ABSTRACT
Lignin valorization is a particularly promising topic. Instead of cellulose which has a linear sub-structure of glucose units, lignin has a high degree of structural variability, which differs from biomass source and the lignin recovery process. It is generally estimated that the research on cellulose to produce ethanol started 20 years ago, research on hemicelluloses including C5 sugar valorization started 10 years ago and lignin valorization starts approximately now.
Lignin applications fall into three categories.
In the category of established applications (within 5 years), lignin is only used as carbon source generating heat and power, and drastic means are used to break its macromolecular structure. In mid-term applications (about 2019), the macromolecular structure is advantageously maintained and those applications should include carbon fibers. The third application category (long-term: about 2025) uses technologies that degrade the macromolecular structure of lignin but maintain the aromatic character of the produced molecules. It includes aromatic monomers such as benzene, toluene, xylenes, and aromatic oligomers.
The effective utilization of lignin is key for the accelerated development of lignocellulosic biorefineries. However, it has been long said in the pulp industry that “one can make anything from lignin except money.” Now, the situation has changed and lignin can be a viable, commercially relevant sustainable feedstock for a new range of materials and uses.
