This blog post is adapted from a webinar, Evaluation of Downwind and Offshore Solutions for Methane Detection and Quantification, held on October 10, 2024. The guests were Camilla Fassio, Wind and Marine Energy Technologist, Eni, and Dr. Peter Evans, Senior Engineer for Methane Measurement and Reduction, bp. The moderator was Brian Redick, Senior Associate, Climate Investment. We thank the above experts for contributing their time and insights.
An old adage holds that you cannot address what you do not measure. When it comes to getting a handle on methane emissions and methane mitigation, this is rule number one. While emissions reduction advocates hammer home the importance of measurement, exactly how to do so can be a tricky task for many organizations.
Many technical options exist for site-level measurements, each with benefits and drawbacks. A common technique involves manually carrying a device that can measure methane concentration around a facility and recording readings. This can provide readings that are fairly close the ground, but such devices only measure methane concentration, not absolute mass of methane particles. This method may also miss leaks that cannot be easily accessed by a person on foot. This prevents managers from performing the fullest, most comprehensive measurements.
Ground-mounted that can “see” methane emissions are an option that can be used to perform measurements over time, since they stay in one place and can, in theory, operate continuously. At the same time, they also may not be able to capture every potential emissions source, since buildings or other structures may block their line of sight. Mobile cameras are another option, but with drawbacks similar to the mobile monitoring device mentioned above. More comprehensive are aerial monitoring devices, like satellites or aircraft mounted with sensors. Although these options growing in popularity, neither can provide extremely granular measurements (although satellites in particular are improving rapidly).
Drones Do It Differently
Drones are another story. They can be launched in direct proximity to methane plumes, capturing the concentration of methane particles in the atmosphere around a facility square-on. They are nimble, easily moveable and do not require complicated set-up or maintenance. In many ways, drones can serve as a low-barriers solution for methane monitoring, able to be deployed without much fuss or fanfare.
This is important because measuring emissions depends on a variety of factors, many of which are outside one’s control. Weather is arguably the most important one, since measurements are being taken in open air. The ideal scenario is clear skies and light, regular wind, since this will allow the drone to hover downwind of the methane plume and intercept a representative sample of emissions. The sweet spot for wind speed is between 2–10 m/s; too slow, and the wind will not push the plume toward the drone; faster wind speed, however, could impair the drone’s ability to fly properly.
Measuring wind can be done with a device called an anemometer; this can be mounted on the drone itself to get a clear picture of wind speed up in the air—which may, crucially, be different than ground-level wind speed. This is especially true in offshore locations, where wind speeds at altitude may be dramatically different than at sea level. Operators also need to make sure they are in full compliance with local regulations regarding drones, as some places are more permissive than others about flying drones over open land.
The Business Case for Measurement
The best approach is a mix of different methods, including handheld devices, cameras, drones, aircraft and satellites where possible. Just as important as measurement itself is laying the groundwork to get a successful assessment. Talk to key stakeholders in the facility under scrutiny to understand the state of play. Do operations change significantly day-to-day, week-to-week, month-to-month, seasonally? When are you most likely to get a representative sample of emissions? These questions will help you know what to expect and calibrate your methodology appropriately.
Ultimately, in a world of limited resources, any quantitative measurement is better than none at all. On-site emissions measurement is still a nascent field, and standards and best practices are evolving rapidly. Each measurement adds to the aggregate body of knowledge and fills in that much more of the global picture. For your organization, it will help to not just meet sustainability aims and regulatory requirements, but to make better business decisions and strengthen your competitiveness.
