Natural lignin-based biodegradable coatings for controlled-release fertilizers

Overview

This technology leverages a unique melt-flow lignin material, a byproduct from a newly commercialized cellulosic ethanol process, to create fully natural and biodegradable coatings for controlled-release urea fertilizers. The lignin can be processed like a plastic and compounded or copolymerized with other bio-based and biodegradable materials to develop functional coatings. This approach addresses the agricultural need for controlled-release nitrogen fertilizers while utilizing a sustainable, bio-based feedstock.

Technical specifications

• Base material: Melt-flow lignin, a byproduct of cellulosic ethanol production with plastic-like processability
• Formulation flexibility: Can be combined with biopolymers, bio-based monomers, and polymers to create graft copolymers, alloys, and mixtures
• Tunable properties: Porosity and wettability can be adjusted through formulation variations
• Application methods: Spray coating applied to granulated fertilizer products
• Preliminary results: A microporous lignin-cellulose acetate coating on granulated phosphate fertilizer demonstrated a 6.5-fold slower release rate in reverse osmosis water compared to uncoated fertilizer
• Formulation variations: Eight formulation variants with different lignin and solvent ratios have been characterized for contact angle, water uptake, and morphology
• Release mechanism: Coatings are designed to disintegrate upon water contact, with pH-driven dissolution enabling controlled release

Technology readiness level

This technology is at an early-to-mid stage of development. Preliminary testing has demonstrated proof-of-concept for controlled-release functionality on phosphate fertilizers, with a 6.5-fold reduction in release rate achieved. Initial experiments on urea coatings have confirmed the expected disintegration behavior upon water contact. Future validation will focus on reformulating coatings to delay water penetration while maintaining pH-driven dissolution, with testing planned in both submerged water and soil conditions to optimize release timing for the growing season.