Tuesday, June 23, 2009

Carbon: Facts and Lies

I was reading "Natural Home" magazine in a waiting room the other day. It's a slick publication full of articles like "Our Favorite 10 Green Gifts" and "Simplify, Redesign, Go Green". In general it purports to show you how to lower the environmental impact of your life and home, albeit it in a rather yuppie-oriented way that usually seems to involve buying expensive, nice-looking things.

Anyway, flipping through the pages, I came across this sidebar tidbit which instantly puzzled me:

This says that the leaf-blower emits 513 times more carbon, per hour of use, than the car. And it implies that this is carbon dioxide, the greenhouse gas which is usually under consideration when people talk about "carbon emissions" and "carbon footprint".

But neither of these is remotely true. Machines are not magical carbon-creating devices. You can't produce more carbon from a combustion process than you put in as fuel. If the blower emitted 513 times the carbon per hour as the car, it would be using 513 times the gas. You would need roughly an 80 gallon tank just to run the thing for ten minutes. You don't see this in practice.

In reality, leaf blowers use very little gasoline. The Husqvarna 225B, for example, uses 470g of gas per hour-- which is 0.17 gallons, or about a half-liter. If we assume that the "light-duty vehicle" being driven at 30mph gets 22mpg, we find that you'd need to run the leaf-blower non-stop for four months to produce an equivalent carbon consumption (and, hence, emissions.)

So how does Natural Home magazine come up with its pronouncement? I suspected the answer, and confirmed it by reading the actual California EPA report. What the leaf-blower actually produces much more of is not net carbon, nor CO2, but unburned hydrocarbons (and, to to a lesser extent, carbon monoxide.) This is true of most small two-stroke engines; about 30% of the gas you put in gets emitted unburned. Four-stroke engines, such as in most cars, spill very little unburned fuel (and, for better or worse, their catalytic converters transform most of the CO into CO2 before exhausting it.)

Now, this unburned gasoline vapor is, of course, probably not great for the environment either. But that's a whole different story. The fact is that a gallon of gas put in a leaf-blower produces the same amount of carbon as a gallon of gas in a car. And, if you want to be technical about it, less of that gallon of gas gets turned into CO2.

I don't mean to be an apologist for leaf-blowers. I think they're ridiculous. And don't even get me started on the noise. What pisses me off is the careless misrepresentation of facts. And what scares me is that there is probably more than one person who read this magazine and thought to himself, "Wow! By just leaf-blowing a tiny bit less, I can drive my SUV a whole lot more!"-- and is now proceeding to do so.

(P.S. In case you were wondering-- yes, my scooter has a 4-stroke engine.)


Blogger Markus said...

I think it's just that some clueless marketing person doesn't know the difference between "hydrocarbon" and "carbon dioxide"... after all, they both contain the word carbon, and that's what carbon dioxide has been dumbed down to now. Back when carbon dioxide was harmless, unburned hydrocarbon emissions were the main villain.

6/23/09, 2:00 PM  
Blogger Dragonfly said...

THe buying expensive stuff is annoying. Like "What can we add to our image to help the environment - ooh look, bamboo table ware" rather than using what you already have or recycling/going second hand.
Loving the leaf blower SUV trade off. "And by raking my leaves instead, I can cleanse my conscience regarding my urban tractor". Good stuff...

6/23/09, 2:46 PM  
Blogger Ladyk73 said...

So I wonder what my "carbon foot print" was when I tilled my compost pile yesterday. I have an ancient roto-tiller that has a little gas leak, and every once in a while emits a smokey puff.

In some ways, I reduces landfill waste by composting, I reduce lots of energy buying pre-packed soil compost (well, I use them too).

I reduce wasteful production by using a machine that is older than me, and the gasoline consumed was about a 10th of a gallon.

Mostly, I do it cause it is fun, I wanted to fill a raised bed, and my plants love it.

6/24/09, 12:15 PM  
Anonymous Jessica Kellner said...

Hello. Thanks for bringing this error to our attention. You are correct. The actual quote from the California EPA was this: “Operating a commercial gas-powered leaf blower for a half hour produces roughly the same hydrocarbon emissions as driving a light duty vehicle 7,700 miles at 30 mph.” An inadvertent but serious error was made in the editorial process, significantly changing the quote's meaning. We regret the error and will print a correction in our next issue. The comparison of the leaf blower’s fuel use with a vehicle’s was offered to represent, in easily relatable terms, the resources wasted by unnecessary fuel-driven yard tools. We do not believe our readers, who are conscientious consumers, will misconstrue this presentation of the information as an invitation to drive more. Again, thanks for bringing this matter to our attention. We appreciate it.

Jessica Kellner
Managing Editor
Natural Home magazine

6/26/09, 4:01 PM  

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