Do the "Shade Balls" Actually Save Water? Maybe We Need a Life Cycle Analysis.

CC BY-NC-ND 2.0. Eric Garcetti via Flickr

All the blogs are excited about the shade balls being poured into a Los Angeles reservoir to save water being lost through evaporation. Brad Plumer of VOX writes:

The black plastic balls help maintain water quality by blocking sunlight, thereby preventing hazardous reactions with the chlorine and bromide in the water. (The shade balls also cut down on evaporation, though this is a relatively minor benefit.)

The mayor of LA stresses the water savings in a press conference.

By reducing evaporation, these shade balls will conserve 300 million gallons of water each year, instead of just evaporating into the sky. That's 300 million gallons to fight this drought.

300 million gallons of water saved. But how much water did it take to make those balls? How many other resources? The balls are four inches in diameter, and made from polyethylene plastic by XavierC. I could not find out how much they weigh, but Bloomberg Business says 96 million of them are being dumped into the reservoir.

When you look at how polyethylene is made, it is essentially a solid fossil fuel, transformed using electricity and natural gas, which these days is made by fracking, using thousands of gallons of water. 1000 lbs of polyethylene = 188 lbs of oil and 827 lbs of natural gas and 159 kWh of electricity.

As Brad Plumer notes, the main reason they are doing this is that there are bromine and chlorine in the water, which react with sunlight to make bromate, a suspected carcinogen. Yet the polyethylene they are using is made through processes that consume a huge amount of fossil fuels and not a few carcinogens.

I am not a chemist, but something is wrong with this picture. It would be interesting to see a full life cycle analysis instead of taking this all at face value.