Carbon dioxide (CO₂) is not a bad gas. It is colorless and odorless and occurs naturally in our atmosphere. It is not toxic or harmful in current concentrations.
The problem is that its accumulation is causing global warming of our planet. That is why this gas is the star of many debates on climate change and sustainability.
We are immersed in an energy transition in which renewables will play an increasingly important role, but fossil fuels will continue to be necessary for decades to produce a multitude of everyday goods in sectors such as construction, health and agriculture, among others. What will we do then with the undesirable CO₂ derived from its combustion?
The greenhouse effect
The cause of the warming caused by carbon dioxide is none other than the greenhouse effect, a natural phenomenon without which there would be no life on Earth.
The greenhouse effect is the ability of some gases in our atmosphere, such as carbon dioxide, water vapor, methane, and nitrogen oxides, among others, to trap and hold heat from the sun. Without these gases, thermal radiation would reflect off the Earth’s surface and escape, causing the Earth’s temperature to drop to around -18℃.
The problem arises when the proportion of these gases is not adequate. Its accumulation causes the atmosphere to retain more heat, which progressively increases the earth’s temperature and produces changes in the climate. Therefore, it is not a question of making CO₂ disappear, but rather of controlling its emission, adjusting the proportion of this gas in the atmosphere to pre-industrial levels.
A new life for CO₂
The capture and storage of carbon dioxide are perhaps the alternatives that first appear on the list to stop emitting that CO₂ into the atmosphere, which, for now, is unavoidable. The Intergovernmental Panel on Climate Change warns that these technologies will need to be coupled to carbon-intensive industries because otherwise they will disappear prematurely, increasing the cost of the transition and reducing public acceptance.
Around 230 million tonnes (Mt) of CO₂ are used each year around the world. The largest consumer is the fertilizer industry, where 130 Mt of CO₂ are used in the manufacture of urea. The oil and gas industry consumes some 70-80 Mt in enhanced oil recovery techniques.
It is also used to stimulate plant growth in greenhouses. It is also used in the carbonated beverage industry and in fire extinguishers to put out some types of fire. Other less known uses, perhaps, are the manufacture of concrete and metals.
However, it is necessary to find new uses for CO₂. Uses in products that are used massively and that allow the creation of a circular market and uses where this gas is fixed in products that do not emit.
Among these new uses, the transformation of CO₂ into synthetic fuels stands out due to its scale over other options, followed by the production of construction materials and chemical substances such as methanol and others.
IEA
synthetic fuels
Synthetic fuels are hydrocarbon molecules indistinguishable from those that come from petroleum, but are made from renewable hydrogen and CO₂. They are used in the same way that we use natural gas, gasoline, diesel, aviation kerosene or fuel for ships today, with the difference that their use does not increase the proportion of CO₂ in the atmosphere. In its combustion, the same amount used in its manufacture is emitted, with which the balance of emissions is neutral.
If they began to be mass-produced, they would be a solution to all current mobility. There are some projects to start up these facilities, such as the Sunfire pilot plant in Germany, a European consortium led by EDL-Anlagenbau to install an aviation fuel production plant at the Rotterdam-The Hague airport.
Another project is the association of Copenhagen Airports, Maersk, DSV Panalpina, DFDS, SAS and Ørsted to develop an industrial-scale production facility for synthetic fuels for road, sea and air transport in the Copenhagen area.
In Spain, Repsol will build a plant in the port of Bilbao.
However, assessing the future market for these products is difficult. Theoretically, the use of fuels could grow to scales of several billion tons of CO₂ use per year, but there are implementation difficulties, more of a commercial and regulatory nature than a technological one.
Chemicals and construction materials
The carbon and oxygen in CO₂ can also be used in chemicals such as plastics and synthetic rubber. The most common conversion route is through methanol, a very versatile molecule from which products are manufactured for sectors such as health and hygiene, cosmetics, agriculture and food, among others.
This carbon dioxide is fixed in the materials, forming part of their structure, that is, it is permanently stored in the product. For example, the companies Asahi Kasei Chemicals and Chi Mei Corp. manufacture a polycarbonate using CO₂ as raw material and can reach up to 20% of the weight of the product.
When it comes to construction materials, CO₂ is used to replace water in concrete. It is about making the CO₂ react with calcium and magnesium to form the carbonates of the concrete.
Special mention should be made of the applications that use waste from other industries and CO₂ as starting resources, a double circularity. Among these residues are the steel slag and the ashes that remain after the combustion of coal. To introduce CO₂, the mineralization process is used. Some companies are already betting on this solution, such as the British Carbon8, which uses some 5,000 tons of carbon dioxide per year along with 60,000 tons of waste to make lightweight aggregates for construction.
Carbon Dioxide Capture and Storage. IPCC Special Report, 2005.
These are just a few examples of how we can use CO₂, but its potential to reduce emissions is enormous. A report from the International Energy Forum concludes that, to meet the goals of the Paris Agreement, we need to boost carbon dioxide capture, use and storage technologies to a whopping 5.6 gigatonnes of CO₂ by 2050, from the barely 40 million tons today.
It will also be necessary to develop CO₂ use technologies and a robust life cycle assessment methodology based on clear guidelines and transparent data sets, as well as regulatory frameworks and incentives for lower carbon products.
