Landfill Gas Generation Curve: 2D LandGEM Decay Model

Landfill Inputs

Waste acceptance rate 180,000 Mg/yr

Decay rate k 0.05 /yr

Methane potential L₀ 100 m³/Mg

Active life (closure) 20 yr

Time

Simulation year t 0.0 yr

View

Mound rotation 30°

Live Readouts

Year

0.0

Phase

Filling

CH₄ generation rate

0 m³/yr

Cumulative CH₄ generated

0 million m³

Peak generation year (est.)

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How it works

This is the U.S. EPA LandGEM first-order decay model, drawn here as a flattened 2D isometric mound instead of a 3D scene. Waste is deposited in discrete annual increments M_i (tonnes). Each increment's methane output decays exponentially from the moment it is buried:

Q(t) = Σᵢ k · L₀ · Mᵢ · e^(−k·(t−i))   for i ≤ t

k  = decay rate (yr⁻¹) — how fast the waste's organic
     fraction is consumed by anaerobic bacteria
L₀ = methane generation potential (m³ CH₄ / Mg waste)
Mᵢ = waste mass placed in year i (Mg)
t  = current simulation year

Every "cell" placed while the site is active starts its own decaying exponential the day it's buried; the isometric mound plots one cell per year on a golden-angle spiral so none overlap, its glow showing e^(−k·(t−i)) — the fraction of its original output still remaining. The lower panel sums every still-decaying cell into the site's total generation rate: it rises while new, high-output cells keep arriving faster than old ones fade, peaks around closure, and then falls exponentially for decades once no new cells arrive — the classic asymmetric landfill-gas curve used to size gas-collection wells and flares.

Waste rate — tonnes accepted each year while the landfill is active (bigger mound, more gas).
Decay rate k — wetter/warmer sites (more rainfall) decay faster; arid sites decay slower.
L₀ — depends on waste composition; more food/paper waste means higher methane potential.
Active life — how many years the site keeps accepting waste before closure; generation keeps rising until this point.
Drag inside the mound panel (or use the rotation slider) to spin the isometric view around the vertical axis.

Year 0.0 — Filling

drag to rotate

Fresh waste cell (high output) Depleted cell (low output) Total generation curve