IPCC Volume 5 Chapter 3 · Scope 1
A landfill you operate: first order decay
Waste buried in 1994 is still making methane in 2026. So a landfill's emission for one year is a sum over every year of waste before it, decaying at a rate set by what it is and where the site is.
On this page you'll learn
- How the decay model works
- What a disposal site needs to hold
- Why this must never be added to a per-tonne waste figure
- Scope
- 1, for the operator
- Method
- IPCC First Order Decay (FOD)
- Assets
- Disposal site and its yearly disposal history
- Category code
operated_swds
The model
- 1
Decomposable carbon deposited
DDOCm = W × DOC × DOCf × MCF: tonnes of each waste type × its degradable carbon × the fraction that decomposes × the site's methane correction factor.
- 2
Carry forward and decay
Each year, what's left decays by e^−k, where k depends on the waste and the climate zone.
- 3
Methane generated
Decomposed carbon × F (methane share of the gas) × 16/12.
- 4
Methane emitted
(Generated − recovered) × (1 − OX), where OX is oxidation in the cover.
- R
- methane recovered and burned or flared
- OX
- oxidation factor; 0 for sites without an oxidising cover
Decay starts on 1 January of the year after disposal, IPCC's default. The record's quantity isn't used: the input is the site's whole history, and in the year a site closes this year's deposit is zero beside a large emission.
Parameters
Decay rate k
From Table 3.3, by material and climate zone. It runs from 0.02 to 0.4, a factor of 20, so a missing combination is refused rather than borrowed from a neighbour.
Degradable carbon
From three tables: municipal waste components, industrial waste by industry, and hazardous and clinical waste. A landfill takes all three.
No k for nappies, rubber and leather
They have degradable carbon but Table 3.3 names no decay class for them, and filing them under "other" would be Slate's guess with IPCC's name on it.
Operator, not sender
Why this matters
A per-tonne waste factor for waste you send away already contains a national average run of this same model. If you operate the landfill, report this; if you send waste to it, report the Scope 3 figure. Never both for the same site and year.