Biodiesel production from waste animal fat

Abstract

The global reliance on fossil fuels has led to environmental concerns, prompting the exploration of alternative energy sources like biodiesel. This study investigated the technical feasibility of utilizing waste animal fat (WAF) for biodiesel production to address environmental concerns. The study evaluated the physico-chemical properties of WAF, process parameters for efficient conversion into biodiesel, and compared the properties of the produced biodiesel with conventional diesel and biodiesel established standards. A quantitative approach along with laboratory experiments was used to explore process parameters' feasibility for production and compared the produced biodiesel properties with conventional diesel. WAF (30kg) at Kampala City abattoir were directly sampled. Melting WAF at 110°C aided in moisture removal, crucial for efficient transesterification. Characterization of WAF oil indicates high free fatty acid (12%) content, necessitating pretreatment. The pretreatment reduced the Free Fatty Acids (FFAs) to 1.8% making the WAF oil feed stock was fit for the transesterification process. Transesterification, influenced by factors; Fat: Methanal ratio temperature, catalyst concentration, and reaction time. Viscosity emerged as the key parameter to select the optimal production conditions due to its influence on fuel atomization, affecting combustion efficiency. Fourier Transform Infrared Spectroscopy (FTIR) was employed to analyze chemical composition, specifically identifying functional groups like carbonyls and impurities, to guide pretreatment and transesterification processes. The success of transesterification was confirmed by the disappearance of certain peaks and the appearance of new ones in the Fourier Transform Infrared spectrum. Biodiesel produced at Run 5 exhibited optimal kinematic viscosity of 4.88 mm2/s, falling within both American and European standards, alongside a recommended fat to methanol ratio of 1:6. At optimal production conditions, the attained WAF biodiesel yield was 95.1% at 2-hour reaction time and 70 ℃. Moreover, the density (0.83 g/ml) conformed well to biodiesel requirements. FTIR was used on raw WAF. Therefore, WAF can be used to produce biodiesel that meets American and European standards and can replace conventional petroleum diesel. WAF biodiesel has a methanol content of 0.17% by volume, within the 0.2% maximum limit set by European Standard (EN) 14214 and American Society for Testing and Materials (ASTM) D-6751. Its kinematic viscosity at 40°C is 4.88 mm²/sec, within the 3.5-5.0 mm²/sec range specified by EN 14214 and the 1.9-6.0 mm²/sec range specified by ASTMD-6751. Exploring alternative catalysts and alcohols to use would yield different results as well as understanding the mechanisms of soap formation and mitigation strategies that improve biodiesel quality.