Author: Jennifer Allford, for the Schulich School of Engineering
Setareh Homayoonnia, left, works with Arindam Phani on a new methane sensor. Photo by Fritz Tolentino
Methane is considered one of the more powerful greenhouse gases (GHG). Researchers at the Schulich School of Engineering have developed a sensor that detects methane at extremely low concentrations inside and outside industrial facilities. This new tool is aimed at helping industry reduce GHG emissions that are contributing to climate change.
Methane quickly dilutes and mixes with other gases in the air, making it difficult to detect. Current laser technologies used to identify methane leaks or fugitive emissions are expensive, complicated to use and cumbersome.
Using a new class of nanocomposites, the Schulich researchers have developed sensors that detect methane at extremely low concentrations, in the order of 10 parts per billion (ppb) or only 10 molecules of methane for every billion gas molecules in a mixture.
The researchers predict this new class of sensor may detect methane as little as 0.22 ppb. Achieving this "hitherto unprecedented" sensitivity in real-world conditions will help guide further development of new, more accurate sensors, say the researchers at Schulich's Nano/Micro-Sensors and Sensing Systems (NMSSS) laboratory.
"It's the first low-cost and miniaturized integrated gas sensor that can detect methane at ppb levels at ambient conditions and in atmospheric pressure," says Setareh Homayoonnia, a PhD candidate in mechanical and manufacturing engineering and lead author of the study, which you can read here.
"Our target was to develop very sensitive as well as a selective methane sensor which can be implemented outside a plant or even indoors to detect leakage or errors in the system," says the head of the NMSSS lab, Dr. Seonghwan (Sam) Kim, PhD, associate professor and Canada Research Chair in Nano Sensing Systems in Mechanical and Manufacturing Engineering at Schulich.
"In the air, there's a background of methane in approximately 1.8 parts per million (ppm)," he says. "If you have sensors which only detect down to ppm level of methane, then you cannot distinguish the background fluctuation. So, we need to have methane sensors with ppb parts per billion-level sensitivity to detect certain unwanted happenings or leaks."
Nanomaterials on chips absorb methane
The nanocomposite materials are on microchips which can be placed around an industrial facility or other area where methane could be present. "We have developed a small miniature sensor that you can deploy in multiple numbers in multiple places, which is selective as well as very sensitive," says Dr. Arindam Phani, PhD, one of the authors and Postdoctoral Fellow in Mechanical and Manufacturing Engineering.
"Then you can create a 3D-concentration map that shows if you have methane anywhere. The unprecedented sensitivity comes from the unique charge transport property of the nanocomposite sensing material that is at the heart of this sensor."
The sensor uses a composite of metal-organic frameworks (MOFs) and multiwall carbon nanotubes (MWCNTs). While these nanomaterials have been used together before, this is the first application that uses them to detect methane, says Homayoonnia.
The methane sensor can fit in the palm of your hand. Photo by Fritz Tolentino
"Our sensor uses a layer of nanomaterials that is porous and can absorb the target gas," she says. "After absorption, because of the interaction between those gases and the sensing material, we have a charge exchange between the two. Our ingenuity is the uniqueness of the nanocomposite that facilitates the charge exchanges. Because of the electron transportation between these target gases and our sensing material, we can detect them by seeing the increase or decrease in the resistance of our sensing material."
Sensor will help Canada meet emission-reduction targets
Methane, a GHG, is the main component in natural gas and occurs naturally as organic materials decompose. It represents 14 per cent of the country's total GHG emissions, and much of that comes from oil and gas operations, agriculture, and landfills.
"Methane is one of the largest GHGs," says Phani, "Most of the oil and gas and agriculture industries have methane all the time. Even at your home you have methane at every moment of time."
Canada has committed to reducing its methane emissions by 30 per cent of 2020 levels by 2030, part of the overall target of reducing overall GHG emissions by up to 45 per cent of 2005 levels by 2030 and reaching net zero by 2050.
Sensor has applications in other areas
The nanocomposite materials on the sensor can be easily produced on a larger scale to be used in a wide variety of applications to detect different gases, says Homayoonnia. "For the first time, we propose a mechanism in our sensor that can be a significant reference guide for future MOF-related composite research for demonstrating and observing the best selectivity performance in other works."
The basic physics of the sensor can be easily scaled up. "It's not just restricted to methane," says Phani. "The scope is big. Methane is the first example that you can go down to that ppb level. Next, we'll try other gases, especially non-reactive gases, say, carbon monoxide. That is another non-reactive gas, and we need to detect it at very low concentration levels."
