A review on lignin sources and uses

Abstract

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.

Non-Formaldehyde, Bio-Based Adhesives for Use in Wood-Based Panel Manufacturing Industry—A Review

“…Technical lignin is obtained as a by-product of several separation processes that most lignocellulosic materials undergo for some of their transformation processes. The composition and characteristics of technical lignin may vary according to the type and characteristics of the separation process, so, in order to assess the usefulness of the obtained lignin for use in other processes, each technical lignin batch must be considered [ 56 ].…”

“…The kraft process implies mixing alkaline chemicals such as NaOH and sodium sulphide (Na 2 S) with lignocellulosic materials and then introducing high temperatures, from 140 to 170 °C, obtaining what is commonly referred to as black liquor, containing degraded lignin, oxidised inorganic compounds, and other organic materials. In order to separate the kraft lignin from the black liquor, it is required to undergo an acidification process [ 56 ]. The resulting lignin may have impurities such as sulphur, which must be carefully considered when assessing its potential uses.…”

“…Organosolv lignin is obtained by the use of organic solvents in the processing of lignocellulosic materials. This lignin extraction process preferentially cleaves the carbohydrate–lignin bonds, leading to high-molecular-weight lignin without significant chemical modifications [ 56 ]. The resulting organosolv lignin is easily recoverable and possesses features similar to native lignin, with high purity, chemical reactivity, being sulphur-free, depending on the organic solvent used, and low molecular weight.…”

Investigating Lignin-Derived Monomers and Oligomers in Low-Molecular-Weight Fractions Separated from Depolymerized Black Liquor Retentate by Membrane Filtration

“…It is widely accepted that we must find a renewable resource to replace petroleum-based raw materials for the production of energy and chemicals. Lignin is one of the three main components of biomass and is the most abundant natural source of aromatic polymers and has attracted attention in this respect [ 1 , 2 ]. The most abundant source of lignin is currently from kraft pulping, which is used in almost 90% of the world’s pulp production [ 3 ].…”

Comparison of organic acid-based organosolv lignins extracted from the residues of five annual crops

“…Their oxidative enzymatic polymerization leads to the phydroxyphenyl, guaiacyl, and sinapyl units found in lignin structure (Ralph et al 2004). The current trends have shown that lignin may be a good alternative for feedstock of phenol-derived products, even the replacement of petrochemical-derived aromatic monomers, technical carbons, fuels, and adhesives (De Souza et al 2020). Nevertheless, technical lignins' physico-chemical properties highly depend on their extraction process (solubility, sulfur content, molecular weight for instance), and on the original feedstock (Watkins et al 2015).…”