Improving the Yield of Biodiesel Production Using Waste Vegetable Oil Considering the Free Fatty Acid Content

Abstract

This paper investigates the use of waste vegetable oil (WVO) for production of biodiesel. The goal of this study was to explore the improvement of biodiesel production to achieve high yields. Different oil streams, including virgin canola oil and WVO, were used as the raw material for the transesterification processes. These oils had different fatty acid contents as a result of environmental or previous processing conditions. The main objective of this study was to assess the impact of free fatty acid (FFA) content on the resulting yield. In addition, the yield was influenced by production parameters such as reaction time, reaction temperature, molar/volume ratios of oil to alcohol, catalyst amount, and mechanical mixing. This was accomplished by automating the biodiesel production from WVO, thereby achieving improved processing and requiring minimal direct human involvement. A biodiesel production apparatus was developed with a Raspberry Pi 3 microcomputer to control the process. It was shown that the particular choice of these process parameters depended on the particular oil type. This research used mixtures of virgin and waste vegetable oils at different volume ratios (oil to alcohol) of 4:1, 6:1, and 8:1, which was determined by the FFA content of the oil. In addition to mechanical mixing, ultrasonication rated at 500W, 20kHz was used to enhance mixing by adding 450 kJ to the process, thereby reducing both the processing time and the amount of methoxide needed to perform a base-catalyzed transesterification. The production temperature was held within the range of 50–65°C. This research demonstrated that optimal yield depends on temperature, catalyst concentration, FFA content of the oil, and the energy introduced by sonication. A 96% yield was achieved with the following parameters: an oil to methanol volume ratio of 6:1, 0.6% weight concentration of catalyst (NaOH) at 6.25 g, and FFA values of approximately 5%. It was determined that the proposed system can produce acceptable quality biodiesel.