This research aims to use low‐cost and easily available chemicals for chemical pretreatment to achieve a high yield of fermentable sugars using biodegradable municipal solid waste as a substrate. Biodegradable municipal solid waste was pretreated with locally available toilet cleaner (acidic in nature) and washing detergent (basic in nature) and to achieve maximum yield of reducing sugars, two variables; chemical concentration and time were selected for optimization using a central composite design. In Central composite design 13 runs for toilet cleaner (acidic in nature) and washing detergent (basic in nature) pretreatment models were created while ranges for two variables were selected as 1, 2, 3 days for time and 1%, 3%, 5% for chemical concentration. In the toilet cleaner (acidic in nature) pretreatment, optimum conditions were 5% (vol/vol) of toilet cleaner (acidic in nature) for 3 days. At optimal conditions, the model for toilet cleaner (acidic in nature) pretreatment released 167.755 g/L of reducing sugars and 2.684 MJ/L energy while the model for washing detergent (basic in nature) pretreatment released 159.141 g/L of reducing sugars and 2.546 MJ/L energy. An enzyme cocktail hydrolyzed the toilet cleaner (acidic in nature) pretreated sample, and the highest value of fermentable sugar was achieved at 36 h of 237.83 ± 11.028 g/L. Thus, the chemical pretreatment using toilet cleaner and washing detergent has a great potential for fermentable sugar production and effectively be used in industrial and household digesters for the conversion of waste into useful products.
This study was conducted to identify and quantify hydrocarbons produced during bio-fuel production using kitchen waste (KW). KW is a complex mixture of hardly digestible compounds, mainly lignin, cellulose and hemicellulose, and easily digestible compounds, mostly starchy materials. Therefore, KW has a high potential for the production of biofuel after the chemical hydrolysis of lignocellulose, starch and carbohydrates. In this study, after the physically pretreatment (dried and crushed) of KW, dilute-acid hydrolysis was used for the hydrolysis of lignocellulose and starchy materials, eliminating the enzymes requirement. The dilute acid hydrolysis was conducted with 1, 3 and 5% (w/w) sulfuric acid at 90 and 120°C for 30, 60, 90 and 120 min. The hydrolysis with 5% acid at 120°C for 120 min resulted in the hydrolysate with the highest reducing sugar concentration of 97.917 ± 0.5 g/kg and Energy of 1.567 ± 0.008 MJ/kg. The reducing sugars were used as substrate in fermentation by fungal strain Aspergillus niger, bacterial strains Lacto-bacillus and Escherichia coli, to produce hydrocarbons. The fermented product was quantified after every day till the fermentation time is over i.e. no more products were formed. Biofuel production from Aspergillus niger, Escherichia coli and Lacto-bacillus was 64%, 45% and 50% after 72 hr. Fermented product contains mainly hydrocarbons as identified by GC-MS analysis. Calorific value of sample and biofuel determined on Differential Scanning Calorimetry were 0.6MJ kg− 1 for sample before fermentation and 3.56 MJ kg− 1, 3.33 MJ kg− 1 and 2.67 MJ kg− 1 for KW fermented by Aspergillus niger, Escherichia coli and Lacto-bacillus, respectively. Hence, maximum of 64% reducing sugars were converted into hydrocarbons (biofuel) after fermentation by Aspergillus niger.
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