as DBB pointed out, because the surface water is warm, it will be as unwilling to sink as the cold water was unwilling to rise.

[edireland]

I don't think they are talking about pumping sufficiently large amounts of water to actually alter oxygen levels on an oceanic scale.
Or we could just inject vast tonnages of oxygen into the water that is pumped up.

[Roger Clifton]

A high biological oxygen demand implies a hefty burden of organic carbon.

The minerals arrived down there as a minority component of "organic detritus", so there's much more carbon than iron, silica, phosphorus etc. Once below the mixing layer, the stuff ferments anaerobically to microbial slimes and a significant backpressure of methane, slowing further decay.

The proposal would bring the mixture back to the surface, where the methane, some ammonia and freshly generated CO2 escapes, while the remaining carbon, along with the silicon, iron, phosphorus etc re-enter the food web. We are expected to believe that after eventually developing a net intake of CO2, all of that water would be collected and pumped back down, permanently removing more greenhouse gas than it released. How "permanently" is yet another matter again.

[John ONeill]

Here's a critique of the alternative carbon sequestration plan of grinding up olivine rock, which reacts exothermicly with CO2 to form limestone.
iopscience.iop.org/1748-9326/8/1/014009/article
From Wired magazine-
"However, Wolf-Gladrow is sceptical that humanity should rely on geoengineering as a main tool to fight against climate change. He told us: "It's a controversial debate. I would prefer other solutions. Germany is going a good way, around 25 percent of energy is renewable. So if I had to invest money, I would put it into renewables. But it's important to know the options. At the end, when we cut down CO2 emissions, how do we take the CO2 out of the atmosphere that's already been released? One way would be to use olivine in smaller amounts."
Most readers of this blog would be equally sceptical of the idea that ' Germany is going a good way ' with its efforts to reduce CO2 emissions. Wolf-Gladrau et al suggest that if coal or gas was used for the energy needed to grind the rock down to micron-diameter particles, the carbon sequestration would be reduced by thirty percent. However if nuclear replaced essentially all fossil fuel generated electricity, there would be a lot of spare off-peak capacity for the grinding mills. The end of the coal industry would also free up all the coal shipping and rail. About half the rail traffic in both China and the USA is currently coal wagons; a comparatively tiny quantity of uranium or thorium could replace that. To avoid crossing climate tipping points there's no sense in restricting ourselves to ' smaller amounts ' and waiting for the dubious outcome of the renewables programme. We need to return carbon from the air to the lithosphere on similar scales but at faster rates than how we've dug it up and burnt it for the last 200 years.
As regards the push-pull scheme for circulating deep ocean water to the surface and back, the down pump- a floating ring, maybe made of old tyres, that waves wash over but can't escape from, supporting a simple plastic tube - sounds feasible, though there are probably a dozen ways for it to fail. The up pump seems much more problematic. You'd either need a rigid pipe all the way down, or the pump would have to be at the bottom, with power transmitted from the surface, and some form of power supply. Wave action could add water to the top of a thousand meter column, but it couldn't lift the whole column, and suction at the top would tend to collapse the tube.

[hank]

Update on the idea (in the original post above)
from Dr. Calvin: williamcalvin.com/bk16/PGA%20acidification%20limits.pdf

His blog: calvinclimate.blogspot.com/
has more on the idea: calvinclimate.blogspot.com/2015/01/plowing-under-carbon-fixing-crop.html

I think this fits well with the 'ecopragmatist' or 'new anthropocene' ideas, though he's expressing greater concern and less techno-optimism than the Breakthrough crowd.

It's consistent with the growing awareness that while we're doing perhaps less damage to the land, we're really severely stripmining the oceans and they could recover -- given a break for a few years as happened when ocean fishing and whaling virtually halted for the duration of World War II: conservationmagazine.org/2010/09/war-fish/
" In general, they found that the closure, which lasted from 1939 to 1945, enabled more fish to live to older ages and start spawning. But that didn’t necessarily translate into immediate increases in the number of younger fish. Instead, the closure caused a kind of ripple effect in the years after the war, with a gradual aging of stocks followed by periodic increases in overall fish numbers, probably during years when ocean conditions were good for spawning...."

Source: Doug Beare & Franz Hölker & Georg H. Engelhard &, & Eddie McKenzie & David G. Reid (2010).
An unintended experiment in fisheries science: a marine
area protected by war results in Mexican waves in fish numbers-at-age.
Naturwissenschaften DOI: 10.1007/s00114-010-0696-5