Human activity—mostly the burning of fossil fuels—has raised Earth’s atmospheric carbon content by 50 percent, from 280 parts per million (ppm) to 420 ppm. Since the start of the Industrial Revolution, we’ve released approximately 950 billion metric tons of carbon into the air. Every year, humans emit more than 40 billion metric tons of carbon dioxide (CO2) into the atmosphere, as of 2021 measurements. Even if we stop burning fossil fuels now, the amount of CO2 already in the atmosphere will cause Earth’s climate to continue warming for decades, triggering heat waves, droughts, rising sea levels, and extreme weather.
Climate scientists warn that if we want to avert catastrophe, a significant amount of excess atmospheric CO2 must be captured and sequestered. The process is called carbon dioxide removal (CDR), and it has been receiving more attention as nations, states, and industries strive to meet their climate goals. But how should we go about doing it?
There are two broad strategies: biological and mechanical. Nature already absorbs and emits about 100 billion metric tons of carbon dioxide every year through the natural processes in the biosphere—including plant growth—an amount 2.5 times humanity’s annual carbon output. So, according to advocates for biological carbon removal, our best bet is simply to help the planet do a little more of what it is already doing to absorb carbon. We could accomplish this through reforestation, soil-building agricultural practices, and encouraging kelp growth in oceans.
On the other hand, advocates for mechanical carbon removal point to technologies that successfully capture CO2 in the laboratory; if these machines were scaled up, those advocates tell us, we could create an enormous new industry with plenty of jobs while removing atmospheric carbon and reducing climate risk…
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