Feasibility of Manufacturing Cellulose Nanocrystals from the Solid Residues of Second-Generation Ethanol Production from
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Feasibility of Manufacturing Cellulose Nanocrystals from the Solid Residues of Second-Generation Ethanol Production from Sugarcane Bagasse L. A. Camargo 1,2 & S. C. Pereira 1 & A. C. Correa 1 & C. S. Farinas 1,2 & J. M. Marconcini 1 & L. H. C. Mattoso 1,2
# Springer Science+Business Media New York 2016
Abstract The reuse of the solid residues generated in the production of second-generation (2G) ethanol to obtain high-value products is a potential strategy for improving the economic and environmental viability of the overall process. This study evaluated the feasibility of using the residual solids remaining after the enzymatic hydrolysis of sugarcane bagasse for the production of cellulose nanocrystals (CNC), a valuable bionanomaterial. To this end, sugarcane bagasse subjected to steam explosion (SEB) or liquid hot water (LHWB) pretreatment was hydrolysed using different loadings of a commercial cellulase cocktail. Samples of SEB and LHWB were hydrolysed enzymatically, resulting in glucose releases close to 40 g/ L, which would be suitable for producing 2G ethanol by microbial fermentation. The solid residues after the enzymatic hydrolysis step presented cellulose contents of up to 54 %, indicating that a significant amount of recalcitrant crystalline cellulose remained available for subsequent use. These solid residues were purified and submitted to acid hydrolysis, resulting in the successful formation of CNC with crystallinity close to 80 %, lengths of 193–246 nm and diameters of 14– 18 nm. The CNC produced presented morphology, dimensions, physical-chemical characteristics, thermal stability and crystallinity within the ranges reported for this type of material. Moreover, the enzyme loading or the type of hydrothermal pretreatment process employed here showed no significant
* L. H. C. Mattoso [email protected] 1
Embrapa Instrumentação, Rua XV de Novembro 1452, 13560-970 São Carlos, SP, Brazil
2
Federal University of São Carlos, Rod. Washington Luis km 235, 13565-905 São Carlos, SP, Brazil
effects on the CNC obtained, indicating that these variables could be flexibly adjusted according to specific interests. Keywords Cellulosic ethanol . Sugarcane bagasse . Steam explosion pretreatment . Liquid hot water pretreatment . Nanocellulose . Cellulose nanocrystals
Introduction In recent years, the impact caused by global warming, together with the growing energy demand and the imminent shortage of fossil fuel reserves, has led to the need to replace nonrenewable with renewable energy sources. Consequently, there has been rapid development of the biofuel industry, especially processes that use lignocellulosic biomass as feedstock [1, 2]. Brazil is a good example of a country with abundant lignocellulosic biomass and is the largest producer of sugarcane used for ethanol production. In the 2014/2015 season, it is expected that more than 640 million tons of sugarcane will be processed by Brazilian sugar and alcohol plants [3, 4], generating huge amounts of lignocellulosic residues, including bagasse, which h
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