Elsevier

Bioresource Technology

Volume 102, Issue 6, March 2011, Pages 4439-4443
Bioresource Technology

Ethanol production from acid hydrolysates based on the construction and demolition wood waste using Pichia stipitis

https://doi.org/10.1016/j.biortech.2010.12.094Get rights and content

Abstract

The feasibility of ethanol production from the construction and demolition (C&D) wood waste acid hydrolysates was investigated. The chemical compositions of the classified C&D wood waste were analyzed. Concentrated sulfuric acid hydrolysis was used to obtain the saccharide hydrolysates and the inhibitors in the hydrolysates were also analyzed. The C&D wood waste composed of lumber, plywood, particleboard, and medium density fiberboard (MDF) had polysaccharide (cellulose, xylan, and glucomannan) fractions of 60.7–67.9%. The sugar composition (glucose, xylose, and mannose) of the C&D wood wastes varied according to the type of wood. The additives used in the wood processing did not appear to be released into the saccharide solution under acid hydrolysis. Although some fermentation inhibitors were detected in the hydrolysates, they did not affect the ethanol production by Pichia stipitis. The hexose sugar-based ethanol yield and ethanol yield efficiency were 0.42–0.46 g ethanol/g substrate and 84.7–90.7%, respectively. Therefore, the C&D wood wastes dumped in landfill sites could be used as a raw material feedstock for the production of bioethanol.

Introduction

The demand for the inexpensive production of biofuels has intensified due to increasing concerns of climate change, depletion of petroleum-based fuels, and environmental problems. Ethanol is one of the most promising alternative fuels with the potential to reduce the problems caused by the enormous utilization of fossil fuels. A key factor in the economy of ethanol production is the choice of raw materials as feedstocks. Although ethanol has been mainly produced from sucrose-containing feedstocks and starchy materials, ethanol from lignocellulosic biomass has recently received increasing attention due to the sustainable availability in large quantities and the avoidance of the conflict with production of food products (Festel, 2008, Zhu and Pan, 2010).

Korea has little starchy biomass available for ethanol production and also has an unfavorable climate for the cultivation of energy crops. Therefore, various waste biomasses containing forest residues, agricultural residues, food wastes, municipal wastes, and animal wastes must be utilized for the production of cellulosic ethanol. In recent, the total quantity and energy potential of waste biomass in Korea have been reported (Kim et al., 2010). According to this report, forest residues have been produced about 7 million tons a year, but the economic feasibility for ethanol production is unproven due to the high cost of collection and transport from the mountainous regions.

The second candidate is municipal wastes, including waste papers and woods from houses, industries, and construction and demolition (C&D) sites, which are classified as domestic, industrial, and C&D wood wastes, respectively. The first two are mainly utilized in recycling or incineration, whereas a huge amount of C&D wood wastes mixed with cement and other materials is buried into landfill sites. It is known that about 2 million tons of C&D waste per year is land-filled near the capital area (SLC, 2009). The C&D waste contains various kinds of wood-based building materials with a wood content of about 20–30%. Therefore, on economic and environmental viewpoints, this C&D waste is worthy of attention as a raw material for the production of cellulosic ethanol.

Wood-based building materials contain structural and nonstructural panels such as plywood, strandboard, particleboard, and fiberboard (Boyer et al., 2006). In the manufacturing processes of structural panels and nonstructural panel, various types of additive (adhesives, paints, lacquers, etc.) are used to make panel products from various shapes of wood (veneer, particle, wafer, and fiber). In the process of pretreatment or hydrolysis for the depolymerization of wood, the mixtures of these additives can be released into the hydrolyzed solution, which could act as inhibitors in the subsequent ethanol fermentation. In addition to these additives, degradation products are also released, including not only sugars but also fermentation inhibitors such as furfural, 5-hydroxymethylfurfural (5-HMF), lignin derivatives, and acetic acid (Palmqvist and Hahn-Hagerdal, 2000). Therefore, in order to ascertain the feasibility for the utilization of C&D wood wastes for ethanol production, the ethanol fermentability in the wood waste hydrolysates needs to be studied.

In this study, we evaluate the possibility of ethanol production from C&D wood waste in landfill sites. The chemical compositions of classified C&D wood waste are analyzed. Concentrated sulfuric acid is used for the hydrolysis of wood waste to obtain the saccharide hydrolysates and the inhibitors in the hydrolysates are also analyzed in addition to the sugar composition. Finally, we investigate the ethanol production from C&D wood waste acid hydrolysates by Pichia stipitis.

Section snippets

Preparation of wood wastes

Wood wastes separated from C&D wastes in Sudokwon landfill site located in Incheon in Korea were used as a raw material for the production of ethanol. The wood wastes were classified into four kinds of wood: lumber, plywood, particleboard, and medium density fiberboard (MDF). Each wood was cut, chipped, and air dried for 1 week. Air dried chips were milled and screened through a 20–40 mesh sieve or 381–864 μm using a Wiley mill.

Hydrolysis of wood wastes

To obtain the wood waste hydrolysates, sulfuric acid hydrolysis was

Chemical composition of wood wastes

The chemical composition of the wood wastes was analyzed by NREL procedure. The major components of the cell wall and intercellular parts of the wood, comprising 90% of the wood, were cellulose, hemicelluloses, and lignin. The minor parts of the wood, existing in the cell wall, cell lumen, and special tissues, could be extracted by acetone and boiling water, which contained respectively the solvent soluble parts and the water soluble parts. Therefore, the polysaccharides fraction of the wood

Conclusion

In this study, the feasibility of using C&D wood wastes for ethanol production was demonstrated. The concentrated sulfuric acid hydrolysis used to obtain the hydrolysates released both sugars and fermentation inhibitors into the saccharide solution. However, these inhibitors in the hydrolysates did not affect the ethanol fermentation by P. stipitis. In addition, the additives contained in the wood wastes were not released into the hydrolysates. The ethanol production from acid hydrolysate based

Acknowledgement

This work was supported by the EcoSTAR project of the Ministry of Environment of Korea and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0002313).

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