OCEANS AND FOSSIL FUELS
From the Smithsonian National Museum of Natural History: Ocean
[https://ocean.si.edu/conservation/gulf-oil-spill/what-are-fossil-fuels]
Fossil fuels are compound mixtures made of fossilized plant and animal remnants from millions of years ago. The creation of fossil fuels—either oil, natural gas, or coal—from these fossils is determined by the type of fossil, the amount of heat, and the amount of pressure.
THE BEGINNING
Fuels are sources of energy and fossil fuels are no different. The energy in fossil fuels comes from the sun, which drives photosynthesis to change carbon dioxide and water into the molecular building blocks of ancient plants and animals. Both plants and animals build their bodies using predominantly carbon and hydrogen atoms and it is the stored energy in the fossilized hydrocarbon-type compounds that serve as fuel when burned.
Plants are the main precursor component of coal. The swampy forests of the Carboniferous Period, a time before the dinosaurs roamed the earth, were an excellent environment for the creation of coal. When the plants died they fell into the water, where decomposition was stalled because of a lack of oxygen, allowing the plants to be buried deep in the earth where they could be subjected to intense heat.
Oil and natural gas mainly form from microscopic plankton.
These microscopic animals, algae, and bacteria flourished in the
warm and shallow seas present millions of years ago. When
they died, they sank to the bottom of the sea where they
became covered in sediment. The oxygen-depleted ocean
floor kept bacteria from consuming the remnants of
decayed organisms and instead allowed for them
to be buried deep underground.
DECOMPOSITION
As the fossil material begins to get buried deeper and deeper underground it is subjected to increased heat and pressure. As the heat rises, the fossil molecules begin to break apart. The initial breakdown creates partially changed materials, like peat from plants and kerogen from plankton. These transitional materials can be used as fuel sources too, however, they have less stored energy than fully formed coal, natural gas, or oil.
As the plant material begins to break down it turns into a
fibrous material called peat. Peat is the partially decomposed
plant material that can eventually turn into coal when
subjected to more heat. Also known as turf, peat has
traditionally been harvested around the world for fuel
after it is cut from marshlands like bogs or fens.
The initial decomposition of plankton leads to a waxy
material called kerogen. Kerogen is the partially
decomposed plankton that can eventually turn into oil and
natural gas when subjected to more heat. It is found in the
form of shale rock or “oil shale” along with other minerals.
Throughout history commercial interests have tried to
produce oil from kerogen, however, the labor,
necessary resources, and hazardous waste
byproduct have halted all attempts.
FOSSIL FUELS FORM
After millions of years underground, the compounds that make up plankton and plants turn into fossil fuels. Plankton decomposes into natural gas and oil, while plants become coal. Today, humans extract these resources through coal mining and the drilling of oil and gas wells on land and offshore. They are sought after because they contain stored energy, and when burned, fossil fuels power machinery and provide transportation, as well as the electricity essential to modern-day life. They also contain essential ingredients used within the chemical industry.
Coal is formed from fossilized plants. As the plants get buried deeper and deeper underground they become subjected to intense heat.
Similar to oil, natural gas is formed from buried plankton, but also from coal in late stages of breakdown. The creation of natural gas, however, requires higher temperatures than oil.
Oil is formed from buried plankton. As sediment accumulates on top of the fossilized plankton over the millennia, intense heat flow from the depths of the earth transform the plankton into oil.
THE CHEMICAL BREAKDOWN
Crude oil is a mixture of thousands of different molecules made up of compounds containing mostly hydrogen and carbon. Every crude oil deposit has a unique composition and proportion of these hydrocarbons. Based upon this chemical composition, crude oil can have a range of densities from thick and viscous to light and fluid. It is designated as either sweet or sour depending upon residual amounts of sulfur and can range from a transparent golden yellow to a deep black.
In order to be used within industry and for transportation the crude oil must be separated into its individual hydrocarbon-based fuels and lubricants. With so many molecule types, there isn’t an industry that doesn’t use oil products in some form or another. Oil is used as lubricants, fuel, in plastics, cosmetics, and even medicine. In general, oil’s composition is classified into four different types of molecules.
OIL IN THE ENVIRONMENT
After all this transformation, oil is naturally found in the environment. It typically is deep below the surface of the earth, but can also be found bubbling up or even in the form of tar balls on the beach.
Humans can expose the environment to massive
quantities of oil in events like wellhead leaks, ruptured
pipelines, and oil tanker groundings. These accidental
oil releases can have devastating impacts to the
surrounding environment. No two oil spills are exactly
the same, and the composition of the spilled crude oil
as well as the circumstances of the spill may impact
how the spill is cleaned up by responders.
Oil naturally escapes from the earth in deep ocean
seeps and in areas on land where earthquakes are
prevalent. Nearly half the oil in the ocean comes from
natural oil seeps. Seeps are slow and gradually release
oil which locally provides food to organisms adapted to
using oil components, especially bacteria.
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| Stalagmites of tar rising from the sea floor |
Oil is used to power industry. Cars, planes, and homes
are powered by fuels refined from oil and when the
fuels are burned it releases carbon dioxide, a
greenhouse gas, into the atmosphere. It is this carbon
dioxide that builds in the atmosphere and acts like a
blanket, trapping heat around the earth and warming
the planet. Once burned, carbon dioxide remains in
the atmosphere for hundreds of years.
Oil is used to produce many different substances
beyond just fuels and many of those products can be
found within the home. This includes plastic products,
paint, the asphalt in driveways, and the shingles
covering home roofs.
WHAT CAN WE LEARN FROM OIL SPILLS?
An oil spill can introduce massive amounts of oil into the environment. The Deepwater Horizon oil spill was the largest marine oil spill in U.S. history, dumping over 3.17 million barrels of oil into the Gulf of Mexico. The fire and explosion of the drilling rig cost 11 people their lives.
Researchers took to the sea to learn as much as they could about the impacts the oil had on the surrounding marine environment, as well as the nearby Gulf communities. Since the spill in 2010, the Gulf of Mexico Research Initiative has funded hundreds of scientists and learned a great deal about what happened to the spilled oil and what impact the spill had on natural environments along the northern Gulf of Mexico coastline. Explore some of the findings below.
The degradation of oil largely depends on how easily
microbes can get access to it. The smaller the oil drops the
more oil microbes can degrade. Wind and waves have a
huge part to play in breaking up oil, and so do animals
swimming in the ocean. Jellyfish are able to break up oil
simply by swimming through the slick and small
zooplankton called copepods can reduce an oil drop by
a fourth when they ingest them. Though it’s a significant
help for an oil cleanup, interacting with the oil
likely harms the animals’ health.
Methane-eating microbes called methanotrophs
exploded in the days after the spill. By day 11 the
microbes were consuming the methane 60,000 times
faster than the rate at natural oil seeps, showing that
nature has its own way of cleaning up a spill. Other
kinds of microorganisms degraded additional
hydrocarbons spilled in this tragic incident, though
many hydrocarbons are too complicated to be
degraded by microbes.
Fish hearts are damaged by oil. Studies of mahi mahi
show that both juvenile fish and adult fish lose the
ability to efficiently pump blood throughout their body,
even when exposed to oil for just a day. This suggests
that other creatures like mammals may also be
affected by oil spills, even as adults.
