Biopolymer-based slow/controlled-release fertilizer (SRF/CRF): Nutrient release mechanism and agricultural sustainability

Excess fertilizer released into the environment from low-efficiency fertilizers has created a global impact on sustainable agriculture, including environmental, economic, and social risks. Slow/controlled-release fertilizers (SRF/CRF) synthesized from renewable biopolymers are considered sustainable fertilizers that can improve fertilization efficiency. Fertilizer nutrients are incorporated in a matrix based on biopolymer composites to engineer the nutrient release kinetics. Using biopolymer-based composites to control the release of nutrients as filler matrices, coatings, and other functions are expected to produce eco-friendly SRF/CRF, which can be biodegradable, result in lower emissions, have reduced toxicity, a high water holding capacity, enrich soil microorganisms, and improve yield and quality of agricultural commodities. This review discusses the application of biopolymers used to synthesize SRF/SRF, including their advantages. We have also succeeded in identifying factors that affect the slow-release profile based on environmental factors (e.g., temperature, pH, soil type, salt solution, and soil moisture) and composite composition (e.g., layer thickness, binder, initiator, material size, barrier properties, and surface charge). Future challenges relate to studies to improve food nutrition based on fertilization, selection of raw materials based on waste/by-products/biomass, approaches to green chemistry and cleaner production, increasing high water retention, and applications in the field.