By
Grace Smoot

Natural gas has grown more in the past decade than any other fossil fuel and accounts for approximately 25% of global electricity generation today. It is often referred to as a cleaner-burning fossil fuel than coal and oil. So, we had to ask: What is natural gas really, and how does it contribute to climate change?

Natural gas (NG) energy is created via the combustion of flammable gas. Per kWh produced, NG emits 490 grams of CO₂ on a life-cycle basis. Although it produces lower levels of CO₂ than the other two fossil fuels, coal and oil, it still directly contributes to climate change.

Keep reading to find out all about what natural gas is, its global capacity, its carbon footprint, its environmental benefits and drawbacks, and how it can contribute to climate change.

The Big Picture of Natural Gas

In the short-term, natural gas (NG) is often seen as a transition fuel from fossil fuels to net zero methods. But its long-term role is not as well-defined due to the increasing interest in renewable energy sources.  

How Is Natural Gas Defined

Natural gas (NG) is a flammable gas composed of predominantly methane (CH₄), some hydrocarbon gas liquids (HGLs), and nonhydrocarbon gases (carbon dioxide (CO₂) and water vapor). It occurs in large quantities naturally below the Earth’s surface. 

“Natural Gas: flammable gas, consisting largely of methane and other hydrocarbons, occurring naturally underground (often in association with petroleum) and used as fuel”

Oxford Dictionary

NG is commonly referred to as the world’s cleanest fossil fuel because it produces mostly CO₂, water vapor, and some nitrogen oxides when burned. It is used primarily for heating and generating electricity but can also be used as a raw material (feedstock) in the production of chemicals, fertilizer, and hydrogen, and as lease and plant fuel. 

What Are the Different Types of Natural Gas 

Conventional NG can be divided into two categories, both of which are used as vehicular fuels:

• Compressed natural gas (CNG): Produced by compressing NG to less than 1% of its volume at standard atmospheric pressure. It is used in light-, medium-, and heavy-duty applications and is stored at a pressure of up to 3,600 lbs per square inch. 

• Liquified natural gas (LNG): Produced by purifying NG and cooling it to -260 degrees Fahrenheit (-162 Celsius). This removes the extraneous compounds in the fuel and reduces the volume of the fuel, leaving behind primarily methane and small amounts of other hydrocarbons and making it much easier to transport across long distances. It is used in medium- and heavy-duty vehicles but is not used as widely as CNG because of its high production, storage, and transportation costs.

Another form of NG is renewable natural gas (RNG), also referred to as biomethane. RNG is a pipeline-quality vehicle fuel generated by purifying biogas. Biogas is created via anaerobic digestion of organic materials (i.e. landfill and livestock waste) or thermochemical processes (i.e. gasification). RNG is chemically identical to conventional NG.

What natural gas is	NG is a flammable gas composed of mostly methane (CH4), some hydrocarbon gas liquids (HGLs), and nonhydrocarbon gases (CO2 and water vapor)
What the different types of natural gas are	Conventional NG can be divided into compressed and liquified NG. Renewable NG is another form of NG.
How natural gas works	NG works by combusting NG in a gas-fired power plant to produce steam which turns a turbine and spins a generator to produce electricity.
The global capacity of natural gas	NG is a finite resource, and if we continue to use it at our current rate we can expect to run out of coal in approximately 50 years.
The carbon footprint of natural gas	On a life-cycle basis, NG emits 490 grams of CO2 equivalent per kWh, the third-highest amount out of all of the fuel types, but the lowest out of the three fossil fuels.
The environmental benefits of natural gas	Although NG does not benefit the environment, improving technology and drilling methods plus reducing CH4 leaks could possibly mitigate its environmental impact.
The environmental drawbacks of natural gas	Burning NG adds to the total levels of CO2 and CH4 in our atmosphere, expedites global warming, and causes air pollution, water pollution, and landscape alterations.
Natural gas and climate change	NG contributes to climate change by exacerbating temperature rise, sea-level rise, ice melting, and ocean acidification.

How Does Natural Gas Work

In general, natural gas works by combusting NG in a gas-fired power plant to produce steam which turns a turbine and spins a generator to produce electricity.

How Does Natural Gas Actually Produce Energy

The process of generating NG energy begins with extracting the NG, constructing the gas-fired power plant, and transporting the NG from the wells to the plant.

NG is extracted via drilling or fracking to expose NG reservoirs. Horizontal drilling, hydraulic fracturing, and acidizing are methods utilized to maximize the amount of NG extracted. 

Extracting NG involves seven main steps:

1. Preparing the rig site
2. Drilling
3. Cementing and testing
4. Well completion
5. Fracking
6. Production and fracking fluid recycling
7. Well abandonment and land restoration

NG and oil are extracted from the same well. NG is dissolved in oil, so pure NG contains contaminants that need to be removed before NG can be transported through pipelines. Processing NG is often complex and consists of many steps to remove impurities such as oil, water, HGLs, sulfur, helium, nitrogen, hydrogen sulfide, and CO₂. Each well site is different, and the steps required vary from well to well.

NG processing typically involves four main steps:

1. Oil and condensate removal
2. Water removal
3. Separation of natural gas liquids
4. Sulfur and carbon dioxide removal

After processing, the NG is transported either directly to consumers or to a gas-fired power plant. At a gas-fired power plant, NG is converted into energy via the following process:

• NG is put into the combustion chamber of a boiler, where it is incinerated. 
• The hot gasses and heat energy convert water into steam. 
• The steam is then passed into a turbine where it rotates the blades at a high speed. 
• The blades then turn a generator which generates the electricity. 
• Once the steam passes through the turbine it is condensed back into water and returned to the boiler chamber to be reheated.

NG plants have an average age of 22 years in the US. When a well is done producing NG it is plugged to stop the flow of methane to the surface. However, over 3 million abandoned oil and gas wells are unplugged in the US alone, and these wells leak millions of metric tons of methane into our atmosphere every year. Simply plugging these wells could reduce methane emissions by 99%, which would help mitigate global warming. 

What Is the Global Capacity of Natural Gas

Fossil fuel consumption began with the Industrial Revolution, and consumption has increased exponentially over the past 70 years. The type of fuel we consume has shifted from solely coal, to coal and oil, and lastly to coal, oil, and NG. 

Since 2010, 80% of NG growth has been concentrated within the US, China, and the Middle East. Russia currently has the largest NG reserves in the world, totaling at least 37 trillion cubic meters.

The top 5 NG-consuming countries (billion cubic meters (bcm) per year) in the world are:

1. United States – 826
2. Russia – 474
3. China – 378
4. Iran – 241
5. Canada – 119

Global NG demand declined by 75bcm as a result of the COVID-19 pandemic. However, unlike the other fossil fuels, NG saw a quick recovery as lockdown measures were eased and  seasonal electricity demand and competitive prices increased gas consumption. The recovery was and still is spurred by fast-growing markets in Asia and the Middle East.

The top 10 largest NG producers in the world account for 73% of global NG global production. 

The top 5 NG-producing countries (bcm per year) in the world are:

1. United States – 934
2. Russia – 701
3. Iran – 256
4. China – 209
5. Qatar – 177

Although the exact date at which we will run out of NG is unknown, if we continue to use it at our current rate, we can expect to run out of NG in approximately 50 years. NG is a finite resource, and finding substitute energy sources will be necessary to sustain our global economy in the future. 

What Is the Carbon Footprint of Natural Gas

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the greenhouse gas (GHG) emissions associated with consumption, but also includes other emissions such as CH₄, nitrous oxide, and chlorofluorocarbons.

“Carbon footprint: the amount of greenhouse gases and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home, driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills). 

On a life-cycle basis, NG emits 490 grams of CO₂ equivalent per kWh, the third-highest amount out of all of the fuel types, but the lowest out of the three fossil fuels. 

Have a look at the illustration below to see the average life-cycle CO₂ equivalent emissions of different energy sources and how they compare to natural gas.

When discussing the carbon footprint of natural gas, we must take into account carbon emissions across the energy’s building, operating, and building back phases.

The life-cycle stages of natural gas	Each stage’s carbon footprint
Building of natural gas	CO2 emissions from extracting and processing NG, transportation of NG through pipes and on ships, construction of NG power plants
Operating of natural gas	CO2 emissions from NG combustion, operation of equipment at NG power plants, and leakage of CH4 from in-service wells
Building back of natural gas	CO2 emissions from plugging wells and decommissioning power plantsCH4 seepage from unplugged wells

The world collectively emitted 7.40 billion tons (bt) OF CO₂ from NG in 2020. 

Burning NG emits 117 lbs of CO₂ per million Btu. Although the CO₂ emissions from the combustion of NG are about 50%-60% less than those from coal and oil, the primary component of NG, CH₄, is 34 times stronger at trapping heat than CO₂ over 100 years. This means that a little CH₄ can go a long way when contributing to global warming.

Because NG emits less CO₂ than coal and oil but also emits a potent GHG, it is important to understand what its carbon footprint is and how its carbon emissions affect the global climate change process.

How Environmentally Friendly Is Natural Gas

NG is one of the world’s most abundant fossil fuel sources, but the combustion of NG produces over 7 bt of CO₂ emissions every year, contributing significantly to global climate change.

“Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

NG is often touted as the cleanest fossil fuel because its rate of CO₂ emissions that contribute to global climate change is lower than that of coal and oil. However, NG still possesses environmental drawbacks that must be taken into consideration, along with the benefits.

What Are the Environmental Drawbacks of Natural Gas

The main disadvantage of NG is its contribution to climate change and global warming.

• Atmospheric CO₂: Levels of CO₂ in our atmosphere have increased as a result of human emissions since the beginning of the Industrial Revolution in 1750. Emissions increased steadily to 5 bt per year in the mid-20th century before increasing exponentially to more than 35 bt per year at the end of the 20th century. The global average amount of CO₂ in the atmosphere was about 280 parts per million (ppm) in 1750 but today registers at over 400 ppm. By the end of the 21st century, this number is expected to exceed 900 ppm. Burning fossil fuels adds to this total, which in turn amplifies the greenhouse effect and causes global warming. 

• Global warming: This phenomenon occurs when CO₂ and other air pollutants absorb sunlight and solar radiation in the atmosphere, trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). Between 1880-1980 the global temperature rose by 0.07C every 10 years. This rate has more than doubled since 1981, with a current global annual temperature rise of 0.18C, or 0.32F, every 10 years. Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must limit global warming to 1.5C by 2040. 

NG is a cleaner-burning fossil fuel than both coal and oil, but it still has environmental drawbacks that are important to understand:

• Drilling: This can disturb vegetation and soil and may require clearing and leveling the area around a well pad. Drilling also produces air pollution and may contaminate water sources via erosion, fracking fluids, equipment runoff, and sedimentation. 

• Landscape alterations: Drilling for NG causes surface distribution from drill pads, roads, and pipelines that alter the landscape. Fragmentation of wildlife habitats and migration patterns have also been documented. 

• Water pollution: Land clearing may cause dirt, minerals, and other pollutants to erode into nearby waterways. Drinking water may become contaminated with hazardous chemicals via drilling, fracturing, processing, and refining the gas, and wastewater disposal. 

• Air pollution: When NG is burned at well sites, it releases CO₂, carbon monoxide (CO), sulfur dioxide (SO₂), and nitrogen oxides into the atmosphere. Burning NG instead of releasing it directly into the atmosphere produces lower levels of GHG emissions because CO₂ is not as potent as CH₄, but it still contributes to the overall level of CO₂ in our atmosphere. 

The easiest way to mitigate the environmental impact of NG is to simply not rely on it in the first place. NG drilling can alter the landscape and contaminate water sources. NG combustion adds to atmospheric CO₂ levels, contributes to global warming, releases toxic chemicals and heavy metals, and leaks CH₄.  

What Are Ways to Make Natural Gas Less Environmentally Detrimental 

Although NG is a fossil fuel, there are ways to reduce its environmental impact. And as a plus, its CO₂ emissions are lower than that of coal and oil. 

• Controlling CH₄ leaks: NG is considered the cleanest fossil fuel because it has lower levels of CO₂, CO, nitrogen oxides, and SO₂ than both coal and oil. However, these emissions and CH₄ still contribute directly to global climate change. The best way to mitigate its environmental impact is to detect, fix, and repair CH₄ leaks from well-pads, processing plants, compressor stations, and large distribution facilities. Doing this can reduce CH₄ output by 1.70-1.80 million metric tons per year. Plugging abandoned NG wells also prevents the seepage of methane into the atmosphere. 

• Prioritize renewable natural gas (RNG): RNG is biogas, the product of organic matter decomposition, that has been processed and purified. It can then be used as a transportation fuel in the form of compressed natural gas (CNG) or liquefied natural gas (LNG). Because there is no drilling or fracking, RNG has a lower carbon footprint than NG.

• Recycle water and use efficient production practices: Fracking uses a large amount of water, so recycling water and avoiding utilizing freshwater sources can reduce water requirements. Constructing wells properly and maintaining them after drilling is complete is crucial for efficiency. 

• Implement practices that reduce the risk of induced seismicity: Fracking can cause seismic activity that leads to earthquakes. Avoiding water injection into active fault lines, limiting injection rates, installing seismic monitors, establishing a protocol for when seismic activity is induced, and abandoning wells with seismic activity are all ways to mitigate this threat. 

NG can be more efficient and environmentally friendly if certain protocols and environmental mitigation practices are followed. 

How Does Natural Gas Contribute to Climate Change

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 33 bt of CO₂ are emitted from burning fossil fuels. 21% (7.5bt) of this comes from NG. The carbon found in fossil fuels reacts with oxygen in the air to produce CO₂. This warms the earth by acting as a heating blanket, and a warmer earth comes with a host of negative side effects. Also with natural gas, CH₄ leaks release GHG emissions that are substantially more potent than CO₂.

CO₂ and CH₄ emissions contribute to climate change in the following ways:

• Increasing temperatures: Earth’s atmosphere has warmed 1.5℃ since 1880. This may not seem like a lot, but these degrees create regional and seasonal temperature extremes, reduce sea ice, intensify rainfall and drought severity, and change habitat ranges for plants and animals.

• Rising sea levels: Global sea levels have increased approximately 8-9 inches since 1880, displacing people living along coastlines and destroying coastal habitats. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, and landfills remain at risk if sea level rise goes unchecked. 

• Melting of sea ice: Since 1979 arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 

• Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.

• Ocean acidification: The ocean absorbs 30% of the CO₂ released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

The more we reduce CO₂ emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

To help keep global temperature rise below 1.5C, as outlined in the Paris Agreement, we must shift at least 80% of our electricity generation to low carbon sources. Over 120 countries have already stated their net-zero carbon emissions ambitions for 2050 or 2060. But only 12 countries have thus far proposed or enacted any legislation, indicating that there is more work to be done.

Final Thoughts

NG energy is produced when NG is extracted from deep underground and combusted in gas-fired power plants. The process creates steam which turns a turbine and spins a generator to produce electricity. NG currently makes up a quarter of global electricity generation today, but if we continue to use this finite resource at current rates we can expect to deplete it in approximately 50 years.

NG is often referred to as a cleaner burning fossil fuel than coal and oil. But cleaner doesn’t mean it is totally clean. NG combustion still releases CO₂ into our atmosphere, albeit at lower levels. But the main concern with NG is CH₄ leakage from wells and from NG combustion. CH₄ is a far more potent GHG than CO₂, so a little goes a long way in expediting global warming.

In the short term, NG can be a viable option to transition away from fossil fuels and toward renewable energy. But in the long-term, NG still pollutes our environment and contributes to global warming.

Stay impactful,

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