The diagram represents the production of ethanol as a biofuel.
At first glance, it is clear that 9-step cyclic ethanol production starts with energy contribution to the growth of trees and plants and ends with biofuel used to reproduce carbon dioxide. This is achieved by processing plants and trees into ethanol that is turned into carbon dioxide by using it as a fuel.
Turning to the details, the process starts with the growth of trees and plants, the raw materials, with an energy contribution that is produced by a combination of sunlight and carbon dioxide. They are then harvested with specialized vehicles; after they are pre-processed, raw materials turn into cellulose before the processing stage.
At 6 steps, as a result of the processing stage, sugars are formed from cellulose. Then specific microbes are added to create ethanol, the final product and biofuel, from sugars. The final product can be used as a fuel for different types of transportation, such as cars and planes. After being used as a fuel, ethanol again turns into carbon dioxide, and the process starts again.