In 2021 and 2022, a natural gas crisis (also called the gas crisis) occurred, mainly in Europe.[3][4][5][6]​.

According to BP, proven reserves at the end of 2017 stand at 193.5 trillion (10) cubic meters,[7] enough to maintain current global production for 55 more years. Reserves have increased by 0.2% in the last year.

The Middle East is the geographical area with the largest reserves with 43% of the world total (Iran and Qatar stand out), followed by Central Asia with 31% (mainly Russia and Turkmenistan).

Although its composition varies depending on the reservoir, its main chemical species is methane gas at 79 - 97% (in molar or volumetric composition) and commonly exceeds 90% (e.g. in the West Sole well in the North Sea). It also contains other gases such as ethane (0.1 - 11.4%), propane (0.1 - 3.7%), butane (less than 0.7%), nitrogen (0.5 - 6.5%), carbon dioxide (less than 1.5%), impurities (water vapor, sulfur derivatives) and traces of heavier hydrocarbons, mercaptans, noble gases, etc. (The figures refer to the purified gas sold in Spain)[8]​.

As an example of a polluting compound associated with natural gas, it is worth mentioning CO (carbon dioxide), which reaches a concentration of 49% in the Kapuni field (New Zealand).

During extraction, some gases that are part of its natural composition are separated for different reasons: due to their low calorific value (e.g. nitrogen and carbon dioxide), because they can condense in gas pipelines (having a low saturation temperature) or because they hinder the gas liquefaction process (such as carbon dioxide, which solidifies when producing liquefied natural gas (LNG). CO is usually determined with the ASTM D1137 or D1945 methods.

Propane, butane, and other heavier hydrocarbons are also separated because they make it difficult for natural gas to burn efficiently and safely. Water (steam) is eliminated for these reasons and because at high pressures it forms methane hydrates, which clog gas pipelines. Sulfur derivatives are purified to very low concentrations to avoid corrosion, the formation of odors and sulfur dioxide emissions (which cause acid rain) after combustion. Detection and measurement of hydrogen sulfide (HS) is performed following ASTM D2385 or D2725 methods.

Finally, for domestic use, traces of mercaptans are added (among them methyl-mercaptan CHS), which allow olfactory detection in the event of a leak.

The combustion of natural gas produces carbon dioxide, which is a greenhouse gas, and water:[9]​.

CH + 2 O --> CO + 2 HO + ∆.

In the century it began to be extracted and channeled into American cities as fuel for lighting. When electricity arrived, it began to be used in heating, hot water and in the metallurgical industry. As welding technology improved after World War II, the depth of the extractions and the transportation capacity to consumers increased.[10]​.

It is a very versatile fuel with fewer CO emissions during combustion than other fossil fuels. Its main uses are:

Its obtaining or extraction is simpler and cheaper compared to other fuels. The liquefaction of natural gas is produced by the combined action of compression and refrigeration at low temperatures. LNG allows for maritime transport over long distances and without the need for land infrastructure, using LNG tankers.

The upper heating value of the fuel is 10.45 - 12.8 kWh/m³ (cubic meter under normal conditions, that is, at 0 °C and 1 atm).[11]​.

Natural gas components (methane, ethane, propane, butane) are important raw materials in the chemical industry. Methane is used for the production of synthesis gas, methanol and ammonia. The first step in the valorization of other alkanes is the conversion into olefin. Oxidative dehydrogenation of ethane leads to ethylene, which can further be converted to ethylene epoxide, ethylene glycol, acetaldehyde[12]​ and other olefins.[13]​ Propane can be converted to propylene,[14]​[15]​ acrylic acid[16]​[17]​ and acrylnitrile.

The CO emitted into the atmosphere after the combustion of natural gas is a greenhouse gas that contributes to global warming of the Earth. This is because it is transparent to visible and ultraviolet light, but absorbs the infrared radiation that the Earth's surface emits into outer space, slowing down its nighttime cooling.

The combustion of natural gas produces fewer greenhouse gases than other fossil fuels such as petroleum derivatives (fuel oil, diesel and gasoline) and especially than coal. It is also a fuel that burns cleaner, more efficiently and safely and does not produce sulfur dioxide (which causes acid rain) or solid particles.

The reason why it produces little CO is that the molecule of its main component, methane, contains four hydrogen atoms for every one carbon atom. Thus, two molecules of water are produced for each one of CO, while long-chain hydrocarbons (e.g. those contained in diesel) produce practically only one molecule of water for each one of CO (in addition, the standard enthalpy of formation of water is very high).

In renewable natural gas, the CO molecule released into the atmosphere in its combustion is equal to the molecule taken from the atmosphere by bacteria to create methane in the putrefaction process.

However, natural gas leaks that occur in wells represent a very significant contribution of greenhouse gases, since methane is equivalent to 23 times the greenhouse effect of carbon dioxide (IPCC data). For example, the March 2012 accident on the Elgin oil platform — operated by the Total oil company in the North Sea — resulted in a leak of about 5.5 million m³ per day.[18] As the density of methane under standard conditions is 0.668 kg/m³[19]​ the leak was 3,674 tons per day, which is equivalent to 84,502 tons of carbon dioxide per day. The duration of the stoppage of said leak was estimated at 6 months, which represents 15 million tons of carbon dioxide equivalent (Estonia's industrial emissions in 2009).

In 2021 and 2022, a natural gas crisis (also called the gas crisis) occurred, mainly in Europe.[3][4][5][6]​.

According to BP, proven reserves at the end of 2017 stand at 193.5 trillion (10) cubic meters,[7] enough to maintain current global production for 55 more years. Reserves have increased by 0.2% in the last year.

The Middle East is the geographical area with the largest reserves with 43% of the world total (Iran and Qatar stand out), followed by Central Asia with 31% (mainly Russia and Turkmenistan).

Although its composition varies depending on the reservoir, its main chemical species is methane gas at 79 - 97% (in molar or volumetric composition) and commonly exceeds 90% (e.g. in the West Sole well in the North Sea). It also contains other gases such as ethane (0.1 - 11.4%), propane (0.1 - 3.7%), butane (less than 0.7%), nitrogen (0.5 - 6.5%), carbon dioxide (less than 1.5%), impurities (water vapor, sulfur derivatives) and traces of heavier hydrocarbons, mercaptans, noble gases, etc. (The figures refer to the purified gas sold in Spain)[8]​.

As an example of a polluting compound associated with natural gas, it is worth mentioning CO (carbon dioxide), which reaches a concentration of 49% in the Kapuni field (New Zealand).

During extraction, some gases that are part of its natural composition are separated for different reasons: due to their low calorific value (e.g. nitrogen and carbon dioxide), because they can condense in gas pipelines (having a low saturation temperature) or because they hinder the gas liquefaction process (such as carbon dioxide, which solidifies when producing liquefied natural gas (LNG). CO is usually determined with the ASTM D1137 or D1945 methods.

Propane, butane, and other heavier hydrocarbons are also separated because they make it difficult for natural gas to burn efficiently and safely. Water (steam) is eliminated for these reasons and because at high pressures it forms methane hydrates, which clog gas pipelines. Sulfur derivatives are purified to very low concentrations to avoid corrosion, the formation of odors and sulfur dioxide emissions (which cause acid rain) after combustion. Detection and measurement of hydrogen sulfide (HS) is performed following ASTM D2385 or D2725 methods.

Finally, for domestic use, traces of mercaptans are added (among them methyl-mercaptan CHS), which allow olfactory detection in the event of a leak.

The combustion of natural gas produces carbon dioxide, which is a greenhouse gas, and water:[9]​.

CH + 2 O --> CO + 2 HO + ∆.

In the century it began to be extracted and channeled into American cities as fuel for lighting. When electricity arrived, it began to be used in heating, hot water and in the metallurgical industry. As welding technology improved after World War II, the depth of the extractions and the transportation capacity to consumers increased.[10]​.

It is a very versatile fuel with fewer CO emissions during combustion than other fossil fuels. Its main uses are:

Its obtaining or extraction is simpler and cheaper compared to other fuels. The liquefaction of natural gas is produced by the combined action of compression and refrigeration at low temperatures. LNG allows for maritime transport over long distances and without the need for land infrastructure, using LNG tankers.

The upper heating value of the fuel is 10.45 - 12.8 kWh/m³ (cubic meter under normal conditions, that is, at 0 °C and 1 atm).[11]​.

Natural gas components (methane, ethane, propane, butane) are important raw materials in the chemical industry. Methane is used for the production of synthesis gas, methanol and ammonia. The first step in the valorization of other alkanes is the conversion into olefin. Oxidative dehydrogenation of ethane leads to ethylene, which can further be converted to ethylene epoxide, ethylene glycol, acetaldehyde[12]​ and other olefins.[13]​ Propane can be converted to propylene,[14]​[15]​ acrylic acid[16]​[17]​ and acrylnitrile.

The CO emitted into the atmosphere after the combustion of natural gas is a greenhouse gas that contributes to global warming of the Earth. This is because it is transparent to visible and ultraviolet light, but absorbs the infrared radiation that the Earth's surface emits into outer space, slowing down its nighttime cooling.

The combustion of natural gas produces fewer greenhouse gases than other fossil fuels such as petroleum derivatives (fuel oil, diesel and gasoline) and especially than coal. It is also a fuel that burns cleaner, more efficiently and safely and does not produce sulfur dioxide (which causes acid rain) or solid particles.

The reason why it produces little CO is that the molecule of its main component, methane, contains four hydrogen atoms for every one carbon atom. Thus, two molecules of water are produced for each one of CO, while long-chain hydrocarbons (e.g. those contained in diesel) produce practically only one molecule of water for each one of CO (in addition, the standard enthalpy of formation of water is very high).

In renewable natural gas, the CO molecule released into the atmosphere in its combustion is equal to the molecule taken from the atmosphere by bacteria to create methane in the putrefaction process.

However, natural gas leaks that occur in wells represent a very significant contribution of greenhouse gases, since methane is equivalent to 23 times the greenhouse effect of carbon dioxide (IPCC data). For example, the March 2012 accident on the Elgin oil platform — operated by the Total oil company in the North Sea — resulted in a leak of about 5.5 million m³ per day.[18] As the density of methane under standard conditions is 0.668 kg/m³[19]​ the leak was 3,674 tons per day, which is equivalent to 84,502 tons of carbon dioxide per day. The duration of the stoppage of said leak was estimated at 6 months, which represents 15 million tons of carbon dioxide equivalent (Estonia's industrial emissions in 2009).