Green-manufacturing nano-coir-pith: a lingo-cellulose waste for fertilizer coating and crop production.
Swami Kanchan K, Nagargade Mona M, Dadhich Ankita A, Kumar Prem P et al.
Urea is susceptible to leaching and volatilization, which reduces the nitrogen use efficiency and causes environmental damage by greenhouse gas addition and groundwater pollution. Here, to overcome this in circular economy fashion, a biodegradable controlled-release urea coating has been developed by directly utilizing recalcitrant coir pith with castor oil as plasticizer and ethyl cellulose as sealer. To form a stable and uniform coating, the coir pith has been engineered to nanoscale by a green phosphate-assisted wet milling process using dipotassium hydrogen phosphate. The lower hydration energy of potassium facilitates penetration and increases turgor pressure to fragment without using toxic strong oxidizers. The phosphate tethers simultaneously and provides charge-based repulsion. The esterification between the carbonyl groups in castor oil and the hydroxyl groups of ethyl cellulose resulted in hydrophobicity (water contact angle: ~125°), alongside ~80% biodegradation under soil burial conditions after 60 days. The coated urea reduced the nitrogen losses, showing a ~ 9% increase in wheat grain yield compared with bare urea. Finally, the life cycle analysis demonstrated the environmental sustainability of the proposed green manufacturing strategy.