## 3 Results and Discussion
These results show very clearly that an excess of alcohol has a positive influence on the reaction yield. A good mixing of the reactants in the T-mixer is generated at a higher flow rate, which is crucial for obtaining high FAEE yields. This principle doesn't apply to the MX-mixer. [PERSON] and [PERSON] [13] found out that increasing the stirring speed in methanolysis experiments (producing fatty acid methyl ethers, FAME) conducted in batch mode had a positive effect on the product yield. Authors conducted experiments with used frying oil (UFO) and neat canola oil and obtained a maximum FAME yield = 88.8 wt-% at optimal reaction conditions (1.1 wt-% catalyst (NaOH), 60 \({}^{\circ}\)C reaction temperature, 15 min reaction time and a molar methanol/oil ratio of 7:1), while the optimal conditions for the neat canola oil (1 wt-% NaOH, 45 \({}^{\circ}\)C, 15 min, methanol/oil ratio 6:1) provided a maximum FAME yield = 93.5%. Other researchers [16] performed ethanolysis experiments with waste cottonseed oil in batch mode and found that at a molar ethanol/oil ratio of 12:1, 65 \({}^{\circ}\)C and 2.5 h reaction time, 98% FAEE were obtained, using 5 wt-% of a 3 wt-% Li/CaO catalyst. Not only the reaction parameters but also the type and oil composition have a high impact on the FAEE yield. Previous works [15; 17; 18], as well as the experiments carried out in this work, showed that the product yield for the alcoholysis strongly depends on the acid value (amount of FFA) of the oil, due to occurring saponification reaction. Since the suitability of different oils for the alcoholysis could only be accurately determined by performing the reactions under otherwise completely equal conditions, a statement on this cannot be made. However, in the past, vegetable oils like sunflower, soybean, palm or rapeseed oil proved to be reasonable feedstocks [13]. But the economic aspect of the production is a very important one, which implies that the oil yield of the crop should be as high as possible. [PERSON] et al. [19] mentioned in their review on the effects of different biodiesel feedstocks on the engine that about 70-80% of the total production cost account for the cost of the raw materials. In view of this, they stated that palm oil is the most suitable edible vegetable oil for biodiesel production, while Jatropha oil is the best non-edible one for this purpose. By optimizing the reaction conditions, the production costs could be further decreased due to possible energy-saving methods. The efficiency of base-catalyzed transesterification, primarily conducted in batch reactors, can be substantially increased by a continuous process in microstructured reactors. Due to the much higher area/volume ratios, faster reaction rates and a faster mass and heat transfer in the base-catalyzed ethanolysis of waste cooking oils can be achieved in microreactors. Other enhancements are shorter diffusion distances and reduced residence times [15]. The techno-economic implication of the atmospheric and subcritical heterogeneous transesterification [20] and results from present work were compared. The authors report the time of reaction about 1-3 h at 70 \({}^{\circ}\)C. The reaction in microreactors needs several minutes at 50 \({}^{\circ}\)C providing lower costs and higher capacities for the industrial application.