Biodiesel production from nonedible feedstocks catalyzed by nanocatalysts: A review

Biodiesel produced from vegetable oil has recently increased in popularity. However, these edible feedstocks (which are the apparent choice of triglycerides) will not be sufficiently sustainable, given the increasing demand for energy and food, and guaranteed inedible feedstocks are needed. Biodiesel can be generated from these alternative feedstocks using various catalysts. Current studies show that nanocatalysts are extensively used for this purpose and are more preferred than usual homogeneous and heterogeneous catalysts. These nanocatalysts exhibit many advantageous features, including efficient separation steps for both products and catalysts, elimination of the quenching process, high catalytic activity, and large surface area, and provide the possibility for reusability. According to recent reports, the use of nonedible oils and nanocatalysts, such as titanium-doped zinc oxide, magnesium oxide-doped magnesium aluminate, zirconium oxide and many others, are potent with an approximately 80-98 wt% yield of biodiesel under optimized conditions, suggesting that this approach is a suitable option for biodiesel synthesis. This review aims to explore the potency of nonedible feedstocks and nanocatalysts for fatty acid methyl ester synthesis. The findings of the most recent published studies are critically summarized. The catalytic reaction mechanism for biodiesel production is highlighted, focusing on the nanocatalysts. Some nonedible seeds have been reported, and their potency for biodiesel production has been assessed in detail.