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HOW CCS WORKS

CO2 CAPTURE

CO2 is separated and captured as high-purity CO2 from gas emitted from thermal power plants and large-scale factories.

One method for CO2 capture is the use of chemicals such as amine solvents to capture the CO2 (chemical absorption).

Scheme of CO2 Capture (Chemical Absorption Method)

Scheme of CO2 Compression and Capture (Chemical Absorption Method) Scheme of CO2 Compression and Capture (Chemical Absorption Method)

CO2 capture at the Tomakomai CCS Demonstration Project

Chemical absorption by amine solvent, which was adopted in the Tomakomai CCS Demonstration Project is widely used in many countries as an established technology, and Japanese industry has long utilized the method in chemical plants and the production process of domestic natural gas. The demonstration project has adopted a system that enables the reduction of the energy required for capture as well as cost, and high-purity CO2 (99% or higher concentration) is stably captured from the CO2 containing gas.

CO2 TRANSPORT

The captured CO2 is then transported to a facility where it is injected underground. Transportation is conducted by such means as dedicated pipelines, transport ships, and tank trucks, rail containers for transportation of small quantities.

Great Plains Synfuel Plant and Weyburn-Midale Project
Great Plains Synfuel Plant and Weyburn-Midale Project (Canada) (Source: Petroleum Technology Research Centre; excerpted and edited by JCCS)
LCO2 transportation ship
Credit: Mitsubishi Shipbuilding Co., Ltd.
LCO2 transportation ship

In the US, approximately 68 million tons of CO2 is transported annually(*1), much of which is used to enhance production by injecting into dwindling oilfields.

*1 Source: Global CCS Institute “How is CO2 transported?”
https://www.globalccsinstitute.com/wp-content/uploads/2018/12/Global-CCS-Institute-Fact-Sheet_Transporting-CO2-1.pdf

In Japan, CO2 used in welding, cleansing of semiconductor substrates, carbonated beverages and dry ice is transported on a daily basis by dedicated vehicles such as tank trucks.

Also, as CO2 emission sources and storage sites are not always in proximity to each other, the development of large-scale ship transportation technology suitable for long distance transportation is being pursued. Ship transportation has the advantage that CO2 emission sources and storage sites can be connected flexibly.

From FY2021, New Energy and Industrial Technology Development Organization (NEDO) has initiated an effort regarding research and development and demonstration to establish liquefied CO2 ship transportation technology with a view towards the social implementation of CCUS technology around 2030.

INJECTION & STORAGE

In the compression and injection process, the high-purity CO2 is sent to underground far away from our living environment, geological layers at depths below 1000m, where CO2 will be stored for a long time.

Storage Area

The reservoir in which the CO2 is stored must be overlain by a formation such as mudstone that does not let the CO2 pass through (cap rock) so that the injected CO2 does not leak. In addition, there must not be active faults nearby.

From previous surveys on available reservoir resources, the total storage capacity in Japan is estimated at around 240 billion tons(*2).

*2 Source: storage potential evaluation results based on RITE (2005), NEDO (2012)

Mechanism of Storage

A main reservoir type is sandstone (rock formed from compacted sand), where there is pore space between the sand grains filled by formation water (brine). CO2 is stored in this pore space. The injected CO2 displaces the formation water in the pores, but remains in the reservoir because it is overlain by a cap rock. It is believed that over a long period of time, the CO2 dissolves in the formation water, reacts with the surrounding rock and mineralizes, thereby becoming stably sequestered.

Injection & Storage