# How much heat did the Sabatier hardware add to the ISS heat profile?

A sort-of follow-up to Why does the International Space Station produce so much methane?

In 2010 Sabatier hardware was integrated into the regenerative environment control. The Sabatier hardware implements the Sabatier process; this retrieves water out of the Carbon Dioxide, Hydrogen present ...

$$\require{mhchem}\ce{CO2 + 4H2 -> CH4 + 2H2O}$$ With a crew of 6, the system is capable of recovering up to 2000 pounds of water annually. I could be wrong, but iirc the reaction liberates some heat-energy in the process.

• How much heat did the Sabatier hardware add to the annual ISS heat profile?
• As a corollary, what is the overload capacity built into the thermal management system on the ISS?

Enthalpy released is about 165 kJ / mol of $\require{mhchem}\ce{CO2}$. 2,000 lb of water is about 50 kmol, requiring 25 kmol of $\ce{CO2}$. Thus long-term average heat output is 165 kJ * 25000 / 1 year = 130 watts, which is trivial compared to the overall ISS heat profile.