I skimmed the paper. It does mention 6 bar of pressure and 250 degrees C, so that's a pretty straightforward answer to one question. It says 5% or less of CO2

I skimmed the paper. It does mention 6 bar of pressure and 250 degrees C, so that's a pretty straightforward answer to one question. It says 5% or less of CO2 converted at 15-25% of input, the rest of which is H2. The number seems to be 500 mg of Ru catalyst can process 30 mL / minute of input gas at 6 bar. So ideal gas law (pV = nRT) we know p = 600 kPa, V = 30 mL, T = 250C = 520K, R = 8.3 J/(K mol). n = 600 kPa x 30 mL / (8.3 (J / (K mol)) x 520 K) = 600 (kJ / m^3) x 30 mL / (4316 J / mol) = 600 (J / m^3) x 30 L / (4316 J / mol) = 4.17 mol x (L / m^3) = 0.00417 mol So 4.17 mmol of gas. I'm tempted to multiply by 25% since it says 25% CO2, but I think that only really applies if it's 25% of moles are CO2, but the paper doesn't say if it's 25% by mole, 25% by mass, or 25% by something else (volume maybe?). Assuming this multiplication is legitimate, we get 1.04 mmol (about 1 mmol) of CO2. It says only 5% is converted. So that means 500 mg of Ruthenium can process 0.05 mmol / minute. So the factor is 0.05 mmol / 500 mg, or 0.1 mmol / minute / g. Multiplying by 60x24, we get 144 mmol / day, or 52.56 mol / year assuming 100% uptime. Some quick Googling shows methane costs $1.40 / L and has a volume of 29 L / mol. So the molar price of methane is $40.60 / mol. That means 1g of ruthenium can process $2100 / year worth of methane. Ruthenium is $525 / ounce, or $19 per gram. So to answer my question, I calculate $20 worth of catalyst can produce $2000 worth of methane per year. My formal education in chemistry ended in high school, and that was many years ago, so there might be bad mistakes in these numbers / calculations. Obviously there are some other costs (atmospheric CO2 is free, but purifying it to 25% is not, nor is swapping out the oxygen and nitrogen for hydrogen), I'm not sure it's been established if the catalyst remains effective forever or degrades over time, and they're not simply using ruthenium -- it's Ru / TiO2 and there's some preparation involved. Regardless of those disclaimers, it seems like a catalyst that can pay for itself in a matter of days by turning CO2 into natural gas could be a game changer.