Baby you can drive my car...

Chris Goodall, author of "How to Live a Low Carbon Life", raises an interesting point, via John Tierney's blog. The point raised is that walking short trips in not necessarily better for the environment than driving. How could this be? It turns out Milton Friedman was right, there really is no such thing as a free lunch. Even though you are walking, you are still burning calories. Depending on what kinds of food you eat to replace those calories, you may actually be harming the environment. This is especially true if you eat animal carcasses.

If you walk 1.5 miles, Mr. Goodall calculates, and replace those calories by drinking about a cup of milk, the greenhouse emissions connected with that milk (like methane from the dairy farm and carbon dioxide from the delivery truck) are just about equal to the emissions from a typical car making the same trip. And if there were two of you making the trip, then the car would definitely be the more planet-friendly way to go.

Mr. Goodall himself posts a most interesting comment on Tierney's blog:

I wrote the piece on walking versus driving that this column comments on. I was extremely naive not to realise that the analysis would be perceived as an encouragement to drivers. I didn’t intend it to be read that way. My purpose was to draw attention to the carbon intensity of modern food production, particularly of meat.

The food supply chain is about 20% of UK emissions, about the same as private transport. Motor vehicle fuel efficiencies are improving in Europe, driven by regulatory fiat. There is no similar push to improve the CO2 performance of the food supply chain. World meat consumption is expected to double by 2050. (source NYT Feb 24 2008). This is incompatible with a stable climate.

Just a couple of further points. In the UK, the CO2 cost actually of making gasoline adds about 15% to the total CO2 impact. Similarly, a European car will typically create about 3 tonnes of CO2 in its manufacture. These numbers are not enough to remotely affect the conclusion that car travel is less carbon intensive than walking, if the walker replaces lost energy with animal products. A home grown potato would produce the reverse conclusion if cooked efficiently. A raw carrot would be even better.

There we have it, the meat eaters are screwing our planet. I believe that environmental protection is one of the few legitimate uses of government power. Unfortunately, empathy for the plight of the environment has become such a flavor of the month that all sorts of simple minded "green" ideas are being put forth that really don't make a difference at the end of the day. They might make us feel good, but they fail to accomplish the objective of making the environment cleaner or reducing our carbon footprint. For example, it is not clear that re-usable diapers are better than disposables, it is not clear that paper bags are better than paper, and I have read lately that ethanol may actually create more carbon than fuel based solely on petroleum.

I think the thing to take away from all of this is that the calculation of environmental impact is much more involved than it may seem at first glance. Our political leaders, especially the ones who have a Ford Escape Hybrid that they probably have not put five tanks of gas through because they are driven around in a Crown Victoria, should keep this in mind.