The Negative Part of Net Zero
Carbon dioxide removal is on the agenda, even if most politicians won’t admit it.
Carbon dioxide removal (CDR) is currently in the news. The Biden administration has committed $100 million to new climate innovation projects such as capturing carbon directly from the air, and new books by science journalist Elizabeth Kolbert and Bill Gates have led to CDR being an issue covered by all the major US newspapers. Meanwhile, the European Union is working to pass the European Climate Law, which says “carbon removal technologies … should be made cost-effective and deployed,” while green campaigners complain that the European Council’s decision to count carbon absorbed by forests toward its new emissions target for 2030 is an accounting trick. The European Parliament, for its part, has said it prefers a target without CDR.
Honestly, the truth is that CDR is always in the news—it’s just usually between the lines.
The reason for the “net” in “net zero” is that experts do not think it is possible to avoid all greenhouse gas emissions. Even if all electricity and heaters and cars become carbon-free, there will be still some hard-to-mitigate residual emissions in sectors like cement and long-distance shipping, which means some sectors must have negative emissions in order for a country to be at net zero.
This logic carries over to the international level, too. Finland, a country of plentiful hydropower resources, nuclear power, and giant forests to soak up carbon, is aiming for net zero by 2035 and net-negative emissions thereafter, whereas coal-reliant Poland will probably still be net positive in 2050. The important thing for the EU-wide target of net zero by 2050 is that the math adds up—to zero.
The CDR Backstop
Methods to remove carbon dioxide from the atmosphere range from cheap and proven (planting trees) to expensive and cutting-edge (using chemicals and machines to capture carbon from the ambient air, known as direct air capture). Every method has its pros and cons, advocates and detractors. For example, you may have seen reports about the well-publicized ETH Zurich study arguing that new forests could store the majority of cumulative anthropogenic carbon emissions; you may not have seen that the authors envisaged planting trees on an area the size of the United States, or that the 2020 forest fires in Australia released more carbon than the country typically does in a year. The climate experts advising the UN are most hopeful about a technology known as BECCS, which stands for bioenergy with carbon capture and storage. This entails burning biomass to generate electricity and then capturing the carbon and storing it safely away.
For politicians more concerned with the political targets than the choice of technology, there are two relevant points. First, all of these technologies (except trees) are in the testing and demonstration phase, nowhere close to the scale needed to offset current emissions. There are only a few dozen operational BECCS or direct air capture plants in the whole world.
Second, today’s leaders are implicitly relying on CDR to hit their temperature targets. Most pathways to the 2-degree-Celsius target require BECCS to provide 20 percent of primary energy by 2100, almost as much as natural gas does today. The path to 1.5 degrees Celsius is even steeper. The IPCC states, “All pathways that limit global warming to 1.5 degrees Celsius with limited or no overshoot project the use of CDR on the order of 100–1000 gigatons CO2 over the 21st century” i.e. enough to remove several years’ worth of emissions at today’s rate of nearly 40 gigatons CO2 a year.
Given the importance of negative emissions when it comes to achieving climate goals, it is remarkable how little attention they get from politicians eager to market their net-zero goals. In an article for the journal Science, climate researchers Glen Peters and Kevin Anderson lament CDR’s “almost complete absence from climate policy discussions.” An advisory board to the European Commission warns that the EU doesn’t even have a legal definition for what constitutes CDR. The EU emissions trading system has no mechanism for allowing a negative emissions operation like a BECCS plant to generate valuable credits. Europe has made little progress capturing carbon coming from fossil-fuel power plants—which doesn’t lead to negative emissions but rather limits positive emissions—let alone sucking carbon out of the air.
Unspoken Assumptions and Moral Hazard
Some people complain that politicians are surreptitiously relying on CDR as a safety net. In her powerful 2019 speech to the European Parliament, climate activist Greta Thunberg accused MEPs of placing “the future living conditions for all living species in the hands of inventions that are yet to be invented.” A related concern is that acknowledging the promise of CDR might distract from the necessity of avoiding emissions. According to this viewpoint, CDR is a classic example of moral hazard, where someone is discouraged from protecting themselves against risk because they are protected from its consequences. (Views on green moral hazards change all the time: for example, Al Gore, the former US vice president turned environmental activist, once viewed adaptation measures like building seawalls as a moral hazard, whereas today it’s accepted as a necessity.) With fossil fuel giants like Shell promising to get to net zero by increasing gas production now and using CDR to make up for it later, it’s easy to see how CDR can facilitate greenwashing.
The trouble is, it’s not just the oil companies that are counting on CDR. So is anyone holding out hope for 1.5 degrees Celsius. In fact, according to some climate models, humans have already exhausted the “carbon budget,” i.e. emissions to-date will already take the Earth past the 1.5-degrees-Celsius threshold, and humans need to remove more emissions than they add over the rest of the century. Theoretically at least, in the fight against climate change it is possible to go over the brink and then claw your way back up (by using CDR to eventually reduce temperatures). Just watch out for the falling rocks you may have dislodged on the way down, like melting permafrost or collapsing ice sheets.
Once a government admits it is counting on CDR to counteract small residual emissions in a few tricky sectors, it can easily get hooked. Imagine a communications advisor pitching a future European Commission president: “Did culture wars and a weak economic recovery derail your climate protection efforts in the 2020s? Have no fear. There’s no need to admit defeat or tell citizens that 2.5-degrees-Celsius warming will be fine after all—simply increase your projections for CDR!”
Clearer Targets, More Research
How to stop CDR from becoming a get-out-of-jail-free card? Some experts are turning away from CDR and the concept of climate neutrality altogether: Claudia Kemfert, a leading economist at the German Institute for Economic Research (DIW), recently announced in Nature that she thinks “net zero” is no longer enough, in part because the top CDR technologies enable the continued use of fossil fuels. For Kemfert, the objective must be to avoid all carbon emissions.
Other scholars want to pursue CDR on a separate track from emission reductions. One idea gaining steam is for countries to split their targets into two, one for emissions reductions and one for CDR. Sweden’s climate law for climate neutrality by 2045 does this: the plan is to reduce emissions by 85 percent and use “supplementary measures” including BECCS for the other 15 percent. This is a sensible approach because it should prevent improvements in CDR technologies from reducing ambition to avoid emissions in the first place. It would also help advance the technologies required to achieve net-negative emissions in the very long term.
There’s no denying that CDR presents a tricky policy and communications issue. It is at once necessary to achieve the best climate outcomes, where emissions fall by over 90 percent in a few decades and CDR cleans up the rest, and potentially an excuse to drift towards the worst of all outcomes, where fossil fuel interests use CDR to justify continued high emissions. What is clear is that the wealthy countries of the world must commit more resources to CDR research and deployment, in part to help clean up the carbon they put in the atmosphere before the developing world industrialized. To adapt an analogy from the academic debate, humanity is headed overboard and it will have to learn how to swim whether or not it is thrown a small lifejacket.