A waste-plastic-material-based triboelectric nanogenerator (W-TENG) from green manufacturing technology is urgently needed in response to sustainable development of smart cities. However, the low output charge density of the previous W-TENGs impedes them from going further in real applications. Toward this issue, an attractive PP/PS composite tribo-layer entirely based on wasted materials is developed in this work. Benefiting from the synergistic effect of the excellent tribo-negative property of PP and strong charge trapping ability of PS, a discarded take-out-box-based TENG (TB-TENG) with high output charge density is presented. The maximum output charge density of TB-TENG reached 16.5 nC/cm2, which is in a leading position among waste material based TENGs and comparable to that of TENGs based on commonly used fluorine-containing polymer materials. To apply in a smart city, we have remodeled the TB-TENG as a smart energy floor to power multiple functional electronics, such as LEDs, a household hygrometer, and a wireless lighting system through harvesting energy from human or vehicle movement. Moreover, an approach of on-road vehicle speed detection is also established when the TB-TENG serves as a self-powered speed sensor in traffic surveillance systems. This work demonstrates a promising example of using a waste take-out box to design a high output and ecofriendly TENG.