Valorization of kitchen waste via garbage enzyme fermentation: optimization and formulation of a sustainable bio-shampoo

Every day, households around the world generate a steady stream of organic waste: fruit peels, vegetable trimmings, and leftover food scraps. When this material is thrown into landfills, it decomposes without oxygen, a process that releases methane, a potent greenhouse gas that traps heat in the atmosphere far more effectively than carbon dioxide. For decades, scientists and environmentalists have searched for ways to turn this problem into a solution, moving beyond simple disposal toward a system where waste becomes a resource. One such approach involves a technique known as garbage enzyme fermentation. This method relies on a simple mixture of organic waste, a sugar source, and water, left to ferment in a sealed container. Over time, natural microorganisms break down the complex structures of the food waste, transforming them into a liquid rich in organic acids and enzymes. These biological tools can dissolve dirt, break down fats, and even act as a cleaning agent, offering a way to recycle household refuse into something useful for the home and the environment.

A researcher at the High School for the Gifted in Ho Chi Minh City, Vietnam, recently set out to refine this process and see if the resulting liquid could be turned into a personal care product. The goal was to create a shampoo that cleans hair without using harsh, petroleum-based chemicals, while simultaneously proving that kitchen waste could be converted into a high-quality, safe, and effective consumer good. The study focused on two main questions: how to make the fermentation process faster and more reliable, and whether the final liquid could be formulated into a shampoo that is gentle enough for human use.

To answer these questions, the researcher began by testing different ways to prepare the ingredients. The standard recipe for this type of fermentation calls for a specific ratio of sugar, waste, and water, but the physical state of the waste and the type of sugar used had not been rigorously compared. The researcher tested four variations in the first round of experiments. Some used whole, uncut fruit peels and vegetable scraps, while others used pieces chopped into small cubes about half a centimeter to one centimeter in size. The sugar source also varied, with some batches using refined white granulated sugar and others using molasses, a thick, dark syrup left over from sugar production. None of these initial batches received any added bacteria or yeast; they relied entirely on the microbes naturally present on the food waste. After thirty days, the results were disappointing. The mixtures with whole, uncut waste showed almost no signs of breaking down. Even the chopped waste fermented very slowly, failing to develop the strong, sour smell that indicates a successful transformation. The natural microbes on the waste were simply not enough to drive the process efficiently within a month.

The researcher then introduced a second set of experiments, this time adding a small amount of a commercial microbial starter called Emzeo to each batch. This preparation contains specific strains of bacteria and fungi known to break down plant fibers and starches. With this addition, the results changed dramatically. The mixtures that used chopped waste and molasses transformed the fastest and most completely. In these containers, the solid food waste dissolved entirely, leaving behind a clear, light brown liquid with a thick, white layer of microbial life floating on the surface. This liquid had a distinct, pleasant scent that was both sweet and sour, like a fruity vinegar. The other combinations, such as those using whole waste or white sugar, still showed signs of incomplete breakdown or weaker microbial growth. The data confirmed that chopping the waste into small pieces increased the surface area available for the microbes to work on, and that molasses provided a richer diet of nutrients and minerals than refined sugar, allowing the beneficial bacteria to multiply rapidly and produce the desired enzymes and acids in just thirty days.

Once the optimal fermentation process was identified, the researcher tested the cleaning power of the resulting liquid. The liquid was filtered to remove any solid particles and then applied to glass, ceramic tiles, and stainless steel surfaces that had been stained with motor oil, cooking grease, and synthetic sebum. The liquid worked remarkably well. Within five minutes, it completely removed all three types of stubborn stains from the hard surfaces without the need for vigorous scrubbing. The cleaning action appeared to come from a combination of factors: the enzymes in the liquid broke down the fats and proteins in the dirt, while the natural acids dissolved mineral deposits and helped lift the grime away. This demonstrated that the fermented waste was not just a theoretical solution but a practical, effective cleaner.

The final step was to turn this cleaning liquid into a shampoo. The researcher took the best-performing fermented liquid and mixed it with natural plant extracts, including those from the gleditsia fruit, lemon peel, and lemongrass. To give the mixture the right texture and thickness, a small amount of a natural thickening agent and salt were added. The result was a clear, light brown liquid with a fresh, herbal-citrus aroma. When tested, the shampoo produced a stable, rich foam and, most importantly, had a pH level of 5.5. This specific acidity is crucial because it matches the natural pH of the human scalp, which helps keep the skin healthy and the hair cuticles smooth. Many commercial shampoos are more alkaline, which can strip away natural oils and irritate the skin. This new formulation, however, was completely free of sulfates, the harsh detergents found in most store-bought shampoos that are derived from petroleum. It cleaned the hair effectively, removing grease without leaving it feeling dry or damaged.

The study concludes that by carefully controlling the size of the waste pieces, choosing the right sugar source, and adding a specific microbial starter, it is possible to turn kitchen scraps into a high-performance, eco-friendly shampoo in just one month. This process offers a dual benefit: it diverts organic waste from landfills, reducing the release of harmful greenhouse gases, and it creates a sustainable product that avoids the environmental and health concerns associated with synthetic chemicals. The research suggests that the principles of the circular economy, where waste is continuously reused to create new value, can be applied on a small scale in the home to produce goods that are both effective for daily use and gentle on the planet. Future work will focus on measuring the exact levels of enzymes in the liquid and testing how long the shampoo remains stable on the shelf, but the initial findings provide a clear and promising path forward for sustainable personal care.