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UC Riverside team wins EPA design contest with lawnmower exhaust aftertreatment device

A team of University of California, Riverside Bourns College of Engineering students have won an EPA student design contest for developing an exhaust aftertreatment device that cuts CO, NOx and PM emissions from lawnmowers. EPA estimates that a standard gasoline-powered lawn mower emits 11 times the air pollution of a new car for each hour of operation.

The device is a L-shaped piece of stainless steel with filter and catalyst that attaches to the lawnmower where its muffler was. When tested, the device reduced carbon monoxide (CO) by 87%; NOx by 67% and particulate matter (PM) by 44%. An improved version of the device eliminated 93% of particulate matter emissions.

The device, with the stainless steel mesh filter and catalyst support structure detached.

A filter captures harmful pollutants. Then, an ultra-fine spray of urea solution is dispersed into the exhaust stream for catalytic NOxreduction. Originally, the catalyst was in a powder form and was prone to blowing out when the lawnmower was being used. The team that just graduated added a honeycombed substrate that solidifies the catalyst.

The team also changed the design of the device so it is essentially one piece of L-shaped stainless steel, instead of several pieces connected through fittings. Also, the new device doesn’t stick out as far off the lawnmower. A muffler provides sound reduction. Click to enlarge.

The team, which calls itself NOx-Out, believes there is a market for the device for lawnmower manufacturers and current lawnmower owners, especially operators of landscape companies, who could retrofit their existing gasoline-powered lawnmower. The device has the added benefits of reducing noise from the lawnmower and the smell of gasoline.

The students—Timothy Chow, Brian Cruz, Jonathan Matson and Wartini Ng, all of whom just graduated—won a phase one grant of $15,000 as part of the EPA’s P3 (People, Prosperity and the Planet) competition. Next year a new group of students—Anna Almario, Priyanka Singh and Alyssa Yan—will take over the project and compete for a $90,000 phase two grant.

All the students have been advised by Kawai Tam, a lecturer at the Bourns College of Engineering, Phillip Christopher, an assistant professor of chemical and environmental engineering, and David Cocker, a professor of chemical and environmental engineering.

The student team that just graduated inherited the project from another team of students that started it before graduating in 2013. They were: Joshua Callihan, Rosalva Chavez, Jonya Blahut, Risa Guysi and Holly Clarke.

The incoming team will work to further improve the device. Possible areas for refinement including scaling it up so that it could be used with rider lawnmowers and develop a way to insulate it.



Well done, Cal Riverside team! Small ICEs are notoriously smelly and downright dangerous. I was at a facility when workers were overcome by exhaust from a very small (3hp or so) engine operating in a very voluminous closed space. Frankly an idling car would not have been nearly as hazardous.

Contract gardener/maintenance teams can't make the conversion to Li battery-powered outdoor appliances because even now there is just insufficient juice. For big cities (particularly those facing pollution-trapping weather challenges as the LA basin does) these kinds of simple fixes will grab a LOT of low-hanging fruit in cleaning up the air. Honestly it's weird to be standing next to several idling cars and the smell of the leaf blower absolutely dominates.


Gardeners who mow lawns at homes can easily use cordless. They can have charged packs in their trucks and be recharging on the way to the next job.


I will echo Herman's "Well Done" comment.


True enough, SJC, although the cost of packs for a day's work when you are running a team at substandard wage is probably not in the cards.

I bought the Worx set up and while I love it (nothing to prep for winter, carry it in the trunk to summer place without stink) it goes through batteries really fast for our little properties. I already use two packs, and I really don't see 8-10 stops a day without a very significant capital outlay for guys who just don't have it to spend.

I hope you're right, though --- it would really take the noise down.


I highly recommend he Al-Ko push cylinder mower. It is inexpensive, light, easy to use and effective. It "just works" out of the box:


Herman, while it would not be difficult to make a man-portable battery pack sufficient to power trimmers and edgers for most jobs, you'd either need connections to "shore power" at each job or rapid charging in the vehicle between jobs.  Neither parking nor vehicles are currently set up for that; even a 200 amp alternator is only good for a couple kW beyond vehicle demand.


Leaf blowers are what, 1/4 HP? 2kW is 3HP, so that would be enough to charge 6 leaf blowers between and during jobs.

I suspect electric landscaping devices are underutilized.

Anyone seen a real analysis??


Leaf blowers have chainsaw-class engines, so I'd say closer to 2 horsepower.  String trimmers are probably less.

Even at 2 kW, a 1.5 kWh battery will support 45 minutes of work.  4 of these LiMnCo packs would do.  They'd be easily belt-portable or fit in a small backpack.

Roger Pham

The real answer will soon to be FC-powered small machines running on H2. Will last for hours and filled up in seconds, once a network of H2 filling stations will be in place.

Meanwhile, battery swapping will do the job. Charge up a bunch of packs the nite before and use them all day. The Kobalt brand from Lowes uses one pack that is compatible with multiple of machines. Perhaps a contractor can buy these packs in bulk to save money. Battery electricity can be cheaper than gasoline given the efficiency of these lawn appliances of about 15-20% the most.


Batteries are expensive; a set sufficient to run all day would cost a lot more than gas plus maintenance for a conventional tool.  What's needed is a way to charge the packs rapidly between jobs.  A vehicle with 10 kW of electric generation (e.g. a hybrid of almost any brand) would do it, but few work trucks have such capability.

Ideally what you'd have is chargers on the work vehicle, and the vehicle supplied by "shore power" while it is at the job.  That eliminates the drain on the vehicle battery while it's parked, and allows the tool batteries to be charged whenever they are not actually in use.  A pair of batteries per tool would probably be sufficient in such a situation.


E-P (or anyone)

Have you seen prices and specs for batteries for portable leaf blowers (or other similar equipment)?

How about the fuel consumption and specs of conventional equipment?


Oddly enough, I use battery-powered leaf blowers every couple of months (an indoor cleanup job), but I've never even priced one.

A quick check of Amazon shows a 40-volt cordless leaf blower at about $140, with batteries at about $85-$90.

AC-powered leaf blower from Amazon for $55.

25cc gas leaf blowers, $100-140.

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