Maestría en Ciencias Químicas · 2026

Development of an Organo-Mineral Nitrogen Fertilizer Derived from Cocoa Pod Husks Grown in the Arauca Region

Resumen

This study evaluated the performance of different carbonaceous matrices derived from cocoa pod husk — biochar, compost, biochar-compost blend, and co-composted material (COMBI) — in formulating fertilizers with enhanced urea release. These matrices exhibited favorable physicochemical properties for soil application, including high cation exchange capacity, moisture retention, and an alkaline pH. Two urea incorporation methodologies were also explored: physical mixing and infusion, to assess the type of chemical interactions between urea and functional groups of carbon-based materials. The pelletized fertilizers were then coated with a mixture of carboxymethylcellulose (CMC) and sodium alginate (SA) to improve the mechanical stability of the pellets. The results showed that the carbon-based materials obtained through controlled heat treatment developed not only an ordered macroporous structure, but also the type of surface functional groups (carboxylic acids, ketones, and alcohols) that can chemically interact with urea, favoring its anchoring and slowing its release, particularly in coated and uncoated urea-infused formulations. In contrast, the materials containing compost did not develop macroporosity or strong interactions that would allow them to accommodate and retain urea for longer, as did biochars. Despite this, the materials containing compost performed better than commercial fertilizer. Kinetic evaluation of the coated and uncoated synthesized fertilizers indicated that the formulation using biochar with infused urea showed better performance in slowing urea release by a factor of 472 times slower than commercial urea. This behavior can be attributed to a combined mechanism: diffusion through the material´s macrostructure, chemical interactions between the urea and the functional groups, and physical restriction imposed by the external polymeric coating. The grass seedling test demonstrated that fertilizers formulated from CPH exhibited a high agronomic potential, exceeding the performance of commercial fertilizers. The development of at least five fertilizers showing differentiated release profiles and mechanisms was achieved, allowing for a strategic application at different crop stages. The employment of rapid release fertilizers such as U:C@ could be potentially used in the early stages s of plant development, including germination and vegetative growth. In contrast, the use of controlled release formulations as an IU:300@ due to its low release could be a good alternative for been used during flowering process. The results support the relevance of using carbonaceous-derived materials from cocoa pod husks as an efficient strategy to enhance nutrient yields, optimize soil conditions and valorize agricultural residues through the development of circular economy fertilizers.