Abstract
BackgroundThe conditions for steam pretreatment of sugar cane bagasse and leaves were studied using CO2 as an impregnating agent. The following conditions were investigated: time (5 to 15 min) and temperature (190 to 220°C). The pretreatment was assessed in terms of glucose and xylose yields after enzymatic hydrolysis and inhibitor formation (furfural and hydroxymethylfurfural) in the pretreatment. Results from pretreatment using SO2 as impregnating agent was used as reference.ResultsFor sugar cane bagasse, the highest glucose yield (86.6% of theoretical) was obtained after pretreatment at 205°C for 15 min. For sugar cane leaves the highest glucose yield (97.2% of theoretical) was obtained after pretreatment at 220°C for 5 min. The reference pretreatment, using impregnation with SO2 and performed at 190°C for 5 min, resulted in an overall glucose yield of 79.7% and 91.9% for bagasse and leaves, respectively.ConclusionsComparable pretreatment performance was obtained with CO2 as compared to when SO2 is used, although higher temperature and pressure were needed. The results are encouraging as some characteristics of CO2 are very attractive, such as high availability, low cost, low toxicity, low corrosivity and low occupational risk.
Highlights
The conditions for steam pretreatment of sugar cane bagasse and leaves were studied using CO2 as an impregnating agent
The overall yields of glucose and xylose included the soluble sugars in the liquid from pretreatment and the soluble sugars obtained in the enzymatic hydrolysis
The sugar cane bagasse consists of 69.9% carbohydrates and 23.6% lignin, while the leaves consist of 57.5% carbohydrates and 36.1% lignin based on dry matter
Summary
The conditions for steam pretreatment of sugar cane bagasse and leaves were studied using CO2 as an impregnating agent. 46% of the domestic supply of energy in Brazil is based on renewable energy, with 31% associated with the utilisation of biomass; 15.9% of the energy based on biomass is directly associated with sugar cane and its derivatives [1] These figures are quite high when compared with those from the world energy matrix, where only 12.9% is associated with renewable energy. According to the above-mentioned reasons and considering that the raw material pretreatment step represents about 20% of the total costs of cellulosic ethanol production [10], the present study was focused on steam pretreatment of sugar cane bagasse and leaves using CO2 as an impregnating agent. Steam pretreatment of CO2 impregnated sugar cane bagasse and leaves was investigated under conditions in the following ranges: time (5 to 15 min) and temperature (190 to 220°C). The results were compared with pretreatment of sugar cane bagasse and leaves using SO2 and with pretreatment of leaves without any impregnation
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