Cocoa pod ash pre-treatment of wawa (Triplochiton scleroxylori) and sapele (Entandrophragma cylindricum) sawdust: Fourier transform infrared spectroscopic characterization of lignin

Abstract

Effective pre-treatment of lignocellulosic materials, to reduce the recalcitrance of lignin, is critical to achieving high yields of bioethanol. The use of local resources in Ghana for the pre-treatment of bioethanol feedstocks would enhance the feasibility of bioethanol production by reducing the cost of production. The present study was conducted to investigate the effectiveness of cocoa pod ash pretreatment of two important feedstocks in Ghana, wawa and sapele sawdust. Extractive-free milled sawdust samples, containing 25.1 and 27.1% lignin, respectively (dry weight basis), were treated with either 2% cocoa pod ash solution or 2% NaOH at 121°C for 60 min or at 25°C for 24 h. Controls were treated with water. Lignin was isolated from untreated and alkali-treated samples and characterized using Fourier Transform-Infrared (FT-IR) spectroscopy. Differences in spectra were recorded in the low wavenumber region as well as the fingerprint region. Treatment with 2% cocoa pod ash at 121°C completely altered the spectral characteristics of lignin indicating disruption of the structure of lignin contained in wawa and sapele. This was similar to results obtained following treatment with 2% NaOH at 121°C. At 25°C, however, cocoa pod ash treatment had little effect on lignin structure. The findings indicate that cocoa pod ash might be a suitable chemical pre-treatment for the production of bioethanol from sawdust. The use of cocoa pod ash, an inexpensive, abundant and readily available local resource, for the pre-treatment step would reduce cost and thereby enhance the profitability and feasibility of bioethanol production in Ghana. © 2013 Asian Network for Scientific Information.