In 2015 96 million ‘shade balls’ were unloaded onto the Los Angeles water reservoir. The black floating balls were promised to be able to reduce the evaporation of the reservoir by 85 to 90 percent during a drought.
The Los Angeles Department of Water and Power said this evaporation reduction could amount to up to 300 million gallons of water, enough to supply drinking water to 8,100 people. But a new report from MIT shows that it may take more water to make the shade balls than what they save.
Shade balls need to be used for at least two years to pay back production cost
The research team determined that to offset the loss of the shade balls they need to float on the reservoir for at least 2 years.
Shade balls were first introduced to Los Angeles water reserves in 2008 as a way to reduce the creation of bromate, which is a carcinogen regulated by the EPA.
Bromate is usually formed when sunlight reacts with chemical treatments in the water. The shade balls prevent the sun from accessing the water and hence reduce the incidences of bromate.
MIT scientists were curious about the larger cost of the balls and conducted a ‘blue’ footprint analysis which works out the amount of water used in the process of manufacturing a product. The shade balls used in LA are made of a plastic called polyethylene.
“We know that high-density polyethylene itself is made using oil, natural gas, and electricity,” said Erfan Haghighi, an environmental scientist and mechanical engineer at MIT, and lead author on the paper. “And each of these energy sources is water intensive.”
The amount of water needed to make each of the three resources used to make the plastic was estimated using both local and global statistics to produce an average. From there the MIT team went through industry reports to determine how much of each resource went into making the shade balls.
With this data in hand, they could then estimate that between 66 and 766 million gallons of water were required to manufacture the balls. This massive amount of water is close to the equivalent of 100 to 1,000 Olympic-sized swimming pools.
So, for the shade balls to break even on their water cost and saving equation they would need to stay on the Los Angeles Reservoir for at least a year or more to save water. Luckily, the LA Department of Water and Power have been looking ahead and since the balls were deployed in 2015, they have already had over two years sitting on the reservoir's surface.
Balls to stay for the long-term
They said they plan to keep the shade balls in place as a permanent solution, replacing them every ten years. While in this instance it seems that the shade balls are actually going to be in use long enough to pay back the water that it took to manufacture them, the case is an important one to note when examining short-term fixes to ongoing environmental problems.
The new study was published in Nature Sustainablity.