Effects of organosolv pretreatment conditions for lignocellulosic biomass in biorefinery applications: A review

Abstract

The concept of a biorefinery that provides valuable bioproducts from biomass conversion instead of fossil based products is presented. One of the main biorefinery products, bioethanol, can be produced from sugar, starch, or lignocellulosic-based biomass. Lignocellulosic-based bioethanol could be a good alternative to sugar- or starch-based bioethanol. While sugar- and starch-based biomass includes mainly glucose or starch, lignocellulosic biomass contains cellulose, hemicellulose, and lignin. While the cellulose is essential for the biomass-to-bioethanol conversion process, hemicellulose and lignin are undesirable in this context, and therefore pretreatment is necessary to break down the lignocellulose structure and separate hemicellulose and lignin from cellulose. Organosolv pretreatment is an attractive method for separating both cellulose and nearly pure lignin from the lignocellulosic material. In a biorefinery, organosolv pretreatment is one of the best options for producing more than one valuable product (bioethanol and lignin) in the same process. For effective bioethanol production, the delignification rate and enzymatic glucose conversion are fundamental parameters. This paper presents a detailed literature review of organosolv pretreatment, focusing on the effects of each of the pretreatment conditions for biorefinery applications. The organosolv pretreatment method is first described in detail and then each of the pretreatment conditions is explored individually. A number of technical studies are reviewed, and the effects of the various conditions on the delignification rate and on enzymatic glucose conversion for effective bioethanol production are described. The current status of development of organosolv-based biorefineries around the world is discussed. In previous reviews of this topic, only the solvent and catalyst effects have been investigated. This review will contribute to the literature by showing the impacts of all pretreatment conditions on pretreatment efficiency.

Recent Trends in the Pretreatment of Lignocellulosic Biomass for Value-Added Products

“…The process is often accompanied by the addition of a catalyst to either lower the pretreatment temperature or improve the delignification rate. Usually mineral acids (hydrochloric acid, sulfuric acid, phosphoric acid), bases (lime, sodium hydroxide, ammonia) and some salts are used as catalysts (Borand and Karaosmanoglu, 2018).…”

“…Most of the organic solvents are too expensive and need to be recovered as much as possible which is an energy-intensive process. In addition, high flammability and volatility of the organic solvents make the pretreatment to be carried out under especially controlled conditions (Borand and Karaosmanoglu, 2018). The organosolv pretreatment process for various feedstocks has been summarized in Table 2.…”

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

“…The black liquor was mixed with cold water (4 ∘ C) in a water-to-liquor ratio of 3:1 (w/w) as previously reported; 18 the precipitate was then dried and its weight was labeled as m LR , assuming it to be mainly lignin. 8,19 The success of each trial was evaluated as the delignification rate (%DR) and lignin recovery (%LR), 20 which were computed by Eqns (2) and (3) respectively as follows:…”

Sugarcane Bagasse Hydrolysis Enhancement by Microwave-Assisted Sulfolane Pretreatment

“…In this type of pretreatment, the lignocellulosic material is subjected to an organic solvent, with or without catalysts [22]. Low-boiling alcohols, such as ethanol and methanol, have been widely used as organosolvs due to their low cost and easy recovery in the process, but they require operating at a high pressure and hence special equipment that is expensive to purchase and operate has to be used [23]. High-boiling alcohols, such as ethylene glycol or glycerol, can also be used at low temperatures and pressure, but their recovery requires more energy [24].…”