National Geographic News
This picture was taking at a Banana Plantation in Costa Rica.  While I was there we got to walk around the plantation and see how everything was done.  It was really neat to see how much time it took to get all of the bananas ready for shipment.
A banana plantation in Costa Rica.

Christina DiPaola

Anne Minard

for National Geographic News

Published March 11, 2011

This story is part of a National Geographic News series on global water issues.

Banana peels are no longer just for composting or comedy shows: New science shows they can pull heavy metal contamination from river water.

Metals such as lead and copper are introduced to waterways from a variety of sources, including agricultural runoff and industrial wastes. Once there, heavy metals can contaminate soils and pose health risks to humans and other species. Lead is known to affect the brain and nervous system.

Traditionally, water quality engineers have used silica, cellulose, and aluminum oxide to extract heavy metals from water, but these remediation strategies come with high price tags and potentially toxic side effects of their own. They work as extractors due to the presence of acids such as those found in the carboxylic and phenolic groups, which attract metal ions.

(Read more: “Predicting the World’s Next Water Pollution Disaster.”)

Bananas, on the other hand, appear to be a safe solution. Banana peels also outperform the competition, says Gustavo Castro, a researcher at the Biosciences Institute at Botucatu, Brazil, and a coauthor of a new study on this new use of the fruit’s peel.

For the study, Castro and his team dried and ground banana peels, then combined them in flasks of water with known concentrations of metals. They also built water filters out of peels and pushed water through them.

In both scenarios, “the metal was removed from the water and remained bonded to the banana peels,” Castro said, adding that the extraction capacity of banana peels exceeded that of other materials used to remove heavy metals.

Previous work has shown that other plant parts—including apple and sugar cane wastes, coconut fibers, and peanut shells—can remove potential toxins from water.

Don’t Try This at Home

Castro doesn’t advise the use of banana peels for home water purification. For starters, the concentration of heavy metals in tap water is usually negligible. Also, while putting banana peels in contact with water will likely remove some metals, the average person isn’t likely to be able to measure success.

Castro said his study findings are most likely to be useful in industrial settings.

The new study appears in Industrial & Engineering Chemistry Research, a journal of the American Chemical Society.

Kyla Criselle Baloca
Kyla Criselle Baloca

I just want to ask if we could apply this as an Investigatory Project. Actually, we've done this before but our professor told us that we must not do it at present 'cause it is just simply obvious that it'll not work. Our methodology accounts to dry the chopped peels under the sun for a week and we will put the dried peels to the diff water samples for a day such that of river water, canal water and that had been used for washing dishes. Thereafter, we will just filter the water into a cloth and pail. Then the before and after samples will then be examined if there's the removal of metals or coliform bacteria? Any improvisation you can suggest please.


The World's Water

The world's increasing population and development of agricultural land are putting pressure on the Earth's limited freshwater supplies. Find out what's at stake and how you can help.

Learn More About Freshwater »

Water Currents, by Sandra Postel and Others

More Posts »

The Future of Food

  • Why Food Matters

    Why Food Matters

    How do we feed nine billion people by 2050, and how do we do so sustainably?

  • Download: Free iPad App

    Download: Free iPad App

    We've made our magazine's best stories about the future of food available in a free iPad app.

See more food news, photos, and videos »

Stories From Experts in the Field

Read More Stories »