Challenges and opportunities on the utilisation of ionic liquid for biomass pretreatment and valorisation

Biomass processing employing ionic liquids is already an established option at the laboratory scale. Ionic liquids can disrupt and deconstruct the lignocellulosic biomass network, giving rise to multiple options for valorisation. However, there is still much work remaining to accomplish the scale-up and commercialisation of ionic liquid-based biomass processing. Important issues such as ionic liquid cost and recyclability, among others, need to be carefully addressed. In addition, ionic liquids modify the structure and properties of the recovered materials, impacting potential applications. Due to the complex nature of ionic liquids, where multiple combinations of anions and cations are possible, these issues should be considered for each process and application, making it difficult to generalise for all cases. This perspective covers the main challenges and opportunities in the employment of ionic liquids for biomass processing, both in the biomass processing stage and in the valorisation of the recovered fractions. Among them, we discuss the importance of solvent recovery and costs as two critical issues to consider in biomass processing, as well as the major role lignin condensation plays in hindering ionoSolv lignin valorisation and different approaches to valorise the recovered cellulose.