Gas collection efficiency
The proportion of generated gas successfully captured by a collection system.
Example
This ratio helps assess how much methane may still escape from a landfill.
The catch
Generated gas is often estimated, so the denominator carries uncertainty.
Related terms
Methane, Anaerobic decomposition, Anaerobic digestion, Biogas, Biomethane, Composting
In more depth
Gas collection efficiency, explained.
Gas collection efficiency is the figure that decides how much of a landfill's methane a capture project can claim. The top of the fraction rests on measurement, since operators meter the flow and methane content of gas drawn through the wells. The bottom comes from a model of how fast the buried waste decomposes, built on tonnages, waste types and moisture.
Efficiency changes as a site ages. Active cells under thin temporary cover tend to lose more gas than closed areas with a dense well field under a well-maintained landfill cover. Keep it separate from destruction efficiency, which describes what happens to gas after collection. A credible estimate of the climate benefit multiplies the two and allows for downtime. Be wary of a single high default value applied for the whole operating period.