And exactly how much carbon they remove can vary a lot based on variables like vegetation health. “One of the biggest risks with some of these biology-based proposals is that an assumption is made that one can easily equate X number of trees with X million tons of carbon without actually looking at what kind of trees they are. , and where they are “being planted,” says Cox. The amount of carbon trapped can end up being negligible. “You have a lot of trees, which is brilliant. You have not necessarily got the climate benefits.”
Another technique known as bioenergy with carbon capture and storage, or BECCS, is also dependent on a monoculture, usually fast-growing grass. In this case, the vegetation is burned to produce energy and the resulting emissions are sequestered underground. But it also comes with its own set of dubious side effects – it would require huge areas of crops and huge amounts of water to make a dent in atmospheric carbon concentrations: A paper published last month found that in the US alone, scaling up BECCS would expose 130 million Americans to water stress by 2100.
But in a global climate that has gone wrong, there are even risks in restoring forests to their former glory because that glory is becoming increasingly dangerous. Supercharged wildfires are now wiping out forests instead of gently resetting ecosystems to make room for new growth. If you spend a lot of time and money restoring one of these forests to bind carbon, and then it burns, all that coal goes directly back into the atmosphere. Or if the political rule of a given country changes, and goes from supporting relating toafforestation to theafforestation, you would have the same problem. Just look at what’s happening in the Amazon.
“I would argue that many proposals for land-based removals can be risky,” Cox says. “Because you have a very, very high risk that either the carbon removal doesn’t happen in the first place, or that it happens, but then in 10 years is reversed.”
The dreaded “Moral Hazard”
Researchers have developed a way to mimic natural carbon sequestration using a technique called direct air entrapment or DAC. These machines suck in air, pass it over membranes to remove carbon dioxide and pump it into the ground, locking it away forever. The tide may shift toward DAC in the United States. Last month, the Biden administration threw 3.5 billion to back up direct air intake. (It comes five years after a California congressman introduced a bill that would fund geoengineering research, but it never went anywhere.)
But this too faces two major problems. The first is that DAC does not exist near the scale needed to make a dent in excess atmospheric carbon. A plant that came online in Iceland last year only catches corresponding emissions of 870 cars. A 2021 study estimated that it would take an investment of 1 to 2 percent of global gross domestic product to capture 2.3 gigatons of CO22 a year in 2050 – and that’s only a fraction of the current annual emissions, which are around 40 gigatons. “There is a risk that we may not be able to scale and implement fast enough,” says Benjamin Sovacool, who is studying risks of geoengineering at Aarhus University in Denmark. “It seems that the speed at which we have to implement these is unlike any previous energy transition we have had because the scale is so enormous.”
The second issue is about “moral hazard” or the temptation to lean on the DAC as a crutch instead of doing what is necessary: dramatic reduction in greenhouse gas emissions. If a nation’s leaders expect to be able to eliminate emissions through the DAC, they do not have to worry about reducing those emissions in the first place. It’s like waiting for a miracle antiviral drug – except that the required dose does not yet exist.
There is a chance that the extreme and desperate nature of geoengineering may do the opposite – instead of encouraging complacency or a reliance on technological corrections at the last minute, it may alert the public enough that they will start addressing climate change. as an emergency. But, says Sovacool, “politicians can be even more receptive to the moral danger because they only think in current terms. They will gladly push as much to future generations as they can.”