Carbon Sinks 2.0

September 29, 2017 by Denis Pombriant

In Carbon Sinks 1.0 we explored the concept of capturing and storing or at least rendering unharmful to the climate, atmospheric CO2. Natural carbon sinks involve green plants that capture CO2 and turn it into various materials based on carbohydrates that can either become food sources or plant matter like wood or cellulose.

Manmade approaches involve mechanically capturing CO2 from the air, compressing into a liquid and then pumping it into old oil wells or other underground places where it is hoped it will stay for millions of years. Unfortunately, CO2 is a gas at ambient temperatures and it decompresses easily turning back to a gas. So sequestering it underground takes a great deal of faith or scientific certainty that the stuff won’t leak out and rejoin the atmosphere. The big problem is that underground formations shift, crack, settle and more.

Here’s a parallel. In Oklahoma, where fracking is commonplace for development of fossil-fuel resources, significant seismic activity—such as earthquakes—has increased thanks to fracking. The fracked rock deep below ground is unstable and settles during gas extraction and because drillers inject wastewater from their activities back into the Earth. In 2016, Oklahoma experienced 623 magnitude 3+ earthquakes (fewer than the 903 in 2015, but more than the 579 in 2014). Perhaps you’ve seen videos of people’s kitchen faucets spewing fire because fracked gas got into the water supply?

Using depleted oil wells to store CO2 opens us up to a similar problem for the environment. It’s too easy for CO2 to re-enter the atmosphere this way. If we were able to capture and store a great amount of CO2 this way we would be passing a big potential problem down the ages to people who are not born yet and who, later, may or may not have the ability and resources to recapture it.

But one of the greatest problems facing manmade carbon capture and sequestration efforts would be the costs in money and other resources but especially energy. Using mechanical means to capture and store atmospheric carbon would necessarily involve machines to do the job and energy, mostly electricity, to run them. Of course there’d be a labor component as well. All of this effort could be wasted later if containment leaked and we only captured CO2 and didn’t try to convert it to things that aren’t gasses and that don’t pollute.

Even if you assume there’s enough money to do the job, the question of energy overshadows everything. If you consider that generating electricity involves burning fossil fuels and that only about 30 percent of the energy in the original fuels can be delivered as usable electricity, you can see that a manmade approach to capturing carbon could likely generate more pollution than it abates. Even if we captured the carbon from the smokestack of electric utilities it’s not as good as simply not burning fuel to make electricity to capture and sequester carbon to begin with. In short, it’s hard to see how manmade carbon sequestration schemes can be effective.

In a last ditch effort some might suggest using renewables like wind and solar to make electricity to drive the process but there’s another set of problems with that. The Earth is running out of fossil fuels and alternatives should be organized to make an orderly transition from fossil fuels to a modern electric paradigm.

But as it turns out, there is a way to capture carbon and to not have to invest precious human produced energy to do it. Natural photosynthesis is the most logical approach to carbon capture but it, too, has drawbacks though, luckily, they aren’t showstoppers. Using photosynthesis uses energy from the sun to make organic molecules that don’t pollute. As we saw in Carbon Sinks 1.0 there aren’t many places on earth where we can plant additional green plants to help with the sequestration effort, unless we’re willing to make some effort to upgrade the location. Also, plant materials decompose too quickly to offer a long-term solution—at least as we’ve defined a solution so far.

If we were to use photosynthesis the potential for doing the job well is high. If, and it’s a big if, we could double the current amount of photosynthesis going on annually, we could generate a trillion tons of biomass in a decade. Admittedly that’s a big ask but now that it’s out there how would or could we accomplish such a feat?

There are two approaches.

First, we could seek to irrigate and cultivate desserts which then converts the question to where would we get the water? That’s an already easier challenge. We’d have to make fresh water by desalinating seawater using renewable electricity. That’s an engineering problem and all of the science is done on the subject. Better still, there are three sources of alternative electricity for the purpose. A full discussion of energy generation can be found here.

The second option doesn’t involve alternative energy production or even farming. It is simply to promote plankton growth in the ocean. We think of the ocean as teaming with life but if you could map ocean life the way you map continents and islands, you’d see that areas supporting life are concentrated near landmasses or underwater geological structures that reliably bring nutrients from the ocean floor to the surface where microscopic plants (phytoplankton) use them in the process of photosynthesis. Other species feed on the plankton or on each other producing the appearance of life.

Other parts of the ocean, often far from land, don’t support much life unless it’s the occasional whale migrating and living on its stores of fat. In the 20th century several scientists discovered that the parts of the ocean with little living matter are deficient in the mineral iron. When they added small quantities of iron to the seawater it was enough to spark growth and reproduction of phytoplankton.

Unlike trees for instance phytoplankton grow and reproduce quickly so that in a short while they can produce many tons of biomass. When the iron is used up, disperses, or sinks, the phytoplankton activity falls back to previous levels.

This discussion is a simplified version of the Iron Fertilization hypothesis. Check out this article for more ideas.  But the hypothesis suggests that an effort to seed areas of the ocean with iron might make a significant change to the amount of atmospheric carbon today. When the phytoplankton dies, some of it sinks to the bottom of the ocean where it’s too dark and cold for life so instead of decomposing this plant matter accumulates. Over millions of years the accumulated sediment gets compressed and warmed enough to turn it into petroleum. Tectonic shifts in the earth’s crust thrust former ocean beds up creating dry land with petroleum deposits.

If you think this is far fetched, consider the Permian Basin, the west Texas oil producing region. The oil extracted there comes from sediments in a shallow sea (i.e. a basin) between 200 million and 300 million years ago.

The Iron Fertilization hypothesis needs more attention from the global community. The UN Law of the Sea and other international treaties currently prohibit “dumping” chemicals into the ocean like iron sulfate that could be used to promote phytoplankton growth. But it’s this kind of out of the box thinking that can have a significant positive impact on global warming. The hypothesis might not be perfect and implementing it might require trade offs which is why a discussion needs to take place. And soon.


Leave a Reply