2 (CH2O) ----------> CH4 + CO2
Answer
If you answered 36 litres x 103, then you were correct
Mass of organic matter oxidised = 3000 mol;
Acc to eqn, 3000 mol CH2O = 1500 mol CH4;
Volume of methane with this mass = 1500 x 24 litres = 36,000 litres (or 36 litres x 103)