Improving Sustainability and Slow-Release Property of Pelletized Agro-Biowaste Compost Fertilizer Assisted by Biodegradable Coating

Today, the use of biodegradable coatings has become an effective solution for pelletized agro-biowaste fertilizers due to the synchronizing of the nutrient release according to the plant requirements and reducing the environmental issues. In this study, three agro-biowaste compost including poultry manure (40%), cattle manure (30%), and agricultural biomass (30%) were mixed at the 40% moisture content, and then the pelletization process was carried out using the screw extruder. A factorial experiment in a completely randomized design with three replications was developed for assessing the effect of four biodegradable coating materials (humic acid, canola oil, corn starch, and nano-silica) and three coating methods (dip coating, spray coating, vacuum coating) on sustainability attributes of coated compost pellets such as pellet disintegration time, water absorption, humidity absorption, and water contact angle. The results showed that the canola oil – vacuum method applied for coated compost pellets with disintegration time (1735 min), water absorption (57.6%), humidity absorption (4.3%), and water contact angle (69°) was the best treatment. This coating method showed a 36-fold increase in disintegration time and a 3.7, 7, and 1.6-fold decrease in water absorption, humidity absorption, and water contact angle, respectively as compared with uncoated compost pellets. The nitrogen release rate of the coated compost pellets showed that the amount of total nitrogen at disintegration time was 25%. Also, 75% of nitrogen was released into the soil during 55 days, which confirmed experimental results and improved the nitrogen release rate by 45 days as compared with uncoated compost pellets. Overall, from the results of this study, it can be concluded that pelletized compost fertilizer which was coated by canola oil-vacuum method, shown a high resistance to water, enhanced sustainability and reduced nitrogen-release rate property as it could supply nutrient to the plant for a longer period.