Biodiesel fuel was produced by the transesterification of microalgae oil using sodium hydroxide as a catalyst. The oil was extracted from heterotrophic cultivated algae biomass. The transesterification process was optimized using response surface methodologyto increase the yield of methyl esters. The Box–Behnken design and fractional factorial design 2^4-1 points were used to investigate the interaction of process variables, such as the methanol/oil molar ratio, the percentage of sodium hydroxide, the temperature, and the reaction time in the production of biodiesel fuel, and to predict the optimum process conditions for the FAME yield. Based on the results, the optimal conditions for the synthesis of biodiesel fuel were as follows: methanol/oil molar ratio, 7:1; catalyst concentration, 1.0% (by weight of algae oil); temperature, 67°C, and reaction time, 51 minutes. The yield of FAME was confirmed by gas chromatography analysis.

Biofuels for diesel engines are produced mainly from rapeseed oil in Lithuania and the Member States of the European Union. In order to minimise an adverse impact of biodiesel fuel on the food sector, it is necessary to look for alternative feedstocks for producing biodiesel fuel including the potential utilisation of the new kinds of oilseed crops and various fatty waste. Camelina (Camelina sativa) could be one of the kinds of such oilseed crops, and therefore the physical and chemical parameters of Camelina sativa oil and biodiesel fuel produced from this oil were determined and the conformity of quality parameters with the requirements of biofuel standard was evaluated. It was found that fatty acid methyl esters made from Camelina sativa oil had a high iodine value (164.6÷169.6 g I2 / 100 g oil), and therefore could be used as fuel for diesel engines only in the mixtures with methyl esters produced from animal fat or used for frying oil. It has been established that similar mixtures can contain 50÷60% of Camelina sativa oil methyl esters. The possibilities of increasing oxidation stability as well as improving the cold flow properties of ester mixtures were investigated. The most effective antioxidant – Ionol (optimal dosage of 500 ppm) and the most efficient depressants Wintron XC-30 (optimal dosage – 1500 ppm) and Infineum R-442 (optimal dosage – 1200 ppm) were selected.

In this study, low-quality rapeseed was used as a raw material for biodiesel fuel production. The application of such seeds with an enzyme catalyst is a green approach to producing renewable biodiesel fuel. During the in situ transesterification process, mineral diesel was selected as an extraction solvent for the simultaneous extraction and transesterification of rapeseed oil (RO). This allowed, at the end of the process, for the production of a mixture of mineral diesel and biodiesel fuel. Energy is saved using this process, as the need to extract the oil separately is eliminated and extraction and transesterification take place together in the in situ process. In this study, 11 different lipases were analyzed from which to select the most effective biocatalyst according to the chosen experimental conditions. The most suitable lipase for in situ transesterification was Lipozyme TL IM (Thermomyces lanuginosus). The impact of the temperature and duration of the reaction was investigated along with the concentration of the lipase. A ethanol-to-oil molar ratio of 5:1 was chosen. The optimal reaction conditions were as follows: a reaction duration of 7 h, a reaction temperature of 30 °C and a lipase concentration of 5% (based on oil weight). Under these conditions, 99.92% of oil was extracted from the rapeseed. The degree of oil transesterification acquired was 99.89%. A mineral diesel and rapeseed oil ethyl ester blend of 9:1 (w/w) was produced.

Recently, there has been a growing interest in the use of new types of cheaper raw materials for biodiesel production. There are many prospects for microalgae, which do not compete for land with conventional biodiesel raw materials, are characterized by rapid reproduction and high biomass accumulation, and under certain conditions, some are able to accumulate a large amount of oil. A number of studies have been conducted on the extraction of oil from microalgae cells and transesterification with various acyl receptors. This paper provides an overview of the results of research on microalgal biomass preparation and oil extraction. Indicators of the quality of the oil are presented and its suitability for biodiesel synthesis is analyzed. The homogeneous and heterogeneous catalysts used for oil transesterification are described and the optimal conditions of the process when using various alcohols as acyl receptors are presented. Much attention is paid to the parameters affecting the transesterification efficiency and biodiesel yield. The physical and chemical, and operational and environmental properties of biodiesel obtained from algae oil are analyzed. The evaluation of the economic efficiency of biodiesel synthesis is also presented.