The production of biodiesel from waste activated sludge by the in-situ transesterification of its lipid content is studied in this work, comparing both basic and acidic catalytic routes. The acid mechanism is chosen as the optimum one, considering that the high percentage of free fatty acids strongly limits the yields obtained by the basic route, due to the saponification competence. Different pre-treatments are proposed (sonication, microwaves, sieving) to enhance the extraction rate, identified as the limiting step of the process. Sludge drying requirements are also analysed, concluding that water contents below 20% (weight base) does not lead to significant decreases in the transesterification activity. The acidic reaction is also chosen once the quality of the final mixture as alternative biofuel is analysed. Almost all the biodiesel properties (higher heat value, iodine number, kinematic viscosity, density, and long-chain saturated factor and cetane number) are in the optimum ranges proposed by the international normative, concluding that pretreatments do not damage the final product. Optimum results were obtained applying microwaves, with a final yield of 46.7% of FAMEs, which is a clear improvement on the previous literature of biodiesel obtaining from sewage sludge.

在这项工作中，通过比较碱性和酸性催化路线，研究了从废弃活性污泥中通过其脂质含量的原位酯交换生产生物柴油。由于皂化能力，高百分比的游离脂肪酸严重限制了基本路线获得的产量，因此选择酸机制作为最佳机制。提出了不同的预处理（超声、微波、筛分）以提高提取率，这被认为是该过程的限制步骤。还对污泥干燥要求进行了分析，得出的结论是，低于 20%（重量基准）的水含量不会导致酯交换活性显着降低。一旦分析了作为替代生物燃料的最终混合物的质量，也会选择酸性反应。几乎所有的生物柴油特性（较高的热值、碘值、运动粘度、密度以及长链饱和因子和十六烷值）都在国际规范提出的最佳范围内，得出的结论是预处理不会损害最终产品。应用微波获得了最佳结果，最终产率为 46.7% 的 FAME，这是对先前从污水污泥中获得生物柴油的文献的明显改进。