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The Nightstar Zoo :: View topic - Lawnmowers, super polluters?
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Lawnmowers, super polluters?
http://zoo.nightstar.net/viewtopic.php?f=5&t=17334
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Author:  bizzybody [ Mon Aug 18, 2008 1:21 am ]
Post subject:  Lawnmowers, super polluters?

I've a problem with this.

This article contains this statement.

"A gas mower creates as much pollution as running eight cars. We saved 22,000 car miles in pollution in our first year,"

Hmmm. If we figure 25MPG as average, that's 880 gallons of gasoline. I wonder what the fuel consumption per hour is for a typical lawnmower at full throttle? (That's how most of them are run when cutting grass.)

From that we could calculate how many hours the boys would have to run their two push mowers to save 880 gallons of gas. That's for "more than two dozen" clients in their first year. Their available working time would be constrained by sleep, eating and during the school year, school time and doing homework.

The only scientifically proper* way to directly compare mower VS car pollution is to determine how much and what types of chemical compounds each produces per gallon of gasoline burned. That of course includes any evaporation from the tank. Do any of these small engines have a method for running evaporative emissions into the combustion chamber?

If the comparison is time based, the eight cars "win" the pollution contest because they'll definitely burn more per time unit.

*OK, there are other ways, but that's the simplest. Even then the fuel use per time unit of the cars could have an effect.

P.S. Don't bother attempting to question the kids about their stuff. Their father screens their e-mail and calls any questions or presentations of contradictory data a 'diatribe' and says you are wrong. (I expect he intercepted plenty of e-mails after that article.) He replied with a couple of URLs they got their information from, one on maintaining your mower (good advice) and one about how small engines are worse polluters than cars. I was simply suggesting to the teens what they could research to conduct their own scientific investigation instead of relying on other people's info. It'd be a project they could use for their Eagle Scout qualifications.

Author:  Dark_Tiger [ Mon Aug 18, 2008 3:01 am ]
Post subject:  Re: Lawnmowers, super polluters?

Might I point out that most lawn mowers, and for that matter many sub 50cc combustion engines have grossly inefficient to non-existent catalytic converters? You can also expect a fair amount of evaporation and outright spillage from a lawn mower.

Ignoring that, a push mower, one without any power going to movement, just grass cutting, can be expected to use up about a gallon of gas for every two average sized suburban home yards. This is observational data from when my pocket money was coming from yards, tempered by the amount of gas I've had to pour into a mower to deal with my own yard.

Using your numbers, that's a little over 32 yards a week, within limits for 2 youths of that age and aptly described as "more than two dozen clients." A power assist mower will use more gas, and larger yards will also push up that number.

Author:  bizzybody [ Mon Aug 18, 2008 5:19 pm ]
Post subject:  Re: Lawnmowers, super polluters?

Changing the composition of the output (ie, with a catalytic converter) doesn't change the mass of the output. (Depending on whom one asks, all emissions from any internal combustion engine is a pollutant.)

This looks interesting. http://smallengines.wikia.com/wiki/Tecu ... nformation

So far the only info I've found about small engine fuel consumption is for a Briggs outboard boat motor @ 0.5 gallon per hour at 4,000 RPM.

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In a related vein, with the surge in popularity of scooters, comes people claiming that they're worse polluters than cars. I don't see how they come to that conclusion, unless they're thinking of old two-stroke ones from the 1950's. A scooter that gets 80 MPG, it's flat out impossible to produce more pollution than any (commercially produced) gasoline burning car.

Author:  gwalla [ Tue Aug 19, 2008 3:05 pm ]
Post subject:  Re: Lawnmowers, super polluters?


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