A review of the production of ethanol from softwood

Abstract

Ethanol produced from various lignocellulosic materials such as wood, agricultural and forest residues has the potential to be a valuable substitute for, or complement to, gasoline. One of the major resources in the Northern hemisphere is softwood. This paper reviews the current status of the technology for ethanol production from softwood, with focus on hemicellulose and cellulose hydrolysis, which is the major problem in the overall process. Other issues of importance, e.g. overall process configurations and process economics are also considered.

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status

“…Fast-growing trees, grass, whole plants, industrial by-products, aquatic plants, waste products (including agricultural, paper industry and forestry waste), municipal and industrial waste streams, all represent examples of plant-derived lignocellulosic resources (Aristidou and Penttilä 2000; Galbe and Zacchi 2002;Howard et al 2003;Lee 1997;Zaldivar et al 2001). The nature and availability of lignocellulosic feedstocks in different parts of the world depends on climate and other environmental factors, agricultural practice and technological development (Claassen et al 1999).…”

“…Conversion of lignocellulosic materials to fermentable sugars is an intensive process that involves a combination of pretreatment (chemical and mechanical) and hydrolysis (chemical and (Galbe and Zacchi 2002). Pretreatment is required to increase the surface area of the feedstock, thereby rendering the lignocellulose accessible for hydrolysis (Klinke et al 2004).…”

“…Pretreatment is required to increase the surface area of the feedstock, thereby rendering the lignocellulose accessible for hydrolysis (Klinke et al 2004). Pretreatment methods include concentrated-or dilute-acid treatment, high-pressure steam explosion, ammonia-freeze explosion and wet oxidation (Galbe and Zacchi 2002;Klinke et al 2004). These methods are most often used in combination, such as in the commonly used combination of dilute-acid hydrolysis (0.5-1.0% sulfuric acid) with high-pressure steam explosion.…”

“…These methods are most often used in combination, such as in the commonly used combination of dilute-acid hydrolysis (0.5-1.0% sulfuric acid) with high-pressure steam explosion. During this pre-treatment, hemicellulose is readily chemically hydrolyzed, while cellulose is essentially inert (Galbe and Zacchi 2002). Pretreatment of hemicellulose results in the release of monomeric sugars and in the production of a complex mixture of compounds that inhibit the bioconversion of these sugars (Ingram et al 1999;Klinke et al 2004;Mussatto and Roberto 2004).…”

“…Pretreatment of hemicellulose results in the release of monomeric sugars and in the production of a complex mixture of compounds that inhibit the bioconversion of these sugars (Ingram et al 1999;Klinke et al 2004;Mussatto and Roberto 2004). It has been proposed that the lignin fraction, which can be separated after pretreatment, may be used as an ash-free, solid fuel for the generation of heat and/or electricity (Galbe and Zacchi 2002). Cellulose hydrolysis can either be done chemically or enzymatically using specific cellulolytic enzymes.…”