The biomass and energy pyramid is a model used by scientists to track the movement of energy from the sun through all the different levels of biomass and back into the earth. It illustrates the amount of energy lost by organisms and their relative mass when compared to the next lower level. On average, only 10 percent of the energy that is transferred from one level to the next higher becomes biomass on the higher level. The rest is lost to the metabolic processes of the lower level.
The measurements in the biomass pyramid are based solely on the energy moving through currently living organisms and their respective predators. The full energy pyramid include energy released from fossil fuels as well as biomass.
The primary energy pyramid used by scientists today is the one based on biomass. For this reason, much of the energy generated by the burning of fossil fuels does not fit into its proper level on the pyramid. For practical reasons, we will be focusing on the biomass pyramid and how it relates to energy currently available.
In a closed system, biomass in the form of plants consumes energy directly from the sun and converts it to carbohydrate molecules. There is a considerable discrepancy between the amount of sunlight available to plants worldwide and the actual amount that is converted to energy. Then a part of that energy is used by the plants in their own metabolic processes.
Herbivorous animals consume the plants and take this energy into their own bodies. The bulk of that energy is utilized by the animal for its own metabolic needs with a small percentage being passed on to predators who consume these animals.
The predators utilize approximately ninety percent of the energy they consume and pass only ten percent on to other predators who feed on them. The conversion of energy to biomass takes on the shape of a pyramid by measuring the biomass present in each successive level.
At the peak of the pyramid are microbes that act to decompose the bodies of all plants and animals that are not consumed by others. This decomposition releases carbon back into the environment where it is taken up by plants and begins the cycle again. Carbon that is not taken up by plants again remains in the environment and is stored. This is the source of the energy from fossil fuels.
Looking at the biomass and energy pyramid along with the carbon stored in the earth in the form of fossil fuels, it is easy to see how burning fossil fuels releases an excessive amount of CO2 back into the atmosphere. The pyramid also shows that replacing fossil fuels with biomass as fuel would result in the carbon released from burning biofuel being taken back up in the normal carbon cycle and would halt the accumulation of greenhouse gases that is affecting the global climate. The largest change that would be seen in the end is a reduction in the number of decomposers needed to fix the carbon and nitrogen so that it would be ready for uptake by plants at the bottom of the pyramid.