Lignin nano/micro-particles from agricultural biomasses: Developing direct precipitation for integrated biorefinery

The state-of-the-art, simple and scalable methods for lignin micro-/nano-particles recovery from agricultural biomasses were evaluated in this review. Being non-wood biomasses, these materials can be easily fibrillated, supporting the usage of mild soda or organic solvent pretreatment. Different approaches in particle recovery were compared to conclude that the bottom-up approach facilitates smaller particles towards the nano-size range whereas mechanical treatment can act as a supporting method to increase uniformity and reduce particle sizes after bottom-up precipitation. By combining with the pretreatment steps, direct one-pot lignin micro-/nano-particle recovery can be achieved using the lignin-containing black liquor or organosolv liquor. These lignin micro-/nano-particles can then be applied as high-value functional products in cosmetics, pharmaceuticals, environmental remediation, and energy sectors. The systematic evaluation of lignin micro-/nano-particles recovery from agricultural biomasses in this review can support the full utilization of these natural resources to aim towards a circular agriculture.