Controlled release of fertilizer thanks to biopolymer chips

In Germany, researchers at Ruhr-Universität Bochum are looking at the benefits of biopolymers for the targeted introduction of fertilizers into agricultural soils and to develop a method to encapsulate fertilizer and continuously introduce it into the soil.

The capsule material forms a barrier to the environment and is intended to prevent a sudden release of the nitrogenous substance. Doctoral student Diana Keddi tried out various packaging techniques. “In order to be able to control the release behavior, we have to build up a specific carrier matrix for the fertilizer,” she explains. “Since the soil should not be contaminated with the capsule material, it is also advantageous if the material is biodegradable.”

The Bochum researchers therefore use a biopolymer foam made of polylactic acid, PLA for short, from the English term polylactic acid, as the capsule material. Lactic acid can be obtained from corn or sugar beet, for example. Diana Keddi used various techniques to test how she can create a nitrogen fertilizer depot in the biopolymer, using urea as a nitrogen-containing model substance. In the end, the encapsulated fertilizer was in the form of chips, similar to the packaging chips that are now found in many shipping boxes instead of Styrofoam.

The biopolymer chips that are loaded with fertilizer in this way could simply be buried in the ground next to the plants, and the nitrogenous substances would then get into the earth step by step. With the study, the engineers have provided evidence that the technology works in principle. Further test series are currently being carried out which transfer the release tests to the real application in soil. The aim is to use the information obtained for industrial application.