An Overview of Extrusion as a Pretreatment Method of Lignocellulosic Biomass

Abstract

Lignocellulosic biomass is both low cost and abundant, and unlike energy crops, can escape associated ethical dilemmas such as arable land use and food security issues. However, their usage as raw material in a biorefinery implies an inherent upstream pretreatment step to access compounds of interest derived from lignocellulosic biomass. Importantly, the efficiency of this step is determinant for the downstream processes, and while many pretreatment methods have been explored, extrusion is both a very flexible and promising technology. Extrusion is well-known in both the polymer and pharmaceutical industries and has been used since the 18th century. However, as a pretreatment method for lignocellulosic biomass, extrusion is relatively new. The first use for this purpose dates back to the 1990s. Extrusion enjoys a high degree of flexibility due to the many available parameters, but an understanding of extrusion requires a knowledge of these parameters and the different relationships between them. In this paper, we present a concise overview of lignocellulosic biomass extrusion by reviewing key extrusion parameters and their associated extruder design components and operating conditions.

Overview of the Biotransformation of Limonene and α-Pinene from Wood and Citrus Residues by Microorganisms

“…Also, the particle size is an important factor in oxygen transfer during solid or semi-solid fermentation. Other important factors are the moisture content, the inoculum size and the fermentation temperature [38]. Regarding terpenes, the volatilisation of molecules and the presence of lignin can be factors slowing down the yield of molecules obtained.…”

“…Furthermore, extrusion does not need significant downstream operations because it does not produce inhibitors and does not use high water amounts as hydrothermal pretreatments do. The short pretreatment time is one of the main benefits of extrusion: while biological, chemical and some physico-chemical pretreatments may last from 30 min to several days, one extrusion pretreatment lasts a few minutes (usually around 2 or 3 min) [38].…”

Acetic Acid Production From Lignocellulosic Biomass Pyrolysis and Recovery via Membrane Processes

“…The lignocellulosic biomass used in biorefinery is mainly produced from forestry waste (softwood and hardwood chips) and agricultural residues including gramineous lignocellulose (rice, wheat straw, corn straw, corn stalks, sugarcane bagasse, miscanthus and switchgrass) [34,35]. Cellulose establishes hydrogen bonds with hemicellulose or lignin molecules, whereas the interconnections between hemicellulose and lignin encompass both hydrogen and covalent bonds, thereby giving rise to resilient microfibres that serve as the structural framework of the cell wall, as described by Konan, Koffi [36] and Vorwerk, Somerville and Somerville [37]. The thermal degradation of biomass can be discerned in four distinct stages: the initiation of extract decomposition (< 490 K), hemicellulose decomposition (490 -650 K), cellulose and lignin decomposition (650 -780 K), and lignin decomposition (> 780 K) [8].…”

Agri-food Waste Valorisation

“…The most important advantages of this pre-treatment are shorter time, less water consumption and low corrosion, among others. 69 Delvar et al (2019) reported an extraction process using a twin-screw extruder for the extraction of polyphenolic compounds from passion fruit residues. 70 Using this technique, the group was able to extract up to 67% of the total polyphenol content of the different studied biomass.…”