BlogCarbon capture / sequestration

Carbon sequestration

This term means the capturing, removal and storage of carbon dioxide (CO2) from the atmosphere. Considering the fact that 45% of CO2 emitted by humans remains in the atmosphere, carbon sequestration plays a vital role in limiting emissions released into the Earth’s atmosphere and consequently tackling climate change.

Importance of carbon capture

The main goal is to resolve the climate crisis by reaching net-zero by 2050. Therefore, it is important to consider and implement all the available solutions that would make this happen. One part of the solution is to eliminate the emission of carbon dioxide. For example, from processes such as power generation and transport by switching to renewable energy resources and electric vehicles (EVs) respectively. The other part is to capture carbon dioxide directly from the atmosphere or at point of emission, store and utilise it by using Carbon Capture Storage and Utilisation (CCUS) technology.

Types of carbon sequestration/carbon capture:

Biological

Also known as an ‘indirect’ or passive form of sequestration. CO2 is stored in the natural environment. This includes what are known as ‘carbon sinks’

• Forests, woodlands, and grasslands
  These are one of best forms of natural carbon sequestration. CO2 binds to plants during photosynthesis, exchanging it for oxygen as a purifying emission. On average, forests store twice as much carbon as they emit, while an estimated 25% of global CO2 emissions are sequestered alongside forests in other vegetative forms, such as grasslands or rangelands (fields, prairies, shrublands etc.). Human activities such as deforestation, construction, and intensive agriculture pose risk to this method of carbon sequestration.
• Soil
  Through bogs, peat and swamps, CO2 can be captured and stored as carbonates. These carbonates build up over thousands of years as CO2 mixes with other mineral elements, such as calcium or magnesium. Eventually, CO2 is released from the earth, but not for a very long time – after more than 70,000 years in some cases.
• Oceans and other bodies of water
  Aquatic environments and large bodies of water are also great absorbers of CO2. They absorb another estimated 25% of emitted CO2 from the earth’s atmosphere. This carbon is mostly held in the upper layers of the oceans. Too much, however, can acidify the water, posing a threat to the biodiversity that exists below – yet another reason to decarbonise our atmosphere.

Geological

This process is largely artificial or ‘direct’. CO2 is stored in places such as underground geological formations or rocks. It is an effective way of decarbonising emissions put into human practices, such as manufacturing or construction.

They include:

• Graphene production
  The production of graphene requires CO2 as a raw material. Although limited to certain industries, it’s used heavily in the production of the tech devices we use on a day-to-day basis, such as smartphones or computer processors.
• Engineered molecules
  A fairly new science, scientists can change the shape of molecules to form new compounds by capturing CO2 from the air. In practice, this could present an efficient way of creating raw materials while reducing atmospheric carbon.
• Carbon Capture and Storage (CCS)
  CCS involves capturing CO2 that’s been produced by power generation or industrial activity, such as cement or steel making. This CO2 is then compressed and transported to deep underground facilities, where it’s injected into rock formations for permanent storage.

Other types of CCS

• Saline aquifers
  Saline aquifers are geological formations consisting of water-permeable rocks that are saturated with salt water, called brine. CO2 can be injected into these and stored permanently – in fact, saline aquifers have the largest identified storage potential among all other forms of engineered CCS. The ‘Endurance’ aquifer, located in the North Sea off the coast of the UK, is one such formation, which sits approximately 1 mile (1.6km) below the sea bed. Roughly the size of Manhattan Island and the height of The Shard or the Empire State Building, its porous composition allows for carbon dioxide to be injected into it and stored safely for potentially thousands of years. In the US, multiple large-scale saline aquifers are now being used for CCS purposes, such as the Citronelle Project in Alabama. During its three-year trial period, it was successful in storing more than 150,000 tonnes of CO2 per year, which was captured from a nearby pilot facility
• Giant Air Filters
  In China, companies have developed experimental commercial air filters – huge towers that clean air of pollutants on a huge scale. These giant air towers purify the air by drawing it into glass rooms, which are heated using solar power creating a greenhouse effect. This hot air is pushed up the tower through a series of filters before being released back into the atmosphere as clean air. One such giant air-purifier tower in Xian has reportedly been cleaning more than 353 million cubic feet of air each day, dramatically improving local air quality. Manufacturers believe they are close to developing even larger towers, where just one could clean enough air on a daily basis for a small city.
• Ionic liquids
  The most recent advancements in CCS technology includes new types of liquids, which are highly effective at absorbing CO2. Two-dimensional ‘ionic’ liquids have a molecular structure that allows for higher rates of CO2 to be absorbed. Scientists believe ‘editing’ liquids can offer more precise control in the chemical engineering process and are considered environmentally friendly.