Biomass Processing Routes for Production of Raw Materials with High Added Value: Prospects and Challenges for the Developing Routes

Biomass Processing Routes for Production of Raw Materials with High Added Value: Prospects and Challenges for the Developing Routes

Rubens Maciel Filho (University of Campinas, Brazil), Laura Plazas Tovar (University of Campinas, Brazil), Yurany Camacho Ardila (University of Campinas, Brazil), Jaiver Efrén Jaimes Figueroa (University of Campinas, Brazil) and Maria Regina Wolf Maciel (University of Campinas, Brazil)
DOI: 10.4018/978-1-4666-8711-0.ch008
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In this chapter sugarcane bagasse may be submitted to a biological route in which the technologies used to obtain lignocellulosic ethanol (2nd generation ethanol) from lignocellulosic materials involve pre-treatment and the hydrolysis of the polysaccharides in the biomass into fermentable sugars for subsequent fermentation. Taking into consideration the use of sugarcane bagasse as a raw material for 2nd generation ethanol, the acid hydrolysis / pretreatment of sugarcane bagasse could be more feasible that others, and must be evaluated in this context. On the other hand, from biomass is possible to obtain products with high added value and energy, mainly by the use of thermochemical processes (e.g. pyrolysis and gasification) and biochemical processes (e.g., fermentation and anaerobic digestion). However, the products obtained from the thermochemical processes can be used as raw material for biochemical processes which multiplies the quantity of products to be obtained from biomass.
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One of the alternatives that could be implemented for the agro-industries to continue increasing their production of biofuels as well as to provide feedstock for chemicals is to use the byproducts formed as a source of energy. Amongst these by-products, sugarcane bagasse occupies a prominent position in Brazilian agricultural activities. The interest in sugarcane bagasse in Brazil is justified by the fact that it is available in the ethanol and sugar production units, without the problems and costs associated with the logistics and transport of lignocellulosic materials. A glance in this material brings huge possibilities for use, amongst which in the production of animal feed, in the chemical industry, in the production of microbial biomass and in the production of 2nd generation ethanol via sugarcane bagasse and straw to generate electricity.

The biological technologies used to obtain ethanol from lignocellulosic materials (2nd generation ethanol) involve pre-treatment and the hydrolysis of the polysaccharides in the biomass into fermentable sugars for subsequent fermentation. Pre-treatment is necessary due to the strong bonds existing between the cellulose, hemicelluloses and lignin. Thus, the lignocellulosic biomass requires selective separation of the components; this implies in rupturing the cellulose-hemicelluloses-lignin complex and the removal of each fraction by pre-treatment techniques for subsequent enzymatic degradation, if that is the route chosen for the hydrolysis step. Various pre-treatment methods have been proposed and developed. These methods can be classified in different methods: physical, chemical and biological pre-treatments or a combination of these, aiming at reducing the recalcitrance of this lignocellulosic biomass (sugarcane bagasse). Among all these methods the chemical and combined pre-treatments have drawn more attention, since they remove the lignin without degrading the cellulose chain (Sun & Cheng, 2002), and more recently physical methods (Boussarsar, Rogé, & Mathlouthi, 2009) and combined methods (Rocha, Martín, da Silva, Gómez, & Gonçalves, 2012) have been more extensively considered.

Nowadays, liquid hot water (LHW) pretreatment associated with high pressure carbon dioxide (HP-CO2) from depicted sugarcane bagasse coupled to enzymatic hydrolysis reported a glucose yield of 30.43 g/L and a cellulose conversion of 41.17% (Gurgel, Pimenta, & Curvelo, 2014). On the other hand, Phan and Tan (2014) proposed a pretreatment of sugarcane bagasse using sequential combination of supercritical CO2 (scCO2) and alkaline hydrogen peroxide (H2O2) and results showed that the glucose recovery reach 97.8% when compared to individual H2O2, ultrasound and scCO2 pretreatment methods (22.9%, 20.2% and 61.3%, respectively).

The hydrolysis process involves breaking the glycosidic bonds of the polysaccharides, which are the pre-treated raw material, into fermentable sugars, monosaccharides (either hexoses or pentoses, depending on the polysaccharide) and the conversion of the sugars of the components of the sugarcane bagasse (cellulose and hemicelluloses). For the feasible production of 2nd generation ethanol, two strategies have been conceived, each with a different stage of development: acid hydrolysis and enzymatic hydrolysis.

On the other hand, the sugarcane bagasse can be used as raw material in the thermochemical route, which is based on pyrolysis and gasification processes to produce Syngas (hydrogen and carbon monoxide mainly) and tar (Jordan & Akay, 2012), that are further processed by either chemical transformation (as for instance by Fischer-Tropsch) or biochemically, trough fermentation. Therefore, the thermochemical route coupled to biochemical route allows full biomass utilization (cellulose, hemicelluloses and lignin), which offers potentially a great advantage over the 2G technology, which it will name as hybrid thermochemical-biochemical route (Liu et al., 2014).

The biochemical route ferments syngas using anaerobic microorganisms, but is a little explored area, when this is connected to the gasification process (Liu et al., 2014; D. Xu, Tree, & Lewis, 2011). Therefore, it is necessary to investigated as well as to evaluate the potential of integration thermochemical to biochemical route, when is used the sugarcane bagasse.

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