Paco Dennis
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Capturing carbon from the ocean could be our future.
Over the past century or so, we humans have inflicted a lot of damage to this precious planet’s climate systems. In fact, we are still harming it at a record pace, with some of the highest levels of carbon emissions ever seen. As such, if we want to avoid a climate catastrophe, we not only need to reduce our emissions as quickly as possible but also repair the damage we have already done. For this reason, carbon capture will be a vital part of our efforts to save the planet. There is only one problem: it is far too expensive!
Right now, it costs around $1,000 to permanently remove a tonne of carbon dioxide from the atmosphere, meaning that completely offsetting our emissions would cost $35 trillion annually, which is simply impossible. Luckily, this could all soon change thanks to MIT and their new astonishing ocean-based carbon capture technology.
Let’s start with why carbon capture is so damn expensive. Most of these systems work by having either a filter or collection unit that can get saturated with atmospheric carbon dioxide, effectively separating the carbon dioxide from the ambient air. Once saturated, these devices need to be heated to blistering temperatures to release the carbon dioxide, which can be captured by a vacuum, allowing the unit to be used again.
The captured carbon dioxide can then be transformed into carbonates to be securely stored. However, all of this intensive heating is very energy-hungry, and the materials (including the filters) are rather expensive, which causes the cost per captured tonne to be exorbitant.
And our carbon emissions don’t just hang around in the air. Carbon dioxide can dissolve in water and turn into carbonic acid. As such, 30%-50% of humanity’s emissions end up in the ocean, which is becoming more and more acidic every day. This high concentration and the unique chemistry of carbonic acid have allowed MIT to develop a hyper-efficient ocean-based carbon capture technology.
There have been previous attempts to remove carbon dioxide from seawater, but these methods have required expensive membranes and a constant supply of chemicals to keep the reactions going. As such, they were just as expensive as current systems or had issues with their supply chain’s environmental impact. Instead, MIT’s system uses the chemistry of acids and alkalis.
First, we need to understand how carbonic acid works in the ocean. You see, it doesn’t just drift through the ocean. It dissolves rocks and shells instead, neutralising the acid and converting it to solute bicarbonates. This is what MIT took advantage of. Their machine consists of two chambers. Seawater enters the first, and reactive electrodes interact with the seawater, causing protons to be released into it, which acidifies the water. This acidic water then reacts with the carbonates dissolved within it, releasing carbon dioxide — this is the same reaction that causes bicarbonate and vinegar to release carbon dioxide. A vacuum is used to syphon off this carbon dioxide so it can be safely stored.
The seawater then passes into a second chamber, where a reverse voltage is used to capture the protons and neutralise the acidic water so that it can be released back into the environment. This process can continue repeatedly, almost indefinitely, as no chemicals or much maintenance are needed to keep this machine going.
Because this machine only needs to power small voltages across water tanks and a vacuum, it is incredibly energy efficient. MIT researchers measured it at 0.77 MWh per tonne captured, and they believe they can do far better in the future. For some comparison, other Direct Air Capture (DAC) systems are over three times more energy intensive, at 2.3 MWh per tonne. Because energy is one of the highest costs for a carbon capture plant, this represents a significant step forward!
Who knows, maybe in the future, the ocean will be teeming with floating solar-powered carbon capture plants, diligently working to atone for our climate sins. There is still a lot of work to do before this vision can come to fruition, but at least now it is a possibility, and we are one step closer to saving this delicate planet we call home.
MIT May Have Just Developed The Ultimate Climate Technology
