Natural Gas is the Least Dirty Fossil Fuel But Still Adds to Global Warming
Natural gas is a non-renewable, flammable fuel, used worldwide for mainly heating and the generation of electricity. Colorless, odorless, and non-toxic, its largest constituent is methane (CH4), a very simple hydrocarbon consisting of one carbon atom and four hydrogen atoms. A typical composition of natural gas is: 85 percent methane, 9 percent ethane, 3 percent propane, 1 percent butane, and 1 percent nitrogen.
In addition, it produces less air pollution than other fossil fuels. For example, it produces much lower emissions of sulfur dioxide and nitrous oxide, and less carbon monoxide, and other reactive hydrocarbons. 3 It also releases fewer particles of black carbon and other particulate matter (PM10 or PM2.5). 4 But see: Health Effects of Air Pollution.
However, since demand for natural gas has risen by 33 percent over the past decade (2009-2019), its greenhouse gas emissions haven risen rapidly in absolute terms. What’s more there is a serious risk that its continuing growth is diverting time, money and research from the development of renewable energy, that does not cause global warming. It’s also worth bearing in mind, that, in the United States, leakage rates of methane from the gas industry’s network of refineries, pipelines and other installations are roughly 2.3 percent, per annum. 5
- Natural Gas is the Least Dirty Fossil Fuel But Still Adds to Global Warming
- A Cause of Global Warming
- How Much Of Our Energy Is Natural Gas?
- CO2 Emissions Released From Burning Natural Gas
- A Brief History
- What Are The Main Categories Of Natural Gas?
- What Are The Main Uses?
- Production Statistics
- Which Countries Produce The Most Natural Gas?
- Which Countries Consume The Most?
- How Much Natural Gas Do We Have Left?
A Cause of Global Warming
Natural gas is less dangerous to Planet Earth than coal or oil – that is, unless pipeline seepage rates exceed 3 percent – but even so it remains a major cause of global warming and is not a safe form of energy in the long term. This conclusion is based on three main facts.
(a) About two-thirds of all new gas production globally over the last decade has been shale gas produced in the U.S. and Canada using fracking, a method which causes more methane emissions and is more environmentally damaging than conventional methods. 6 7
(b) All natural gas, fracked or not, is about 90 percent methane, and pound-for-pound methane boosts the greenhouse effect much more than carbon dioxide (CO2). It traps 34 times more heat than CO2 over a 100-year period and 84 times more over 20 years. 8
(c) When burned, natural gas produces nothing more than CO2 and water. But any leakage during drilling, fracking, refining and transportation is almost pure methane. And high rates of methane leakage from gas pipelines and other installations makes natural gas much more harmful to Earth’s climate system than its reputation suggests.
In 2016, the U.S. Environmental Protection Agency reported that methane seepage from natural gas and petroleum infrastructure amounted to a massive 8.1 million tonnes per annum: 6.5 million tonnes from the natural gas system, 1.6 million tonnes from petroleum supply chains. This represents a leakage rate of 1.4 percent. 9
Then, in 2018, a review of emissions studies revealed that the figure of 8.1 million tonnes quoted by the EPA was actually a huge underestimate. The true figure, the review said, was 13 million tonnes – roughly 60 percent more than the EPA figure. This new figure represents a leakage rate of 2.3 percent. 10 See also: Why Are Methane Levels Rising?
The IPCC’s Special Report on Global Warming of 1.5°C (2018) is very clear: in order to avoid the worst effects of climate change, emissions of greenhouse gases must be reduced by 45 percent by 2030, reaching net-zero by 2050. Thus, natural gas is no more than a slightly less harmful stop-gap until sufficient renewable energies come on stream. For more about the ecological dangers of natural gas, petroleum and coal, see: What Are the Environmental Effects of Fossil Fuels?
Why is natural gas called natural gas?
There’s no particular reason for its name, especially since natural gas is always first sent to the refinery or processing plant so it can be purified by separating impurities and removing common contaminants such as water, carbon dioxide (CO2) and hydrogen sulfide (H2S). The end product is known as pipeline quality dry natural gas, which is then piped to residential, commercial and industrial consumers. That said, the prefix ‘natural’ does distinguish it (in America at least) from gasoline (petrol), which is commonly referred to as ‘gas’.
How Much Of Our Energy Is Natural Gas?
As shown in the following tables, natural gas supplies 24.2 percent of the world’s energy but 21 percent of global emissions. This compares favorably with coal, which accounts for 27 percent of global energy but 39 percent of emissions.
Table 1. Global Primary Energy Consumption (2019)
Table 2. Global CO2 Emissions By Source
CO2 Emissions Released From Burning Natural Gas
When natural gas is burned it emits carbon dioxide, thus contributing to global warming and its impact on ecosystems around the world. But how do these emissions compare with those from coal and petroleum? The following charts show that natural gas emissions of CO2 are the lowest of all fossil fuels, but can’t be compared with the tiny emissions of renewable energies.
Table 3. CO2 Emissions From Different Fossil Fuels
Natural gas consists mostly of methane (CH4). This has a higher energy content relative to other fuels. Therefore, natural gas has a lower CO2-to-energy content. Also, some fuels contain higher amounts of sulfur and other compounds that reduce their heating values and thus raise their CO2-to-heat emissions.
Table 4. CO2 Emissions From Electricity Generation
Table 5. Life Cycle Emissions From Electricity Power Sources
A Brief History
Like all fossil fuels natural gas comes from the partially decayed remnants of organic material, such as plants, trees and marine plankton. Combined with sand and silt, this organic sediment built up in thick layers – either on land or on the sea bed – and, over millions or hundreds of millions of years, was chemically transformed by enormous heat and pressure into coal, oil or natural gas.
Humans first discovered natural gas in ancient China, sometime between 1000 and 500 BC, but at any rate well before the start of the Han Dynasty in 206 BC, by which time Sichuan engineers were drilling down hundreds of feet to obtain gas and brine. 16
Much later, in the early 17th century, Canadian Indians were igniting methane seeping from vegetation around Lake Erie, and about 1785 the British began using natural gas produced from coal to light houses and streets, a practice which spread quickly across the Atlantic to America, where Baltimore became the first city in the United States to illuminate its streets with gas. Two decades later, in 1836, Philadelphia created the first municipally owned natural gas distribution company.
For most of the 19th century, it was used primarily as a source of light. Without a system of pipelines to transport the gas, it was difficult to connect it to homes to be used for cooking or heating. Most of the gas produced was made from coal, rather than from a well head. Then towards the end of the 19th century, lighting became electric and gas producers were forced to find new customers.
Fortunately, in 1885, Robert Bunsen invented the Bunsen burner. This device mixed natural gas with air in the right proportions, creating a flame that was safe to use in cooking and heating. The efficiency was further improved by the introduction of temperature-regulating thermostatic devices.
Pipeline technology continued to lag, which meant that no more real progress was made until after World War II, when new pipeline technologies led to a post-war pipeline construction boom which continued into the 1960s, and led to the construction of thousands of miles of pipeline across the United States and Europe. This enabled gas to be connected to homes for a variety of domestic uses. At the same time, industry began to use natural gas in manufacturing and processing plants. Since 2000, with its inflated reputation as a cleaner greenhouse gas, compared to coal and oil, the popularity of natural gas has never been higher.
What Does Natural Gas Contain?
Natural gas is 70-90 percent methane. It may also contain up to 20 percent of four other naturally occurring gases, mainly ethane (C2H6), and possibly propane (C3H8), butane (C4H10), as well as pentane (C5H12), carbon dioxide (CO2) and nitrogen. Some gas has very small amounts of hydrogen, carbon monoxide, argon or even helium. A typical composition of natural gas is: 85 percent methane, 9 percent ethane, 3 percent propane, 1 percent butane, and 1 percent nitrogen. However, bear in mind that nearly everything except methane is removed during the refining process, so the gas delivered to consumers is almost pure methane. (Note: The characteristic smell we associate with natural gas is due to the deliberate addition of methanethiol to make gas leaks detectable.)
What Are The Main Categories Of Natural Gas?
Natural gas is traditionally considered to be either conventional or unconventional, according to where it’s found. Conventional natural gas is located deep underground (or under the ocean floor) in large cracks and spaces between layers of rock. Or it’s mixed in with oil reservoirs or coal deposits (coalbed methane). Conventional natural gas can be recovered using regular drilling methods. 17
By contrast, unconventional gas is found in more difficult locations – such as tiny spaces within formations of shale rock, sandstone, or other types of sedimentary rock – and cannot be extracted using regular drilling procedures. Instead, special techniques are needed, the most popular of which is “fracking” (short for hydraulic fracturing).
Natural gas can be cooled for more efficient storage and transportation. The resulting liquefied natural gas (LNG) – mostly methane (CH4), with some mixture of ethane (C2H6) – occupies about 1/600th the volume of normal natural gas. The process of liquefaction also involves removal of any heavy hydrocarbons, as well as other constituents like helium, water and dust. The gas is then condensed into a liquid by cooling it to approximately minus 162°C (minus 260 °F). LNG is much cleaner than any other fossil fuels and can even be used as a replacement for gasoline. New technologies have made LNG a global alternative to other fuels.
Over the last decade or so, the technique of fracking has revitalized the gas industry. In the United States, for example, fracking (and tar sands extraction) have helped to transform the country into the world’s leading producer of both natural gas and oil. 18
How Does Fracking Work?
- A vertical hole (well bore) is drilled to depth of about 2500m (about 8,000 feet), or the approximate level of the gas-rich shale rock formation. This can take a month or more. The drill then turns 90 degrees and continues drilling horizontally into the shale formation for about 1.5 km (about 4,900 feet). The well is lined with a steel casing to prevent the contamination of local groundwater. Horizontal drilling technology reduces drilling costs substantially, since several different horizontal wells can be drilled off one vertical well, like the spokes of a wheel, thus maximising the amount of gas that can be recovered.
- A special instrument is then used to create a series of small holes in the casing of the well. At the same time, the fracking fluid is prepared. This contains 99 percent water and sand. Each fracking well uses about 2-7 million gallons of water during its lifetime – roughly 200 to 1,200 giant truck-loads. (Bad news for dry areas. Hence five out of eight Australian states/ territories have banned fracking.) The other 1 percent consists of a mixture of chemical additives. These may include: friction-reducing additives to lubricate the well with a slippery form of water known as slickwater; acids, to dissolve minerals and other debris; and disinfectants to kill bacteria. Fracking firms have used about 2,500 different fracking chemicals so far, of which at least 650 have been identified as toxic.
- The fracking fluid is then pumped down the well at such a high pressure that it cracks the shale rock, creating fractures through which the trapped gas can escape. Proppants like sand or other ceramic materials are mixed with the fluid to prop open fissures when the pressure is released, so the gas can keep leaking out.
- The trapped gas escapes up the well to the surface, along with millions of gallons of used fracking liquid which now contains a variety of contaminants, including radioactive material, heavy metals, salts, and hydrocarbons. The fluid is stored or disposed of on-site in pits or in underground “injection wells”, or off-site at water treatment facilities. The gas is stored in on-site storage tanks before being piped to the refinery. A typical fracked gas well can pump out thousands of cubic feet of gas each day, for 20-40 years.
What Are The Main Uses?
- Natural gas is used primarily in the northern hemisphere, with the United States, Canada, Europe, China and Japan being the largest consumers.
- In the United States, 35 percent of natural gas is used to generate electricity; 29 percent is used for heating/cooking (58 percent residential, 42 percent commercial); 33% is used by industry; and roughly 3 percent for transportation (mostly accounted for by installation and pipeline leakage). 19
- It is used by industry in the manufacture of inorganic chemicals including ammonia (15 percent) and organic chemicals (12 percent), while ethane and propane can be processed into ethylene and propylene for use in the manufacture of plastics.
- In the United States, industrial use of natural gas is concentrated in a relatively small number of sectors, namely: the petroleum refining, chemicals, plastics, pulp and paper, metals, stone, glass melting, and food processing industries. In addition, gases such as butane, ethane, and propane may be separated from natural gas to be processed and used as feedstock for fertilizers and pharmaceutical products. These areas account for more than 80 percent of all industrial use.
- In addition to these applications, there are a number of innovative uses being developed. Natural gas desiccant systems, used for dehumidification, are becoming popular in the pharmaceutical, plastics, chocolate, and even recycling industries.
- Natural gas absorption systems are also in widespread use across several sectors to heat and cool water in an efficient, economical, and environmentally conscious way.
- Natural gas co-firing technology is another development which is helping to increase industrial energy efficiency, and reduce greenhouse gas emissions. Co-firing is the use of gas in the combustion of other fuels, like coal, wood, and biomass. For example, wood burning inside a traditional industrial wood boiler, results in the discharge of a high level of harmful emissions. But when natural gas is added to the combustion mix, emissions are significantly reduced.
Global consumption of natural gas has grown at an average of 6.3 percent per year, since 1990.
In 2019, gas production increased at a steady pace for the third year in a row (+4%), spurred mainly by the USA and Russia. American domestic gas production rose by more than 10 percent, triggered by new developments in shale formations in Pennsylvania and Texas. Gas production rose steadily in Russia (+3.4%) and significantly in Australia (+18%), pushed by the development of LNG projects. Total global production in 2019 was 3,989 billion cubic meters. 20
What Are the Best Alternatives to Fossil Fuels?
The best alternatives to fossil fuels like natural gas, are renewable energies such as: hydropower (hydroelectricity), wind power, natural biomass and biofuels, solar power, and geothermal energy. Ocean energies like wave power and tidal power are still in the early stages of development. Nuclear fusion remains somewhat futuristic.
Which Countries Produce The Most Natural Gas?
Table 6. Top 10 Producers Of Natural Gas (2019)
|Country||Billion Cubic Meters|
Which Countries Consume The Most?
Over the past decade global consumption has climbed 33 percent. 21
In 2019 global gas consumption continued to rise (+2.6%), though at a slower rate than in 2018 (record year with +5.1%). In the USA, the largest gas consumer, it grew by 3.1 percent , thanks to lower prices and new gas-fired capacity in the power sector. In Asia – it continued to decline in Japan and South Korea, mainly due to lower electricity consumption and increased competition from nuclear reactors and renewables.
Table 7. Top 10 Consumers Of Natural Gas (2019)
|Country||Billion Cubic Meters|
How Much Natural Gas Do We Have Left?
According to BP’s Statistical Review of World Energy (2020), there are 198.8 trillion cubic meters (7019 cu ft) of natural gas reserves in the world. This is sufficient to satisfy almost 49 years of global production at 2019 levels. The largest reserves are held by Russia, Iran and Qatar.
Table 8. Countries With The Largest Proven Reserves Of Natural Gas (2019)
|Country||Trillion Cubic Meters|
|United Arab Emirates||5.9|
Climate science is very clear – there’s no such thing as a clean fossil fuel. So while natural gas may be cleaner than coal or petroleum – and this is no longer a given, since the discovery of how much methane was leaking from pipelines – it’s no solution to our climate crisis and that’s a fact. That said, it can act as a temporary stop-gap, to help us transition to a carbon-free energy system. See also: Is Nuclear Energy a Replacement for fossil Fuels?
Does the gas industry support the climate change denial movement? I’ve no idea, but the US Republican Party got 88 percent of the industry’s political contributions. (Source: New York Times. Dec. 12, 2019.)
Why are governments and fossil fuel companies dragging their feet over climate action? For the answer, see: Root Cause of Climate Change.
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