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They could soon be used to clean waste water.

March 27, 2017

When we think of “food waste,” we tend to think of things like throwing out bagged salad we accidentally let expire, tossing leftovers we brought home that we never ate, or disposing of an untouched wedding buffet because the bride left the groom at the alter after discovering he had a secret second family living in Sao Paulo. But food waste also comes in more innocuous forms that we often overlook – things like orange peels. Sure, tossing the peel is a natural part of the orange eating process, but just because peels are natural, that doesn’t prevent them from ending up in landfills. However, a team of researchers believes they’ve found a use for all that excess citrus waste – developing a method for using peels to create a water filtration system.

According to the University of Granada, scientists from the Spanish college, together with Mexican researchers, have figured out a way to turn leftover citrus peels from fruits like oranges and grapefruits into a new absorbent material that’s able to clean wastewater by filtering out heavy metals and organic pollutants. Though these peels might seem innocent enough, the university stresses that the global fruit industry produces 38.2 million tons of these inedible fruit outsides every year. As Modern Farmer points out, peels can be an especially pesky problem for companies who make products like orange juice and orange concentrate that then have to deal with this waste on an industrial scale.

Using a relatively new, versatile process known as Instant Controlled Pressure Drop, scientists were able to modify the structure of citrus peel waste to make this material more absorbent. These altered peels are then given an additional chemical treatment “to add functional groups to the material, thus making it selective in order to remove metals and organic pollutants present in water.” From there, this altered material is ready to be used in the columns of a water filtration system. “The results show a great potential for the use of said materials as adsorbents capable of competing with commercial activated carbon for the adsorption and recovery of metals present in wastewater, in a way that it could be possible to carry out sustainable processes in which products with a great commercial value could be obtained from food industry residues,” the University of Granada’s Luis Alberto Romero Cano said in a very scientific manner. Long story short: Orange peels could prove a viable way to filter water.

Granted, none of this really helps people who just polished off an orange as a snack wondering what to do with the rind. So until you start eating oranges on an industrial scale, you’re best bet is probably composting.