Does a catalytic converter change the methane and nitrous oxide for a petrol vehicle in the Intergovernmental Panel on Climate Change road transport table?
In the Intergovernmental Panel on Climate Change (IPCC) 2006 road table, a petrol car with an oxidation catalyst has less methane (CH4) than an uncontrolled one, 25 against 33 kilograms per terajoule (TJ), but 2.5 times the nitrous oxide (N2O), 8.0 against 3.2. Fleet totals can rise.
The petrol and other road rows
- Motor gasoline, uncontrolled: CH4 33 (range 9.6 to 110), N2O 3.2 (range 0.96 to 11).
- Motor gasoline, oxidation catalyst: CH4 25 (range 7.5 to 86), N2O 8.0 (range 2.6 to 24).
- Motor gasoline, low mileage light duty vehicle, vintage 1995 or later: CH4 3.8 (range 1.1 to 13), N2O 5.7 (range 1.9 to 17).
- Gas or diesel oil: CH4 3.9, N2O 3.9. Natural gas: CH4 92, N2O 3. Liquefied petroleum gas: CH4 62 and N2O 0.2, with no ranges given.
- All in kilograms per TJ. Carbon dioxide (CO2) for motor gasoline is 69,300 kilograms per TJ in Table 3.2.1.
Where the factors come from
The table notes say the petrol rows are based on United States Environmental Protection Agency values for a United States light duty petrol car: uncontrolled, oxidation catalyst, and Tier 1 for the 1995 or later row. They were converted to a per-TJ basis by assuming 10 kilometres per litre for petrol vehicles and 5 for diesel.
The guide says to adjust the petrol defaults downwards if motorcycles are a significant share of the vehicles. It also recommends that, where you know typical fuel economy, you use it with total fuel use to estimate distance, then apply the distance-based Tier 2 factors for N2O and CH4. Table 3.2.3 holds those, in milligrams per kilometre and per cold start, by control technology.
Which row fits an Indian petrol car is your call. The guide's rows describe United States vehicle classes, and the guide does not say which Indian emission standard matches which row. Write down the row you chose and why.
Reading the three petrol rows
Moving from uncontrolled to a catalyst cuts CH4 by a quarter but multiplies N2O by 2.5. In kilograms of carbon dioxide equivalent per TJ at the example global warming potentials below, the three rows come to about 1,772, 2,820 and 1,617, which is 2.6, 4.1 and 2.3 percent of the CO2. So the catalyst row is the highest of the three, and the newest row the lowest.
Road diesel at 3.9 and 3.9 comes to about 1,143 kilograms per TJ, 1.5 percent of its CO2 of 74,100.
10,000 litres of petrol in a company car fleet (example quantities)
- CO2: 10,000 x 2.31 = 23,100 kilograms, which is 23,100 / 69,300 = 0.333 TJ
- Uncontrolled: CH4 0.333 x 33 = 11.0 kilograms; N2O 0.333 x 3.2 = 1.07 kilograms
- Oxidation catalyst: CH4 0.333 x 25 = 8.33 kilograms; N2O 0.333 x 8.0 = 2.67 kilograms
- Vintage 1995 or later: CH4 0.333 x 3.8 = 1.27 kilograms; N2O 0.333 x 5.7 = 1.90 kilograms
- At example global warming potentials (GWP) of 28 for CH4 and 265 for N2O, in kilograms of carbon dioxide equivalent: uncontrolled 308 + 283 = 591; catalyst 233 + 707 = 940; vintage 1995 or later 35.5 + 503.5 = 539
The 10,000 litres and both GWP values are example numbers. 2.31 kilograms of CO2 per litre of petrol is the factor used elsewhere on this site.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records, so the litres of petrol bought show up once uploaded. The records do not show the age or emission class of each vehicle, so keep that list yourself.
- Methane and nitrous oxide from diesel
- CNG three-wheeler cargo vehicles
- Fleet fuel card statements as evidence
- Free calculators
Sources: IPCC 2006 Guidelines, Volume 2 chapter 3: Mobile Combustion (Tables 3.2.1 to 3.2.3)
Last reviewed 2026-11-05. Factors are the 2006 IPCC Tier 1 defaults, based on United States and European vehicle data. Confirm with your verifier which row you use for each vehicle type.