July 22nd, 2024
Written By: Richard Xu
Hello! Richard here again! Today, I’m blogging to detail my findings with Nikira’s Portable Methane Analyzer or PMA at Shoreline park in Mountain View, CA. Over the days of June 25th, 27th, and 28th, I collected data that really displays why the PMA is in a class of its own!
For context, Shoreline, though a beautiful man-made lake, is actually built on top of an old landfill! Landfill decomposition produces biomethane, which travels up into the atmosphere through man-made venting standpipes, as well as through the various cracks in the park ground. As bad as that sounds for our environment, it is necessary to prevent CH₄ gas pressure buildup which can cause a deadly explosion.
Knowing that the Shoreline park area is guaranteed to produce methane means that we can test our PMA’s ability to sniff out spots in which methane consistently leaks, and potentially find spots that exhibit reproducible results.
Our June 25th Date
On June 25th, I drove out to Shoreline’s kite lot with a PMA unit in tow to explore possible spots emitting significant CH₄ signals. In the trunk of my Toyota Corolla, I was easily able to set up the PMA within a few minutes. All I had to do was remove it from its case, attach the shoulder strap, connect the GPS dongle, and click-on the inlet filter, then turn the unit on and then…off we went to find some leaks!
With the PMA strapped around my shoulder (messenger bag style), I began to walk around the kite lot. While monitoring the PMA’s real-time updating screen, I was also able to receive double the insight with my mobile phone which offered additional real-time insights after pairing it with the analyzer. With the CH₄ background level being around 2.104 ppm (parts per million), I began to search for spots that would yield a significantly higher CH₄ signal.
The first half of the loop was pretty unremarkable. There were the occasional 3 to 4 ppm blips, but nothing “massive” that could be replicated. However, as I finished the initial half of the loop and was beginning to turn back, I hit a relatively “massive” 11 ppm blip that made the real-time graph spike. I stayed in the area to see if it would consistently stay at a high ppm level and amazingly it did! In order to mark it as a consistent source for CH₄ leakage, I had to attempt to locate the source. Unfortunately, after five minutes of scanning the path and looking for pipes jutting out of the ground, I was unable to pinpoint the CH₄ source.
Disregarding it as a strong gust of wind blowing over air from a distant leak source, I decided to finish up the rest of the loop which, unfortunately, was just as unremarkable as the rest.
Using GPS Visualizer, I plotted the data graphically, as shown below, to visually share the results with the Nikira Labs team. Based on it, I was given two new objectives for a later date:
I was tasked to head back in order to check if the spot where I had detected a high CH₄ reading was a consistently “leaky” spot or just a fluke.
Check the lower half of the kite lot to check for high-methane releasing standpipes since they tend to be more in the lower half.
And so, my second scheduled date with my PMAte was set for the 27th of June. Talk about a strong first impression!
The Follow-Up: June 27th
As planned, on the 27th, I took my PMAte out again to get more readings at the same location in order to confirm the previous outing’s data; the results this time were indeed remarkable.
For starters, upon doubling back on the same path towards the significant CH₄ leak spot from June 25th, the analyzer was able to detect a NEAR IDENTICAL methane signal, as expressed in ppm units, in the EXACT SAME SPOT. Using the graphic below, it shows that the coordinates of the leak are now detected within a step or two away, at most, from one another and that the gradient of CH₄ buildup to the peak CH₄ concentration is the same.
Unfortunately, despite spending an even longer time searching for the source compared to the previous attempt, I was still unable to locate the methane leak source. However, there was no doubt in my mind that it wasn’t just a gust of wind that had brought about the first CH₄ strike, as I’m certain it wouldn’t be as gracious to bring me a second one. Thus, I deemed this spot reproducible in terms of location and concentration.
To me, this closeup of the heat map just gives more proof to how sophisticated and sensitive the PMA technology is for it to output an identical result for such an intricate, precise process that is measuring methane leakage.
But it gets even better.
During this outing, as promised, I also measured multiple gas valve covers on the lower half of the park to see if any of them were leaking. After a bit of searching, I found one where the plastic sealing had chipped away, and wanting to see if it’d do anything, stuck the inlet of the PMA into the tiny hole in the cover. I was able to constantly measure over 6000 ppm (0.6% CH₄!!!), an amount that dwarfed the other instance, by all means.
This spot was going to be our new test location for methane leak detection given its consistent leak rate and ease of access.
Afterwards, I proceeded to the other gas valves where I measured 7 to 8 ppm, an amount that is significantly above noise, but was relatively nominal compared to what I had just measured prior.
When I got back to the lab, I hastily imported the data of the PMA to my computer and began to plot it. Upon initial inspection of my heat map, I quickly realized that 6000 ppm was an amount so relatively large that it completely dwarfed anything under 50 ppm and made reading the heat map irrelevant.
Using the power of the programming language R, I removed all observations with a ppm above 50 then replotted the heat map to better show the intricate detection during the Shoreline walk.
Third Time's The Charm! June 28th Outing
Now that we had confirmed our consistent methane leakage spot, the Nikira team assigned a new task for my fellow intern Sam and myself. Sam had just finished writing some wonderful Python code that allowed us to pair a 3D anemometer with the PMA along with realtime GPS and wind speed and direction data logging. His algorithm would also use published Gaussian Plume Dispersion Models to calculate the CH₄ emissions leak rate in realtime and on-the-go!
On June 28th (three dates within four days!), we brought the anemometer equipped PMA to our “favorite spot” and began to set up shop to test and evaluate Sam’s newly coded algorithm. This required having the PMA as low to the ground as possible and stable, hence the use of a short tripod, then measuring exactly six feet/two meters downwind from the CH₄ leak source.
We sat out of the wind's way as the PMA gathered data for two separate 20 minute long trials. As planned, the PMA consistently detected CH₄ leaks blown by the wind ranging from 10 to 50 ppm! Once we had gathered enough data for us to work with, it was time to show the practicality of the anemometer attachment via realtime data visualization and analysis.
After bringing the PMA back to Nikira Labs and looking through the data, the Nikira team plotted the data into two polar plots that allowed for the convenient visualization of the wind direction and its associated CH₄ leak rate as detected by the PMA+Anemometer bundle.
The center of the plot represents the zero leak rate of CH₄, while the outward increasing concentric circles represent the increasing CH₄ leak rates. The angle at which the bubble is coming from indicates the wind direction at six feet/two meters downwind from the leak source. The size of the bubble indicates the leak rate magnitude. With post-processing enhancement, we color-depicted the bubbles according to the heat scale located on the right, for ease of visualization.
Afterthoughts
At the expense of tooting our own technology’s horn, the power of this technology bundle (PMA+Anemometer) never fails to blow my mind. As a young, curious adult, there’s nothing more important to me than exploration and getting real hands-on experience; so, being able to do a full new product trial and produce the first evaluation data for this Nikira product is priceless.
Needless to say, it also makes me proud of what I’ve learned and practiced as I was able to witness and use the power of programming (Sam’s and mine) to produce some of these awesome visuals that help our readers to visually grasp the story I am trying to tell. Until the next blog!
Comments