Assessment of Waste Plant Oils as Sustainable Feedstocks for Biodiesel Production

Thesis Abstract

The escalating demand for sustainable energy sources has intensified interest in biodiesel production from alternative feedstocks, particularly waste plant oils, which offer the potential to mitigate environmental pollution and reduce reliance on conventional vegetable oils. This study aims to assess the viability of waste plant oils as sustainable feedstocks for biodiesel production by analyzing their chemical properties, process efficiencies, and environmental impacts. The specific objectives include evaluating the physicochemical characteristics of various waste plant oils, optimizing transesterification parameters for biodiesel yield, and comparing the performance and emissions profiles of biodiesel derived from waste oils with those from virgin feedstocks. Employing a mixed-methods research design, the study integrates quantitative laboratory analyses with qualitative assessments. The quantitative component involves collecting samples of waste plant oils from 15 different agricultural processors and oil extraction units, ensuring diversity in oil types such as palm, soybean, sunflower, and castor waste oils. Analytical techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), and titration methods are used to determine free fatty acid (FFA) content, iodine value, and acid value to assess suitability for biodiesel production. Response Surface Methodology (RSM) guides the optimization of transesterification conditions—including catalyst concentration, temperature, and molar ratio—to maximize biodiesel yield. The qualitative component involves semi-structured interviews with industry stakeholders and environmental impact assessments through Life Cycle Analysis (LCA). Data analysis employs regression analysis to determine the relationships between feedstock properties and biodiesel yield, Analysis of Variance (ANOVA) to test the significance of process parameters, and thematic analysis for stakeholder insights. Expected findings indicate that certain waste plant oils, notably palm and soybean residuals with FFA levels below 2%, can be efficiently converted to biodiesel with yields exceeding 90% under optimized conditions. Furthermore, biodiesel derived from waste oils displays comparable engine performance metrics to conventional biodiesel, with a significant reduction in greenhouse gas emissions (up to 30%) as evidenced by LCA. The study anticipates identifying key factors that influence biodiesel quality, including feedstock variability and processing parameters. This research contributes novel insights into the resource potential and environmental benefits of utilizing waste plant oils, filling existing knowledge gaps regarding their physicochemical suitability and process optimization. It advances the theoretical framework by applying the Theory of Planned Behavior to understand industry stakeholder perspectives and the Green Supply Chain Management theory to evaluate sustainable practices in waste oil valorization. The findings are intended to inform policy frameworks, encourage adoption of waste oils in biodiesel production, and promote circular economy principles within the agricultural and energy sectors. The study concludes that waste plant oils are viable, sustainable feedstocks for biodiesel production, offering environmental, economic, and social benefits. It recommends scaling up collection and processing infrastructures, establishing quality standards for waste oils, and encouraging policy incentives for waste-to-energy initiatives. For future research, further investigations into post-treatment methods for high-FFA waste oils and long-term engine performance tests are suggested to enhance the commercial applicability of waste-derived biodiesel. Overall, the research underscores the strategic importance of waste plant oils in fostering sustainable energy solutions and advancing circular resource management in biodiesel production.