This idea came from a group of 10 students whose ages range from 9 to 14. The impact of carbon on the environment is an important issue for human future. CO2 is an emission that results from human activities, such as burning fossil fuels, raising livestock, decomposing waste, and logging forests. CO2 has the ability to absorb and reflect heat radiation from the Sun, creating a greenhouse effect. CO2 gas is a chemical compound that plays an important role in the Earth's biological cycle. However, it is also the main course for climate change. Minimizing the amount of CO2 emitted into the air is one of the necessary conditions for sustainable development. For that reason, the students chose the idea of recycling C02 on the farm (Circular farm). On the farm, C02 will be collected from animal raising areas, vegetable growing areas, factories, residential areas... and then stored in the ground. Connecting the C02 gas pipe system in the storage area to the greenhouse through the control circuit and sensor system to measure the appropriate C02 concentration to supply to the plants in the greenhouse. During photosynthesis, O2 from the greenhouse will be transferred to supply residential areas and farms.