How do I calculate the CO2 from a process flare?
Measure the gas sent to the flare and its composition, then convert each carbon-bearing gas to CO2 by chemistry: one kilogram of methane burns to 2.75 kilograms of CO2. Report it as Scope 1, and report any unburnt methane separately with its global warming potential.
Data you need
- Flow meter readings for the flare line.
- Gas composition from lab analysis or an online analyser.
- The flare efficiency your method uses, stated as an assumption.
Fossil or biogenic
Flaring fossil gas is Scope 1 fossil CO2. Flaring biogas or landfill gas releases biogenic CO2, reported outside the scopes, while unburnt methane from either still counts in Scope 1.
Pilot and purge gas
The pilot flame and purge gas burn all the time. Meter or estimate them and add them, since they run even when no process gas is flared.
Worked example: one month of flaring (illustrative inputs)
- Flare gas: 2,000 kg methane burnt in the month
- Combustion: 1 kg CH4 burns to 44 / 16 = 2.75 kg CO2
- Burnt at 98% (illustrative): 2,000 x 0.98 x 2.75 = 5,390 kg CO2
- Unburnt methane: 2,000 x 0.02 = 40 kg CH4, reported separately with the AR6 GWP for fossil methane
Gas mass and efficiency are illustrative; use your flow meter, analysis and stated method.
What Senseible does here
Senseible reads the plant's electricity bills (CEA grid factor 0.710 kg CO2 per kWh) and fuel invoices (IPCC 2006 defaults) into dated, fingerprinted Scope 1 and 2 records. A per-unit figure divides those by the output you enter, and purchased materials are added from supplier data on the Scope 3 trail, labelled by source.
Sources: GHG Protocol Corporate Standard, IPCC 2006 Guidelines, Volume 2 Energy (fuel defaults), IPCC AR6 WG1, Chapter 7, Table 7.15 (GWP100)
Last reviewed 2026-10-21.