The diagram illustrates the process of producing ethanol, which is a kind of a biofuel. The production consists of several stages. From the begining of plant growth to the ending with the use of the ethanol as a fuel.
The process begins with the growth of plants and trees, which gain energy from sunlight and carbon dioxide. Once mature, farmers start to harvest and transport to the factory where can pre-processing with the special machine. On to the next step, professionals take the cellulose and process in the laboratory. Once the processing stage is done, sugars from the plants are extracted. With microbes added to sugars, ethanol is finally ready to provide the fuel to the vehicles and planes. Eventually, the cars and aircrafts release carbon dioxide to the atmosphere. And then the nature absorb it to make the cycle repeat again and again.
In summary, the ethanol production is sustainable. And the process involves both natural and industrial stages.