Choosing Water Part 1: It’s Easy Being Green
September 8th, 2008 by Kishore
As we approach next week’s conversation: Water Wars - Bottled vs. Tap, I’m blogging about how we choose our water. All week I’m examining the various factors that go into that choice. I’m focusing on the 5 biggies: Environmental, Taste, Convenience, Long Term Health, and Cost.
First up…Environmental Carbon Footprint.
Let’s start on the outside…i.e. the bottle. Most water bottles are made from PET (polyethylene terephthalate). It is easily identifiable from the #1 symbol on the bottom of the container. The two major environmental issues with this plastic is energy used in production (carbon footprint) and recycling/waste.
PET production is a 3 stage process. The first step is production of PTA (Terephthalic acid) and MEG (monoethylene glycol) which are both derived from crude oil. Both are produced at oil refineries. The two are then mixed to form PET resin, typcially performed at a plastic manufacturer. The resin is then sent to a bottling plant, where it is heated and formed into the plastic container we know and love.
Because of the multi-stage process, PET production uses a lot of energy, especially compared to some other plastics. The energy of production for a standard 1 L bottle is 3.4 MJ (Represents the feedstock energy & energy content of the delivered fuel used to produce the plastic/50 g - the typical weight of a 1 L plastic bottle). Expanding that number out to oil equivalence shows US consumption of bottled water plastic equates to about 17 million barrels of oil per year. The number is slightly misleading in that some of the feedstock are byproducts in the production of gasoline.
That energy usage accounts for 2.5 millions tons of CO2 production. Finally, about 55 billion liters of water is used in the production process of the plastic, mainly for cooling the power plants providing energy to the various manufacturing facilities (water is often used in power plants). When you add in the water used to fill the bottles, we’re talking almost 3 liters per liter sold.
Takeaway:
Because of its many stage manufacturing process, PET takes A LOT of energy to produce and account for a heck of a lot of CO2 production.
References (most numbers are circa 2006):
Pacific Institute
How PET is manufactured
Relative Energy usage for different plastics
In my next post, we’ll look at recycling rates for PET.
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September 9th, 2008 at 7:11 pm
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