Microalgae has become a potential resource of biodiesel in recent years for its fast growth, non-food source, and CO₂ capture ability. However, efficient and economic production of biodiesel from microalgae is still a challenge. In this study, we presented a novel strategy of direct saponification–esterification conversion (DSEC) from wet microalgae (Chlorella vulgaris) to biodiesel and its associated kinetic model.

The process was accomplished with two consecutive additions into wet algae. Firstly, addition of NaOH/methanol solution, lipids including triglycerides (TG) and free fatty acids (FFA) of wet algae were released from disrupted algae and primarily converted into soaps by means of saponification. Then with further HCl/methanol addition, soaps were acidified into FFA and esterified into fatty acid methyl ester (biodiesel). The experimental results supported the proposed mechanism and observed several advantages of DSEC process. Primarily, DSEC eliminates lipid extraction/purification step in the conventional process, which usually accounts for more than half of production cost. Secondly, compared with the alkali catalyzed transesterification process, DSEC completely alleviates the restriction of incapable of dealing with high content of water and FFA. On the other hand, compared with acid catalyzed transesterification process, the production time of DSEC was only a fraction, less than 15 mins.

近年来，微藻类因其快速生长，非食物来源和CO ₂捕获能力而成为生物柴油的潜在资源。然而，从微藻类高效经济地生产生物柴油仍然是一个挑战。在这项研究中，我们提出了一种从湿微藻类（小球藻）到生物柴油的直接皂化-酯化转化（DSEC）的新策略及其相关的动力学模型。

通过连续两次向湿藻中添加来完成该过程。首先，添加NaOH /甲醇溶液，从破坏的藻类中释放出包括湿藻类的甘油三酸酯（TG）和游离脂肪酸（FFA）在内的脂质，并通过皂化作用首先转化为肥皂。然后在进一步加入HCl /甲醇的情况下，将肥皂酸化为FFA，然后酯化为脂肪酸甲酯（生物柴油）。实验结果支持了所提出的机制，并观察到了DSEC工艺的一些优点。首先，DSEC消除了传统工艺中的脂质提取/纯化步骤，这通常占生产成本的一半以上。其次，与碱催化的酯交换反应相比，DSEC完全缓解了无法处理高含量水和FFA的限制。