Iman Akbarpour,
Volume 4, Issue 1 (9-2023)
Abstract
On a global scale, the pulp and paper industry lead to produce significant amounts of effluents, solid wastes and gaseous wastes, and these wastes originate mainly from the pulping process, deinking and wastewater treatment. Solid biomass in wood waste as well as black liquor of pulping process can be converted to synthetic gas, mainly CO and H2 by thermal processes, with small amounts of methane, Co2 and H2o, and this can be a good opportunity to revive the pulp and paper industry. The main raw materials of biomass in the biorefinery process include hemicellulose, cellulose, lignin and skin, and with mechanical-thermal methods including biomass gasification, black liquor gasification, pyrolysis or liquefaction and carbonization of biomass, synthetic gas can be converted into electricity as well as liquid fuels and chemicals. The results obtained by comparing different hemicellulose pre-extraction technologies of lignocellulosic materials indicate that the steam explosion method is much more environmentally friendly than other alternative methods requiring less investment cost. At present, the use of steam explosion method has increased at the commercial level due to its cost-effectiveness and this method is very efficient for hardwood residues as well as crops leftovers. Also, the organosolve fractionation technology for the separation of hardwoods is well operational and leads to the production of high purity cellulose and the selective dissolution of lignin and hemicellulose. Nanofiltration is a desirable separation method for the recovery of hemicellulose from hydrolysates, and in this regard, the combination of a twin-screw extruder system can be the best way to extract hemicelluloses from hardwood chips. Nanofiltration is much better than ultrafiltration to separate hemicelluloses from hydrolysates by alkaline methods.
Aliasghar Tatari, Mohammadreza Dehghani Firouzabadi,
Volume 4, Issue 1 (9-2023)
Abstract
The gradual reduction of fossil resources has caused increasing concern about their supply and the emission of greenhouse gases and global warming, and in this context, biofuels can play an important role in solving these problems. Meanwhile, ethanol produced from corn starch, sugarcane molasses, lignocellulosic materials and biodiesel produced from rapeseed oil are the most important commercial uses in recent years. Ethanol production is a complex biochemical process in which yeasts, fungi, and certain bacteria are able to convert fermentable sugars into ethanol, carbon dioxide, and other metabolic byproducts. These byproducts contribute to the chemical composition and sensory properties of fermented foods. Ethanol production is important in a wide range of secondary products (such as health, medical and industrial). Controlling the fermentation process is usually a prerequisite for determining the quality of the final product. In this regard, monitoring the fermentation process is a basic need to ensure effective control of variable factors at all stages of the ethanol production process. Reducing the rate of fermentation in the process of ethanol production due to inhibitory compounds is considered a fundamental and significant problem in the economics of the process. In this review paper, the main aspects of ethanol fermentation and inhibitory compounds and their reduction methods in the ethanol production process from lignocellulosic materials have been discussed.
