How do you convert Methane volume to Carbon mass?

Question

Cows produce 500 liters of methane per day. I'm trying to convert this to Carbon Dioxide tonnage to understand the potential equivalent in carbon emissions, and its carbon credit potential.

Answer 1

Use PV = nRT to find the number of moles.

You could multiply your answer by the molar mass of carbon dioxide.  This is what methane released into the atmosphere eventually gets turned into.  However, in the meantime, methane, mole for mole, is the more serious greenhouse gas.  The effect is not negligible; another reason for going vegetarian.

Answer 2

1 mol of methane gas has a volume of 22.4litres

500litres of metane gas is therefore 22.32mols CH4

CH4 + 2 O2 = CO2 + 2 H2O

1mol CH4 produces 1mol CO2

Therefore 22.32mol CH4 will produce 22.32mol CO2

Molar mass CO2 = 12+16+16 = 44g

22.32 mol of CO2 has mass of 22.32*44 = 982 g CO2

In round terms you can say that each cow produces 1kg of CO2 per day