– Liquid fertilisers made from fermented banana peels can effectively replace synthetic nutrient solutions in hydroponic lettuce cultivation, leading to robust crop growth.

– It outperformed both orange peel and mixed fruit waste formulations, offering the most effective results among tested organic materials.

– Hydroponic lettuce grown outdoors under direct sunlight responded better to organic fertilisers than crops grown indoors under artificial lighting.

A new study conducted by a team at Caraga State University has demonstrated that liquid plant feeds derived from fermented fruit waste can successfully replace standard synthetic chemicals to drive robust crop growth.

The researchers evaluated how organic nutrients extracted from common fruit scraps performed in soilless agriculture. They specifically tested liquid feeds made from banana (Musa) peels, orange (Citrus × sinensis) peels, and mixed fruit waste on commercial lettuce (Lactuca sativa) crops.

The commercial push for green hydroponics

Commercial hydroponic farms grow vegetable crops directly in nutrient-enriched water rather than soil. While this method saves massive amounts of land and water, operators rely heavily on manufactured chemical feeds known as synthetic nutrient solutions. These chemical inputs represent a major ongoing operational expense for business-to-business crop producers.

The research team set out to find a commercially viable, sustainable replacement that would help growers reduce their overhead costs while tackling the issue of food waste. The primary goal of their project was to investigate the efficacy of fertilisers derived from banana, orange, and mixed fruit peels in promoting lettuce growth in a hydroponic system as a sustainable alternative to synthetic nutrient solutions.

Putting food waste to the test

The team monitored the growth of young lettuce seedlings over a period of approximately two weeks. This specific testing window captured the early vegetative stage, which is the crucial initial phase of leaf development before the vegetable begins to form a head.

To understand how environmental conditions impact the organic feeds, the researchers tested the crops across two different lighting setups. Half the hydroponic lettuce seedlings grew outside under direct sunlight, while the remaining crops grew indoors under artificial grow lights. The team also evaluated individual peel types against mixed organic blends to identify the single most effective formulation for commercial vegetable production.

Blending the first batch of organic feeds

During the initial trial, the research team prepared three distinct organic nutrient recipes. The first formulation relied on five pieces of orange peel, the second used five pieces of banana peel, and the third featured a mixed blend containing five pieces of potato peel, five banana peels, and five orange peels.

The researchers combined each separate peel batch with one litre of water and placed the mixture inside a one-litre container to undergo fermentation (a natural chemical breakdown process that unlocks the trapped minerals inside organic matter).

To boost the overall nutritional value of the liquid feeds, the team added five grams of brown sugar to feed the fermentation process, along with two grams of Epsom salt and one gram of baking soda. Epsom salt supplies plants with vital magnesium and sulphur, while baking soda acts as a sodium base. The team then applied these finished liquid ferments to both the indoor and outdoor crop groups.

Scaling the mixtures for larger trials

Following their initial test, the researchers scaled up their recipes to test larger ingredient weights and higher water volumes. For their second orange trial, the team took 400 grams of orange peel and submerged it in three litres of primary water and five litres of secondary water. They fortified this mixture with two grape boxes, two grams of Epsom salt, and one gram of baking soda.

The scaled banana formulation followed an identical process, using 800 grams of banana peel mixed into the same eight-litre water volume alongside the grape box and mineral additives. For the scaled mixed trial, the researchers combined 500 grams of banana peel with 500 grams of orange peel in the eight-litre water setup. By testing these different ingredient weights, the team aimed to establish the exact concentration of raw organic waste required to produce a stable agricultural feed.

Sunlight and banana peels produce top results

When the researchers analysed the crop measurements at the end of the two-week vegetative window, clear patterns emerged. Reporting their core measurements, the researchers stated: “Findings revealed that optimal concentrations of 400 to 1,000 grams of peels per litre of water and a three-litre fertiliser combination yielded favourable outcomes under direct sunlight.”

The environmental setup played a decisive role in crop success. The lettuce seedlings grown outdoors under direct sunlight achieved significantly better growth than the seedlings grown indoors under artificial lighting. When comparing the raw materials, both the pure banana feed and the mixed fruit feed generated healthy crops.

However, the researchers confirmed that banana waste stood out as the superior ingredient. Delivering their final verdict, they wrote: “The study concludes that banana and mixed peel fertilisers supported robust lettuce growth, with banana being the most effective.”

Takeaways for future research

The researchers acknowledged that “a key strength of this study is its adaptive methodology”. Running the trials inside a strictly controlled hydroponic setup allowed them to adjust variables like light exposure and feed strength with total precision. This controlled environment minimised outside interference, meaning the team could react to their early data, adapt their methodology, and focus their efforts entirely on the most promising organic materials.

The authors urged agricultural scientists to test other abundant, readily available fruit scraps. Because different types of organic waste break down at different speeds and release distinct mixes of minerals, testing a wider variety of food by-products could uncover new nutrient formulations tailored to specific crop types or traditional soil-based farms.

They also recommended testing the liquid fertiliser at concentrations both above and below the current 400 to 1,000 grams per litre window. Testing a wider range of application rates will allow researchers to pinpoint the maximum possible dosage for crop growth, while checking that overly concentrated mixtures do not damage the growing medium or harm overall plant performance.

They concluded: “Additionally, future researchers should explore more precise methods to regulate and stabilise the pH of the nutrient solution. This could involve testing natural pH buffers or using additives more carefully to avoid adverse effects on plant health.

“By implementing these recommendations, future research on fruit peel-based fertilisers will be better equipped to provide valuable insights that support sustainable agricultural practices and effective utilisation of organic waste.”

Source: Engineering Proceedings

“Development of Fruit Peel Fertiliser Using Banana (Musa) and Orange (Citrus × sinensis) Peels Through Lettuce Cultivation”

https://doi.org/10.3390/engproc2026143024

Authors: Mary Nena M. Faulve, et al