(210a) Biomass Derived Membranes for Controlled Release Fertilizers

Controlled-release fertilizers (CRFs) are a type of fertilizer designed to deliver nutrients to plants and crops over an extended period, as opposed to traditional fertilizers that release nutrients immediately upon application. Controlled release helps to optimize nutrient uptake by plants, reduce nutrient leaching, and minimize environmental impact. CRFs are particularly beneficial in agricultural and horticultural practices where precise nutrient management is essential. Common methods involve encapsulating granulated fertilizer prills with either a semi-permeable or a porous but otherwise impermeable polymeric coating. This coating regulates the release of nutrients by controlling the diffusion of water into the granule and the diffusion of nutrients out of the granule. Coatings can be designed to release nutrients over various durations, ranging from weeks to several months.

A key goal is to repurpose cellulose-based biomass waste into controlled release coatings. Cellulose is a major constituent of most plant life (it is the most abundant extracellular structural polysaccharide) and is a source of food for a wide variety of organisms (including bacteria and fungi). Hence, cellulose does not persist as microplastics, as it is eventually broken down into simple sugars that are then recycled into the biome.

Pure cellulose, nevertheless, is difficult to process. Aqueous slurries lead to relatively brittle coatings that are prone to cracking that reducing their relative effectiveness. Essentially, as the slurry dries, the cellulose coating is not able to densify and stress cracks are formed as the solvent evaporates. In general, this issue can be overcome with the use of plasticizers (or low molecular weight diluents), which maintains flexibility of the coating and minimizes coating defects.

In this talk, we will discuss research efforts to esterify celluloses with fatty acids with the end goal of processible coatings for controlled release. First, fatty acids are sustainable and contribute to a truly “green” product. Second, fatty acids offer an entire library of various chain lengths to be able to fine-tune processing and coating properties. Third, the hydroxy side groups in cellulose can be reacted with the fatty acids to form a permanent bond, preventing leaching of the fatty acid.

In conclusion, current controlled-release formulations incorporating petroleum-derived polymers (including polyurethanes and polyolefins) degrade slowly over the course of years. Even long after the fertilizer has leached from the coated prill, the polymer coating remains in the soil column, which adds to the accumulation of microplastics, which is widely recognized as a major source of plastic pollution. In terrestrial ecosystems, microplastics have been demonstrated to reduce the viability of soil ecosystems and to negatively affect the physiology of earthworms. Microplastics can also accumulate at distances far from their source having unknown and hard to predict environmental consequences. By replacing current technology with cellulose-based coatings, the end goal to mitigate such consequences.