Along with cattle and landfills, natural gas is a top source of methane in the US. A big reason why is that our natural gas systems, which are large and complex, have a leak problem. They leak methane from fracking sites, from pipelines, from customer gas meters. These leaks amounted to about 13 million metric tons of methane in 2015. (1) Since methane is a particularly potent greenhouse gas, that means that natural gas is not as clean as we’ve been led to believe.
How big are the leaks? Pictures can help. The chart below shows carbon dioxide emissions in the US from burning fuel for electricity. (2) Even though we generate less electricity from coal than from gas, coal creates over twice the emissions. Coal burns much dirtier than natural gas.
Source of carbon dioxide emissions from US electric power (2017)
But that chart only reflects the burning of the fuel -- it doesn’t account for the leaks in processing and distribution. If you incorporate one-third of the gas leaks into the chart (this is an approximation, reflecting the fact that one-third of our natural gas is used for electricity) the picture for electricity emissions is quite different. With the leaking methane going straight into the air, providing much more of a warming effect than carbon dioxide, natural gas starts looking a lot more like coal. (3)
Accounting for natural gas leaks in emissions from US electric power, measured in CO2 equivalents over a 20-year timeframe
Gas leaks are a major problem. Not only are they a big source of methane, they are costly and dangerous. We need to track them down. But how do you find an invisible gas leak?
Too often, we don’t. Take the Aliso Canyon leak almost 3.5 years ago, which spewed about 100,000 metric tons into the environment. Here’s what it would have looked like if methane were black. (This snapshot is from a video that was shot with a special infrared camera almost two months after the leak was first detected.)
This leak was so big that it was doubling the daily methane emissions for California’s entire gas production early on. But methane is invisible, so despite the size of the leak, we don’t even know when it started. (4)
Detecting (and repairing) methane leaks is essential to hitting California’s goal of reducing greenhouse gas emissions by 40% by 2030. California Senate Bill 1371, passed in 2014, aims directly at this, requiring utilities to improve leak management practices and be more transparent about which leaks they are finding and when they are fixing them. The bill is driving some promising changes. Detection is getting more comprehensive, timely, and accurate. As one example, PG&E is testing specially outfitted cars that will detect large leaks along streets and enable faster repairs. This follows an earlier collaboration between the Environmental Defense Fund and Google Earth, which had customized StreetView cars driving around 15 cities looking for methane leaks. Their easy-to-read writeup has interactive maps showing leaks in each of those cities. Take a look to get a sense of what is going on underground.
But what can each of us do? We don’t have custom cars or methane “sniffers”. I noticed an interesting stat when I was reviewing some of the many reports that have been coming in as a result of SB 1371. It turns out that PG&E reports that 20% of its emissions come from customer meters. As you can see in their presentation, when they examined 200 PG&E meters, they found 58 leaks! They report identifying leaks with a simple soap solution. So I thought I’d take a look at my meter. I mixed some dish soap and water together and rubbed it on the pipes of my meter. To my surprise, I found a leak, which you can see below and in this video. I could smell it when I got close enough.
I live in Palo Alto, so I called the Utilities Dispatch line at 650-329-2579. Within an hour or so, Paul came out to take a look. He reported that it was a decent sized leak, about 40% of the "lower explosive limit". He tightened it and remeasured, and it was gone. He also repainted the meter for good measure.
Paul said that leaks often occur in the "isolation joints", which have a rubber seal intended to prevent electrical conduction. The city puts a small charge on the gas pipes to help prevent corrosion (this is called “cathodic protection”), and workmen sometimes mistakenly ground things to gas pipes instead of to water pipes. So the isolation joint helps to protect both the home and the pipeline.
So, next time you have a minute or two, mix up some dish soap and water, or have your kids do it. Rub it around the joints of the meter and look for bubbles. You can also do this on pipes near your water heater or furnace. If the soap bubbles show a leak, here are some numbers to call:
- PG&E: 1-800-743-5000
- Palo Alto: 650-329-2579
Hopefully you won’t find anything. But if you do, you will decrease your emissions, make your home safer, and perhaps even lower your gas bill!
Next week we’ll take a look at some work going on at Stanford to improve estimates of how much methane is leaking into the air, from oil and gas systems and from our homes.
Notes and References
1. A widely cited 2018 Science article reported this updated value for methane leaks in our oil and natural gas systems. No access? No worries. This writeup by one of the authors has a summary and some background.
2. The electrical mix for the US is available from the Energy Information Administration (EIA). The EIA also provides the emissions figures, and the stat that one-third of natural gas is used for electricity.
3. Methane degrades faster than carbon dioxide. It is 86x worse than CO2 over a 20-year timeframe, but only 34x worse over a 100-year timeframe. I look at the shorter timeframe in this blog post because of the urgent need to turn around our emissions. Experts use both, depending on the context. As you can imagine, there is often contention over which factor to use.
4. An impassioned writeup in Vox, written while the Aliso Canyon leak was still in progress, has this stat and many others.
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