What is the first-order decay model for landfill gas?

It models gas generation as G(t) = k × L0 × M × e^(−k×t), where k is the decay rate constant (yr⁻¹), L0 is the gas generation potential (m³/Mg), M is the waste mass (Mg), and t is waste age (years). Generation peaks near placement and declines exponentially as degradable organic content is consumed.

What is a typical k value for municipal solid waste?

For MSW in a humid climate, k is commonly 0.04–0.10 yr⁻¹. Arid climates use lower values (0.02–0.04) because moisture limits decomposition. Wet-cell or bioreactor landfills can reach 0.10–0.30 yr⁻¹. The EPA Landfill Gas Emissions Model (LandGEM) default for conventional MSW is 0.04 yr⁻¹.

What is L0 and how is it determined?

L0 (gas generation potential) represents the total LFG that one metric ton of waste can produce over its lifetime, typically 100–200 m³/Mg for MSW and 40–100 m³/Mg for C&D debris. It depends on the organic content of the waste stream and is measured by laboratory testing or derived from EPA defaults.

Why is methane 50% of landfill gas?

Anaerobic decomposition of organic matter produces roughly equal volumes of methane (CH4) and carbon dioxide (CO2), so LFG is approximately 50% CH4 and 50% CO2 by volume. The exact ratio varies (45–60% CH4) with waste composition, age, and moisture; 50% is the standard engineering default.

How is the energy content of landfill gas calculated?

Methane has a higher heating value of approximately 35.8 MJ/m³ (about 1,000 BTU/scf). Energy output = methane volume (m³/yr) × 35.8 MJ/m³, then converted to MWh by dividing by 3,600 MJ/MWh. Actual electrical output depends on conversion efficiency (typically 25–35% for internal combustion engines).

Does this tool account for gas collection efficiency?

No. The calculator estimates gross LFG generation. A real collection system captures 60–85% of generated gas depending on cover type, infrastructure design, and regulatory requirements. Apply a collection efficiency factor to the output when sizing equipment or projecting recoverable energy.

Landfill Gas Calculator

Name: Landfill Gas Calculator
Availability: InStock
Author: Nham Vu

Enter waste mass, age, and decay constant to estimate annual landfill gas generation, methane volume, and equivalent energy output.

Landfill Parameters

Waste Mass (Mg = metric tons)

1 short ton ≈ 0.907 Mg | 1 Mg = 1 tonne

Waste Type

k — Decay Constant (yr^-1)

L0 — Gas Yield (m³/Mg)

Waste Age — Years Since Placement

Use 0 to see peak generation at time of placement.

Default values by waste type

Enter landfill parameters and click Calculate.

LFG Generation at Year —

LFG Generation

—

m³/year

LFG Flow Rate

—

MMscfd

Methane Volume

—

m³ CH4/year

Energy Potential

—

MWh/year

BTU/year

—

Avg MW Output

—

gross

CH4 (scf/year)

—

LFG Generation Over 20 Years

Year	LFG (m³/yr)	CH4 (m³/yr)	Energy (MWh/yr)	% of Peak

Based on G(t) = k × L0 × M × e^−kt. Does not account for gas collection efficiency or cover losses.

Summary

Enter waste mass, age, and decay constant to estimate annual landfill gas generation, methane volume, and equivalent energy output.

How it works

Enter the mass of waste placed in the landfill and select the waste type to load a default decay constant (k) and gas yield (L0).
Set the current age of the waste (years since placement).
Adjust k and L0 if site-specific data are available.
The calculator applies G(t) = k × L0 × M × e^(−k×t) to find the current annual LFG generation rate.
Methane volume is 50% of LFG by volume; energy is methane volume × 35.8 MJ/m³ converted to MWh.
The year-by-year table shows how gas generation declines over the first 20 years.

Use cases

Size a gas collection and control system (GCCS) for a new or existing landfill.
Estimate energy recovery potential for a landfill gas-to-energy (LFGTE) project.
Screen sites for EPA Landfill Methane Outreach Program (LMOP) eligibility.
Compare LFG yield from municipal solid waste versus construction and demolition debris.
Support greenhouse gas inventory and carbon credit calculations.
Generate preliminary design data for landfill flaring or power generation equipment.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu