The figure illustrates the process of how ethanol is produced which is a type of biofuel. Overall, The production of ethanol have three phases that contains harvesting, pre-processing and processing in a cyclic manner.
At the initial stage, plants absorb sunlight and carbon-dioxide to produce energy that help them to grow. After that, when plants are fully grown, they are harvested to enter the pre-processing stage where a cutting machine is used to make smaller segment and produce cellulose from them.
Next phase started by processing the cellulose to produce biofuel. During the processing phase, cellulose are taken to some chemical process to generate sugar, where microbes are added to make ethanol. Furthermore, the produced chemical is distributed among vehicles which uses ethanol to run, for instance, car, plane.
Notably, All these vehicles emit carbon dioxide in the nature so that plants can reabsorb and produce energy, thereby completing a sustainable carbon cycle.