All the physical material that go into making a computer were created by creating heat to melt metal in the computer and then shape it. The oil to make plastics took energy to get the oil out of the ground, took lots of gasoline to ship the oil to a processing plant. then processing plant used energy to process the oil. Then once computer is built it use electricity to function. Electricity is created at a coal burning plant that burns thousands of tons a day. And computers are needed to manage all this.