Circular Economy is one of the most important policies of international and Taiwanese governments. In fact, it is not a new concept, people have been discussed circular economy since the last century. The goal of circular economy is to establish a renewable and recyclable system. By slowing down, closing or reducing the cycle of material and energy use, the total input and the waste of resources can be greatly reduced. As the current global trend is moving towards Net Zero, how should SMEs be part of the sustainable green supply chain? According to the research of the Legislative Yuan on actively promoting corporate carbon reduction, 78% of multinational corporations are considering to stop working with suppliers who cannot cooperate with carbon reduction transformation policy by 2025. So far, countless SMEs in Taiwan are waiting for the best solution for carbon reduction, and the most efficient way to reduce carbon emissions in the manufacturing process and transportation is to use biofuels and raw materials made from wastes (such as SAF, biodiesel and industrial bio-based cutting fluid, etc.). In the past, Taiwan had gutter oil food safety incidents, and there were bio-diesel companies being prosecuted because of using waste cooking oil from unknown sources to gain government subsidies in EU. According to the EU Agriculture and Rural Development Department, 68% of the waste cooking oil in EU relies on imports, of which 75% is from Asia. It is very difficult to trace and supervise the origin of the imported waste cooking oil, resulting in fraudulent criminal acts continue to occur (including mixing with animal fat and palm oil). Therefore, how to effectively use IOT technology to increase traceability and to confirm the source of the waste is a necessary step towards circular economy.