Negative emissions Big hit or empty promise?

Negative emissions Big hit or empty promise?

Negative emissions Big hit or empty promise?

In search of new weapons in the fight against global warming, scientists are squinting at Iceland in northern Europe. There, a special system reminiscent of an oversized air conditioning system filters carbon dioxide (CO2) from the air. The greenhouse gas is dissolved in water and pressed 700 meters deep into the ground – and thus permanently withdrawn from the atmosphere. That sounds like a clean solution, but so far it has only been operated on a tiny scale.

There are great hopes for the project and a handful of other test facilities. Because negative emissions – i.e. the removal of CO2 from the atmosphere – must play a major role in a few years’ time. Hardly any model scenario for the 1.5 or 2 degree target can do without it. “It is unrealistic to stop global warming without taking at least some CO2 from the atmosphere,” says Sabine Fuss from the Mercator Research Institute on Global Commons and Climate Change (MCC).

The potential is enormous in theory. In practice, however, CO2 has so far only been extracted from the atmosphere in homeopathic doses. The Icelandic prototype system, which is part of the so-called DACCS process, extracts an estimated 50 tonnes of CO2 from the ambient air per year. It is part of the CarbFix2 project and is located on the site of the Hellisheidi geothermal power plant. According to the manufacturer, Climeworks, a larger system that can filter several thousand tons of CO2 per year will be built in the next year and a half. The Canadian company Carbon Engineering wants to build a plant with an output of one million tons of CO2 per year by 2023.

But mankind emits more than 40 billion tons (gigatons) of CO2 a year – with no noticeable decline. If things continued as before, the temperature increase would be 3.4 to 3.9 degrees by the end of the century, according to the UN environmental program Unep. If, on the other hand, global warming is to be limited to 1.5 degrees, according to the Intergovernmental Panel on Climate Change, net emissions must fall continuously, to zero in 2050.

According to experts, the emission of greenhouse gases cannot be completely avoided. “Certain residual emissions will probably remain,” says Gunnar Luderer from the Potsdam Institute for Climate Impact Research (PIK). He cites air traffic and cement production as examples, which are difficult to fully decarbonise. In order for the calculation to work out anyway, negative emissions are necessary.

In addition to technical solutions, huge forests could theoretically absorb gigantic amounts of CO2. In addition, a more sustainable agriculture could store a lot of CO2 in the soil. But Fuss from the MCC points out that agriculture and forestry are currently adding greenhouse gases to the atmosphere instead of removing them.

Around 20 percent of the current CO2 emissions would have to be offset by negative emissions in 30 years, estimates Andreas Oschlies from the Geomar Helmholtz Center for Ocean Research in Kiel. That would be around eight gigatons a year. “That is highly ambitious and very optimistic, but feasible,” says Oschlies.

So far, the successes with negative emissions through technical approaches have been extremely manageable – also because they are often expensive. There are only a few test facilities. According to Fuss from the MCC, Germany does not play a role: “Germany as a technology nation did not care.”

One of the most effective systems to date is part of a factory in the small town of Decatur in the US state of Illinois. Here maize is fermented into ethanol. This creates CO2, which is then pressed into an underground storage facility. The carbon dioxide that the maize has bound from the air while it was growing is therefore permanently withdrawn from the atmosphere. In 2018, according to the operator, just over half a million tons of CO2 were stored with the so-called BECCS principle. But BECCS also has a catch: the method requires huge agricultural areas on which no food is produced.

Other approaches such as artificial weathering have so far only been researched on a laboratory scale. Certain rock is to be finely ground and scattered on fields or into the sea, as Helmholtz researcher Oschlies, who himself researches the technology, explains. The particles then react chemically with the CO2 from the air or the surface water of the sea, thereby removing CO2 from the atmosphere. According to Oschlies, it would take around a ton of rock to bind one ton of CO2 from the air.

Luderer from PIK doubts that, without active political control, one of the technical processes can make a significant contribution to climate protection in the next 30 years. This requires “extremely high growth rates over a long period of time” for CO2 removal, which has so far hardly been observed in any other branch of industry of comparable complexity. The PIK researcher believes that a few hundred million tons globally through DACCS and BECCS are possible by 2050. “One to two gigatons are theoretically achievable,” he says. “But only if you mean business and start commercial CO2 extraction now.”

What has to happen in order for technologies for CO2 extraction to get going? Fuss demands more research funding so that negative emissions become cheaper. In addition, a high CO2 price is necessary, which puts pressure on companies to remove CO2 themselves or to buy negative emissions from other companies. In any case, it is necessary to develop concrete plans for technologies and measures at national level, as in Sweden for example.

Oschlies advocates certificates for negative emissions so that companies can sell CO2 removal as a service. Greenhouse gas producers could then offset negative emissions against their emissions and the bottom line would be zero CO2 emissions. The Helmholtz researcher also relies on the power of consumers: “If the mood changes, the topic of emissions-neutrality, which is effective in advertising, will create new levers for CO2 extraction.”

Whether negative emissions will actually grow out of their infancy at some point is in the stars. “The best thing is not to emit CO2 in the first place,” says Fuss from the MCC. “It’s better not to make any mess at all, then you don’t have to clean up afterwards.”