Optimization of bio-oil obtained from fast pyrolysis of greenhouse wastes by response surface methodology

Different parameters are effective on bio-oil yield and quality during the production of bio-oil from biomass through fast pyrolysis. Knowing the optimum values of these parameters is important to obtain bio-oil in the desired yield and quality and therefore economic production of energy. Therefore, the objective of this thesis study is to investigate the optimum process conditions during high yield and quality bio-oil production from biomass (the mixture of wastes of greenhouse vegetables such as tomato, pepper, and eggplant) through fast pyrolysis. Experimental design was formed by using the response surface methodology (RSM) with central composite design (CCD) in order to optimize the process parameters of fast pyrolysis. In optimum conditions, catalytic fast pyrolysis experiments were conducted by using catalysts such as potassium carbonate (K2CO3), copper oxide alumina (CuO), aluminum oxide (Al2O3), and ZSM-5 to investigate the effects of these catalysts on bio-oil quality. The optimum process parameters for fast pyrolysis of biomass from the mixture of greenhouse vegetable wastes were determined as 400oC temperature, 1.5 mm particle size, and 300-350 mL/min nitrogen gas flowrate. Bio-oil yield obtained from optimum fast pyrolysis condition was found about 49%. When chemical compounds of bio-oil samples obtained under two different nitrogen gas flowrates (300 and 350 mL/min) were analyzed, bio-oil had higher hydrocarbon and acid contents in cafe of 300 mL/min. The catalysts used in this study had no significant effect on bio-oil yield. However, H/C increaed and O/C decreased during the application of K2CO3. When the effects of catalysts on bio-oil compounds were considered, the use of K2CO3 increased hydrocarbon production. On the other hand, the other catalysts increased the production of acetic acid. In general, the application of different catalysts produced different chemical compounds.