Innovation & Technology

Fenugreek, Okra Are Promising Solutions to Microplastic Pollution

Okra and fenugreek extracts can attract and remove up to 90% of microplastics from waterways — offering non-toxic, plant-based alternatives to conventional solutions.

Published 3 weeks ago | About a 3 minute read

Image: Valeria Aksakova

Microplastics — tiny particles less than 5 mm in size that originate from the breakdown of larger plastics and textiles such as polyester, nylon and fleece — are now a worldwide concern: A 2023 study estimated 171 trillion microplastic particles are now floating in the world's waterways, from oceanic gyres to freshwater lakes.

While researchers continue to study their effects on human, animal and environmental health, microplastics can breach the body’s natural defenses; serve as a substrate for other contaminants; accumulate in vital organs; and potentially trigger inflammation, toxicity and chronic diseases. A 2019 WWF study estimated the average human is consuming roughly 5 grams of plastic every week, which is approximately the equivalent of a credit card. And a study published in PLOS Water in January revealed that France’s drinking water is saturated with microplastics smaller than 20 micrometers (µm) — which falls below the threshold of the EU’s current detection methodology, pointing to an urgent need for updated water-safety protocols.

A number of emerging innovations show promise in cleaning up the small but mighty menace, but they remain notoriously difficult to collect and remove from the environment — and conventional wastewater treatment using inorganic and organic polymeric flocculants is nonbiodegradable and can be toxic to ecosystems. A widely used solution uses polyacrylamide — a water-soluble polymer derived from acrylamide monomers. While polyacrylamide is generally considered safe and is used in everything from cosmetics and water treatment to soil conditioning, the residual acrylamide monomer is a primary focus of safety assessments.

Dr. Rajani Srinivasan and her colleagues at Texas’ Tarleton State University have been working to address this by exploring non-toxic, plant-based solutions for attracting and removing contaminants from water.

In a new study recently published in the journal, ACS Omega, the team found that polymers from okra, fenugreek and tamarind extracts stick to microplastics — clumping together and sinking for easy separation from water.

“Utilizing these plant-based extracts in water treatment will remove microplastics and other pollutants without introducing additional toxic substances to the treated water, thus reducing long-term health risks to the population,” said Dr. Srinivasan — who in 2020 was awarded a patent for an invention related to the use of polymers from plant-based extracts to separate solids, pathogens and both organic and inorganic pollutants from water.

To extract the sticky plant polymers, the researchers soaked sliced okra pods and blended fenugreek seeds in separate containers of water overnight. They then removed the dissolved extracts from each solution and dried them into powders. Their analyses showed that the powdered extracts contained polysaccharides, which are natural polymers.

Initial tests in pure water spiked with microplastics showed that:

one gram of either powder in a quart of water trapped microplastics the most effectively
dried okra and fenugreek extracts removed 67 percent and 93 percent, respectively, of the plastics in an hour
a mixture of equal parts okra and fenugreek powder reached maximum removal efficiency (70 percent) within 30 minutes
both natural polymers performed significantly better than the synthetic, commercially available polyacrylamide conventionally used in wastewater treatment.

Effects on polluted waterways

The researchers then tested the plant extracts on real microplastic-polluted water — collecting samples from water bodies around Texas — and found that the removal efficiency of each plant extract changed, depending on the original water source:

okra worked best in ocean water (80 percent)
fenugreek in groundwater (80-90 percent)
a 1:1 combination of okra and fenugreek was most effective (77 percent) in freshwater.

The scientists hypothesize that the difference in efficiencies is due to the different types, sizes and shapes of microplastics in each water sample. Regardless of water source, they conclude that okra and fenugreek extracts could be viable as biodegradable and nontoxic alternatives to polymers such as polyacrylamide in wastewater treatment and filtration.