The other camp believes that bottled water is convenient and much healthier than soft drinks. And bottled water sure is popular.
I think it's important to compare the environmental impact of bottled water to other human activities. For me, it's most intuitive to compare the impact with driving around in a car. So, let's suppose I drive with a few friends from Mountain View to Lake Tahoe on a weekend and back (450 miles) while consuming 20 plastic water bottles. It turns out that very roughly, the environmental impact of the water bottles makes up about 2% of the trip.
Here is my rough calculation:
- The Pacific Institute says that "the total amount of energy embedded in our use of bottled water can be as high as the equivalent of filling a plastic bottle one quarter full with oil".
- These water bottles are usually 500 ml (16.9 FL OZ), so that's 125 ml of oil per bottle.
- Wikipedia says that "on average, about 19.5 US gallons (16.2 imp gal/74 L) of gasoline are available from a 42-US-gallon (35 imp gal/160 L) barrel of crude oil (about 46% by volume), varying due to quality of crude and grade of gasoline". This means that the bottle is equivalent to roughly 58 ml of gasoline, or 0.0153 US gallons.
- My car gets about 30 miles per gallon on lengthy trips, so that's 0.460 miles of driving for the 0.0153 gallons of gasoline.
- It's around 450 miles to Tahoe and back, so the 20 bottles are equivalent to an additional 9.2 miles of driving, which is 2% of 450+9.2.
- The estimate by the Pacific Institute may be inaccurate.
- There is more environmental impact from the car than just burning the gasoline. Relatively speaking this would lower the relative impact of the water bottles.
- The conversion from oil to gasoline may be more or less efficient. That is, one may need to invest additional energy to convert from oil to gas - this would lower the relative impact of the water bottles.
- Perhaps we should compare with a diesel engine (since diesel fuel is closer to oil) or more efficient cars - this would make the relative impact of the water bottles greater.
- The trip might involve other activities with environmental impact (e.g. sleeping at a hotel, eating ribs, etc.). This would lower the relative impact of the water bottles.