Decarbonisation Technology - February 2023

Mineralisation to capture and use CO 2 from steam methane reforming

Where CCS with underground CO 2 storage is not possible, mineralisation of the CO 2 to chemicals such as soda ash or sodium bicarbonate is an emerging solution

Stephen Harrison sbh4

Carbon capture is an essential tool in the global decarbonisation tool kit Much has been said about CCS – carbon capture and storage. The need to decarbonise is clear. Renewable power generation and green hydrogen may do much of the heavy lifting as they scale up in coming decades, but there are legacy assets that must also be decarbonised, and there are several processes that release CO 2 from within the process chemistry. Neither renewable power nor green hydrogen will be able to avoid CO 2 release from calcium carbonate rock during the calcination of limestone to make lime or cement. Also, steam methane reformers (SMR) release CO 2 from the process chemistry. So, even if the required heat for the endothermic reaction is provided by renewable power, CO 2 emissions from the conversion of the methane to hydrogen-rich syngas would still occur (see Figure 1 ). While the benefits of capturing CO2 emissions before they reach the atmosphere are widely accepted, the possibility of storing CO 2 underground in depleted gas fields or saline aquifers relies heavily on having the right sub-surface geological conditions. In addition to geological constraints, public opinion and political will must also be aligned before underground CO 2 storage can be considered a sequestration method. Carbon capture and mineralisation (CCM) is an alternative to CCS. The starting point is, in principle, the same: CO 2 emissions are captured before they are released into the air. However, instead of storing the CO 2 underground, it is reacted with chemicals to form inert mineral

salts. CCM is, in essence, an example of carbon capture and utilisation. The chemicals that react with the CO 2 to form the minerals can also be used to capture the CO 2 from the flue gas, thereby differentiating from established carbon capture technologies that consume either high amounts of steam or electricity at the CO 2 capture location. Airovation Technologies, based in Israel, has developed an innovative CCM process that reacts commonly available chemicals, such as sodium hydroxide, with CO 2 from flue gases to produce mineral salts, such as sodium carbonate and sodium bicarbonate, which have a wide range of commercial applications.

Steam methane reformer

Notes: – CO is released from the reforming process chemistry. – CO emissions are also associated with heat energy required to drive the reforming reactions. – The heating process can potentially be decarbonised with renewable power and electrical heating or microwaves. _ CCS to capture CO from the process and/or the associated heat energy production is possible.

Figure 1 Steam methane reforming decarbonisation