A new form of carbon capture could solve one of the major problems facing the most efficient versions of the technology: energy. Whether through the direct input of electricity or the use of expensive and delicate catalysts, carbon capture tends to be quite a burden on energy companies, limiting its potential impact without legal requirements. Now, researchers have created an electrochemical cell that can sequester carbon without the need for expensive catalysts or electrode materials, and it actually generates electricity as it works.
An electrochemical cell can be run in two directions: either input electricity to drive a chemical reaction, or use a chemical reaction to produce electricity. In this case, what we want is the reaction of chemicals in a waste gas, for instance from a power plant, to “sequester” any CO2 in a solid while driving the production of electricity. In the past, electrochemical cells useful for condensing CO2 into a solid have used reactive electrode materials like lithium or sodium, and gotten less useful products like carbonates out at the other end — most promising among those applications is a sort of power plant-born limestone.
This new electrochemical cell, on the other hand, produces industrially useful oxalates that could be sold to chemicals companies and manufacturing companies. Coupled with profits from selling the extra generated power, these carbon capture rigs could plausibly pay for themselves. According to the researchers, the cell generates some 13 ampere-hours per gram of carbon captured — or about 13 million ampere-hours per metric tonne. That means that a single gram of carbon could produce enough electricity to charge a (very hefty) cell phone battery four or even five times over. Global carbon emissions are measured in gigatons, so there’s plenty of power available.
This gets rid of another of the main problems with sequestration of carbon from emissions: the full name for the process is CCS, or carbon capture and storage. It’s fine to design a coal plant that keeps all its carbon in a solid or liquid form, but those solids or liquids still have to go somewhere. Carbon has been stored in big pits, injected into underground rocks, and even dumped at the bottom of various seas — but right now, there’s still no sufficiently affordable, abundant, and environmentally safe spot to put all the carbon we might soon be capturing.
With a salable product as a result of carbon capture, we may end up storing captured carbon within the products that litter our store and warehouse shelves. It might sounds far-fetched, but remember that all the wood in your house is made of atmospherically fixed carbon — CO2 pulled from the air by trees and made into our primary global building material.
Best of all, the cell achieves this by using the cheap and abundant element aluminum, which is also less reactive than those other electrode materials. This not only makes the aluminum-based cell cheaper, but safer to work with and less likely to generate a catastrophic failure. The electrolyte in this system, the liquid connecting the anode to the cathode by allowing molecules to diffuse back and forth between them, is extremely sensitive to water, however. Industrial processes, not to mention regular old air, are often heavily laden with water, so additional research to develop a less water-reactive electrolyte will be needed for many applications.
Carbon capture, on its own, is not the answer to mankind’s many carbonaceous troubles. Solutions like this one take carbon out of highly concentrated environments, but it can’t draw meaningful amounts of carbon from the atmosphere at large, with is vastly lower concentration of CO2. And CO2 is, at the end of the day, only the first name of a fairly long list on mankind’s molecular hit-list. Carbon capture does nothing to filter out sulfur-based compounds and other greenhouse gasses.
We’ll need better forms of power like nuclear and solar, those that naturally produce zero carbon emissions, and we’ll need to directly remove carbon from the atmosphere at large.