Landfill Methane Monitoring: Compliance vs. Performance (and How to Win at Both)

rreale5
Oct 5, 2025
3 min read

Updated: Oct 28, 2025

Methane monitoring requirements for municipal solid waste (MSW) landfills are tightening under federal and state enforcement. Operators are increasingly faced with the decision: stick with EPA Method 21, switch to OTM-51, or add drone-based emissions studies (non-compliance) for proactive insights.

Each path has advantages and trade-offs, and the wrong choice—or poor execution—can expose landfills to fines, consent orders, and costly corrective actions.

Method 21: The Traditional Approach

Overview: Method 21 is the longstanding EPA standard for surface emissions monitoring (SEM). A technician walks the landfill with a flame ionization detector (FID), checking methane concentrations along a grid.

Pros

Widely recognized and accepted by regulators.
Low upfront equipment cost.
Simple to implement with existing staff or contractors.

Cons

Labor-intensive and time-consuming.
Operator-dependent; higher chance of missed leaks.
Inconsistent data collection.
Limited spatial resolution (typically 30-meter grid spacing).
Safety risks on uneven terrain.

OTM-51: Aerial Remote Sensing

Overview: OTM-51 allows remote sensing technologies (ie: SnifferDRONE™) to measure methane emissions with greater coverage and precision.

Pros

Provides higher-resolution, repeatable data.
Safer—no need for staff to traverse hazardous terrain.
Pinpoints emissions plumes for faster, targeted repairs.
Faster coverage of large areas.

Cons

Requires specialized equipment and trained/licensed operators.
Permit modifications may be needed.
State-specific adoption and revert clauses can create unnecessary "red tape" when changing methods.

View the infographic comparison of Method 21 to OTM-51

The Cost of Non-Compliance

Failing to control methane emissions can lead to consent orders, enforcement actions, and large fines.

Real World Example 1: ~$671,000 penalty for emission calculation failures and delayed gas collection system installation.
Real World Example 2: ~$104,000 penalty for insufficient monitoring and toxic air emissions violations.

In addition to penalties, consent orders usually require:

Installing or upgrading gas collection systems.
Enhanced monitoring and reporting (often at a higher, more costly frequency than normal compliance).
Technology upgrades, often including drone or remote sensing systems.
Ongoing oversight, with stipulated penalties for future lapses.

Converting from Method 21 to OTM-51: Opportunity & Hesitation

Converting to OTM-51 is the most effective way to identify methane and achieve consistent quarter-to-quarter results. But many operators hesitate because:

Statewide adoption is uneven, creating uncertainty.
Permit modifications are time-consuming and expensive.
Revert clauses (red tape) may sound daunting to landfill operators.

Why You Don’t Have to Choose

While Method 21 ensures compliance and OTM-51 enhances it, operators don’t have to lock themselves into one option. Drone-based emissions studies (non-compliance) provide an additional layer of insight and protection.

Tighter spacing, more often – Conduct emissions studies once, twice, or multiple times per year at resolutions beyond regulatory minimums.
Actionable data – Identify leaks early (<200 ppm) and direct repair crews with precision.
Preemptive repairs – Fix issues before quarterly compliance checks, avoiding exceedances and rechecks.
Avoid fines and consent orders – Reduce the chance of repeat violations and costly enforcement.
Operational efficiency – Eliminate rush repairs and improve long-term O&M outcomes.

Enforcement Costs vs. Preventive Monitoring

Here’s how the cost trade-offs look when comparing Method 21, OTM-51, and proactive drone-based emissions studies:

The takeaway is clear: investing slightly more in non-compliance emissions studies upfront saves exponentially more by avoiding consent orders, emergency repairs, and reputational damage.

Quarterly Method 21 monitoring at 30-meter spacing carries the highest risk profile and the greatest chance of regulatory fines and consent orders. Consent orders are the most costly due to fines and heightened requirements for monitoring, which can be as frequent as weekly. Automating the inspection (data collection) process reduces these risks, while performing additional, non-regulatory studies at 15-meter spacing provides landfill operators with the best data for managing fugitive emissions and avoiding penalties.

Final Thought

Choosing between Method 21 and OTM-51 isn’t just about compliance—it’s about balancing risk, cost, and operational efficiency. Drone-based emissions monitoring changes the equation by offering proactive, high-resolution insights that go beyond compliance to protect budgets, reputations, and community trust.

The smartest move? Use compliance monitoring as your baseline—and then leverage emission studies for proactive emissions management.