The best comparison of the relative ecological impact of personal choices?

Question

What is the best existing non-interactive comparison of the ecological impacts of different personal lifestyle choices? The obvious domains might be housing, transport, food, personal consumption and waste. Perhaps it could be by dollar spent, or dollar saved, or hour spent, or year of commitment. A good carbon-impact comparison would be a second-best alternative.

The public debate on these issues is full of sweeping generalizations supported by absolute figures (usually tons, sometimes hectares), which are meaningless to most people. What is most needed is relative figures, if possible with a graphical component.

Clearly there is a huge knowledge gap on this subject, and as a result at least some people are focusing their efforts in the wrong areas. The net outcome may not be positive if consumers make trivial changes, sometimes involving real effort, and then consider themselves absolved of further responsibility for the global ecological crisis.

The obvious example of a "micro" choice is low-energy lightbulbs, but there are plenty of others:

• recycling household plastic
• passing up meat more often
• replacing a car or electrical appliance with a more efficient version
• taking shorter showers or turning down heating or aircon
• postponing the replacement of a mobile phone

Such deeds can certainly add up to something significant. But how significant? Together, can they ever become as significant as a single "macro" choice? Such as:

• becoming vegetarian
• moving to an urban apartment
• not flying
• cycling to work

How many avoided hamburgers does it take a suburbanite to cancel out the SUV? Roughly. :)

"Ecological footprint" – the amount of land required to support an individual lifestyle – is supposed to measure these things. Calculators include:

• http://footprintnetwork.org/en/index.php/GFN/page/calculators/
• http://ecologicalfootprint.com/
• http://myfootprint.org/

In general these are either unusably ugly or extremely simplistic, and more importantly (1) they require fastidious form-filling and (2, as pointed out in a similar question here) they do not detail the figures behind their algorithms.

Answer 1

In general these are non-trivial questions. I don't know of a single source of answers, other that possibly the SL branch of StackExchange .

Your best option, I think, is to learn how to reason about such things. For this you will need to do a bit of digging: Most of the carbon cost is really the energy cost. So you learn how to convert kWh to pounds of CO2. This one is fairly easy to find. You will also need BTU (as in house and water heating) to pounds natural gas used.

Once you have the energy units nailed down, the rest is fairly easy, athough it's good to seek several points of view. All of these tend to be rough calculations, and different people will make differing assumptions.

Some are not obvious.

Example: Recycling household plastic.

This one is full of pitfalls: Can you drop the plastic off when you shop? If you have to make a separate trip, it might be better to throw it away.

Is your community set up to recycle plastic. If most of it ends up in the garbage, you aren't ahead.

Recycling plastic may not be a benefit in terms of greenhouse gasses. It may reduce oil use,but tehre may not be any net gain in energy efficiency. Sure, you don't have to make the feed stock, but there is a lot of transportation tied up in recycling.

First approximation: It's a wash, unless you have a local market for the plastic.

Passing up meat

North Americans eat too much meat. But there is some evidence that we should not be complete vegetarians. However you did say more often.

If you are talking about cow fed on grain, then yes, you could make the argument that a pound of cow takes about 6-10 lbs of grain, and that it would be cheaper in terms of energy to eat the grain.

Outside of the first world, grain fed beef is uncommon. Most of the meat is raised on grass. Much of that grassland is unsuitable for agriculture. Even where I live, west of Edmonton, locally about half the cleared land is pasture, either with grazing cattle, or managed for hay production for winter feed. A few miles to the west grain farming vanishes, and it's all cattle or sheep country. There isn't a reliable enough growing season to grow annual crops.

With climate warming and increasing variability more land may become unsuitable for annual cropping. The optimum choice may go the other way.

Replacing a car or appliance with a more efficient one.

Depends greatly on the use pattern. Unless the vehicle is a junker, when you trade your car in, someone else will buy it and use it. The costs to make it are a sunk cost, and the amount of embodied energy in a car is considerable. If you are a high mileage user, then replacing the car may be a net win. Let someone else putter around a few thousand km per year for 10 years to finish wearing it out.

But another option is to keep it and buy a highly efficient but different optimization vehicle. E.g. Suppose at present you have that classic family vehicle, a Dodge Caravan. Intead of trading it in on whatever new hybrid would replace it, perhaps it would be better to get a Mercedes Smartcar, or a Focus, and use that when you could, and use the Caravan only when you must.

With cars, the waste comes from under utilization. A Caravan carrying a soccer team gets more passenger miles per gallon than a Prius taking a single commuter to work.

For appliances a good rule of thumb is to compare the lifespan energy use. Something like a refrigerator uses 1500 - 2000 kWh/year. For me that 200-300 dollars worth of energy per year. Suppose I could replace it with one that used half the power. The new unit however cost $1000. Suppose in addition that ALL of that thousand bucks represents energy. So the new reefer costs 6000 kWh. So a new reefer pays for itself in 6-10 years under this simplified energy model. (While not terribly accurate, I think you will find that the errors when comparing similar items will cancel out.)

The same argument for a toaster oven would probably result in you keeping the old one. You don't use it that often, so the time to pay back the power use is much longer.

As you can see, I took oddball stances on these. You will need to develop your own criteria.