For decades, the conversation around waste has revolved around what to do after we have used something. Composting, recycling, and upcycling are all about managing leftovers. But researchers at the Indian Institute of Technology Gandhinagar (IITGN) have taken a different route. They have looked at waste itself as a starting point for invention, not just an endpoint of consumption. Their study, published in Bioresource Technology Reports, is transforming banana peels into a potent, low-cost fertiliser that could change how we feed our crops and care for the planet.
“We used nature’s design to solve nature’s problems,” remarked Dr Bhaskar Datta, Professor of Chemistry (Jointly with Biological Sciences and Engineering) and principal investigator of the study. Every day, the world throws away nearly 57 million metric tons of banana peels, nearly 40% of each fruit’s weight, creating a massive waste problem. These discards are rich in carbohydrates, proteins, and minerals, all of which are valuable nutrients and essential compounds for plant growth. The team dried, crushed, and processed the peels into nanoscale powders of high porosity, shrinking the material to dimensions so small that its surface area and chemical reactivity increased dramatically. “It was interesting to note that these nanoscale particles could soak up nitrogen in the form of ammonium ions and release it slowly over time, acting like tiny nutrient reservoirs for plants,” said Dr Datta, who directs the Food, Environment & Health Laboratory at IIT Gandhinagar.
In doing so, the researchers turned banana waste into a smart fertiliser. The study compared the performance of the whole peel against its separate outer (yellow) and inner (white) layers. The inner layer, richer in certain organic components, showed distinct advantages in capturing the ammonium ions. When tested, the whole peel formulation showed the highest nutrient absorption capacity, capturing up to 30.85 milligrams of ammonium per gram of material.
“Our experiments indicated that the peel powders showed remarkable efficiency in capturing and delivering ammonium ions, outperforming many other plant-based adsorbents, like orange or pineapple peel biochar. Also, these specimens exhibited excellent reactive oxygen species (ROS) scavenging activity,” explained Dr Himarati Mondal, the first author of the study and former IITGN Postdoctoral Fellow who is currently a Research Professor at Gachon University, Republic of Korea. “Furthermore, experiments also showcased that the outer layer of the peel released ammonium ions more rapidly than those of the inner and intact layers,” she added. The variegated release kinetics could help tailor fertilisers to specific crop needs.
Additionally, unlike conventional nitrogen fertilisers, which can leach into rivers or evaporate into the atmosphere, these peel-based formulations gradually release ammonium over time. This controlled nutrient release makes them promising as fertilisers. “We tested the fertiliser’s effectiveness on Arabidopsis thaliana, a model plant widely used in agricultural research,” stated Dr Charli Kaushal, co-author and an IITGN Postdoctoral Fellow at the Plant Molecular & Developmental Cell Biology Laboratory. Seedlings treated with the ammonium-loaded banana peel formulations showed significant improvements in root development, leaf growth, and overall plant health over an 11-day observation period. “These changes could be indicative of antioxidant properties,” observed Dr Subramanian Sankaranarayanan, senior author and an Assistant Professor at IITGN’s Department of Biological Sciences and Engineering. “The plants could be receiving protection because the peel formulations scavenged harmful reactive molecules, providing seedlings an extra boost,” he added.
The interdisciplinary study combined chemistry, biological engineering, and agricultural research. By successfully converting discarded banana peels into a highly efficient, nanoscale sponge, the research team has created a technology that shows promise for simultaneously treating agricultural wastewater and recovering valuable nutrients for reuse. As global food security becomes increasingly critical and environmental concerns intensify, technologies that transform agricultural byproducts and food waste into sustainable inputs reinforce the principles of a circular economy.
“This work is a component of our broader efforts towards managing liquid waste, including transforming human urine. We are exploring avenues for further optimisation, including testing different processing methods, applications with other crops, and scaling up production,” said Dr Datta. The work was performed as part of a project funded by the Gujarat Council on Science & Technology (GUJCOST), and the findings could offer developing countries with large banana industries a low-cost method for environmental remediation, sustainable agriculture, and yield enhancement.