Disclosed herein is a method of regenerating a sorbent of gas in a capture process of said gas, wherein the capture process comprises recirculating the sorbent between a gas capturing system and regenerating reactor system, the method comprising the regenerating reactor system performing the steps of: receiving a solid sorbent to be regenerated, wherein the sorbent is a sorbent of carbon dioxide gas; generating heat by combusting a fuel with an oxidising agent in the presence of a catalyst; regenerating the sorbent by using the generated heat to indirectly heat the sorbent so that the sorbent releases carbon dioxide gas; outputting the regenerated sorbent; and outputting the released carbon dioxide gas. Advantages of the gas capture system include a higher efficiency than known techniques.