Methaneis the smallest and simplest hydrocarbon. It is an organic compound with only one carbon in its chain. It has tetrahedral geometry and forms a polar, colorless, gaseous and flammable substance. It is one of the gases produced in processes:
- in decomposition of organic matter;
- of digestion;
- abiogenic (not from living organisms), such as forest fires.
It is also possible to find methane in the Petroleum and in the earth's mantle as one of the primary substances in the formation of the earth. It is one of the gases responsible for accelerating the greenhouse effect. It has a shorter stay in the atmosphere compared to carbon dioxide, however, it is highly capable of absorbing heat and infrared rays. The combustion of methane has as a product gases such as CO2, water vapor and soot.
Read too: Sulfuric acid - chemical compound widely used by industries
What is methane?
Methane is the smallest and simplest of the hydrocarbons, organic molecule with only one carbon atom linked to four hydrogens.
Methane characteristics
- organic molecule
- saturated
- tetrahedral geometry
- Polar substance (does not dissolve in water)
- Colorless
- Gaseous under normal conditions of temperature and pressure
- Flammable (when in contact with atmospheric air)
methane formula
The molecular formula of methane is CH4, a carbon bonded to four hydrogen atoms.
Methane gas sources
Biotic (from other living beings
→ Digestive process of herbivorous, carnivorous and omnivorous animals: the animals' digestive process releases methane gas into the environment. O ruminant digestive process, like cattle, emits methane in greater amounts.
→ Fermentation by methanogenic bacteria: are microorganisms that participate in the anaerobic decomposition process (decomposition without the presence of oxygen), transforming more complex organic matter into methane gas, carbon dioxide and other simpler molecules. Process that takes place in swamps, where there is an ecosystem rich in moist organic matter in the process of decomposition.
See too: What is the waste decomposition time?
Abiotics (natural and petrochemical sources)
→ geological faults: at the earth mantle the highest concentration of methane on Earth is located, either because of a geological fault that could lead to its leakage, or because of temperature conditions that favor reactions that release it.
→ Fossil fuels: Methane is one of the hydrocarbons that can be extracted from petroleum. There is also the formation of methane as a product of chemical reactions with larger hydrocarbons.
Uses and importance of methane
Methane is mainly used as power supply. The gas produced (biogas) inlandfills or dumps it is drained by a pipe and then sent to a plant that converts it into energy. In São Paulo, 700 thousand people benefit from the energy that comes from biogas extracted from urban waste.
In the case of agriculture, biodigesters are used to treat and remove the biogas contained in the animal excrement (stool). The energy acquired through biogas is used to operate the farm and benefit local communities. Energy from methane is also used in negotiations for carbon credits (initiative based on the reduction of global warming).
Methane Combustion Reaction
The combustion of methane can happen completely, forming carbon dioxide (CO2) and water (H2O), or it can be partial or incomplete combustion, in which case carbon monoxide (CO), soot (C) and water are the product. See below the balanced reactions of the complete and partial combustion of methane:
complete:
CH4 (g) + 2.02(g) ◻ CO2(g) + 2.H2O(g)
Incomplete with carbon monoxide (CO) formation):
CH4 (g) + 2/22(g) ◻ CO(g) + 2H2O(g)
Incomplete forming soot (C)
CH4(g) + O(g) 2 ◻C(s) + 2.H2O(g)
See too:What is combustion?
dangers of methane
Methane gas is one of those responsible for accelerating the greenhouse effect, being in smaller amounts in the atmosphere, when compared to carbon dioxide. However, its energy potential is 60x greater, in addition to its high capacity to absorb infrared radiation. Therefore, despite the fact that methane does not remain in the atmosphere for a long time, the damage caused to the environment is up to 20 times greater than that caused by carbon dioxide.
For human health, methane also presents poisoning risks. Inhalation of gas can cause asphyxia, nervous system breakdown and cardiac arrest.
solved exercises
Question 1 - (Enem - 2016) The collection of feces from domestic animals in plastic bags and their disposal in conventional dumps can create conditions of degradation that generate products harmful to the environment environment. (Figure 1)
Figure 2 illustrates the Park Spark Project, developed in Cambridge, MA (USA), in which animal feces household items are collected in biodegradable bags and thrown into a biodigester installed in parks public; and the products are used in equipment in the park itself.
An innovation of this project is to enable the (a):
A) Methane gas burning
B) Carbon dioxide storage
C) Aerobic decomposition of feces
D) More efficient use of fossil fuels
E) Carbon fixation in organic molecules
Resolution
Alternative A. It enables the burning of methane gas, which is converted into energy that can be used to supply the park's electrical systems.
Question 2 - (Enem) According to the report "The great shadow of livestock" (Livestock's Long Shadow), made by the United Nations for the Agriculture and Food, livestock is responsible for about 18% of global warming, a greater contribution than the livestock sector. transport.
Large-scale livestock farming contributes to global warming through the emission of
- methane during the digestion process.
- nitrous oxide during the rumination process
- chlorofluorocarbon during meat transport.
- nitrous oxide during the respiratory process.
- sulfur dioxide during pasture consumption.
Resolution
Alternative A. The digestive process of ruminant animals happens by methanogenic bacteria, having as one of the main end products methane gas, which is the second main gas responsible for the worsening of the greenhouse effect.
By Laysa Bernardes Marques de Araujo
Chemistry teacher
