Straw
is one of the main lignocellulosic wastes produced during
cereal crop cultivation. The abundance of barley straw makes it a
good candidate for bioethanol production. This work deals with barley
straw pretreatment by means of autohydrolysis in order to get xylooligosaccharides
in the liquid phase, followed by an organosolv treatment using ethanol
to increase the solid phase enzymatic susceptibility. Up to 17.4 g
oligomers/L were obtained in the hydrothermal stage, in which practically
all the cellulose and lignin remained in the solid phase. The solid
phase from the hydrothermal-delignification was subjected to an experimental
design in order to study the effect of pretreatment conditions on
the bioethanol production, with values of solids concentrations in
the range 7.7–20 wt % and values of enzyme loading in the range
14 FPU/g to 6 FPU/g. In the experiments carried out at a liquid to
solid ratio =4 g/g, it is possible to obtain 31.6 g ethanol/L in just
9 h (corresponding to 100% ethanol conversion), with optimum results
of 44.5 g ethanol/L in 46 h (90–93% glucose to ethanol conversion)
and with a maximum concentration of 48.7 g ethanol/L in 89 h (79%
conversion). The combination of a hydrothermal pretreatment (under
conditions that lead to the recovery of high amounts of hemicellulosic
byproducts), followed by an organosolv treatment under mild conditions,
turns out to be suitable for second generation bioethanol production,
applying a high solids loading, by means of fed-batch simultaneous
saccharification and fermentation.
The pulp yield of orange tree wood was tested under various conditions including processing with soda-anthraquinone (soda-AQ), kraftanthraquinone (kraft-AQ), or ethanol under different temperature, time, reagent concentration, and PFI laboratory beater beating regimes. Beating grade and stretch properties were studied, with a view to identifying the optimum operating conditions. Polynomial equations were derived that generally reproduced the dependent variables, with errors in most cases much less than 20%. Kraft-AQ pulping was the most efficient. The values of the tensile, burst, and tear indices obtained with kraft-AQ (78.04 Nm/g, 4.84 kN/g, and 2.97 mNm 2 /g, respectively), were in most cases higher than those found for soda-AQ and ethanol pulps. Using lower values of operational conditions than those required to maximize the studied paper properties (170 °C, 65 min, 13% active alkali, and 2700 number of PFI beating revolutions), it was possible to provide a more energy-and chemically-efficient process for industrial facilities.
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