My Quest to Create and Eco-Friendly Fertilizer

Statistics show that the manufacturing and application of synthetic fertilizers are responsible for about 21.5% of annual emissions (5,800 million metric tons) from agriculture alone. They also contain many heavy metals which contaminate the soil causing soil pollution. The build-up of these chemicals can alter the soil’s pH and even result in plant death. With knowledge of these negative effects I recently participated in the Massachusetts Science and  Engineering Fair to formulate an eco-friendly, sustainable, and cost-effective fertilizer made of scrap waste, providing the nutrients of calcium and potassium.

On a yearly, 9 million metric tons of calcium-rich eggshells and 3.5 tons of banana peels abundant in potassium are discarded yearly and dumped into landfills. Landfills contain many gases such as methane and carbon dioxide. These gases can contribute to air pollution and lead to respiratory problems for nearby residents. Additionally, toxic chemicals that seep into groundwater, pose a threat to rural communities that use wells for drinking water. It only made sense to channel these substances into creating an eco-friendly fertilizer.

A vital part of the experiment was figuring out how the nutrients of calcium and potassium would be administered to plants. Calcium carbonate, the form of calcium found in eggshells, is not readily absorbed by plants, yet other ionic forms of calcium are. By combining eggshells and vinegar in the correct, calculated proportions, a chemical reaction occurs, producing water, carbon dioxide, and calcium acetate. Calcium acetate is a form of calcium readily available for plant uptake. Meanwhile, banana peels contain ionic forms of potassium and potassium complexes. Some ionic forms of potassium, such as potassium chloride are available for uptake, while other potassium ions are not as accessible due to being trapped in those complex molecules. To release these potassium ions and make them bioavailable, the process of diffusion took place.

Organic molar solutions consisting of varying concentrations of calcium acetate and potassium were tested on random samples of 30 wheatgrass seeds. Their efficacy was analyzed in terms of stem heights as well as stem and root masses. They were then compared against that of plants given distilled water and those given synthetic fertilizer.

Two different trials were performed, narrowing down the molarities of solutions to reap the best result. In the second trial, 0.002M, 0.005M, and 0.01 M solutions of calcium acetate were tested with 0.03M, 0.05M, and 0.07M banana peel solutions.

The eggshell-based organic fertilizer statistically significantly improved wheatgrass plant growth and could be a viable alternative to synthetic fertilizer during the growth cycle. Calcium acetate derived from calcium-rich eggshells positively affects plant stem length, stem mass, and root mass, as well as the germination rate. Moreover, banana peel-based organic fertilizer does not show positive effects for the molarities tested on wheatgrass plant growth, but statistically significantly improved seed germination, thus could be used as an organic seed starter. The varied use of these solutions could lead to even better results in terms of plant growth and germination rate.

The unfavorable results that the potassium solutions produced in terms of height could have originated from the high sodium content in banana peels. Sodium ions compete with potassium ions for plant uptake which suggests the high probability of doing so. Root exposure to excessive salt impedes the uptake of water to the plant, which dries plant tissues, stunts plant growth and discolors plants. Furthermore, short stems of the plants given the 0.03M and 0.07M potassium solutions suggest an imbalance of nutrients, resulting from sole reliance on frequently applied potassium with no other nutrients supplemented. 

Adverse effects of calcium acetate seen with molarities tested of 0.005M and 0.01M calcium acetate solutions could be sourced from a few main reasons. First, calcium acetate binds to phosphates in the soil which can make these nutrients unavailable to the plant. Also, the overuse of calcium acetate can lead to an over adjustment of pH in the soil. This could very well have happened in the 0.005M and 0.01M potassium plants as the increased molarities led to decreased plant growth. 

  The big picture for this project is to create a fertilizer that results in a healthier environment, better industrial farm yields, and a beneficial green cycling process for organic waste. Hopefully, this fertilizer can be further curated with different ratio trials for more prosperous results. The potential is to upscale and commercialize this fertilizer for agricultural purposes worldwide.