How are microorganisms used to generate energy

Conventional energy sources

Conventional energy sources are fossil fuels and nuclear fuels. In contrast to renewable sources, their supplies on earth are limited.

Around 80 percent of global primary energy consumption is covered by fossil fuels. They include coal, oil and natural gas. The energy contained in fossil fuels can be converted into thermal energy through combustion. Sulfur dioxide, nitrogen oxides and hydrocarbons are emitted, but also dust. In a second step, this can in turn be converted into electrical energy.

Coal, oil and natural gas are largely of vegetable origin. Around 300 to 400 million years ago, plants converted solar energy into chemical energy through photosynthesis. They absorbed carbon dioxide from the air through their leaves and water through the roots. When exposed to sunlight, high-energy carbohydrates were created, which are mainly sugar and starch. At the same time, oxygen was released. In this way, plants have bound the carbon to the surface of the earth.

Origin and use


Presumably, huge swamp forests and moors shaped the Carboniferous and Permian ages 350 to 250 million years ago. Dying horsetail, club moss and giant ferns did not rot in the low-oxygen swamp water, but were converted into coal in the course of time in the extensive basin landscapes: in the absence of air, microorganisms initially transformed the plant material into peat (1). Numerous generations of plants were deposited and were each covered by sand and rock. Several layers of peat and coal were created. In today's Ruhr area, this process was repeated about 200 times (2). With increasing depth, pressure and temperature increased, the layers were pressed (3). In a lengthy process, the peat was first turned into lignite and then hard coal (4).

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Coal is used to generate energy

Lignite and hard coal are burned in boilers in power plants to heat water. The resulting water vapor is used to generate electrical energy and for district heating. Coal also ends up refined in coke in the blast furnaces of the steel industry or as briquettes for heating in the furnace.


The origin of petroleum

Dead marine organisms are the starting material for most of the petroleum that is extracted today. These sank to the bottom of the shelf seas and over time were covered with sand and debris (1). Enclosed airtight, this biomass was gradually transformed into digested sludge by bacteria. Further layers of sediment covered the mixture, solidified it and lowered it further (2). Under great pressure and high temperature, the organic materials in the digested sludge were converted into kerogens. These consist mainly of carbon and hydrogen (3). As the pressure continues to rise and temperatures of 60 degrees Celsius or more, the kerogens are split into gaseous and liquid hydrocarbons. The oil drifts out and migrates up through porous rock layers. It finally collects in a deposit below an impenetrable layer of earth (4).

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So oil is used to generate energy

In order to convert the chemical energy of crude oil into electrical energy, it is burned and the resulting heat generates water vapor. The steam drives a turbine, the kinetic energy of which is finally converted into electrical energy in a generator.

natural gas

Natural gas is, so to speak, a by-product that is produced when crude oil or coal is produced. In the first case - in the case of crude oil - it is located in the same deposit above the oil horizon or is dissolved in the crude oil under high pressure. The formation of natural gas is described in more detail in the section on oil.

When the oil is extracted, the natural gas is then released. In the second case it was formed as methane when coal was formed. It comes to lie over deep coal seams. Natural gas is a mixture of up to 95 percent methane and other saturated hydrocarbons. Carbon dioxide, nitrogen, hydrogen sulfide, water and helium are contained in small amounts.

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