Proceeding of The 13th Kyoto University Southeast Asia Forum
Evaluation of Lignocellulosic Biomass from Leucaena leucocephala for its Potential Conversion to Energy and Biomass-derived Chemicals Zul Ilham a,b , Nur Nabiha Zulkarnaina, Normaniza Osmana, Rofina Yasmina,c and Norzulaani Khalida,c a
Institute of Biological Sciences, Faculty of Science, University of Malaya 50603 Kuala Lumpur, Malaysia Center of Energy Science, Faculty of Engineering, University of Malaya 50603 Kuala Lumpur, Malaysia c Center of Research in Biotechnology for Agriculture, Faculty of Science, University of Malaya 50603 Kuala Lumpur, Malaysia b
Abstract
Lignocellulosic biomass is the most abundant organic material on the earth. It consists of three main components, i.e., cellulose, hemicellulose and lignin. Chains of sugar molecules are building blocks for cellulose as well as hemicellulose and these chains can be broken down to form various monomeric sugars which can easily be converted to alcohols. However, there are also substantial amount of other non-glucose sugars (hexoses and pentoses) and lignin-derived compounds in the matrix, with high potential for conversion to value-added products. Although their composition varies among plant species and differs in their various parts, they have emerged as promising feedstock for biomass-derived chemical production. Therefore, in this study, a rapid growing non-food crop called Leucaena leucocephala is being evaluated for its potential to produce biomass-derived chemicals, either to be used for energy or drop-in chemicals. Keywords: Leucaena leucocephala; biomass-derived chemicals, bioenergy, lignocellulosic; biomass
1. Introduction Utilization of lignocellulosic biomass for production of energy and chemicals is gaining a serious attention in recent years due to the increasing concern towards environmental and sustainability issues of fossil-based products, which is the still the major source of energy today. Variety of crops could be used as the source for lignocellulosic biomass, but a measure must be taken so that food production will not be affected. Leucaena leucocephala is a leguminous tree of Mediterranean origin, high in biomass productivity (>50 tonne/hectare annually)1, beneficial in the recovery of degrading soils2 and has been described for various uses, ranging from paper production to ethanol3 and animal feed. In this study, the potential of utilizing Leucaena leucocephala for production of energy and chemicals was analyzed by evaluating its calorific value, holocellulose, glucan, xylan, arabinan, lignin, oligomers and monomers contents in liquid and solid phases after the subcritical water hydrolysis. This study will also consider the influence of important parameters in the hydrolysis process and discuss its advantages and disadvantages.
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Ilham et al. / Proceeding of The 13th Kyoto University Southeast Asia Forum (2014)
2. Materials and methods 2.1 Sample preparation Leucaena leucocephala samples were collected from the University of Malaya Glami Lemi Biotechnology Research Center in Jelebu, Negeri Sembilan, Malaysia before it was milled to pass the 10 cm screen. The chips were reduced again to pieces from 2 to 10 mm in order to prevent alterations of their components and remove the fines by sieving through 0.6 mm mesh. Samples were air-dried, homogenized in a single lot to avoid differences in compositions among aliquots, and stored. Characterization parameters were; 1% NaOH soluble (TAPPI T 212 om-98), hot water soluble (TAPPI T 207 cm-93), acetone extractives (TAPPI T 280 wd-06), α-cellulose (TAPPI T 203 om-93) and holocellulose contents3. All treatments in this study were done in four replications with variation coefficient less than 3% and less than 1% for holocellulose and cellulose contents. Aliquots from the homogenized wood, without extractable compounds that have been extracted in the stage of acetone extractives (TAPPI T 280 wd-06) were subjected to moisture determination (drying at 105̊C to constant weight) and quantitative acid hydrolysis with 72% H2SO4 at 121̊C for 60 min (TAPPI T 249 cm-85). The solid residue after subcritical hydrolysis was recovered by filtration and considered as Klason lignin (TAPPI T 222). Acid soluble lignin was determined accordingly (TAPPI T 290 um-85). The monosaccharides (glucose, xylose and arabinose), 5-hydroxymethylfurfural (HMF), furfural and acetic acid contained in the hydrolysates were determined by high performance liquid chromatography (HPLC), using an ionic exchange column (Aminex HP-87H, 30̊C, mobile phase: 0.05M H2SO4, flow: 0.6 mL/min). Uronic acids in the hydrolysates were determined using colorimetric method. Ashes were determined by calcinations (TAPPI 244 0m-93). The gross calorific values were determined according to UNE 164001 EX standards by using a Parr 6300 Automatic Isoperibol Calorimeter. Parts and parcels of these analysis were modified from Feria et al. (2011)3. 2.2 Subcritical hydrolysis and oligosaccharides determination Raw materials and water were mixed in the desired proportions and treated in a 500mL stainless steel reactor (Toyoko Atsu, Yokohama) using liquid/solid ratio of 8 kg water by kg raw material, on a dry basis (moisture content of the material was considered as water). Previous works demonstrated that the influence in the variation of the liquid/solid ratio is practically negligible when 7 to 10 kg water by kg raw material is used4. The reactor was heated by external fabric mantle, and cooled by cool water circulating through an internal loop. The reaction media was heated to reach the designated temperature and time zero was considered to be the beginning of the isothermal stage. The temperature was automatically controlled via an internal cooling coil equipped with circuit opening electrovalves which was used to stop the reaction after the desired operating time. At the end of the treatment, the solid residue was recovered by filtration and washed with distilled water for gravimetric yield determination. A fraction was used for pulping and another fraction was air-dried and milled to a particle size
