Friday, January 26, 2007

Carbon Footprint of a Mobile Phone

In my on going quest to figure out the environmental impact of every product that I purchase, today I look at cellphones.

After reading this TreeHugger post, I became aware of the LCA of the Mobile Communication System UMTS report which I found at the ESU Services website. This is an excellent report on the energy used and environmental impact of mobile phones, looking at the entire mobile phone infrastructure. I decided to do some further analysis from their numbers to determine the energy use and carbon footprint of manufacturing a mobile phone as well as using it for a year.

How much energy and emissions does manufacturing a mobile phone cause?

Manufacturing a cellphone uses approximately 1390 MJ of energy and produces 60 kg of CO2 emissions (see calculations below).

To put this in perspective, a gallon of gasoline has 131 MJ of energy and emits 8.8 kg of CO2. Therefore, manufacturing a cellphone uses as much energy as 10.5 gallons of gasoline and emits as much as 6.8 gallons of gasoline (energy is higher than emissions due to fossil free electricity from sources such as hydro and nuclear).

A computer and monitor take 6400 MJ to manufacture, or 4.6 times as much as a mobile phone.

The 1.019 billion phones produced in 2006 create approximately 60 million metric tons of CO2 emissions.

What is the impact of using a cell phone for a year?

According to the report, using a cellphone for a year on average uses 4,221 MJ of energy (equivalent to 32 gallons of gasoline) and emits 112 kg of CO2 (equivalent to 12.8 gallons of gasoline). These values take into account the entire system and all the energy and materials needed to manufacture and run it: the phones, base stations, switching system, cable system, and administration. It assumes that each phone is used for one year and then replaced.

To put that in perspective, the average American emits 22 metric tonnes of CO2, so 112 kg works out to .5% of that total. The average American eats 150 hamburgers leading to 600 kg of emissions, so mobile phone usage is about 1/5 of that.

What causes the largest environmental impact in the mobile phone system, and what is the best way to reduce it?

Based on the Hierarchist Eco-Indicator'99 method (whatever that is), looking at the entire system, the mobile phone makes up 50% of the impact, the cell antennas 5%, cell base stations 25%, switching system 3%, administration 14%, connection network 3%. Of the phone's impact, 95% is caused by manufacturing and 5% by usage. So, the key environmental impact is caused by the manufacturing of cellphones.

Looking at that manufacturing:

The production of printed wiring boards (PWB) and integrated circuits (IC) make up about 40–50% of the environmental impacts. For these components, the energy consumption, the production of semiconductor dies, and the supply of gold and partly silver is of importance for the assessment.
Just like computers the integrated circuits and printed wiring boards have the largest impact on the process. Even though the weight of the final product of PWB and IC are small, the amount of raw materials, energy required to manipulated those materials and waste is quite large.

More environmentally friendly ways of production or improvements in the efficiency of their production would have a big effect on the overall environmental impact of cell phone usage. Another way to have reduced impact is to use each phone longer.
Increasing service life from one year to four years would decrease the environmental impacts of about 40%. On the contrary, a life time of only half a year results in about 40% more impacts.
I calculate that replacing a cellphone every 2 years rather than one would save 30 kg of CO2 emissions (about 3.3 gallons worth) and 700 MJ. This is a decent savings, approximately equal to reducing your driving 100 miles each year (8 miles a month). If you are trying to decrease your carbon footprint, this will have an impact, but there are other areas that would make a much larger impact.

Surprisingly, whether the phone is recycled or incinerated has little effect on the overall environmental impact.
Despite the fact that a relatively pessimistic scenario for the disposal was selected (incineration of 20% and 80% take back, instead of 100% take back), the environmental impacts for this life cycle phase can be neglected.
Even a take back rate of 0% would not significantly change the environmental impact.

Calculations

From Table 6 in the report, we find that transferring 1 Gbit in a UMTS system uses 801 MJ of non-renewable energy, 138 MJ of renewable energy and 27 kg of CO2 equivalent emissions. From Figure 6 in the report, I estimate that phones use 35% of non-renewable energy, 20% of renewable energy and 50% of emissions. Multiplying that out, phone usage for 1 Gbit is: 280 MJ of non-renewable energy, 28 MJ of renewable energy and 13 kg of emissions. From this report we find that 0.223 cell phones per GBit, which means 4.5 GBit per cell phone (which is used during 12 months). And no I don't speak German, but Rolf Frischknecht was kind enough to email me the information. So multiplying our values by 4.5 we get 1260 MJ of non-renewable energy, 126 MJ of renewable energy (or 1386 MJ combined) and 58.5 kg of emissions per phone.

Besides manufacturing the phone, this value also includes running it for a year. The report does not spell out what percentage of energy or emissions are used in this phase, but it does say that:
The use of the phone is responsible only for approximately 5% of a UMTS phone's environmental impacts.
I am not sure if the value for energy and emissions is similar, and for the purposes of this analysis will ignore it. Possibly I should reduce the values by 5%, but I would be extremely happy if these calculations were accurate with 25%, so I am not too concerned with it.

For the entire impact of one mobile phone user on the system for one year, we take the 801 MJ of non-renewable energy, 138 MJ of renewable energy and 27 kg of CO2 equivalent emissions per Gbit and multiply it by the 4.5 GBit per year to get 3605+ 621 = 4226 MJ and 112.5 kg.

Assumptions and potential issues

As always, the analysis is only as good as the underlying numbers and the assumptions they hold.

It is not specified what type of phone is being used, or whether it is a generic aggregate of many phones. It is also unclear how much variation in energy use and environmental impact there is between phones.

This is based on the UMTS cellphone protocol. Different protocols could use more energy and have a larger environmental impact.

The data is based on manufacturing the phone in Germany and using it in Switzerland. If the source of fuel to generate electricity is different than assumed this will impact the final results.

Phone usage is assumed to be 4.5 Gbit a year. Greater usage would increase the energy needed to use the mobile phone but also decrease the relative impact of phone manufacturing.

Anonymous said...

Hey Fat Knowledge, This is very nice work. My new business specifically aims at encouraging consumers to trade their eloectronics in and buy pre-owned so that it increases the lifecycle of cosumer electronics like mobile phones and reduces their carbon footprint. If yoou check these comments, I'd appreciate your imput. chriswhittome@trade2save.com. Check out the trade2save website too.

chris

Fat Knowledge said...

Chris,

Best of luck with trade2save. Reusing electronic goods is good for the environment and the pocketbook.

fonegeek said...

hi fat knowledge,
wondering how you came to the carbon footprint numbers above (ie 4221 mj/energy + 60 kg/c02 to manufacture and use a cell phone for one year)? you mention in the post doing "further analysis" and i'm wondering what sort of formula you used to come up with those numbers?
any other studies out there similar to this one (ie carbon footprint of production + use of a cell phone)?
thanks!

Fat Knowledge said...

Hi Fone Geek,

My data came from this report plus the analysis that is in the "Calculations" section of the post. If that doesn't answer your question, let me know in more detail what you want to know and I can look into it for you.

As for other studies, this is the only one I have come across. You might be able to find something if you contact this LCA discussion list.

Good look on your quest and let me know if you find anything good. :)

Innoviate Communicaiton Systems said...

Yeah, I actually just spoke with a guy over at phone systems Austin office and he said that cell phones are the worst on the enviornment. I guess that office phones aren't so bad, even though they're bigger, they often get used for much longer periods of time, where as the cell phones get swapped out like 8 times over the course of 10 years. Anyway, cool post.

Anonymous said...

Wow, really nice post!
Obviously mobilephones have a impact on the environment just as all electronics, however i must say i think it is acceptable if one looks at the pro's & con's. What really shocked me was the amount of Co2 the average american emitts; 22 tons is alot!

Anonymous said...

very useful work thank you! Only thing I'd point out is "Surprisingly, whether the phone is recycled or incinerated has little effect on the overall environmental impact" - do you mean 'carbon emissions' not 'overall environmental impact' since incineration means unrenewable and scarce resources are lost (resulting in more mining etc)?

Fat Knowledge said...

Actually in the quote that follows in the report, they are using the eco-indicator 99' Hierarchist test, which takes into account other environmental impacts besides just CO2. As for how exactly it is calculated or if it takes into account the additional mining that is needed for non-recycled goods, I do not know.

Chris MK said...

Hi! I'm making a proyect about the CO2 kg the usage of mobile phones produce, can anyone tell me where can I find this information? I don't want to know de LCA, I just want to know what's the number of CO2 kg produced for using the phone

Fat Knowledge said...

Hi Chris, according to this report and my calculations, producing a phone emits 60 kg of CO2, and running it for a year emits 112 kg of CO2. Of course there are a lot of assumptions in this analysis and it is a few years old now, so take everything with a grain of salt.

Anonymous said...

Great post. Just curious..would you know the approximate c02 emissions from the production of a computer?

Fat Knowledge said...

Anon,

Check this post on the Carbon Footprint of a MacBook and this one on 50 Gallons of Gasoline in Each PC

Grey Cell Traffic said...

Hey Fat Knowledge, the link that you provided to access the LCA report no longer exists. I'm quite interested to read this report. If you have it downloaded with you or you know a fresh link that has the document uploaded, would you mind sharing it with me? Thanks for the helpful post :)

Fat Knowledge said...

Hi Grey Cell Traffic,

Unfortunately, I don't have a copy on my machine any more. But, when I emailed the author Rolf Frischknecht http://www.esu-services.ch/index.php?id=61 he responded to me. You might try emailing him and seeing if he can hook you up with a copy.

Anonymous said...

Hey Fat Knowledge,
Do we have any figures for "What is the amount of CO2 saved when we sell an used mobile or buy an used mobile?