Have you ever considered what will become of our remains in the distant future when we are long dead? We don’t mean in a few decades, or even a few hundred years, we mean eons into the future when the human race may have gone the way of the dinosaurs. Is it possible some of us may experience the transformative processes that have turned long-dead organisms into the substances we use to fuel our world today? In short, could humans ever become fossil fuels?
Hypothetical qualification
This is a tricky question, but it seems the answer is one of sheer improbability rather than impossibility. Essentially, it is theoretically possible that human bodies could become something like the substances we recognize as fossil fuels, but it would require several extremely unlikely conditions to occur in order to produce this type of transformation. Even then, if a body did somehow achieve this outcome, it wouldn’t leave much behind.
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However, no fun was ever had in stopping our speculation about such limitations. So, let’s assume this is going to happen – what type of things would need to occur to complete this alchemy of the human body?
To imagine how our remains could possibly become fossil fuels, and to appreciate why it is so unlikely to actually happen, we need to understand what these substances are and how they were formed in the first place.
Fossil fuels are not dinosaurs
The most important point to make is that fossil fuels are not dinosaurs, as is commonly believed. It is not entirely clear where this misconception comes from, but it likely has something to do with our modern idea that fossils, more often than not, refer to dinosaurs specifically. This was not always the case.
Until the mid-18th century, the word “fossil” actually referred to something that was “dug up” or the process of digging something up, rather than referring to a long-dead organism. The meaning we understand today was therefore a later development, and it was not until the mid-19th century that we started to see the term “fossil fuel” being used in its broader sense.
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Rather than being dinosaurs, most of the organisms that became fossil fuels were far smaller in size and, in some cases (though not exclusively), died long before the “terrible lizards” started roaming the planet. As such, you are not pouring liquid dinosaur into your cars when you refuel, at least not in large amounts.
Despite the name, fossil fuels are not even fossils. They are carbon compounds that were created by decomposition or the breakdown of dead organisms that were not as complex as dinosaurs (or humans for that matter).
Instead, fossils tend to be either impressions left behind by an animal or the remains of their hard parts that resist decay – skeletons, bones, or shells. If these bits are buried quickly, then some of the surrounding tissue – soft parts – could be preserved but even then, they may simply petrify (become a stony substance). Equally, bones, shells, and tissues can mineralize (become solid minerals) over time that do not contain carbon. As such, they would make terrible fuels if burnt.
So, what are fossil fuels made from?
Fossil fuels – coal, petroleum (oil), and natural gas – are mostly formed from prehistoric plants and small animals that existed tens of millions of years ago. For instance, coal holds the energy that was once contained by plants living in swampy forests. When they died, their remains sunk to the bottom of the water where they experienced partial decay in an oxygen-deficient environment. This turned them into peat.
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Over time, the wetlands dried out and other materials covered the peat. The pressure and heat caused by burial beneath these materials turned the plant material into what we call coal. Most of the coal we use today started out on this long process around 350-300 million years ago during the Carboniferous period (literally meaning “coal-bearing” period).
Petroleum (literally Latin for “rock oil”) mostly comes from a similar process that started in the prehistoric oceans. Here, ancient plankton sank to the ocean floor after they died. Their tiny bodies were then covered with more debris as they drifted down from the surface and mixed with sand, silt, and rock.
As with coal, the accompanying heat and pressure from these layers transformed the remains into what we would recognize as petroleum or crude oil. It should be noted that this process is not necessarily unique to marine microorganisms, however, as petroleum can also be recovered from prehistoric lakes where algae underwent the same process.
Petroleum comprises various hydrocarbon compounds and exists in liquid form. Generally speaking, the liquid pools deep underground in sedimentary rocks, but can also sometimes occur in hard rocks, such as fractured granite. It can also appear closer to the surface where it bubbles up as tar or bitumen.
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Depending on its composition, petroleum’s color can vary quite a bit – if it contains few metals or sulfur, it can be lighter. In some cases, it can almost be clear.
What about gas?
In addition to petroleum and coal, there is also natural gas. This fuel is mostly made of methane, though it can also contain small proportions of ethane, propane, butane, and pentane (which will likely evoke memories of GCSE exams for many readers), which have been produced by long-dead marine microorganisms (some ancient terrestrial plants also produced natural gas when they decomposed).
Under the same conditions that produced petroleum, the gas appears as the organisms undergo transformations from the heat and pressure they experience as they are buried in oxygen-free environments. Methane is the lightest and simplest hydrocarbon. It is colorless and odorless in its natural state but is also highly flammable.
Once the gas has formed, it will try to rise to the surface, but its progress depends on the nature of the rock surrounding it. If the rock is porous and permeable (having large numbers of interconnected spaces), the gas can more easily escape.
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Most of the gas deposits exploited today come from deposits in porous rock buried below impermeable rock. This type of gas is sometimes referred to as conventional natural gas. However, sometimes the gas is stuck in the tiny pores within some shale, sandstone, or other sedimentary rock formations. This gas is referred to as “shale gas” or “tight gas”, or sometimes unconventional gas. In other cases, the gas is located with crude oil deposits, which are then called associated natural gas.
Humans: The fossil fuels of tomorrow?
Fossil fuels are the stuff of hundreds of millions of years of specific and complex processes that all came together to create the hydrocarbons we use today. The fact that they primarily come from plants and microorganisms means that it is extremely unlikely that humans could ever experience the same transformational processes that created them. That is not to say it is not possible, but it very much remains the type of idea that is better suited to science fiction rather than scientific probability.
More likely, though this too would be extremely rare, our soft fleshy bits would decompose away, which could give our bones, which consist of minerals and largely lack carbon or hydrogen, a chance to mineralize into fossils if conditions were perfect. But as mentioned above, they would not be good fuel.
Generally speaking, some of the organic molecules in our bodies could undergo the process, but they would be so miniscule in quantity that they would never be useful – probably not even sufficient to power a toy car, let alone a road-worthy one.
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But ultimately this is a moot point. If we could become fossil fuels, would we want yet another source of pollution to damage the environment?
Even if we are not likely to ever transform into the substances that make up fossil fuels, our legacy as a species will undoubtedly leave other marks on Earth’s geological history that are unique to us.
All “explainer” articles are confirmed byfact checkersto be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.
