Non-renewable energy sources are natural resources that cannot be replenished in a short time frame. These include fossil fuels like coal, oil, and natural gas, which are formed from the remains of ancient plants and animals over millions of years. When burned, they release energy that can be used for electricity, heating, and powering vehicles. Another non-renewable source is nuclear energy, which is generated from uranium through a process called nuclear fission. While it produces a large amount of energy with low greenhouse gas emissions, it generates radioactive waste that must be carefully managed. Non-renewable energy sources are finite and contribute to environmental concerns like climate change.