In an apocalyptic report, the Intergovernmental Panel on Climate Change (IPCC)—a United Nations agency focused on climate change—warned the world the planet has 12 years, or until 2030, to reverse global warming.
Without drastic change, the Earth is on track to see average temperatures rise by almost 5 degrees C by 2100. That’s far beyond the 2 degrees scientists consider the plausible goal to contain global warming.
Reaching that target requires significant carbon emission reductions to reach a net output of zero by 2030. And it’s not just that: We need a method to remove future greenhouse gases from the air, operating as a kind of air filter for the atmosphere.
Removing gas, however, requires “negative emissions,” a carbon removal strategy which doesn’t exist yet.
“There isn’t really a negative emissions technology that’s been shown to work at the scale we would need,” said climate scientist Drew Shindell, a professor at Duke University and one of the lead authors of the IPCC report.
The most straightforward way to get to net zero is to plant trees, or what scientists call “afforestation” (converting unused land into forests) and “reforestation” (returning land that was once deforested for farming or other purposes, back into forests).
But Shindell says this model can only take us so far.
“For something like afforestation there’s only a finite amount of land we can convert back to forest,” Shindell told the Daily Beast. “We still need a lot of that for agriculture, and the population is only going to increase. That’s why stuff like changing diet—eating less red meat—would affect land use.” Plus, when trees die, they release carbon dioxide back into the atmosphere as they degrade, negating any positive effects.
Another proposal is to season the oceans with iron dust, creating algae blooms that soak up huge quantities of carbon dioxide and sink to the ocean floor when they die. Yet another idea is to spread rocks like basalt or a condensed wood called “biochar” into soil in order to increase storage of carbon. And three startups globally, bankrolled by billionaires, are attempting “direct recapture,” where machines suck carbon from the air, much like plants do, and store it underground. Although direct capture has been shown to work on a small scale, it requires a lot of money to operate, and some of the research has stalled due to under-funding.
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But the method which has gained the most traction in the scientific community—and the one the IPCC report discusses the most—is bioenergy with carbon capture and storage.
BECCS is a controversial combination of two separate techniques: bioenergy, or the burning of biological matter like wood for heat and power, and carbon capture and storage, which pushes carbon into rock foundations deep under the surface of the earth, an inverse fracking.
The method was first outlined in the early 2000s, when Swedish PhD student Kenneth Möllersten and Austrian scientist Michael Obersteiner co-wrote a paper published in the journal Science called “Managing Climate Risk.”
What made it stand out was that it was a negative emissions method, perhaps capable of saving the Earth from otherwise likely climate catastrophe.
It hinges on burning wood for energy as “carbon neutral,” only releasing as much carbon as the tree had formerly absorbed when it was alive, leaving a net output of zero greenhouse gasses. By pairing bioenergy, in lieu of dirty energy sources like fossil fuels, with a technology for storing carbon deep underground, the two scientists believed they could drastically chip away at the amount of CO2 in the atmosphere.
But there are several problems with BECCS. For one, it’s not certain that using bioenergy is actually carbon neutral. It depends on how you calculate the life cycle of the biological matter. Growing trees en masse would require a massive expenditure of machine energy to plant, cut and transport the wood, which could produce a carbon footprint of variable size. It would also require lots of land and water, which could heighten food and water scarcity in an increasingly insecure climate.
“We’re not sure we could do this without having very severe effects,” Shindell said, “like, not having enough fresh water to grow food.”
BECCS also costs a lot of money. At current estimates, BECCS would cost between $100 and $200 to remove just one metric ton of CO2 from the atmosphere. For context, we dump about 40 billion tons of CO2 into the air in a single year.
Still, not all the options on the table involve complicated scientific gymnastics or exorbitant costs. One of the most promising natural methods is simple: coating undeveloped land with compost. The technique, called “carbon farming,” relies on the fact that, given appropriate sunlight, water and minerals, green waste can absorb CO2 from the air and lock it down for several decades. One organization in California, the Marin Carbon Project, has shown that a single, thin layer of green waste drastically increases carbon storage—by roughly 1 ton per hectare over the course of just three years.
Despite significant challenges facing a rapid transition to net zero carbon emissions, authors of the IPCC report were not entirely pessimistic. Climate scientist and IPCC report contributing author Kristie Ebi told the Daily Beast that world governments have demonstrated an unprecedented interest in the panel’s findings.
“This is the first IPCC report that was specifically requested by the world governments,” Ebi said.“As part of the Paris Agreements, the world governments asked the IPCC to address this particular topic. I’ve never seen such interest by the governments in the report.”