Organomineral fertilizers pastilles from microalgae grown in wastewater: Ammonia volatilization and plant growth

Abstract

With the increasing demand for food, it is increasingly important to maintain soil fertility with the application of fertilizers to supply the nutritional needs of plants. However, the nutrients applied to the soil can suffer significant losses, impacting the environment, and increasing production costs. Using alternative sources, such as microalgae biomass (MB) generated in the treatment of wastewater, in the production of organomineral fertilizers is a way to recover nutrients from the sewage, in addition to contributing to the improvement in soil fertility and favoring crop growth, which can guarantee agricultural sustainability. In the present study, MB was grown in the effluent 00from the food industry and, subsequently, a pelleted organomineral fertilizer (POF) was produced consisting of the combination of MB and synthetic fertilizer (urea), in different proportions. The performance of the proposed fertilizer was analyzed for losses due to ammonia volatilization (N-NH3) over time, for nitrogen assimilation capacity (N) by corn plants (Zea mays L.), and its structure was evaluated by scanning electron microscopy. The study concluded that the highest accumulated volatilization of N-NH3 was in the proportion of 40% of MB and the maximum content of N is reached in the proportion of 24.55% of MB. From the proportion of 25% of MB, there is no increase in N absorbed by plants, at the same time that the volatilization of N-NH3 grows with the increase in MB. The most important factors for obtaining these results were the interaction between MB and urea in the produced organomineral fertilizer tablet, where an increasingly thicker physical barrier was formed with the increase in the proportion of MB; in addition to the POF pH, in which the increase in MB proportions directly favored the pH increase.