What default methane and nitrous oxide does the Intergovernmental Panel on Climate Change give for composting and for anaerobic digestion of solid waste?
The Intergovernmental Panel on Climate Change (IPCC) 2006 default for composting is 4 grams of methane (CH4) and 0.24 grams of nitrous oxide (N2O) per kilogram of wet waste. For a digester at a biogas plant it is 0.8 grams of CH4 and N2O is assumed negligible. The ranges are very wide.
Table 4.1, grams per kilogram of waste treated
- Composting, CH4: 10 on a dry weight basis (range 0.08 to 20), 4 on a wet weight basis (range 0.03 to 8).
- Composting, N2O: 0.6 dry (range 0.2 to 1.6), 0.24 wet (range 0.06 to 0.6).
- Anaerobic digestion at biogas facilities, CH4: 2 dry (range 0 to 20), 0.8 wet (range 0 to 8). N2O: assumed negligible.
- The assumptions behind composting: 25 to 50 percent degradable organic carbon in the dry matter, 2 percent nitrogen in the dry matter and 60 percent moisture. The dry figures for digestion come from the wet ones on the same 60 percent moisture.
What the digester number already includes
The table note says the default for digestion already accounts for CH4 recovery. Equation 4.1 also subtracts recovered CH4 (R). Our reading is that R matters only if you use a factor that excludes recovery; the chapter does not reconcile the two statements, so say which you did. The text adds that unintentional leaks from a biogas plant will generally be between 0 and 10 percent of the CH4 generated, and to use 5 percent as a default value in the absence of further information. Where technical standards ensure leaks are flared, the emission is likely to be close to zero.
The defaults cover only CH4 and N2O. The chapter says composting turns a large share of the waste's degradable carbon into carbon dioxide (CO2), and that CO2 from digestion is of biogenic origin and should be reported only as an information item in the energy sector. Gas burnt for energy is reported under energy, and the guide says the CH4 and N2O from burning it are very small.
Two sets of default figures on this site
The page on this site about the composting tool of the Indian carbon credit scheme gives, as it reports the tool, 0.002 tonnes of CH4 and 0.0002 tonnes of N2O per tonne of wet waste, which is 2 grams and 0.2 grams per kilogram. That is half the IPCC CH4 figure and 17 percent below its N2O figure. They are different documents for different uses. Pick one set, name it in your method note, and do not mix the two within one year.
Poor compost makes more
The IPCC wet-weight figures assume 60 percent moisture; if your waste is wetter or drier, convert through the dry-weight factors. The chapter says poorly working composts are likely to produce more of both gases. The defaults describe typical operation, so a heap that goes without air and turns putrid is not covered by them. Say how the heaps are turned and how long they run.
500 tonnes of food waste a year (example quantity)
- Composted: CH4 500,000 kilograms x 4 grams = 2,000,000 grams, which is 2,000 kilograms. Range 15 to 4,000 kilograms
- Composted: N2O 500,000 x 0.24 grams = 120,000 grams, which is 120 kilograms
- At example global warming potentials (GWP) of 28 and 265: 56,000 + 31,800 = 87,800 kilograms of carbon dioxide equivalent, about 87.8 tonnes
- On the credit tool figures instead: CH4 500 x 2 = 1,000 kilograms and N2O 500 x 0.2 = 100 kilograms
- Digested: CH4 500,000 x 0.8 grams = 400,000 grams, which is 400 kilograms. Range 0 to 4,000 kilograms. N2O assumed negligible
The 500 tonnes and both GWP values are example numbers. The IPCC figures are for wet waste, so weigh the waste as it arrives.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records, so diesel for the shredder and power for the digester show up once uploaded. Tonnes of waste composted or digested come from your own weighing records.
- Food waste: landfill, compost or biogas
- Composting emissions under the credit tool
- Digester methane leakage under the credit tool
- Free calculators
Last reviewed 2026-11-05. Defaults are the 2006 IPCC Tier 1 values, built from a small number of studies. Replace them with measured values if you have them, and check the GWP set your report names.