The diagram illustrates the process of biofuel production, specifically how ethanol is generated from plant sources. It highlights the various stages from plant growth to the end use of ethanol as a fuel, and the associated carbon dioxide emissions at each step.
Initially, plants and trees absorb sunlight and carbon dioxide for photosynthesis, promoting their growth. Once mature, they are harvested using machinery. The harvested material, primarily cellulose, undergoes a pre-processing stage where it is refined into smaller components. During this phase, carbon dioxide is released.
The cellulose is then subjected to processing in specialized facilities, where it is broken down into sugars. These sugars are combined with microbes, initiating a fermentation process that converts the sugars into ethanol. The ethanol produced is then transported via trucks, airplanes, and cars for various applications. Notably, the combustion of ethanol in these vehicles releases carbon dioxide back into the atmosphere.
Overall, the diagram depicts a cyclical process where carbon dioxide is absorbed by plants during growth and subsequently emitted during the production and consumption of ethanol, suggesting a closed carbon loop inherent to the biofuel production process.