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.

BackgroundPrevious studies on the use of SO2 and CO2 as impregnating agent for sugar cane bagasse steam treatment showed comparative and promising results concerning the cellulose enzymatic hydrolysis and the low formation of the inhibitors furfural and hydroxymethylfurfural for the use of CO2 at 205°C/15 min or SO2 at 190°C/5 min. In the present study sugar cane bagasse materials pretreated as aforementioned were analyzed by scanning and transmission electron microscopy (SEM and TEM), X-Ray Diffraction (XRD) and Infrared (FTIR spectroscopy) aiming a better understanding of the structural and chemical changes undergone by the pretreated materials.ResultsSEM and TEM data showed that the structural modifications undergone by the pretreatment with CO2 were less pronounced in comparison to that using SO2, which can be directly related to the combined severity of each pretreatment. According to XRD data, untreated bagasse showed, as expected, a lower crystallinity index (CI = 48.0%) when compared to pretreated samples with SO2 (CI = 65.5%) or CO2 (CI = 56.4%), due to the hemicellulose removal of 68.3% and 40.5%, respectively. FTIR spectroscopy supported SEM, TEM and XRD results, revealing a more extensive action of SO2.ConclusionsThe SEM, TEM, XRD and FTIR spectroscopy techniques used in this work contributed to structural and chemical analysis of the untreated and pretreated bagasse. The images from SEM and TEM can be related to the severity of SO2 pretreatment, which is almost twice higher. The crystallinity index values obtained from XRD showed that pretreated materials have higher values when compared with untreated material, due to the partial removal of hemicellulose after pretreatment. FTIR spectroscopy supported SEM, TEM and XRD results. CO2 can actually be used as impregnating agent for steam pretreatment, although the present study confirmed a more extensive action of SO2.

Ethanol is being considered worldwide as a promising fuel and the reasons are twofold: a substantial rise in the price of oil and environmental, social and geographic issues. This study aims to present a scientific and technological evaluation of ethanol development during the period of 1995-2009. The scientific data was collected and processed using statistic tools available at the Web of Science Ò . Research on patents was made on Esp@cenet-the European Patent Office, and the results were processed using the Matheo Patent Analyzer program. The US and Brazil are the two largest world producers and therefore, corn and sugarcane are the most used feedstocks. There has been a significant increase in the number of scientific publications and patents since 1995. However, since 2001 this growth has skyrocketed, with an almost ten-fold increase in the number of scientific publications and a fivefold increase in the number of patents. When different raw materials for fuel ethanol production were evaluated, it was found that the greatest interest lay in the use of wood residues, corn (stover) and sugarcane (bagasse), demonstrating that there is a strong interest in second generation ethanol, i.e., cellulosic ethanol. The evaluation of patent documents showed that most of the applicants (88%) are of two kinds: biotechnology companies and companies that produce enzymes, corroborating the scientific consensus that the enzymatic hydrolysis step and the fermentation process (hexoses and pentoses) are the two bottlenecks to the development of cellulosic ethanol technology.

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