An overlooked part of the climate issue for many people has been carbon reabsorption and sequestration. It’s a complex topic with the same convoluted set of choices as finding acceptable alternative energy sources.

In energy there are good and bad choices like increasing reliance on nuclear energy or hydroelectric power. You can go through the possible alternatives and find all types of reasons not to deploy one alternative or another. Nuclear has a big waste problem, hydro is elegant and appealing but the number of rivers we can dam has dwindled. Similarly, wind and solar are intermittent so what do you do when power generation is not keeping up with demand?

Elsewhere we’ve looked at solutions to these challenges and come up with geothermal power generation and leveraging the intermittency of wind and solar to advantage, plus there’s the promise of space based solar power (SBSP). Together these approaches provide an interlocking set of supports that mitigate any challenges. Here we’ll take a brief look at carbon absorption possibilities, they all look good in theory but some are more practical than others.

First up, there is a list of mechanical techniques to both absorb and sequester or store carbon. Absorbing carbon from the air isn’t hard, it’s a simple chemical process that results in quantities of CO₂ that are then condensed into liquid form at high pressure and low temperatures. But capture and compression in this scenario are expensive because they require machines and they cost energy which raises the issue of not doing anything rather than generating more electricity, along with its pollution, to do the work. That’s a valid concern.

Then there’s the issue of transporting and storing the liquefied gas. Popular proposals call for injecting the gas into spent oil wells and sealing them for more or less perpetuity in which case we successfully remove carbon from the air. But don’t pop champagne corks just yet, there’s still the issue of potential leakage. We can’t be certain that the gas that we store underground will stay there and if it leaks some future people would have to deal with the problem. But we can’t know how the deep future will unfold and assuming a future civilization will have the resources to re-do our work is speculative at best. It’s unnecessary too, given our options.

Green plants have been capturing and sequestering carbon for about 2.5 billion years, give or take. Using chlorophyll, water, and sunlight they make biomass, the stuff of themselves. Humans use some of that biomass for food and building materials. We also eat things that eat biomass like salmon, chicken, and beef. Every year the earth’s natural systems and its farmers generate in excess of 100 billion tons of biomass. If we could find ways to double the amount of biomass made here on mother earth, it would result in a massive carbon sink that could contribute to a climate solution. But of course there are gotchas with this approach just as there gotchas in energy production.

For instance, green plants make things that decompose rather rapidly. Green plants that failed to fully decompose due to some happy accidents of biology and geology produced the vast reserves of fossil fuels that we are rapidly depleting. But most of the time green plant matter decomposes because it burns or something eats it whether that’s people and animals or fungi. So any solution to the carbon crisis would be temporary and would require a chronic approach to a solution. Into this mix I give you open ocean iron fertilization a term that only a geek could love but a process that might help save the planet.

The ocean is a vast place that many of us expect teems with life. After all we get seafood from the sea and whales and sharks live there, and there’s all that seaweed at the beach when all you want to do is swim. But all of that life lives rather close to shore; way out in the blue ocean there isn’t a lot going in. The middle of the ocean would be a desert if it wasn’t so wet; it’s blue because there isn’t much green plant activity. That’s exactly where we could grow green things to capture vast amounts of carbon but there’s a gotcha.

The gotcha is this; the middle of the ocean is deficient in one mineral, iron, that acts as a sort of fertilizer for encouraging green plant growth. In this case the green plant is called phytoplankton, which is considered the grass of the ocean, the bottom of the food chain. It’s true that in the ocean big fish eat smaller fish but the smallest fish eat plankton.

So the thought is to fertilize parts of the blue ocean with dilute quantities of iron sulfate or other easily dispersed forms of iron to make phytoplankton bloom. When the plankton dies some of it will sink to the bottom taking its carbon with it. In experiments conducted over the last 30 years, iron fertilization has been proven to work but there’s a lot more applied research needed to turn this interesting idea into a commercially viable solution to climate change. How much iron needs to be added? At what frequency? Where? What are the potential pitfalls or gotchas of this process?

We have tentative answers to these questions but scientific certainty requires more effort and that’s where we hit a snag. According to the Law of the Sea treaty administered by the UN, iron fertilization is a form of waste dumping and waste dumping is strictly controlled. But what the UN prohibits, the UN can allow though it hasn’t considered doing so for decades.

What’s needed is international consensus about investigating this solution to see if and how we might ramp it up to commercial scale and with that begin to lower earth’s temperature. This process might sound exotic but organizing to make it possible and pestering your representatives in government are simple and easy things that any citizen could do.