You are correct: >4. Sabatier reactor >Inside this machine, a blast of roughly 750°F heat breaks the bonds inside CO₂, forcing it into its constituent element

You are correct: >4. Sabatier reactor >Inside this machine, a blast of roughly 750°F heat breaks the bonds inside CO₂, forcing it into its constituent elements. The carbon and oxygen combine with hydrogen from the station’s ­oxygen ­generating system to make H₂O and methane (CH₄), the latter of which vents into space. https://www.popsci.com/how-iss-recycles-air-and-water/ https://www.popsci.com/how-iss-recycles-air-and-water/