ABSTRACT
The most popular alternatives to fossil fuels are Biodiesel and Ethanol. However, both of them have limitations such as being susceptible to separation in the presence of water. Biobutanol has been reported to overcome these challenges associated with biodiesel and bioethanol. This study therefore investigates the production of butanol via organosolv delignification of almond seed shells. Sample was pretreated with various organic solvents which included; isopropanol, methanol, ethanol, water, n-butanol, acetone, cyclohexane, tetrahydrofuran, toluene, and 1-4-dioxane. The best solvent with highest delignification extent was selected prior to enzymatic hydrolysis by cellulase and fermentation by Clostridium acetobutylicum for the improvement of acetone, butanol, and ethanol (ABE) production from almond seed shells. Delignification experiment was performed on a thermostatic heating mantle equipped with a 1000ml flask and a reflux condenser.
The various organic solvents used for organosolv pretreatment resulted in different delignification yields and extents. Results obtained showed that acetone had the highest delignification yield with 84.22%, followed closely by water having a delignification yield of 81.01%. This implies that acetone and water do not totally remove the lignin content in the almond seed shell. On the other hand, delignification extent revealed that isopropanol with 91.41% had the best performance in delignification of almond seed shell when compared with acetone which had the lowest performance with 86.60%. This performance can be attributed to the ability of isopropanol to possess high diffusion capacity into the biomass matrix causing disalignment and detachment of hemicellulose, cellulose and lignin.
Sugar test was carried out using a refractometer to determine the sugar concentration obtained during fermentation at 24 hours intervals. Results showed that 0.96g/L of total sugars was produced after fermentation for 4 days (0.16g/L after 24hours, 0.18g/L after 48hours, 0.27g/L after 72hours and 0.35g/L after 96hours). This implies that the amount of sugar produced during fermentation increased with time. Acid test was also done via titration with 0.05M KOH in the presence of phenolphthalein indicator to determine the amount of acid formed during fermentation. The acid values after 4 days of fermentation resulted in 0.0149mgKOH/g, 0.0048mgKOH/g, 0.0045mgKOH/g, and 0.0039mgKOH/L at 24 hours intervals. This showed that an increase in time resulted in a decrease in the amount of acid that was formed during fermentation. The acid was gradually reduced with time as it was utilized by the microbe to produce a range of solvents containing acetone, butanol and ethanol.
