What is CCUS?

What is CCUS?

There are several different answers to the question, what is CCUS? 

CCUS stands for carbon capture, utilisation and storage. CCUS is an umbrella term for several different technologies.¹ Generally speaking, CCUS refers to capturing carbon dioxide (CO2) released by power plants or industrial processes.² Then, the CO2 is transported to be utilised in various products and services. Alternatively, it is permanently stored underground in geological formations.³ 

Storing CO2 keeps it from the atmosphere and prevents it from contributing to global warming. However, 80 per cent of the carbon currently captured by CCUS is employed in enhanced oil recovery.⁴ Subsequently, it helps to produce more fossil fuels, which release additional carbon and drive climate change.⁵ The potential for CCUS as a climate change solution depends upon storing it permanently. 

What is CCUS: Post-combustion carbon capture

Unsurprisingly, post-combustion capture is the most common CO2 capture technique.⁶ What’s more, it is relatively easy to modify existing power plants and industrial facilities to incorporate this technology.⁷ New plants can also be designed to include end-of-pipe capture capabilities.⁸ 

Post-combustion CCUS and CO2

Post-combustion CCUS involves separating CO2 from the exhaust of a combustion process.⁹ When fossil fuels are burned, they produce flue gases composed of CO2, water vapour, sulphur dioxides and nitrogen oxides.¹⁰ The flue gas is passed through a solvent which absorbs the CO2.¹¹ This is subsequently heated to release any water vapour and leave behind a concentrated stream of CO2.¹² 

The post-combustion method can capture 80 to 90 per cent of the carbon emissions produced by power plants or industrial processes.¹³ However, it requires a large amount of energy to compress the remaining gas sufficiently to transport it.¹⁴ For instance, the coal-fired power station Boundary Dam in Canada uses 25 per cent of the plant’s total output to operate its CCUS facilities.¹⁵ This has negative environmental repercussions since the CCUS technology necessitates burning more fossil fuels to work.

What is CCUS: Pre-combustion carbon capture

Some industrial facilities are using commercially available pre-combustion capture technology.¹⁶ However, its applicability for power plants remains underdeveloped.¹⁷ 

Pre-combustion capture removes CO2 from fossil fuels before combustion. First, the fuel must be oxidised into synthesis gas – or syngas – containing CO2, hydrogen, carbon monoxide and other components. Second, the syngas undergoes a water-gas shift reaction to produce a hydrogen and CO2-rich gas mixture. From here, the CO2 can be captured and transported. It leaves the remaining hydrogen gas for combustion without producing carbon emissions.¹⁸

The complexities of pre-combustion carbon capture

One problem with pre-combustion carbon capture lies in its complexity. The fuel conversion steps make it more difficult to apply to existing power plants. Therefore, it must be incorporated into new-build power plant projects. However, it is used in industrial facilities, such as natural gas processing.¹⁹ 

What is CCUS: Oxy-fuel combustion

The third technology for carbon capture and storage is oxy-fuel combustion. With this, fuel burns in oxygen rather than in the air.²⁰ As a result of removing the presence of nitrogen, the purer mixture burns at a higher temperature, increasing the efficiency of combustion.²¹ 

It also produces a flue gas that is predominantly H2O and CO2, making the CO2 simpler to capture. The water vapour is easily condensable, and it leaves behind a highly concentrated CO2 stream that can be compressed and stored. However, this technique is still under development.²²

Is carbon capture a solution to climate change?

Some proponents regard CCUS as a solution to climate change.²³ Its potential to prevent CO2 emissions from entering the atmosphere would undoubtedly help stop power plants and industrial complexes from eating away our remaining carbon budget. Capturing and storing the carbon stops it from entering the atmosphere and contributing to global warming. This is significant because raising the atmospheric concentration of CO2 is the most important long-term “forcing” of climate change.²⁴ 

Current carbon dioxide (CO2) CCUS efforts: Are they enough?

However, as a feasible solution to climate change, time is running out for CCUS. In fact, there are just 19 large-scale industrial and two large-scale CCUS power facilities in operation today. Collectively, their capacity for CO2 capture is 40 million tonnes per year. Sadly, the estimated mitigation needed to stay on a 1.5°C increase climate trajectory requires an increase of 35 from the current capacity.

What is CCUS’ future impact?

There are only 20 additional projects in development, and such large capital projects require six to ten years from conception to completion. Therefore, it is doubtful that CCUS will capture sufficient carbon by 2030.²⁵

Repurposing of CO2 and its repercussions

Moreover, even the CCUS facilities in operation do not necessarily help to solve climate change. 80 per cent of the carbon captured today is used for enhanced oil recovery.²⁶ This means that although CCUS prevents CO2 from entering the atmosphere, the majority of facilities repurpose it to produce more fossil fuels. In fact, 89 per cent of global CO2 emissions came from fossil fuels and industry in 2018.²⁷ Using captured carbon for enhanced oil recovery to obtain more oil thereby negates the technology as a solution to climate change.

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