Synthesis of lignin-based hydrogels and their applications in agriculture: A review

Increasing population underlies every single issue that we have inflicted on this planet which causes enormous demand for petro-based polymers. These polymers are non-biodegradable, non-renewable and have toxic degradation products leading to increasing stipulation for environment benign biomaterials which could drive bio-based economy as well. Lignin, as it is the third most abundant polymer in plants, can be utilized to form multipurpose valuable polymers. Lignin has been accepted widely as the raw material for the synthesis of bio-based hydrogels due to its hydrophilic nature. This work complies the review of different methods for the synthesis of lignin-based hydrogels, i.e., interpenetrating polymer network, crosslinking copolymerization, atom transfer radical polymerization and reversible addition-fragmentation chain transfer polymerization and its applications in agriculture. These hydrogels have known to be used in decontamination of soil, to combat drought stress and as fertilizers. These applications paved avenues for lignin valorization and environmental sustainability. To the best of our knowledge, this is the first review discussing applications of lignin-based hydrogels in agriculture.