For several centuries now, Fossil fuels have been the primarily source of energy to the human-world
80% of global energy supply comes from Fossil Sources, even today. Despite its finite nature, we have learnt to extract and harness power from fossils to sustain essentially all our energy supply, industries, transportation, built environment, agriculture among others – touching various aspects of our ‘modern’ world.
[ Oil has the highest energy density, followed by natural gas, while coal has the lowest energy density among the three fossil fuels]
But this has not come free!!
Burning of fossil fuels produces large quantities of carbon dioxide - a greenhouse gas that traps solar heat within our atmosphere, leading to global warming and hence climate change.
We have burnt so much Fossil fuels, over the years that it has come to become the largest contributor to global warming. So much so that Climate Action in many ways today, is all about re-inventing our world systems without fossils!
A fossil fuel are hydrocarbons that act as a type of energy source.
The primary variants are coal, oil (petroleum), and natural gas.
When burnt they release large quantities of energy that can be put to use in our modern world – making them extremely valuable.
Fossil fuels are formed from the remains of ancient plants and animals, subjected to heat and pressure over millions of years within the Earth's crust. This biological process is called anaerobic decomposition, where microorganisms break down organic materials (such as plants and marine organisms) in the absence of oxygen.
Among various aspects, fossil fuels vary in their formation process, chemical composition, physical state and energy density.
Fossil Fuels extraction is a complex industrious process involving extensive drilling, mining, and fracking, depending on the fossil type. It requires significant manpower, advanced technology, and substantial financial investment.
Coal is extracted primarily through mining (either surface or underground), while oil is extracted from wells drilled into the earth, either on land or offshore. Natural Gas extraction tends to be similarly to that of oil, as they are often found in pockets above oil deposits or in separate gas fields.
Formation Process: Formed from ancient plant materials in peat bogs, subjected to heat and pressure over millions of years.
Chemical Composition: A complex mixture of long-chain hydrocarbons and other elements, predominantly carbon.
Physical State: Solid form, primarily composed of carbon.
Energy Density: Varies between 15-19 MJ/kg depending on the type of coal
Coal classification is usually based on their formation process, carbon content, and energy efficiency - which in turn dictate their uses and applications.
Primarily there are 4 types of coal.
• Peat, the initial coal stage, is partially decayed plant material with high moisture, used in some regions for heating and soil conditioning.
• Lignite, or brown coal, forms from compressed peat with 25-35% carbon, and is primarily used in electricity generation.
• Bituminous coal, with 45-86% carbon, is denser and used in power generation, steelmaking, and coke production.
• Anthracite, the highest rank of coal, has 86-97% carbon, low moisture, and is used for residential heating and industrial applications.
Coal is primarily used in industrial processes as a source of energy.
In fact in 2021, 83% of all energy produced from coal was consumed by Industries.
Coal is also used for the production of more than one-third of the global electricity generation
Formation Process: Derived mainly from ancient marine organisms (like algae) that are buried under sediments and transformed into hydrocarbons under heat and pressure.
Chemical Composition: Composed of shorter hydrocarbon chains that can be refined into various products like gasoline, diesel, and kerosene.
Physical State: Liquid form, mainly a mixture of hydrocarbons.
Energy Density: Varies between 42-45 GJ/metric tonne, depending on the type of oil/oil product
Oil classification is usually based on their physical properties and chemical composition - which in turn dictate their uses and applications.
It can be classified in different ways, primarily based on Crude Oil & Refined Petroleum Products Types.
Crude Oil varieties include,
• Light crude oil is low density, easy to refine, and yields more gasoline and diesel.
• Heavy crude oil has higher density, is more viscous, and is often used for asphalt and other heavy products.
• Sweet crude oil has low sulfur content, is less corrosive and easier to refine – making it more valuable.
• Sour crude oil has high sulfur, requiring extra processing to remove it. – making it cheaper than sweer variant.
Refined Petroleum varieties include,
• Gasoline, a light, volatile oil refined from crude oil, primarily used as fuels vehicles.
• Diesel, heavier than gasoline, with higher energy density, primarily used in powers diesel engines.
• Kerosene, distilled from crude oil, is light and primarily used for heating and jet fuel, as a solvent
• Lubricating oils, heavier and refined for specific viscosity, primarily used to reduce friction in engines and machinery.
Other classifications include Very Light, Medium and Heavy Oils.
Oil is predominantly used in the transportation sector (fuels for vehicles).
In fact, in 2021, 62% of all energy produced from oil was consumed by the transport sector.
It also find use in the building sector and industry, among others.
Formation Process: Can form alongside oil from the same organic materials or through the decomposition of organic matter in landfills and waste treatment processes.
Chemical Composition: Mostly methane, which is a simple hydrocarbon, making it cleaner burning than coal or oil.
Physical State: Gaseous form, primarily composed of methane with some ethane and other light hydrocarbons.
Energy Density: About 38.3 MJ/m3, primarily methane
There are several types of natural gas found, classified based on their composition and extraction methods (with some requiring more advanced techniques to access and process).
Conventional Natural Gas
• Trapped in permeable materials beneath impermeable rock
• Considered economical and easily accessible to extract
Unconventional Natural Gas
• Found in other geological settings, not always easy or practical to extract
• Includes types like deep natural gas, shale gas, tight gas, and coal-bed methane
Associated Gas
• Natural gas found dissolved in oil reservoirs at high pressures
• Often considered the gaseous phase of crude oil, may contain light liquids like propane and butane
Non-Associated Gas
• Natural gas reservoirs that contain no crude oil
• Comes from reservoirs not connected to any known liquid petroleum source
Conventional and associated gases are generally the most economically viable to extract with current technologies.
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Other types of Natural Gas include,
Wet Gas & Dry Gas
• Wet gas contains higher amounts of heavier hydrocarbons like propane and butane
• Dry gas is mostly methane with few other hydrocarbons
Biogas
• Produced from the anaerobic decomposition of organic matter like animal waste, sewage, or industrial byproducts
• Contains less methane than conventional natural gas but can be refined for use as an energy source
Natural Gas use case are more equally spread out.
It is primarily used in the build environment for heating, electricity generation, and as a cleaner alternative (compared to coal and oil) for powering vehicles and industrial processes.
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