Diatomic Sequestration

The Green Nuclear Deal addresses ways that nuclear power can lower CO2 emissions, but atomic power is not the only way to lower CO2 concentrations. We can pull carbon out of seawater and send it to the bottom of the ocean if we are willing to use the power of the diatom.

Diatoms are single-celled organisms that build their cell walls out of silicon instead of cellulose. These little plants literally “live in glass houses.” Given the right conditions and nutrients, they can double their numbers every 24 hours. Thus, if you start with just one diatom and fertilize it (and its offspring!) in a sunny place, you could have a thousand diatoms in ten days, one million diatoms in twenty days, one billion in thirty days, one trillion in forty days, and so forth. Keep shoveling in the right nutrients and you could cover the entire planet in diatoms by the end of one growing season.

Assorted diatoms as seen through a microscope. Public domain image.

Because their cell walls are made of “glass,” diatoms that float in water while they are alive tend to sink to the bottom when they die. (The average life span of a diatom is six days.) The ocean floor has layers of dead diatoms that are as much as a half mile thick.

Diatoms grow where there are sufficient nutrients. Like almost every other species of green algae, they need iron for photosynthesis. Unlike other species, they also need silicon. Silicon is the second most abundant element in the earth’s crust (after oxygen). The ratio of elements in a diatom is as follows:

  • 106 carbon atoms
  • 15 nitrogen atoms
  • 16 silicon atoms
  • 1 phosphorus atoms
  • trace amounts of iron, magnesium, etc.

Shrimp farmers routinely fertilize shallow waters to promote diatom growth. We need to consider fertilizing the empty waters of the deep ocean, which is a biological “desert” due to the lack of necessary nutrients. If humans “farm” deep water diatoms, we can send six carbon atoms to the bottom of the ocean for every silicon atom we transport.

Diatom farming could be one of the cheapest carbon-sequestration options available. It is a low-technology process–all you need is the right species of diatom, lots and lots of fertilizer, a freighter to transport it, and a mid-ocean platform to dispense the fertilizer over time.

The environmental impact of diatom farming can be minimized as long as the operator provides the right balance of nutrients. The limiting factor for green algae in the deep ocean is iron. The diatom farmer should provide iron and silicon to promote the growth of a species of diatom that reproduces rapidly, dies off quickly, and sinks to the bottom of the ocean with a minimum of carbon loss. But the farmer must take care to replenish certain other nutrients that diatoms consume; otherwise the ocean water will be unable to support other species later on.

There are at least five deep ocean areas that are optimal for diatom farming. The North Pacific Gyre is a vast area that is poor in nutrients but high in CO2. It has been called the “Great Pacific Garbage Patch” because human debris gets sucked into this giant whirlpool and never escapes. Adding nutrients to the middle of this vast rotating “desert” would have minimal effect on the surrounding areas.

The surface waters of this area are very low in nutrients, but the deeper waters (and the ocean bottom) have more of the minerals required for life. A solar concentrator on the surface could be used to heat a fluid and then pump that heat into deep water using a simple “closed loop.” This should cause an upwelling of more-fertile water to the surface. This would dramatically reduce the amount of fertilizer that must be shipped from the shore; humans would only need to provide those nutrients that are not already present in deep waters.

With a Green Nuclear Deal, the mid-ocean platform would house a Gen IV reactor to provide vast amounts of power at a minimal cost. Electricity from the reactor could power a heater on the ocean floor, which would create a mid-ocean “oasis” of life. The “farmers” on this platform would harvest this marine life; freighters (ideally, nuclear-powered freighters!) would transport fresh fish to shore and bring essential nutrients back.

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