چكيده انگليسي :
Increasing global population and fuel demand by transportation systems have led to an increase in fossil fuel consumption. In addition, fossil fuels reserves are limited and there is a need to replace them with renewable resources. Sunflower is a plant with high growth rate and potential to generate valuable biofuels, including ethanol. Accordingly, the goal of this study is to employ this energy crop in a biorefinery for production of bioethanol, biogas, and biodiesel fuels. Two different routes were suggested for biorefinery, i.e., using individual components and a mixture of components. Three pretreatments of hot water (180°C, 1h), phosphoric acid (85%, 50°C, 1h), and sodium carbonate (4%, 140°C, 18min) were used to improve polymeric carbohydrates to simple and fermentable sugars. Afterward, the solid and liquid phases were separated and the solid phase was used to produce ethanol and biogas. The liquid phase and fermentation residue underwent the biogas process. The highest ethanol efficiency and methane production for most components were achieved when phosphoric acid pretreatment was conducted. The highest production of ethanol and methane from solids were attained from the stem and meal samples pretreated with phosphoric acid, respectively. Phosphoric acid pretreatment yielded the highest amounts of ethanol and biogas that could be derived from the solid phase of stalk, leaf, seed hull, and mixture samples. In this way, 11.2, 6.4, 9.7, and 9.8 g ethanol /L and 317.5, 277.9, 276.6, and 322.7 mL CH4/g volatile solid (VS) were produced, respectively. The liquid phase of the phosphoric acid pretreatment and fermentation residue of these four samples produced 110.0, 90.5, 70.4, and 35.4 mL CH4/g VS, 158.7, 168.5, 151.8, and 172.0 mL CH4/g VS, respectively. The highest amount of ethanol from solid phase of the head was gained by hot water pretreatment (8.0 g/L), and 80.6 and 236.4 mL CH4/g VS were produced from the fermentation residue and liquid phase of this pretreatment, respectively. The highest amounts of methane obtained from the head was from the solid and liquid phase of sodium carbonate pretreatment, valued at 315.9 and 271.9 mL/g VS, respectively. In the case of meal, the highest production of ethanol was from solid and liquid phase of sodium carbonate pretreatment (8.9 and 2.7 g/L, respectively). The liquids obtained from this pretreatment and the residue from fermentation of its solids also produced 380.1 and 201.3 mL CH4/g VS, respectively. Besides, the highest amount of methane was from solid and liquid phase of phosphoric acid pretreatment (342.7 and 56.9 mL/g VS, respectively). The yield of biodiesel production using 6 to 1 methanol to oil molar ratio with 0.7% catalyst concentration at 50°C for 65 min was 96.2%. Biodiesel was the favorable sample with low kinematic viscosity and acid number, and heating value of 37.2 MJ/kg. For each of the two scenarios, application of individual components or mixtures of components, three biorefining pathways were considered. The overall mass balance showed that the energy production equivalent to 314.6 liters of gasoline per ton of sunflower waste resulted from the best biorefinery pathway of the sunflower energy crop. This pathway used the solid and liquid phases of five pretreated components, i.e., leaf, stem, head, seed hull, and meal in the biogas production and the seed oil extracted in the biodiesel production. Using the mixture of components produced energy equivalent to 301.3 liters of gasoline per ton of sunflower waste in the same pathway and was the best case. Overall, the application of individual components produced slightly more energy than that of the mixture of components in all biorefining pathways. Therefore, the separation of components is not necessary to produce fuel. In conclusion, sunflower plant is a suitable substrate for producing biofuels after pretreatment with phosphoric acid.
