Does a CNG truck emit less CO2 than a diesel truck?
Not automatically. A litre of diesel and a kg of CNG carry almost the same CO2, 2.68 and 2.69 kg, so the result comes down to km per litre against km per kg on your routes. Use your own logbooks, and note that methane slip adds to CNG.
What to compare
- Diesel: litres per km from fuel records.
- CNG: kg per km from filling slips, which record kg.
- The same route, load and season for both.
What tailpipe CO2 leaves out
Unburnt methane from gas engines and leaks in gas supply add to a CNG truck's footprint. A well-to-wheel comparison under the GLEC Framework includes upstream fuel emissions for both fuels.
Reporting
Own trucks burning either fuel are Scope 1. Keep CNG and diesel as separate lines so the factor matches the fuel.
Worked example: 10,000 km on each fuel (illustrative mileages)
- Diesel truck at an assumed 4 km per litre: 10,000 / 4 = 2,500 litres x 2.68 = 6,700 kg CO2
- CNG truck at an assumed 3.5 km per kg: 10,000 / 3.5 = 2,857.1 kg x 2.69 = 7,685.7 kg CO2
- At these mileages the CNG truck emits 985.7 kg CO2 more over 10,000 km, tailpipe CO2 only
Both mileages are assumed inputs; replace them with your own fuel records.
What Senseible does here
Senseible reads fuel invoices and fuel card statements (diesel 2.68 and CNG 2.69 kg CO2, IPCC 2006 defaults) into a fingerprinted Scope 1 record. Hired transport goes to the Scope 3 evidence trail, and distance or tonne-km estimates are labelled as estimates.
Sources: IPCC 2006 Guidelines, Volume 2 Energy (fuel defaults), GLEC Framework for logistics emissions (Smart Freight Centre), GHG Protocol Corporate Standard
Last reviewed 2026-10-21.