CFL bulbs - do the math

[speedy 0]

Australia announced it would phase out the sale of inefficient incandescent light bulbs by 2010, replacing them with highly efficient compact fluorescent bulbs that use one-fourth as much electricity. This is all done in the name of saving CO2 emissions and thus the planet. So let's look at it in more detail.

In general, the coefficient is about 2.3 lb CO2 per kilowatt-hour (kWh) of electricity. You can calculate the kWh of electricity by multiplying the number of watts (W) the appliance uses times the number of hours (h) it is used, then dividing by 1000. For example a 60-W light bulb operated for 24 h uses (60 W) x (24 h) / (1000) = 1.44 kWh.
This use of electricity would produce an emission of (1.44 kWh) x (2.3 lb CO2 per kWh) = 3.3 lb CO2 if the electricity is derived from the combustion of coal. Thus if you have your 60W bulb burning 24/7 you could conceivably cause the emission of ~1200 lb CO2/year but even heavily used lights would be pushing to be on 6/7 rather than 24/7, so total emission caused might be 300 lb/year, a 1/3rd increase in efficiency could then "save" 100 lb CO2/year.

For comparison, a person (at rest) exhales about 800 lb CO2 per year, so changing out 8 heavily used incandescent bulbs for CFLs delivers a theoretical "saving" equivalent to preventing one such couch potato breathing but you'd need to change many times more to equate to people who engage in physical exercise, play sport or whose work involved 8 hours of manual labor per day since respiration rises significantly with effort.

Dave

Fallschirmsport Marl

[steveorino 7]

1) Every bit helps.
2) It doesn't matter if you make a difference, only if you care.
3) It is suppose to make you feel good.

steveOrino

[Andrewwhyte 1]

Unless the couch potato eats hydro-carbons he is co2 neutral. All our energy comes from green plants or from those who ate green plants.

[rehmwa 2]

What's the price difference if you go to the store and buy one.

Just the price, up front.

If there's a discussion about if one lasts 5 years vs 20 years, blah blah blah, then that's fine, but the price delta first, then the lecture.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[billvon 3,118]

Your math is a bit off.

Humans produce about 2.2lbs of CO2 a day. Most of that is carbon neutral, since the food we eat came primarily from plants (corn, rice, wheat, potato) that USED CO2 to make the carbon in the food.

Replacing one 100 watt light bulb with a 100W equivalent CFL saves 75 watts, or 1.8khwr/day, assuming it runs all day. That's about 4.2 lbs of CO2 a day saved - and this is NON-closed cycle, so we're not reabsorbing it. Most of it (in the US) comes from coal.

So for every 100 watt CFL you use all day you save the equivalent CO2 of two couch potatoes. Change that to 12 hours operation a day (common for businesses) and you're at about 1 couch potato per CFL bulb. (3 CFL's replace 2 potatoes in domestic use.)

And again, the CO2 that we produce does not result in any _net_ increase in CO2, because that CO2 has to go back into the crops we eat. The CO2 we are saving with CFL's is CO2 that is not reabsorbed.

[speedy 0]

Quote

Unless the couch potato eats hydro-carbons he is co2 neutral. All our energy comes from green plants or from those who ate green plants.

Thanks, I knew there was a catch somewhere.

Dave

Fallschirmsport Marl

[willard 0]

Quote

Your math is a bit off.

Humans produce about 2.2lbs of CO2 a day. Most of that is carbon neutral, since the food we eat came primarily from plants (corn, rice, wheat, potato) that USED CO2 to make the carbon in the food.

Replacing one 100 watt light bulb with a 100W equivalent CFL saves 75 watts, or 1.8khwr/day, assuming it runs all day. That's about 4.2 lbs of CO2 a day saved - and this is NON-closed cycle, so we're not reabsorbing it. Most of it (in the US) comes from coal.

So for every 100 watt CFL you use all day you save the equivalent CO2 of two couch potatoes. Change that to 12 hours operation a day (common for businesses) and you're at about 1 couch potato per CFL bulb. (3 CFL's replace 2 potatoes in domestic use.)

And again, the CO2 that we produce does not result in any _net_ increase in CO2, because that CO2 has to go back into the crops we eat. The CO2 we are saving with CFL's is CO2 that is not reabsorbed.

Serious question here....no sarcasm intended.
If I decided to chnage all my household bulbs to CFL and made a trip to Home Depot just to buy them, how much CO2 would I put in the air in a round trip that was, say, 10 miles total and my car used 1 gallon of gas? Just wondering if the CO2 created by my car would be greater than saved by swithching to CFL.
Oh, I have 8 bulbs in my apartment.

[speedy 0]

So there is no benefit in removing the potatoes from the system
I do have some CFL's in my house, it's not an enviromental thing, it's a potatoe thing. I can't be bothered with changing the bulbs so often

Dave

Fallschirmsport Marl

[billvon 3,118]

>how much CO2 would I put in the air in a round trip that was, say, 10 miles total . . .

Depends on the car, of course, but a Honda Civic produces about .8lbs CO2/mile. So call it 10 lbs. So you'd have to run one bulb for about 57 hours, or 8 bulbs for 7 hours, to "compensate" for the trip.

[willard 0]

ok, thanks. I was curious as to if the benefits would be worth the extra trip. I guess it would be a worthwhile trip.
I drive a Focus so the comparison to a Civic is a good one.

[shropshire 0]

That's a perfectly valid question... as is the one that asks how much CO2 was created (transformed from other stuff?) during the fabrication and subsequent delivery through the supply chain?

I work for a major retailer and Food Mileage is todays big buzz word (even going to be displayed on packaging). It's good to know where your products come from and how far around the world that they have travelled (too far, in general).

.

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[rushmc 23]

Quote

Quote

Your math is a bit off.

Humans produce about 2.2lbs of CO2 a day. Most of that is carbon neutral, since the food we eat came primarily from plants (corn, rice, wheat, potato) that USED CO2 to make the carbon in the food.

Replacing one 100 watt light bulb with a 100W equivalent CFL saves 75 watts, or 1.8khwr/day, assuming it runs all day. That's about 4.2 lbs of CO2 a day saved - and this is NON-closed cycle, so we're not reabsorbing it. Most of it (in the US) comes from coal.

So for every 100 watt CFL you use all day you save the equivalent CO2 of two couch potatoes. Change that to 12 hours operation a day (common for businesses) and you're at about 1 couch potato per CFL bulb. (3 CFL's replace 2 potatoes in domestic use.)

And again, the CO2 that we produce does not result in any _net_ increase in CO2, because that CO2 has to go back into the crops we eat. The CO2 we are saving with CFL's is CO2 that is not reabsorbed.

Serious question here....no sarcasm intended.
If I decided to chnage all my household bulbs to CFL and made a trip to Home Depot just to buy them, how much CO2 would I put in the air in a round trip that was, say, 10 miles total and my car used 1 gallon of gas? Just wondering if the CO2 created by my car would be greater than saved by swithching to CFL.
Oh, I have 8 bulbs in my apartment.

How come no one wants to talk about the fact that these bulb contain mercury? These cost the envionment more than they save. Much like hybred cars

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[Zipp0 1]

I have some CFL's in the house, but, to be honest, the light they produce is ugly. The warm glow of an incandescent is so much more pleasant.

Will they ever be able to produce a similar light with a CFL?

--------------------------
Chuck Norris doesn't do push-ups, he pushes the Earth down.

[billvon 3,118]

> I have some CFL's in the house, but, to be honest, the light they produce is ugly.

There are two parts to light quality - CRI (color rendering index) and color temperature (how "warm" or "cool" it is.) Some relative color temperatures:

2000K - candle
2500K - incandescent light bulb
5000K - daylight
9000K - "northern light" (blue sky)

Yes, "bluer" (cooler) color temperatures are actually higher; it's confusing.

Anyway, most modern CFL's use tricolor phosphors which give you CRI's between 75 and 90. (Sunlight is 100.) Incandescents are usually around 80 to 96 (halogen.) Color temperatures are available between 2700K ("warm white") and 5000K ("daylight.")

Traditional "cool white' fluorescents are 4100K. Offices mostly use 3500K now because it looks warmer.

Popular Mechanics did a test a while back between several CFL's and an incandescent, and in all cases the light from the CFL was judged better (for reading, rendering colors, making faces "look natural") than the incandescent.

So anyway if you don't like the light - just get another one that you like better. There are literally dozens of combinations available.

[shropshire 0]

I agree.. the lamps take a while to come on and the light quality is not as goods as I'd like.

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[Andrewwhyte 1]

Zippo has a good point; although there are dozens of CRI/temp combinations available for traditional tubes, not so much down at the Home Depot for compacts.

[Remster 30]

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How come no one wants to talk about the fact that these bulb contain mercury? These cost the envionment more than they save. Much like hybred cars

Yeah... Its a hush hush secret that's not addressed anywhere...

http://en.wikipedia.org/wiki/Compact_fluorescent_lamp#Environmental_issues

http://www.eartheasy.com/live_energyeff_lighting.htm#3c

http://www.google.com/search?hl=en&q=mercury+in+CFL+bulbs

Remster

[jakee 1,595]

Quote

If I decided to chnage all my household bulbs to CFL and made a trip to Home Depot just to buy them, how much CO2 would I put in the air in a round trip that was, say, 10 miles total and my car used 1 gallon of gas? Just wondering if the CO2 created by my car would be greater than saved by swithching to CFL.
Oh, I have 8 bulbs in my apartment.

You will drive to Home Depot anyway when your current lightbulbs burn out. Also CFL lightbulbs will require replacing less often than incandescent, so you will drive to Home Depot less often in the future, meaning further energy savings!

(That is, of course, assuming that you would ever make an entire trip just for lightbulbs anyway)

Do you want to have an ideagasm?

[idrankwhat 0]

Quote

Humans produce about 2.2lbs of CO2 a day. Most of that is carbon neutral, since the food we eat came primarily from plants (corn, rice, wheat, potato) that USED CO2 to make the carbon in the food.

Wouldn't that figure depend on the diet of that human? Considering trophic efficiency is poor, ~10%, and that most of our grillable protein sources are fed grain instead of grasses, wouldn't that make the average carnivorous American much less than carbon neutral?
Also, won't the trend be away from CFL's and towards LED's in the near future? If I'm not mistaken I believe that LED's are brighter and dimmable as well as efficient.

[billvon 3,118]

>Considering trophic efficiency is poor, ~10%, and that most of our
>grillable protein sources are fed grain instead of grasses, wouldn't that
>make the average carnivorous American much less than carbon neutral?

Grain uses as much CO2 as grass does. A cow has to eat approximately 10x the number of calories in grain to produce 1x calories of meat. That's 10x the amount of grain, and thus 10x the amount of CO2 absorbed for 1X calories eaten by humans.

If you bury all the grain waste then you're removing all that carbon from the atmosphere. If you also feed the cow's waste to a methane digester (and use the methane for fuel) then it's even better. If you do those two things, you actually USE UP more CO2 than you emit throughout the whole cycle.

OTOH if you burn all the waste and leave the cow's wastes sitting around it goes back to being neutral, because all that CO2 (minus the food taken out) goes back into the atmosphere.

>Also, won't the trend be away from CFL's and towards LED's in the near
>future? If I'm not mistaken I believe that LED's are brighter and dimmable
>as well as efficient.

Right now they're not as efficient as fluorescents at making white light. If they get about 50% more efficient they'll be competitive, and if they get approx 5 times cheaper then they will be cost competitive as well.

[idrankwhat 0]

Quote

Grain uses as much CO2 as grass does. A cow has to eat approximately 10x the number of calories in grain to produce 1x calories of meat. That's 10x the amount of grain, and thus 10x the amount of CO2 absorbed for 1X calories eaten by humans.

If you bury all the grain waste then you're removing all that carbon from the atmosphere. If you also feed the cow's waste to a methane digester (and use the methane for fuel) then it's even better. If you do those two things, you actually USE UP more CO2 than you emit throughout the whole cycle.

OTOH if you burn all the waste and leave the cow's wastes sitting around it goes back to being neutral, because all that CO2 (minus the food taken out) goes back into the atmosphere.

That seems reasonable from a biomass mass balance standpoint but what's missing is the amount of fuel that it takes to produce the grain for the raising of the cattle. This is from the National Geographic article that came to mind when I started reading the thread.

"Weighing in at 1,250 pounds (567 kilograms), Marina Wilson's champion steer Grandview Rebel is ready for auction at a county fair in Maryland. Raising this steer has taken an agricultural investment equal to 283 gallons (1,071 liters) of oil, represented here by the red drums. That includes everything from fertilizers on cornfields to the diesel that runs machinery on the farm. Overall, it takes three-quarters of a gallon of oil to produce a pound of beef."
http://green.nationalgeographic.com/environment/global-warming/end-cheap-oil.html

[billvon 3,118]

>That seems reasonable from a biomass mass balance standpoint
>but what's missing is the amount of fuel that it takes to produce the grain
>for the raising of the cattle.

Right.

There's a basic equation at work here - you have to put CO2 into the system to get carbon (in the form of food) out, no matter how the system works.

Now on top of that add in the energy cost associated with growing and transporting the grain (if they're not grass-fed) and getting the meat to market (if the cows aren't local.) Those are additional energy costs (and a higher associated carbon burden) that you may incur, depending on where you live and what you buy. And as someone else pointed out it may take gas to get you to the store to buy hamburger.

[billvon 3,118]

> What's the price difference if you go to the store and buy one.

Cheapest seen at Home Depot today -

6 pack of 60w equivalent soft-white* CFL's: $9.97 ($1.66 ea)

6 pack of 60w GE soft white incandescents: $2.92 ($0.49 ea)

* = soft white is closest to incandescent. They also had "bright white" (3500K) and "daylight" (5000K.)

[Zipp0 1]

Quote

* = soft white is closest to incandescent. They also had "bright white" (3500K) and "daylight" (5000K.)

Yeah - the best CFL's still suck. I'm hoping the LED light folks can do better.

--------------------------
Chuck Norris doesn't do push-ups, he pushes the Earth down.

[rehmwa 2]

Quote

> What's the price difference if you go to the store and buy one.

Cheapest seen at Home Depot today -

6 pack of 60w equivalent soft-white* CFL's: $9.97 ($1.66 ea)
6 pack of 60w GE soft white incandescents: $2.92 ($0.49 ea)

* = soft white is closest to incandescent. They also had "bright white" (3500K) and "daylight" (5000K.)

Simple, then, get the CFLs down to about $5, and we have a deal for most people. Right now, 3X price, even if they last 4 times longer doesn't matter to Joe Normal that needs a couple replacement bulbs and wants to buy the big bag beef jerky by the cash register too. (Or trail mix bag if the concept of jerky makes someone uncomfortable - can't have that).

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants