1. Your Table 3 and Table 4 are identical for the “Steam Reforming Unit” rows. You say the “improved” scheme (with flare/CO2 recycle) has higher emissions from the downstream Steam Reformer due to extra load, but the CO2 and CH4 numbers for that unit are exactly the same (0.465 kg, 0.034 kg) in both tables. How can the emission factors be identical if the process load changed? Is this a copy-paste error in the manuscript, or is the modeling flawed?
2. Your Scope 2 emission numbers in the Results (Section 4) seem implausibly huge. You state the Distillation Unit produces “34.57 and 20.28 tons of CO2-eq per ton of methanol” from electricity. Producing a single ton of methanol results in twenty to thirty-five tons of CO2 from electricity? That would mean electricity is tens of thousands of times more impactful than the direct process emissions (which are in kg/ton). This looks like a major unit error (maybe it’s kg, not tons?). Can you clarify and correct these figures?
3. Your Conclusion claims integrating a carbon capture unit can reduce Scope 2 emissions by “up to 160%.” A reduction of more than 100% is impossible, it would imply negative emissions from that source. What do you actually mean here? Is this a typo (should it be 60%?), or is there a specific calculation (like a net reduction including avoided emissions) that explains this >100% figure?
4. You use the UK’s electricity grid emission factor for a study focused on Qatar. Qatar’s grid is almost entirely natural gas-based and has a significantly different carbon intensity. How does using the UK factor (0.0005 tCO2-eq/kWh, Table 2) affect the validity of your indirect emission results for a Qatari case study? Shouldn’t the analysis use local data?
5. In Section 4, you state that a 30% production increase leads to a 190% increase in some direct emissions. While possible, a near 200% increase in emissions for a 30% increase in output is extreme. Is this driven by a non-linear process inefficiency, or could it point to an issue in the simulation’s scaling assumptions? This needs more explanation.
