Carbon Dioxide Emissions from Automobiles
The reason we focus on CO2 is that emission of this gas changes the climate. Natural emission of CO2 is much greater than that produced by humans. The natural carbon cycle in nature absorbs much of the CO2 produced. However, vegetation and oceans only absorb about 40% of CO2 produced. In addition, human activities such as livestock production add significantly to the production of both CO2 and methane. So what are some of the numbers?
CO2 released by consumption of vegetation by animals and microbes – 220 gigatonnes of CO2/year CO2 released by respiration of vegetation – another 220 gigatonnes of CO2/year CO2 released by the oceans – 332 gigatonnes of CO2/year
CO2 released by human activities – 29 gigatonnes of CO2/year
Offset – the absorption of CO2 by plants (450 gigatonnes/year) and the oceans (338 gigatonnes/year) for a total of 788 gigatonnes/year. What this tells us is that vegetation produces about 440 gigatonnes and absorbs about 450 gigatonnes. The oceans produce 332 gigatonnes and absorb 338 gigatonnes. Considering variations from year to year, this produces a rough balance. Adding 17.5 gigatonnes/year through human activities is the real concern because this is not absorbed by natural processes and we have to consider the cumulative effect.
We hear a lot about carbon dioxide emissions from everyday activities. Where does all this CO2 come from? It all starts with combustion. Combustion is a chemical reaction producing heat and light. It often involves a fuel and oxygen although combustion can occur with other compounds (hydrogen will burn in chlorine to produce hydrogen chloride with heat and light being given off). However, for many everyday situations, combustion involves a carbon based compound and oxygen. Oxygen combines with carbon in the fuel to generate CO2.
1. In general, each gallon of gas weighing about 6.25 pounds gives rise to about...