Carbon dioxide (CO2) levels in the atmosphere are higher than they have been in more than 800,000 years and they’re projected to keep increasing for decades to come.

And yet, the only way global temperatures can be kept from rising above 2 degrees Celsius — the primary goal of the Paris climate agreement — is to dramatically reduce greenhouse gas emissions like CO2 and methane.   

This mismatch between aspirations and reality has forced policymakers to turn their attention to a growing field known as carbon capture, use, and storage (CCUS) — which essentially covers all efforts to extract CO2 from the atmosphere and then store it in some way to eliminate its environmental impact. The International Panel on Climate Change (IPCC), the leading authority on the subject, says that there’s almost no way to achieve global climate goals without pulling huge amounts of CO2 from the air.

A new report by the United Nations Economic Commission for Europe (UNECE) describes how the full potential of CCUS technology can be fully unlocked. 

While existing CCUS technology is unable to neatly cancel out current rates of emissions, it can play a significant role in mitigating the climate crisis alongside concerted efforts to phase out fossil fuels. 

In fact, the report notes that 10-30 gigatons of CO2 can be removed per year by 2050 thanks to CCUS technologies and efforts. Countries currently emit around 40 gigatons of CO2 per year, and emissions could rise to 50 gigatons by 2030. If countries invest in renewable energy and reduce their overall energy consumption, then net-zero CO2 emissions could be achieved within the UN’s desired timeframe. 

But CCUS faces significant challenges that can only be overcome if countries work together. Most immediately, financing must be mobilized. The processes by which CO2 is removed from the atmosphere, transported, and stored can be very expensive and, to further complicate things, there’s really no way to turn a profit with this technology. As a result, it’s up to governments to take the lead and invest. 

The report calls on policymakers to build economies of scale to both accelerate the adoption of these technologies and drive down costs. For instance, if countries share the costs of building international pipelines to transport extracted CO2 for storage, then it will be a lot easier for countries with little storage capacity to invest in extraction methods with the understanding that they’ll be able to transport the CO2 somewhere else. In the process, the amount of CO2 that exists in the borderless atmosphere will be gradually reduced. 

Because climate change is a global problem, it requires a collective approach.

Since leading climate scientists expect CCUS technology to play an increasingly vital role in the years to come, it’s important for policymakers to begin developing frameworks and standardized procedures today to ensure the field grows in the right direction. 

Here are five of the best ways to store CO2 that’s been removed from the atmosphere. 

1. Underground Storage

Essentially, after CO2 is removed from the exhaust of a factory, it’s heated and compressed, and then injected deep into porous rock formations in the Earth. If the area is left undisturbed, the CO2 will eventually turn into rock. If the area is disturbed, however, it can leak CO2 and undermine the whole initiative.

This system hasn’t been rolled out on a large scale, the UNECE notes, because of how expensive it is, how much energy it paradoxically consumes, a general lack of lack of transportation infrastructure, and a lack of storage capacity. Only some countries, for instance, have adequate subterranean rock formations for CO2 storage. 

The amount of infrastructure and underground storage needed for this technique is staggering. If countries managed to remove 10% of annual CO2 emissions in this way, the amount of liquid that would need to be pumped underground would be equivalent to all of the oil used each year.

2. Nature-Based Solutions 

Forests, swamps, algae, and other natural areas offer a nature-based solution to CO2 storage that's cheap and incredibly beneficial for the planet.

By restoring and conserving land and marine habitats, countries can create carbon sinks that remove a significant amount of CO2 from the atmosphere. In fact, the Nature Conservancy estimates that nature-based solutions can provide 37% of the emissions reductions needed to keep temperatures under the 2 degrees Celsius threshold.

3. Concrete 

CO2 that has been recovered from the atmosphere is increasingly being used to manufacture concrete. During the industrial manufacturing process, CO2 can be substituted in for some components and become a part of the final product. While concrete can’t hold the CO2 indefinitely — it eventually breaks down — it’s one of the longest lasting ways to store the substance.

4. Plastics 

While many types of plastics are an environmental hazard and need to be phased out, the group of chemical substances known as plastic have become a core part of the global economy. The UNECE report describes how some companies are incorporating CO2 that has been extracted from the atmosphere into the manufacturing process of plastics that can potentially hold onto it for centuries. 

5. Synthetic Fuels 

The fossil fuel industry uses a lot of energy on its own to extract coal, oil, and natural gas from the Earth, process it, and then ship it around the world. 

The environmental footprint of this system can be dramatically reduced by making synthetic fuel with CO2 pulled from the air and other elements. This shift could both satisfy some of the demand for fossil fuel products, while also minimizing the harm of burning them. 

Synthetic fuels are ultimately a stop-gap measure as societies transition away from fossil fuels, but, when they become economically viable, they could help to reduce overall emissions.