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View Full Version : Are refridgerants such as r134a and r12 more harmful than emissions from exhaust?



stevedmc
06-17-2011, 07:29 PM
I have been wondering this for a while and am curious what others have to say.

I would think that a few thousand miles of driving would cause far more damage to the atmosphere than emptying a can or two of refrigerant into the air. Does anyone have an opinion or facts on which is worse?

Michael
06-17-2011, 08:18 PM
Neither. Political correctness/global warming BS. Hey, you asked.

we are on the verge of becoming political.:bash:

RIUM+
06-18-2011, 11:10 AM
This can easily turn political with people's opinions. But more importantly, you could argue all sorts of things about this one way or another, even when backed up by facts. You can even argue one way or the other just by changing the timescale of how long you're talking about, since all gases slowly decay. Putting that all aside and inserting a very large disclaimer that this all depends GREATLY on what you're talking about and simplifying it to one single number is fraught with problems, here's at least some numbers I'll throw out there.

Comparisons of "Global Warming Potential" of various gases, measured as equivalent by weight to Carbon Dioxide in the atmosphere over 100 years (numbers sourced from the 2007 IPCC AR4):
Carbon Dioxide (CO2) - 1 (it's the reference gas)
Methane (CH4) - 25
Ethane (C2H6) - 5.5
Propane (C3H8) - 3.3
Butane (C4H10) - 4.0
Nitrous Oxide (N2O) - 298
R-12 (CCl2F2) - 10,900
R-134a (CH2FCF3) - 1,430

Assuming the engine is properly tuned and running efficiently and you haven't removed the catalytic converter, the average impact of petrol (sourced from the Code of Federal Regulations at 40 CFR 600.113-78): 1 Liter of petrol = 2.32 Kilograms of CO2 (or 1 Gallon = 19.37 pounds of CO2 for those that are crazy enough to do chemistry calculations in the Imperial system :p ). A liter of petrol weighs 711 grams. 1 kilogram of petrol = 1.64 kilograms of CO2 (or 1 pound of petrol = 3.62 pounds of CO2... crazy imperial chemistry calculations :p ).

After a little number dividing, here's what you get:
R-12 = 6,650 times worse than petrol by weight
R-134a = 870 times worse than petrol by weight

The owner's manual recommends 1125 grams (2.5 lbs) of R-12. This means emptying a full system of R-12 coolant from a stock DeLorean into the atmosphere is roughly equivalent, as measured by its global warming potential over 100 years, to 7,480 Litres (1,980 gallons) of petrol.

DeLorean fuel efficiency is all over the chart depending on the transmission, driving style & how well-maintained you keep your car so the driving distance varies so much it's hardly a useful number. However, if you assume a value of 20mpg, that much fuel will get you 150,000 kilometers (or 93,000 miles).

These numbers may sound "low" at first if you do a lot of driving, but avoiding a breach that dumps all your refrigerant is a lot easier than avoiding the need to drive a hundred thousand miles. Also, R-134a may be eight times "better" than R-12, but it's still a thousand times "worse" than using compressed CO2 as your refrigerant.


(disclaimer - I'm not a mechanic! Or a mathematician! Or a chemist! Or a milkman! I could be wrong! They might be giants!)

Chris4099
06-19-2011, 12:53 AM
RIUM,
Good job. Way more detailed then I would have posted. I feel sad for people that try to make this stuff political. It's science, nothing more. Politics should only come into play when it comes to laws and regulations on how to deal with this stuff. Of course there's other factors too as exhaust has more then just CO2. For example hydrocarbons is pretty nasty stuff too.

Still, having refrigerants go into the atmosphere is completely avoidable. If you have a leaking AC system, it should be fixed, not simply topped off. Hopefully as R-134a (and other refrigerants too) get more expensive, this practice will become less common.

RIUM+
06-19-2011, 02:49 AM
hmm252000,
According to the source, the number I quoted for petrol is said to be its total "CO2 equivalence" of all exhaust gases in various ratios with their respective GWPs of their impact over 100 years, assuming it was being burnt in an average small passenger car with a catalytic converter and well-maintained engine. So traces of other gases were already included.

But again with the disclaimer that there are so many "gotchas" that simplifying it down to just one number is nearly universally a bad idea. That leads to inevitable misunderstandings & that's the cause of most disagreements in this area.

Chris4099
06-19-2011, 12:13 PM
I see. That explains why your figures are a little higher then what I usually go by. I recall it being somewhere that about a mile of driving puts out a pound of CO2. Using the 1,500 GWP figure for R-134a, I always calculated that a can (less then a pound) equaled about 1,000 miles of driving. But that's only based on one component of exhaust with very rough numbers.

As you mention, trying to really calculate this down to an exact number is next to impossible. Let's just say refrigerates are nasty stuff that should not be casually vented into the atmosphere. :approve:

stevedmc
06-19-2011, 02:24 PM
Thanks for the info RIUM. So if my math is right, dumping 2.5 pounds of r134a into the atmosphere is about the same as driving 12,000 miles.

Gee, most people where I live drive that much in just a year.

stevedmc
06-19-2011, 02:26 PM
I always calculated that a can (less then a pound) equaled about 1,000 miles of driving.

I must be really bad with math. Looks like I was wrong.