Monday, February 16, 2009

Green cell phones?

In the New York Times, technology writer and long-distance walker Eric Sylvers asks of new "green" cell phones: "Is it better to save the earth, or to save money?"

What if you were actually doing neither? Sylvers' article details "green" products with even smaller environmental impacts:

1) Most Nokia phones now beep when they are fully charged, alerting the owner to detach the charger from the wall socket...Sony Ericsson presented a concept phone called GreenHeart, made with recycled biodegradable components. The charger draws a fraction of the power of most chargers when it is plugged into an outlet, but not connected to a phone.

Remember that as battery-powered devices, cell phones were already designed to maximize battery life by minimizing energy use. Chargers, which plug into the wall, had no such constraint. In response to consumer concerns, phone chargers have become increasingly efficient - where five years ago, cheap ones might have burned half a Watt while not in use, the market average is now 30 mW. Ericsson's Greenheart uses 3.5 mW. Assuming the charger's plugged in without a phone connected 22 hours per day, Ericsson just saved 0.25 kWh per year, which would be subject to about 1.4 cents of carbon tax.

However, manufacturing the charger likely consumes far more than 1 kWh, so if you have a choice of buying a new low-standby phone charger or keeping your old one, it's better to keep the old one until it doesn't work anymore.


2) A light sensor that detects natural light, allowing the phone to save energy.

Solar cells can harness something like 0.2 kW/m2 of surface area. So a 1 cm2 cell would generate 20 mW. If it's not in your pocket, this could probably power the phone when it's on but not in use, but it would provide less than 15% of the power needed during a call. Annual impact: less than 0.5 cents of carbon offset.

3) The [Morotola] W233 is made using plastic from recycled water bottles and can itself be entirely recycled...The phone is also sold in packaging made of 100 percent recycled paper...

This is a bit less gimmicky - using recycled paper and plastic is far less wasteful than new material, and switching to recycled plastic could reduce individual carbon output by 20 kg/year. But it ignores the fact that most of the environmental destruction involved in producing a cell phone occurs during the manufacturing of electronic components - chips, circuit boards, LCD displays. Nobody's making a dent in those processes. So recycled packaging still only represents a minor reduction in the overall impact of the phone.

4) ZTE, a Chinese manufacturer of telecommunications equipment...said they would introduce what they called the first solar-powered, low-cost mobile phone on Wednesday in Barcelona.

This is definitely a bigger step than everything above. But, including manufacturing, the phone's lifetime emissions would only be 30% lower than present technology.

So what's the bottom line? You won't reduce your cell phone's carbon emissions and energy usage by running out and buying new energy-efficient products. As with most electronic equipment, the key is to use your cell phones for as long as possible - by the time a new phone gets to you, the bulk of its lifetime emissions have already been spent.