Lime pretreatment of crop residues bagasse and wheat straw |
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Authors: | Vincent S Chang Murlidhar Nagwani Mark T Holtzapple |
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Institution: | (1) Department of Chemical Engineering, Texas A & M University, College Station, 77843, TX |
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Abstract: | Lime (calcium hydroxide) was used as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues:
bagasse and wheat straw. A systematic study of pretreatment conditions suggested that for short pretreatment times (1–3 h),
high temperatures (85-135°C) were required to achieve high sugar yields, whereas for long pretreatment times (e.g., 24 h),
low temperatures (50–65°C) were effective. The recommended lime loading is 0.1 g Ca(OH)2/g dry biomass. Water loading had little effect on the digestibility. Under the recommended conditions, the 3-d reducing sugar
yield of the pretreated bagasse increased from 153 to 659 mg Eq glucose/g dry biomass, and that of the pretreated wheat straw
increased from 65 to 650 mg Eq glucose/g dry biomass. A material balance study on bagasse showed that the biomass yield after
lime pretreatment is 93.6%. No glucan or xylan was removed from bagasse by the pretreatment, whereas 14% of lignin became
solubilized. A lime recovery study showed that 86% of added calcium was removed from the pretreated bagasse by ten washings
and could be recovered by carbonating the wash water with CO2 at pH 9.5. |
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Keywords: | Crop residues pretreatment lime cellulase sugar |
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