Affordable AND effective? I'd add that to my mower.

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.

At that price I'd use it!

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!

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.

Still using the old 2-cycle mower/ 11 car analogy. How many 2-cycle mowers are manufactured these days?

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

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.

Just don't forget to make them retro-fit capable, and size them for lawn and garden tractors as well.

How much of an improvement would just switching to propane/butane fuel make. It would certainly reduce the amount of spilled fuel.