Chemical and Biological Delignification of Biomass: A Review

Abstract

Lignin is a highly abundant biopolymer with a complex polyphenolic structure, making it a potential source of aromatic precursors, polymers, and energy. However, its thermal stability limits its economic potential, with less than 3 wt % of waste lignin transformed into commodity products. This review focuses on the chemical and biological extraction methods for lignin to promote its valorization, which involves extraction, depolymerization, and fermentation or derivatization. As there is no universal method for extraction due to the heterogeneity of lignin, a range of methods each with their advantages and disadvantages are discussed, including sulfite pulping, Kraft, Organosolv, ozonolysis, steam-explosion, ionicliquids and supercritical CO 2 extraction, and microwave-and ultrasound-assisted extraction. Biological methods, such as bacterial, fungal, and enzymatic delignification, are also explored. The review aims to provide insights to tailor extraction methods to individual needs and promote the sustainable utilization of lignocellulosic biomass.

Materials and Methods for All-Cellulose 3D Printing in Sustainable Additive Manufacturing

“…Common agents for each of these steps include ethanol, toluene, or petroleum for the pretreatment; hydrochloric or sulfuric acids for acid hydrolysis; sodium or potassium hydroxide and organic solvents for base hydrolysis; and sodium chlorite with hydrogen peroxide for the bleaching step [16,17,[21][22][23][24]. Woody biomass also requires a delignification step to isolate cellulose from lignin, which can be carried out through a number of different chemical and/or biological methods according to the target end uses of the lignin and cellulose [25]. Interest in the development of more mild, environmentally friendly processing techniques has resulted in the use of enzymatic methods to mimic the natural processes of breaking down biomass such as wood pulp into useful cellulosics such as cellulose nanofibers, as reported in the work by Henriksson et al [26].…”

Ultrasound and sonochemistry enhance education outcomes: From fundamentals and applied research to entrepreneurial potential

“…“Use Renewable Feedstock” presents several challenges as renewable feedstock is often either physico-chemically heterogeneous or target molecules are found diluted in a matrix. Once again sonochemistry can help disintegrate the outer matrix to release these interesting molecules and accelerate the processes to transform renewable feedstock into valued chemicals [23] , [24] , [25] , [26] . Finally, as ultrasound-assisted processes use less solvents and auxiliaries or allows these later to be replaced with safer ones, and energy requirements are often minimized, “Inherently safer chemistry for accident prevention” is another green chemistry trait that can characterize sonochemistry.…”

Investigation of Microwave Irradiation and Ethanol Pre-Treatment toward Bioproducts Fractionation from Oil Palm Empty Fruit Bunch

“…A study was conducted on the sugar extraction from bamboo wood subjected to microwave pre-treatment at 121 • C, where a 36.9% conversion with 16.8 g/100 g of sugar yield was obtained [9]. Furthermore, a three-component deep eutectic solvent (DES) comprising of lactic acid, glycerol, and choline chloride, subjected under microwave irradiation at 393 K for a duration of 30 min, with a solid-to-liquid ratio of 1:50, was able to achieve a delignification rate of 45 wt% for the pre-treatment of wheat straw [10]. Moreover, the use of a physical pre-treatment such as the microwave irradiation on wheat bran, corn stalks, and miscanthus stalks was able to achieve hemicellulose solubilization of approximately 30%, which in turn led to an enhanced recovery of cellulose in these low-lignin yielding plants [11].…”