The diagram illustrates the production of biofuel, namely ethanol, in several stages. Overall, the process cycle starts from harvesting green resources to extract ethanol, which will be consumed as fuel before the released CO2 goes back to the forest to supply energy to plants and woods.
The initial stage takes place in forests where plants generate energy in the process of photosynthesis, ulitising sunlight and carbon dioxicide as their nutrient source. Trees and plants sufficiently grown are then harvested, and pre-processed in a factory to be changed into a form of cellulose fibers. Subsequently, sugar is produced from the processed cellulose, and finally a substance called ethanol is made by adding certain microbes.
The finished product is then consumed as biofuel, which is primarily used to substitute for fossil fuels, in various ways such as for automobiles, lorries, and airplanes. After that, these vehicles emit CO2 in the atmosphere as a result of engine conbustion, which will eventually float back to the forest to be re-used as a main ingredient of the large-scale photosynthesis to grow trees and plants.