Engineers in Singapore and Vietnam decided to turn the hundreds of millions of tons of pineapple waste that accrued in their nations into something useful, in this case insulation for their piña coladas. Not only does their new material keep drinks chilled better than many commercial coolers, but it could also offer a final resting place for the world’s pineapple waste.
Pineapples make up about 20% of the world’s tropical fruit production, with more than 25 million tons harvested each year—but more than half of this forms waste by-products like leaves, peels and seeds.
To find a use for those leftovers, the researchers mixed pineapple fibers, which they shredded in a blender, with polyvinyl alcohol as an adhesive agent and deionized water as a solvent. They then treated the mix with ultrasound and heated it in an oven at 80°C for 2 hours. The suspension that formed was then chilled before being freeze-dried.
The result was a pale yellow aerogel that is lightweight, flexible, and more than 96% porous—properties that make it ideal as an insulating material against both heat and sound.
When the researchers wrapped a sheet of the pineapple aerogel around a military-style canteen bottle, they found that the gel could provide three times the thermal insulation of commercially available alternatives, they report this month in Materials Chemistry and Physics. The gel-wrapped bottle kept –3°C water cooled below 0°C for 6 hours and liquid heated to 90°C above 40°C for 2.5 hours. What’s more, the pineapple gel also acted as a sound barrier; in another test, the gel did a better job of damping noise than Basmel, a popular kind of soundproofing panel.