100 kilos (220 pounds) to 1 ton
New York City to Niagara Falls (405 miles) and back
53 kg (117 lbs.) CO2e banana-powered bike
66 kg (146 lbs.) CO2e coach
120 kg (265 lbs.) CO2e train
330 kg (728 lbs.) CO2e small, efficient car
500 kg (1,100 lbs.) CO2e plane
1,100 kg (2,530 lbs.) CO2e large four-wheel drive
All these scenarios are based on one person traveling each way on his or her own. I’ve based the figures for the small efficient car on a Fiat 500 traveling at a steady 70 miles per hour and getting 45 miles per gallon. The four-wheel drive, meanwhile, is based on a Land Rover Discovery doing 16 miles to the gallon. If it goes above 70 miles per hour or puts the air-conditioning on, its impact will be higher still.
For all the road vehicles, the exhaust-pipe emissions make up about half of the footprint. About one-third lies in the manufacture and maintenance of the vehicle itself, and the remaining one-sixth is down to the supply chain of the fuel (see Gasoline). I’ve assumed that you keep to the speed limit and look after your car with about average care.
The bike is the outright winner if you can afford the time, you are careful about what you eat (see Cycling), and you don’t have a headwind. Of the more practical options, the coach comes out on top, with a footprint more than 15 times smaller than the gas guzzler. One reason that the coach beats the train is that it travels more slowly, which is significant because the energy needed to overcome air resistance goes with the square of the speed. Another reason is that although a coach is heavy, the weight per passenger is much less than it is for a train (see A mile by train).
Some analyses that I’ve seen put a train ticket and a solo drive closer together in carbon terms. But I’m suspicious of these claims because the embodied emissions of the car per passenger mile are often ignored or underestimated. Whatever the precise difference (and it will of course vary widely depending on the particular vehicles), the train also lets you get some work done, read a book, or sleep instead of arriving at the other end stressed and frazzled.
The plane could actually be better than driving if you have the wrong kind of car. (My sums are based on flying economy class.) But please don’t take this as an advertisement for flying: it’s just a reminder of quite how carbon-profligate some road vehicles are.
As soon as there are more people on the trip, of course, cars become a lot more efficient. If we load the whole family into my C1, along with everything for a week’s holiday and put bikes on the back (it is possible, but only just), the fuel consumption goes down by at least 10 percent. But the emissions per passenger fall so low that we’d be better going that way—in carbon terms, at least—than all traveling by train.
When it comes to both speed and safety, trains and planes win. When you are calculating how much of your life will be taken up by the journey, my back-of-the-envelope calculations tell me that a driver with a fairly typical life expectancy should add about 2 hours each way to the car journey time to take account of the 1 in 200,000 chance that they will lose the rest of their life in a crash.1 If you are in your twenties and in good health you might want to call it 3 hours. This is a very significant chunk to add on to the expected journey time of 7 hours2. For trains and planes the average loss of life expectancy through injury or death is vanishingly small, despite the lavish media coverage that any crash does get. I’m sad to have to report, for the sake of even-handedness, that the bike will lose hands down on safety grounds unless you are careful with your route choice.
A common myth is that huge four-wheel-drive guzzlers are safer for their occupants. This is generally not true. They are, however, more dangerous for everyone else on the road.
4 kg (8.8 lbs.) CO2e per adult low-carbon scenario
280 kg (617 lbs.) CO2e per adult U.K. average
1,500 kg (3,300 lbs.) CO2e per adult high-carbon scenario
> A full-on Christmas could cost you a couple of months’ worth of 10-ton living.
I said at the beginning that this book was about picking your battles. Christmas has got to be a good place to go looking, even if it might entail breaking a few habits and engaging in some delicate family negotiations. For most of us there is a golden opportunity here to escape some mindless consumerism, stress, and perhaps even debt.
In my numbers I have only included unwanted presents, wasted food, avoidable travel, Christmas lights, and cards. Clearly it’s not a complete list, but it’s enough to give a flavor. The numbers are per adult and are based on three scenarios, none of which is intended to be ridiculous.
The average U.K. adult spends a massive £440 ($660) on presents, of which 20 percent will be totally unwanted.3 The U.S. figure is similar at $430 per person (not just adults).4 There will also be a lot of “partly wanted” middle ground, so I’ve assumed an average “wantedness factor” of 50 percent for all presents. In the festive season we spend about £150 ($225) more than usual on food, and I’ve allowed one-third for waste, thinking that this will be slightly higher than it is in the rest of the year because of the “Oh-no-not-turkey-again” effect and the fact that the big meals tend to keep coming over the whole period long after most of us have reached our “wafer-thin mint” threshold.5 The Christmas lights burn through about 45 kilowatt-hours. The average adult mails about 20 cards, with most of the footprint coming from the delivery, not the paper. We typically travel 50 miles each above what we would do anyway, and it is generally by car.
FIGURE 7.1: The footprint of Christmas waste in the three scenarios.
In the high-carbon scenario, you spend $1,500 on presents (yes, that feels extreme to me, too, but it’s only a little over double the average). Sadly, in this scenario the “wantedness factor” turns out to be just 30 percent because you are even worse than me at choosing presents. People are too embarrassed to tell you or to sell them, so they gather dust or even get sneaked into landfill. You decorate your house with a wild lighting display that doesn’t use LED bulbs. You mail 200 rather large cards. You also clock up 500 miles on a tour of relatives in a thirsty car.
I think the low-carbon scenario could be at least as festive and a lot less hassle. The food is great but none gets wasted. You might eat a bit too much, but you make up for that over the coming months, so it’s not additional. Your presents are thoughtful but not necessarily expensive. You encourage people to be honest in their reaction and you’ve kept all the receipts. You have LED Christmas lights. You stay at home and you send cards only to a few people that you haven’t seen for ages and with whom you really don’t want to lose touch. You video-Skype your distant relatives and make plans to see them properly another time.
Some British friends of ours spread the word that only children were going to get presents worth more than a strict limit of £1 ($1.50) . They asked everyone to reciprocate, packing any cash saved off to the charity of their choice. Both giving and receiving became an exchange of gestures and altogether more fun.
350 kg (770 lbs.) CO2e outlay for a three-bedroom house
35 tons CO2e payback over 40 years
> The payback of insulating an attic can be a remarkable three and a half years’ worth of 10-ton living.
My calculations are based mainly on figures produced by the U.K.’s Energy Saving Trust6 and assume you are adding 270 mm (10 inches) of insulation to the previously uninsulated attic of a three-bedroom house. According to the EST’s figures you save 800 kg (1,760 lbs.) CO2e per year, but I’ve rounded this up to 880 kg (1,940 lbs.) to take account of fuel supply chains that I know they don’t include.
The embodied energy of the insulation material pays back in less than six months and is good for at least 40 years. You will therefore save about 35 tons of greenhouse gas.
In terms of money, even without a government grant, you’ll get payback on your $750 investment in 4 years, even when a 10 percent discount rate is applied. In other words, the decision to insulate your attic tomorrow will save you $1,450 on top of paying back your outlay compared with investing the money in a bank account with a 10 percent interest rate. (See discount rates.) In other words, it’s a no-brainer. In the U.K., the EST may well offer you a 50 percent grant, too, which makes it a no-brainer even if you are suspicious that they may have been optimistic with their numbers.
Table 7.1 gives a detailed breakdown for the scenario discussed so far and also for someone increasing their insulation from 50 mm to 270 mm (2 to 10 inches). This is a good move, too, but only if you care about the carbon savings or can get a grant. If you are just in it for the money, and you apply a discount rate, then I don’t think you ever quite get it back again. However, at just $7.5 per ton, the CO2e saved improving your existing insulation is still a hugely cost-effective way of investing in a lower-carbon world.
The EST’s calculations that I’ve used here are based on the assumption that rather than cashing in on all the financial and carbon savings that would be possible if you kept your home at the same temperature that it used to be, you will in fact allow your home to be warmer once it is insulated. In other words the sums here assume that you will lose some of the available savings in exchange for a warmer and perhaps more comfortable home.
| From no insulation to 270 mm (10 inches) | From 50 mm (2 inches) insulation to 270 mm (10 inches) | |||
| Cost without a grant | $775 | $775 | ||
| Annual payback | $225 | $225 | ||
| Embodied emissions in the material7 | 380 kg/830 lbs. | 380 kg/830 lbs. | ||
| Annual carbon savings (including fuel supply chains) | 880 kg/1,940 lbs. | 880 kg/1,940 lbs. | ||
| Financial payback period (with 10 percent discount rate applied) | 4 years | Never quite makes it | ||
| Payback period (with 10 percent discount rate applied) | $1,400 | -$75 | ||
| 40-year carbon savings | 35 tons | 10 tons | ||
TABLE 7.1: Insulating the loft in a three-bedroom house without a government grant: the money and the carbon.
Various types of attic insulation are available: you can get the standard synthetic kinds as well as varieties from sheep’s wool, paper, and a range of other options. Some of these sound good, but you should choose them only if you are 100 percent convinced that there is no compromise on performance or the longevity. Those are the priorities.
Zero CO2e handed down or made from driftwood and seashells
200 kg (440 lbs.) CO2e $750 worth of new Welsh gold
400 kg (880 lbs.) CO2e $750 worth of gold and diamonds sweated out of mines in developing countries
Who would have thought that something so small could have such an impact! But think about it for a moment, and it makes sense: gold and diamonds are precious precisely because it takes effort and sweat to extract them.
At the bottom of my scale are items for which the value is in the art and not the materials. Also at the low end of our scale is a piece of jewelry that has been passed on or reforged from an existing item. The carbon impact here is simply from the energy required to melt it down.8
To arrive at my ballpark figure for the carbon footprint of jewelry—265 g CO2e per dollar spent—I have once again used the technique of working out the carbon footprint of an industry and dividing it by that industry’s total output. The same model that we used to get the overall figure can give us an idea of where that footprint comes from. Not surprisingly, it turns out to be attributable to the extraction of metals and minerals, such as gold and diamonds.
For my “average” example, I have chosen a necklace from virgin Welsh gold, simply because although it has been mined especially for you, this has been done using relatively efficient mining technologies and in a country where machinery tends to be more fuel efficient than in developing countries. The price of the Welsh gold will reflect the relatively high fuel taxes in the U.K., and this reduces the footprint per dollar spent somewhat.
At the top end of the scale is jewelry obtained using inefficient technology and cranky machinery. My figure of 530 kg (1,168 lbs.) CO2e per $1,000 is simply a crude estimate based on twice the carbon intensity of typical U.K. industry.9
While on the subject of gold and diamonds, I should mention that chunks of the Amazon are being deforested in the pursuit of gold. Poor people in developing countries are being exploited in the production of both gold and diamonds. Is it worth it? Can it really be a romantic gesture to give someone something that has an embodied footprint of exploitation? Or can there be beauty and elegance without the extravagance?
The machine itself
200 kg (440 lbs.) CO2e a simple low-cost laptop
720 kg (1,590 lbs.) CO2e a 2010 21.5-inch iMac
800 kg (1,760 lbs.) CO2e an all-the-frills desktop
Electricity consumption
13 g CO2e per hour an energy-efficient laptop10
69 g CO2e per hour a 2010 21.5-inch iMac
165 g CO2e per hour an old desktop machine
Your use of servers and networks
Typically 55 g CO2e per hour
> This is the fastest-rising part of the footprint of computing (see Data centers). Add a bit more for any peripherals and the demands you place on other machines via your use of the Internet.
The machine itself
Even before you turn it on, a new iMac has the same footprint as flying from Glasgow to Madrid and back.
Apple has carried out a detailed life-cycle carbon assessment of their business and their products.11 This analysis suggests that the company’s mid-sized desktop machine— the 21.5-inch iMac—comes in at around 570 kg (1,250 lbs.) CO2e.12 However, the devil is in the details, and the life-cycle approach that Apple has used has a nasty habit of “leaking”—missing little bits of the footprint. The footprint of a computer comes from the complex mass of activity that has had to go on throughout the economy in order for minerals in the ground to turn into machines in the stores. Each component is in turn made of materials and other components, behind each of which lies a whole life cycle of its own. To trace this by mapping out the different processes one by one is impossible because the ripple effect is mathematically endless. You have to miss some processes out, cutting the pathways short, and the result is a shortfall in your footprint calculations that is known as “truncation error.” And it’s the reason that I think Apple’s figure is almost certain to be a little on the light side.
The “input–output” approach of tracing carbon impacts through the economy by modeling the way in which industries buy and sell from each other has, for all its generalizations, the huge advantage of not systematically missing bits out. Based on a 21.5-inch iMac costing $1,800 in the store, input–output modeling gives me a footprint estimate of about 720 kg (1,590 lbs.) CO2e. Just as expected, that is a bit higher than the figure produced by Apple’s process-based approach, so it is the one I have gone with.13
Apple, on its website, talks about reducing its impact by making machines lighter, but the bulk raw materials are just a small part of the issue. If a laptop were just a lump of plastic, steel, and semiconductor, you could get its footprint to below 50 kg (110 lbs.) CO2e. The problem is that microprocessors come in at around 5 kg (11 lbs.) CO2e for a 2 g chip because of the high-tech process that is involved and the incredibly clean environment that is needed.14 Apple also talks about reducing packaging; this, too, is good practice but makes a marginal difference in the scheme of things.
It’s hard to give guidance on what makes a low-carbon computer because the processes involved in making one are so complex. The guidance we would get from input–output analysis is that the cheaper your machine, the less its footprint is likely to be. This is probably a reasonable rule of thumb, although it may mask the impact of some cheap, carbon-intensive production in developing countries. Another guiding principle could be to choose the products from a country that has efficient industry and not too much reliance on coal for electricity—but this is tricky because assembly might take place in a country other than the one in which the most energy-intensive 2 gram components are made.
Using the computer
The electricity emissions typically equal the footprint of manufacture after 15,000 hours—that’s 9 hours every day for 5 years.
Apple reports that the iMac we’re talking about consumes 91 watts of electricity in use.15 The company also reports that the power supply is 87 percent efficient, so, if I understand them correctly, that makes a total of 105 watts leaving your plug. If that is right, in the U.K. the emissions from use would equal my estimate of embodied emissions after 11,500 hours (that’s 7 years at 8 hours per day for 200 days of the year), and by this time the cost of the electricity will probably also have worked out about the same as you paid for the machine. In Australia it would take just 7,000 hours because more of the electricity comes from coal (see Booths supermarkets’ greenhouse gas footprint model). In the U.S. it would take 10,500 hours and in China about 8,000. Most people would change their machine before clocking up those hours, so the embodied emissions in the machine are the biggest deal.
However, the sums don’t necessarily always work out like that. The iMac is a high-value computer, and I have associated that with a relatively high footprint. In addition, some machines are a lot more power hungry. Apple says they have worked on becoming more efficient. Traditionally, laptops consume less than desktops, because it has always been important to conserve battery life. Some, but not all, desktops are catching up. I recently encountered an office full of fairly new HP and Compaq PCs that were burning through 24 watts even when they were switched off. Since they were only on during office hours, they were consuming more when turned off than on. The answer was simply to unplug them at the end of the day.
I haven’t taken into account the use of peripherals or the activity you might stimulate in other machines around the web through your emails and web searches (see Data centers). Despite all this, computing can be a fairly low-carbon way of spending time.
To summarize, computing could be a few percent of your carbon footprint. The embodied footprint of a computer is significant and could easily be the dominant factor, so it probably doesn’t make sense to buy a new, more efficient machine on carbon grounds—better to make an old one last. However, when choosing a computer, do think about its power consumption, especially if you will use it a lot. Laptops are still usually better in this respect than desktops, but whatever you use, switch it off when not in use and unplug it if that’s what it takes to get the power to zero.
800 kg (1,760 lbs.) CO2e per year for $150,000 on 5 percent interest
> That’s a whole month of 10-ton living.
How can a mortgage have a carbon footprint? Surely it just boils down to a few bits of paper or electronic transactions? Look more closely. The bank or building society runs offices, buys computers, sends mail (probably mainly junk; see A letter), and stores data. Its people travel. It outsources everything from cleaners to building maintenance, from design work to corporate lunches, and maybe even still buys in the odd paper clip.
What I am saying is that when you take out the loan, you feed the financial services industry along with all its direct and indirect environmental impacts. This is another example of a set of ripple effects across the economy that we can’t see and don’t stand a chance of counting up one by one. Happily, our input–output model comes to the rescue and produces a ballpark figure of 106 g CO2e for every dollar spent on financial services.
If you have a $150,000 mortgage on a 5 percent interest rate, you pay $7,500 per year (plus any actual repayments) and this incurs an annual footprint of the order of 800 kg (1,760 lbs.) CO2e. The same story applies to all loans, and the principle goes wider still. All the intangible services have fairly similar carbon intensities: solicitors, lawyers, accountants, therapists, architects, and so on.
There are two basic lines of attack if you want to cut the carbon. The first is to take out a smaller mortgage and spend the money you saved on something that decreases carbon emissions, such as an investment in an offshore wind farm, a “save the rainforests” project, or, if you want your neighbors to know what a good person you are, a solar roof. You could stick the money in the bank where it may seem harmless, but even then you may be enabling the bank to lend more to profligate consumers. The other line of attack is to be discerning about the way the mortgage company goes about its affairs. I have based the footprint estimate on general figures for the industry, but actually there will be good and bad practices within it. To begin with, one-tenth of the sector’s footprint comes from printing and postage, so supporting a bank or building society that doesn’t do junk mail is a good first step. About 30 percent of the industry’s footprint comes from air transport, but I’d be surprised if, for example, the Ecology Building Society, based in Yorkshire, goes in for much of this. They run a simple, lean operation out of eco-friendly premises and make a real effort to walk the walk. If I had to guess, I’d put their carbon intensity at less than half of the industry average. Furthermore, their footprint is in the cause of encouraging a sustainable building stock, because they vet their loans by the sustainability of the project and also support lenders in improving their buildings.
The job of choosing between more mainstream lenders is trickier. The most important question is probably to ask yourself how much you trust them to take the carbon issue seriously. If the answer is that you don’t, then they probably haven’t done much to be any better than the industry norm, no matter how much they are talking about it. That is my experience in most of the industries I work in.