Good Thinking

Student-designed device reduces gas lawnmower air pollution by over 90 percent

Student-designed device reduce...
The UCR NOx-Out device replaces the muffler on an existing gas mower
The UCR NOx-Out device replaces the muffler on an existing gas mower
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The UCR NOx-Out device replaces the muffler on an existing gas mower
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The UCR NOx-Out device replaces the muffler on an existing gas mower
The device with its filter (top left) and catalyst (bottom left)
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The device with its filter (top left) and catalyst (bottom left)
This year's team, from left: Wartini Ng, Timothy Chow, advisor Kawai Tam, Jonathan Matson and Brian Cruz
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This year's team, from left: Wartini Ng, Timothy Chow, advisor Kawai Tam, Jonathan Matson and Brian Cruz
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Gas-powered lawnmowers are notorious polluters. According to the US Environmental Protection Agency, running a new gas mower for one hour produces as much air pollution as would be generated by 11 typical automobiles being driven for the same amount of time. Switching to an electric or reel mower is certainly one option, but for those applications where it's gotta be gasoline, a team of engineering students from the University of California, Riverside are developing another: an attachment that they claim reduces noxious emissions by over 90 percent.

Known as UCR NOx-Out, the device takes the form of an L-shaped stainless steel pipe, that replaces an existing mower's muffler. It cleans up the exhaust via a three-step process.

First, a stainless steel filter removes the bulk of the particulate matter. Next, a fine spray of urea is released into the exhaust stream. Finally, that urea reacts with a copper zeolite catalyst to convert the exhaust's nitrogen oxide and ammonia content into innocuous nitrogen gas and water, which are released into the air. That catalyst also converts the carbon monoxide into carbon dioxide.

The device with its filter (top left) and catalyst (bottom left)
The device with its filter (top left) and catalyst (bottom left)

NOx-Out was initially developed by another team last year, and will likewise be further developed by a third team next year. All of the students have been (or will be) advised by Dr. Kawai Tam, Prof. David Cocker, and Assistant Professor Phillip Christopher.

The previous version of the device was reportedly shown to reduce carbon monoxide content by 87 percent, nitrogen oxides by 67 percent, and particulate matter by 44 percent. In the current version, the figure for particulate matter removal jumps to 93 percent.

Other improvements introduced by the most recent team include the longer-lasting steel filter (it was formerly made of quartz), a honeycomb-structured solid catalyst (which previously took the form of a powder that could get blown out), a less obtrusive one-piece design, and the addition of a noise-reducing muffler.

The device is about to be trialled on the lawnmowers used to maintain the campus grounds. Once commercialized in an estimated four to five years, it is estimated that NOx-Out should be available for about US$30. Dr. Tam tells us that an 8-oz (237-ml) container of urea should be good for approximately 10 to 13 weeks of use, in cases where an average-sized lawn is being mowed for around one hour per week.

Sources: UC Riverside, UCR NOx-Out

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25 comments
David Finney
Affordable AND effective? I'd add that to my mower.
thk
So you need a supply of urea for it to work. Another way is to miniaturize EURO VI technology, but it will not be so affordable, I suppose.
MadMaxx
At that price I'd use it!
The Skud
Yaay! The first practical looking catalytic converter for motor mowers ... License the manufacturing to a big maker and sit back to watch the $$$$ roll in! Seriously though, congratulations to the team who brought this to its present state, absolute genius!
christopher
They pollute more, because they're 2-stroke, which spews unburned fuel. This seems not to mention that, but this would be the main fact that makes the "11 car" comparison stand up.
Fairly Reasoner
Still using the old 2-cycle mower/ 11 car analogy. How many 2-cycle mowers are manufactured these days?
Expanded Viewpoint
Christopher, the percentage of two stroke engines on lawnmowers has never really been very high, and the actual number of them still in operation since the late 1980s is so low as to not even be worth mentioning. But instead of using an exhaust-side solution that requires a chemical additive and plumbing/parts to make it work, why not use a better fuel delivery system to vaporize the gasoline instead of trying to burn droplets? Oh, they can't do that, it would make too much sense!! Randy
Sweepman
The motor in the photo appears to be a 4-cycle. Note the yellow cap for the oil fill. The article seems unclear about whether this device works on both 2 and 4-cycle engines. Certainly the 2-cycles are bigger polluters than the 4's. Adding urea would be an inconvenience, but maybe not a big expense.
Glen Jacobsen
Just don't forget to make them retro-fit capable, and size them for lawn and garden tractors as well.
Slowburn
How much of an improvement would just switching to propane/butane fuel make. It would certainly reduce the amount of spilled fuel.