On climate, a fraught Plan B: Carbon capture helps, but not enough

If a tree that falls in the forest is fed into a power plant, and the carbon emitted is captured and stored, is it helping to save the planet?

Under United Nations carbon accounting rules, it would be: Provided the tree is replaced, the entire process takes more heat-trapping carbon out of the atmosphere than it puts in.

This and other experiments in carbon removal and storage offer leaders at the U.N. Climate Change Conference here a morally fraught Plan B: If they fail to reduce carbon emissions sufficiently to curb disastrous global warming, then they attempt to make nature or technology do the work.

The experiments also pose a puzzle. If such fixes are to be considered, where is the line between natural solutions – planting trees, restoring mangroves, or protecting wetlands – and artificially engineered ways of drawing down carbon?

That line can be blurry, say analysts, but neither option is a substitute for the hard task of making deep and rapid cuts in emissions.

“Capture [of carbon] only makes sense in a world where you’ve already gotten down pretty close to zero” emissions, says Zeke Hausfather, a climate scientist at Carbon Brief, a specialist website.

In Glasgow, the gap between where those emissions of heat-trapping gases need to be and where they’re headed remains a major sticking point in the final stretch of negotiations.

Carbon capture’s appeal

Even if governments meet their new pledges, global temperatures would likely rise to a catastrophic 2.7 degrees Celsius above pre-industrial levels by 2100, according to the U.N. Environment Program. The 2015 Paris Agreement committed to holding temperature rise close to 1.5 degrees.

That’s why the lexicon of “negative emissions” – capturing emissions that don’t fall fast enough – is echoing on the sidelines of the Glasgow summit known as COP26, even among environmentalists who have spent decades turning their backs on such ideas.

“The world will be cooked without [carbon capture]. There are no scenarios bringing us under two degrees,” says Frederic Hauge, founder and president of Bellona, a Norwegian environmental nonprofit.

Some experts propose a purely technological fix: Suck and filter carbon out of the air using giant fans. A Swiss company is already doing this on a small scale in Iceland. The downside to such a simple solution? It costs about $600 per ton of carbon stored in Icelandic rock. And direct air capture machines would use up a quarter of global electricity supply by 2100 if enough of them were operating to make a significant difference to atmospheric CO2 levels, according to one study.

Proponents of natural systems to adapt to a warming planet are wary of such technological fixes to remove carbon. And they appear to be winning the debate: A draft of the COP26 final declaration refers to the “critical importance of nature-based solutions and ecosystem-based approaches ... in reducing emissions, enhancing removals and protecting biodiversity.”

More than 100 countries also signed on to a Glasgow declaration against deforestation, which if upheld would protect much of the world’s remaining forests after decades of cutting that has sapped their capacity to store carbon. 

As to that tree ...

So what about that tree that fell in the forest? In fact, the forest may be in Mississippi, where Drax, a U.K. power-plant operator, sources its wood chips. And the carbon that would otherwise float into the atmosphere? It would be buried in the rock under the North Sea off the coast of England, where miles of gas pipelines and other offshore oil fixtures are being repurposed.

This technology, known as Bioenergy with Carbon Capture and Storage (BECCS), is backed by the U.K. government, which is aiming for net-zero emissions by midcentury. But while Drax has converted a giant coal plant to burn biomass to produce electricity, it is far from carbon-neutral. It may be several years before it can start to bury any captured emissions. Critics say it’s a risky and unproven experiment that will never recoup billions of dollars in public investment.

Even if BECCS does eventually remove carbon, it doesn’t provide any of the benefits that come with restoring and protecting diverse ecosystems, says Nathalie Seddon, who directs Oxford University’s Nature-based Solutions initiative. Another drawback is that reserving land for timber means less for food. And monoculture forests are at greater risk of disease and fire. “It will go up in smoke,” Professor Seddon warns.

That should give pause to anyone who thinks we can rely on nature to sequester unchecked carbon emissions, says Joeri Rogelj, director of research at the Grantham Institute for Climate Change at the London School of Economics. “Relying on the natural system to function fantastically in taking up carbon is not the most robust approach to safeguarding the future,” he says.

Limits of natural sequestration

This is another reason why the idea of natural carbon sequestration is not as appealing a green solution to emissions as it looks, says Mr. Hausfather, of Carbon Brief. Extracting and injecting carbon into rocks may be expensive, he acknowledges, but rocks aren’t at risk of wildfires or pests, or being felled in the future.

“The problem with focusing on nature-based solutions is that there’s a real risk the carbon isn’t going to stay there,” he says.

Mr. Hauge says a better alternative to harvesting trees to burn purely for electricity is to process plant matter into biochar that can fertilize land, thus increasing crop yields, while extracting biofuels for power. His nonprofit is also working in Jordan to grow trees in deserts that would otherwise yield no crops. “You need to plant now to get the biomass you need in 10 years,” he says.

Professor Rogelj, one of the authors of the UNEP report on the COP26 emissions gap, reckons some form of carbon capture will be necessary to abate the emissions that can’t easily be decarbonized, such as air travel and production of cement and steel.

But he warns that carbon-capture technologies like BECCS won’t solve the immediate problem: Emissions are warming the planet beyond the point where either natural or engineered drawdowns can bend the curve. “We still need emission reductions,” he insists. “We need to emit less CO2 because we cannot compensate for it with BECCS.”