A review on lignin sources and uses

The efficient use of renewable resources has become a driving force for the worldwide industry aiming to improve the competitiveness. Considering the available natural raw materials, the lignin present in the lignocellulosic biomass such as trees, is the unique natural polymer that presents aromatic rings in its constitution. In this way, this review details the structure of native lignin as well as the technical lignin, including information on the characteristics that this polymer must have for the most promissory applications as feedstock for bioproducts. Approximately 50 million tons of lignin are produced worldwide annually, of which 98% to 99% is incinerated to produce energy and steam in the pulp mills. Only a small fraction of the lignin, derived mainly from the sulfite pulp mill is recovered commercially in a biorefinery concept. There are many opportunities for producing high value-added products from technical lignin, mainly considering the pulp mills growing, and environmental restrictions using non-renewable raw materials. The currently trend have shown that technical lignin sources may also be used as feedstock for phenol derived products, technical carbons, fuels, and adhesives. On the other hand, there are some technological hurdles must be overcome to make these uses feasible.