Investigation of the potential for use of waste black cumin (Nigella Sativa) in bioethanol production in anaerobic bioreactor

The increasing worldwide energy demand has forced the pursuit of alternative energy sources. This has led to growing interest in renewable energy sources, including biomethane, biohydrogen, biochar, biodiesel, and bioethanol. In biofuel production, the preference for using various types of organic wastes instead of raw materials has become more appealing in recent years, considering cost and waste management. Organic wastes cause environmental problems, including greenhouse gas emissions and water and soil pollution. To minimize these issues, it is necessary to develop strategies for organic waste management. In this regard, the utilization of organic waste biomass types for environmentally friendly bioethanol production has been the focus of researchers in recent years. In this respect, in Turkey, the waste pulp generated from cold-pressed black cumin oil production can also be utilized for bioethanol production. This waste is mostly disposed of in the garbage. Occasionally, it is also used as animal feed. The unique aspect of the thesis is to determine the potential of bioethanol production using organic black cumin pulp waste, and no study has been found in the literature in this context. Therefore, in this study, waste obtained by producers after oil production was acquired. These wastes were examined as raw material for bioethanol production with mixed bacteria. The thesis aims to determine the bioethanol production performance in anaerobic batch reactors (ABRs) operated at different organic loading rates and initial pH value of 5.0 by using black cumin pulp waste (i) directly (5 gr black cumin/L ve 10 gr black cumin/L) and (ii) as extracted liquid after decoction pretreatment (5 gr black cumin extract/L ve 10 gr black cumin extract/L). In the study, a maximum bioethanol production of 5.53 mL and 8.07 mL was determined in the direct use of 5 g black cumin/L and 10 g black cumin/L, respectively. In addition, 2.89 mL bioethanol production was determined in bioreactors using 5 g black cumin extract/L, and 2.79 mL bioethanol production was determined in bioreactors using 10 g black cumin extract/L. As a result, it was determined that black cumin pulp can be used as a raw material for bioethanol production. This study is envisioned to make a significant contribution to the strategies and literature on global bioethanol production and waste management.