0.014 g CO2e one message
32,000 tons CO2e all world’s texts for a year
The biggest part of a text message’s footprint is the power used by your phone while you type—and of course by your friend’s phone while he or she reads what you’ve written. If the two of you take a minute between you to type and read the message, and you each have phones that consume 1 watt of power when in use, the message’s footprint will be about a hundredth of a gram. This figure takes into account the transmission of a 140-character message across the network.1
Around the world, about 2.5 trillion texts are sent every year.2 Don’t be fooled into thinking that the 32,000-ton footprint for this total is a big number. It isn’t. 32,000 tons is about one ten-thousandth of a percent of the world’s carbon footprint. In other words, texting is not a big deal. It wouldn’t even be a big deal if my numbers were out by a factor of a hundred.
Incidentally, as of 2008, nearly a quarter of all text messages were sent in China, and about a fifth in the Philippines, where they average an impressive 15 messages per day for each phone. The average North American phone sent just a couple of messages a day, whereas British phones manage six texts per handset.
In summary, we can relax about sending texts (but no spam, please).
0.06 g CO2e one cup
23 kg (51 lbs.) CO2e a year’s tap water for a typical U.S. citizen
> A year’s supply for one person is the same as a 27-mile drive in an average passenger car.3 That includes drinking, washing, cleaning—the lot.
Unlike the bottled alternative, which has around 1,000 times the impact (see A 500 mL (16 oz.) bottle of water), cold tap water is not a major carbon concern for most North Americans. In the U.S., for example, the provision and disposal of household water accounts for less than third of a percent of the national carbon footprint.4 Climate change looks set to cause serious water stress in some places while other areas are going to have plenty. Interestingly, if our cup of tap water is poured down the drain, its footprint leaps almost fourfold to a quarter of a gram because it is more carbon intensive to treat waste water than to supply the water in the first place.5 If the eventual fate of the drink is to be flushed down the loo along with another couple of gallons, that takes the total to 4 g CO2e.
Tap water itself is one thing. Heating it up is another matter, accounting for a decent chunk of the typical person’s emissions (see A person). See also Swimming pool, and Desalination.
0.2 g CO2e Google’s estimate for the energy used at their end
0.7 g CO2e from an efficient laptop (a lower estimate)
4.5 g CO2e from a power-hungry machine and making higher estimates of power used in the network
> So that is between 2 and 14 seconds’ worth of 10-ton living for a 30-second single search.
At the low end of the scale, I’ve started off with Google’s estimate of 0.2 g CO2e for the electricity they use at their end when you put in a single search enquiry.6 Add to it just 30 seconds of machine time at your end on an efficient 20-watt laptop while you tap in the search, wait for the result, and scan it for what you want. That’s another 0.1 g, bringing the total so far to 0.3 g. Your local network and the servers that actually host the information you are digging for probably come to at least 50 percent of the amount of power used by your machine, even if they are super-efficient, like your laptop,7 so that takes us to 0.35 g. Wear and tear and depreciation of hardware throughout the whole system probably doubles this because of the emissions that are required in the manufacture of all that kit. That takes us to 0.7 g CO2e for a single enquiry that might let you, say, find the location of the restaurant you’re heading to.
On a more power-hungry desktop computer that uses 150 watts of power, your web search might burn through about 0.75 g CO2e. If you apply the same markups for networks and hardware, we get to a grand total of 4.5 g, with Google accounting for just 0.2 g of that.
You can search for information about the footprint of web searches. You’d find blogs and articles all coming up with different figures based on different assumptions and all including different things. Some look at multiple searches and therefore produce much higher headline figures.8
At the high end of my estimate, the activity of surfing clocks up a carbon footprint at about half the rate of the 10-ton life. In other words, if you spent a whole year browsing the web nonstop, you’d trigger about 5 tons of emissions. That sounds good until you remember that at the same time you might also be wearing clothes, keeping warm, burning calories, getting closer to your next need for medical attention, living in a building that needs periodic maintenance, and so on. Even while you are sitting at the machine, your browsing is just one part of your footprint.
Google is estimated to deal with 200 to 500 million enquiries per day. If we go with the top estimate, and the high-end figure for the footprint of a single search, Google searching accounts for 1.3 million tons CO2e per year. That is a big number, but it is only about one forty-thousandth of our global footprint. We can probably relax about it. Reading the stuff we find is an altogether more carbon-hungry activity—see A computer (and using it).
Zero CO2e a normal household door on a summer’s day
3 g CO2e getting in through your front door on a cold New York winter’s day
84 g CO2e big electric doors opening into a large stairwell on a cold, windy day in New York
> At the high end, that’s a banana’s worth of greenhouse gas every time you enter the building.
The entrance door of the building where I work has no manual option.9 To get in, you have to press a button and wait while two electric motors whir and double doors swing slowly open, creating a space 2 m wide by 2.5 m high (about 6.5 feet wide by 8 feet high). You enter a spacious stairwell with two large radiators. It takes 18 seconds for the doors to finish closing. This three-year-old building was amazingly rated environmentally “Excellent.”10
The power used by the electric motors themselves isn’t the problem. They account for just 1 g CO2e. The problem is the size of the space you have to open, the time it has to stay open for, and the vast heated space that the doors open onto.
For this building there must have been lots of other options, such as manual doors that swing shut and can be opened singly, with an override button for disabled access. Rotating doors attached to turbines that generate electricity as you pass through have been trialed in Holland but sound like the kind of gimmick that can tarnish the reputation of the renewables industry.
In a typical home on a cold, blustery day, the numbers are more likely to come out at about 3 g, based on opening it by hand and closing it straight away.
0.3 g CO2e a spam email
4 g CO2e a proper email
50 g CO2e an email with long and tiresome attachment that you have to read
> A typical year of incoming mail adds up to 135 kg (300 lbs.) CO2e: over 1 percent of the 10-ton lifestyle and equivalent to driving 200 miles in an average car.
The annual figure provided here is for the typical business user and includes the sending, filtering and reading of every incoming message. According to research by the spam and virus protection specialists, McAfee, a remarkable 78 percent of those incoming emails are spam. Around 62 trillion spam messages are sent every year, requiring the use of 33 billion units of electricity and causing around 20 million tons of CO2e per year. McAfee estimated that around 80 percent of this electricity is consumed by the reading and deleting of spam and the searching through spam folders to dig out genuine emails that ended up there by accident. Spam filters account for 16 percent. The actual generation and sending of the spam is a very small proportion of the footprint.
Although 78 percent of incoming emails sent are spam, these messages account for just 22 percent of the total footprint of your email account, because, although they are a pain, you deal with them quickly. Most of them you never even see. A genuine email has a bigger carbon footprint, simply because it takes time to deal with. So if you are someone who needlessly copies people in on messages just to cover your own back, so that you can claim they should have known about it, the carbon footprint gives you one more good reason for changing your ways. You may find that after a while everyone at work starts to like you more, too.
The average email has just one-sixtieth the footprint of a letter (see A letter). That looks like a carbon savings unless you end up sending 60 times more emails than the number of letters you would have mailed in days gone by. Lots of people do. This is a good example of the rebound effect—a low-carbon technology resulting in higher-carbon living simply because we use it more.
If the great quest is for ways in which we can improve our lives while cutting carbon, surely spam and unnecessary email have to be very high on the hit list, along with old-fashioned paper junk mail.
If only email were taxed. Just a cent per message would surely kill all spam instantly. The funds could go to tackling world poverty, say. The world’s carbon footprint would go down by 20 million tons even if genuine users didn’t change their habits at all. The average user would be saved a couple of minutes of their time every day, and there would be a $170 billion annual fund made available. If one cent turned out to be enough to push us into a more disciplined email culture—with perhaps half the emails sent—the anti-poverty fund would be cut in half, but a good few minutes per day would be liberated in many people’s lives, and the carbon savings would be around 70 million tons CO2e—that’s nearly 10 percent of all of Canada’s emissions.
Zero CO2e letting them drip
3 g CO2e Dyson Airblade
10 g CO2e one paper towel
20 g CO2e standard electric drier
> On average, if you used public toilets six times per day, your hand drying would produce around 15 kg (33 lbs.) CO2e per year; equivalent to 1 kg (2.2 lbs.) of beef.
“What’s the greenest way to dry my hands?” is a frequently asked question, so I’ll answer it even though I have already made the point that if you really want a lower-carbon lifestyle, you should be asking about something more important.
Close to the low end of the scale is drying your hands with a Dyson Airblade. This dryer does the job in about 10 seconds with 1.6 kilowatts of power. Its secret is that it doesn’t heat the air. It just blows it hard. This makes it far more efficient than conventional hand driers.
In the middle of the spectrum I have put paper towels, based on 10 g of low-quality recycled paper per sheet, and only one towel used each time.11 (Of course, if you use two or three towels, the footprint doubles or triples.)
At the high end are conventional heated hand driers. These take a shade longer than the Dyson and use around 6 kilowatts of power. The big difference is explained by the fact that it always takes a lot of energy to create heat.
Right at the bottom of the scale comes not drying your hands at all—or indeed using a small hand towel that is reused many times in between low-temperature washes. I am not a hygiene expert, but I’m told that neither option is good from that point of view: they may even end up adding to the already substantial footprint of the health service (see A heart bypass operation).
3 g CO2e very lightweight variety
10 g CO2e standard disposable supermarket bag12
50 g CO2e heavyweight, reusable variety
> So that’s 2.5 kg (5.5. lbs.) per year if you use five standard bags per week: about the same as one large cheeseburger.
Over the past few years many supermarkets have been making an effort to reduce the use of plastic bags, and Rwanda has set a dazzling example for the world by banning them altogether. This is fantastic news for other environmental reasons but doesn’t constitute a response to climate change. When someone in the developed world walks home from the store with a disposable plastic bag full of food, the bag is typically responsible for about one-thousandth of the footprint of the food it contains. In other words, it is good if your supermarket is taking action on plastic bags, but don’t let that stop you from asking what it is doing about the other 999 thousandths of its carbon agenda.
Carbon emissions are not the only environmental problem associated with plastic bags, of course. They also have a habit of hanging around in the ecosystem where they can sit for hundreds of years, clogging up animals’ stomachs, killing fish, and being ugly. National Geographic estimates that the world uses between 500 billion and 1 trillion disposable grocery bags per year.13 That’s an awful lot of trash—even if the bags contribute only around one ten-thousandth of the world’s total carbon footprint.
How best to get rid of them, then? Burning releases nasty toxins as well as carbon, although the technology is improving. From a purely climate change perspective, landfill is not too bad. They won’t degrade, so all those hydrocarbons are returned to the ground where they came from for fairly long-term storage. But landfill is nasty for other reasons.
So, although disposable plastic bags aren’t a serious carbon issue, they are still nasty for other reasons. Better alternatives are a backpack (which makes things easier to carry and keeps your hands free), a wheelie basket (which prevents you from having to lift things at all), or sturdy, reusable bags. If you do use reusable plastic bags, make sure you really do reuse them: if you get less than five uses out of one, you’d be better off, in carbon terms, with disposable ones.