South African scientists have discovered that pineapple leaves, long regarded as agricultural waste, can be transformed into a powerful, low-cost material that tackles two pressing challenges: water pollution and forensic investigation.

By Lebogang Mashala, editor at African Farming

Every year, manufacturers of pineapple juice and other pineapple products discard thousands of tonnes of pineapple leaves, most of which end up in landfills or are burnt. Now, researchers at Nelson Mandela University have shown that this overlooked byproduct can be converted into advanced nanoparticles capable of cleaning contaminated water and assisting police to detect invisible fingerprints.

According to Bienvenu Gael Fouda Mbanga, a research fellow at the university, pineapple leaves can be processed into carbon-based nanoparticles – extremely small materials measuring less than 0.0001mm – with remarkable properties.

“I’m part of a team of nanomaterial chemists working on creating new materials from agricultural waste such as pineapple leaves,” said Mbanga. “We wanted to find out whether these leaves could be turned into a nanoparticle powder that can adsorb copper ions from wastewater.”

The results exceeded expectations.

Once the pineapple leaf-based nanoparticles absorb copper from polluted water, they can be dried and ground into a fine powder that forensic investigators can use to dust for latent fingerprints, the invisible prints left behind by sweat and natural skin oils.

“This is the first time agricultural waste-derived nanoparticles have been used to remove heavy metals from water and then reused in forensic science,” Mbanga explained. “The process is low-cost and fills an important research gap.”

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Cost-effective Water Pollution Treatment

Copper pollution is a persistent problem in South Africa, particularly in areas affected by mining, electroplating and manufacturing. Industrial wastewater and sludge often contain copper levels far above safe limits, posing serious risks to human health and aquatic ecosystems.

Excessive copper exposure can lead to stomach problems and long-term damage to the liver and kidneys. In rivers and dams, it can poison fish and other aquatic organisms.

Current methods for removing heavy metals from wastewater rely on adsorbent materials that are often expensive, making large-scale water treatment costly. Contaminated water also cannot be reused in agriculture or industry until these metals are removed.

“Our material offers a cheaper alternative,” said Mbanga. “By using waste that costs nothing, we reduce both environmental pollution and treatment costs.”

How Pineapple Leaves Do the Job

To create the nanoparticles, the researchers first converted pineapple leaves into carbon nanoparticles and then coated them with zinc oxide. This combination proved highly effective at removing copper from water.

“The zinc oxide coating helps the particles bind to copper ions, while the porous carbon structure provides a large surface area for adsorption,” Mbanga explained. “Together, they significantly boost performance.”

After testing the material’s water-cleaning ability, the researchers explored whether the copper-loaded nanoparticles could be repurposed. When powdered and applied to surfaces, the spent adsorbent produced clear ridge patterns, making it suitable for fingerprint detection.

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Safer Fingerprints, Circular Economy Gains

Traditional fingerprint powders often contain chemicals that pose health risks to forensic investigators. A powder derived from pineapple leaves offers a safer, more environmentally friendly alternative.

The discovery also supports the principles of a circular economy, keeping materials in use for as long as possible through reuse and regeneration. While some pineapple leaves are composted or used in products such as disposable diapers, the majority are discarded as waste.

“Transforming this biomass into a multifunctional product shows how agricultural waste can be upgraded into something valuable,” said Mbanga.

What Comes Next

The researchers believe the technology has strong potential for scale-up in both wastewater treatment facilities and forensic laboratories. Further testing is needed to assess long-term performance, stability in water and cost-effectiveness under real-world conditions.

They are calling on universities, government bodies, forensic laboratories and industry partners to collaborate in advancing the technology. Support through funding, incentives and appropriate regulation will be key.

“Nanoparticles that add value to agricultural waste while addressing environmental and societal challenges should be prioritised,” Mbanga said.

If adopted widely, pineapple leaves could move from dumpsites to treatment plants and crime scenes, proving that even farm waste can play a role in protecting water, health and public safety.