Science For Everyone - Fossil Fuels

Copyright © Karl Dahlke, 2022

Why are coal, oil, and natural gas called fossil fuels, and why are we so concerned about them?

In an earlier chapter, we described the process of photosynthesis, whereby plants use sunlight to push certain chemical reactions "uphill", so that the products contain more energy than the reactants. The sun provides the energy; in physics there is no such thing as a free lunch. The resulting energy storage substances could be sugars, starch, or protein, which we know as food, or the leaves, stems, and roots of the plants themselves. The other important, yet often overlooked, energy-laden substance is oxygen.

When you burn the wood of a tree, you are releasing years of sunlight in just a few hours. If a few hunter gatherers do it, it's no big deal, nature can keep up, but if millions of people do it, entire forests disappear. This is happening right now, and is of grave concern, since we have no practical way to replace those forests, which took thousands of years to develop. Centuries of sunlight is liberated for short-term gain, while we clear away the plants that could gather more sunlight for the next generation. To make matters worse, the animals that lived in that forest have lost their home, and cannot adapt to the grassland, farmland, or city, that displaced it. This topic is worthy of 2 or 3 chapters, but let's set it to the side for now, as we continue to explore fossil fuels.

Before there were humans, forests would, on occasion, release decades of solar energy in just a few days, when lightning sparked a forest fire. Even then, stumps remained. All the wood was not gone. Furthermore, seeds found a way to hunker underground, and sprout new growth in less than a month. It is not surprising that evolution developed several mechanisms whereby a forest could survive, and recover from, an occasional fire.

Most years passed without such a catastrophe. The trees grew, and dropped leaves and branches onto the forest floor. Old trees died, and fell over, perhaps making a sound - and new ones took their place. Bacteria and insects digested some of this wood, releasing small amounts of solar energy back into the environment, but some of the leaves and branches were buried, as the next layer fell on top of them. Some of the sun's energy was never released, but remained locked up in the plant material in the ground.

The next step is beyond our imagination, since we only live 80 years, but let's try. Consider a span of 100 million years. Forests grow, and die, and grow again, as layers of plant material accumulate on the forest floor. Occasionally, the body of an animal is also entombed. Over geologic time, rocks and dirt and volcanic ash might cover this layer, and press down with a weight of several tons per square centimeter. This squeezes the water out of the organic material, and simplifies the compounds to hydrocarbons, or, in some cases, pure carbon. The hydrocarbons are oil and natural gas, and the carbon is coal. In extreme cases, the pressure is sufficient to turn coal into diamond. Obviously we're not going to burn diamonds, although they are flammable; diamonds are too rare and valuable for the Franklin stove. All the other material acts as fuel, for our benefit. This is called fossil fuel, because it is the fossilized remains of plants and animals across geologic time.

Much of this fuel came from the forests of the carboniferous period, from 358 million to 298 million years ago. Vast swaths of forests covered the land, perhaps due to a favorable climate, and high concentrations of CO2 in the air. Advancing glaciers marked the end of this period however, pressing down on the forest floor. At the same time, mountains rose, as continents collided, and the resulting volcanoes added their ash to the landscape. Over the next 300 million years, the weight of all this material transformed the organic layer into the coal and oil that we know today. Obviously fossil fuels have been created before, and since, but a large percentage was laid down during the carboniferous, thus the name of that period.

The value of this gift is almost unimaginable. Tens of millions of years of sunlight, captured and stored in a convenient form for our benefit. Once we invented the steam engine, there was plenty of coal to power it - and the industrial revolution began. What if humans had evolved much earlier, or intelligence arose in the early dinosaurs, or there was no Carboniferous period at all? Perhaps someone discovered the laws of thermo dynamics some 200 million years ago, and used this information to develop a practical steam engine. It burned wood, and turned water into steam, and drove a piston back and forth, and performed useful work for society. A few trains carried passengers and freight around the country. However, in a few decades, all the nearby forests were gone, and there was no alternative source of fuel. Steam engines fell into disrepair, before these intelligent creatures could develop hydroelectric plants, or solar panels, or windmills, or nuclear reactors. They were just as smart as we are, but they reverted back to a hunter gatherer society, and there is no evidence, 200 million years later, of their brief accomplishments. This might not be a work of fiction; it could have happened that way, and we would never know.

In contrast, we are blessed. We evolved intelligence, and stumbled onto technology, when there was a compact source of energy beneath our feet, ready to power the industrial revolution, and propel us to a higher level of science and engineering. How fortunate is that?

Bear in mind, we are burning 100 million years of captured sunshine in just a few centuries. This is somewhat like burning wood in your fireplace, whence years of sunshine escape in just a few hours. However, fossil fuels take this process to an extreme. Hundreds of millions of years of stored energy, spent in just a few hundred years.

This is a necessary step for the human race. We couldn't develop the high tech industries we enjoy today, or even feed ourselves, without this energy. But it is finite. We must remember, as we heat our homes and drive to work, that oil and coal will run out some day, just as Thomas Edison predicted in 1931. “I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that.” We can argue about when it will happen, but it will happen. We need new sources of energy before that happens, else we will revert back to the bronze age, after a brief yet apocalyptic period of mass starvation, disease, and war. Those are the only two options in front of us.

Let's pretend, for a moment, that global warming does not exist, that it is not a consideration as we develop public policy. We should still invest in new forms of energy, sufficient to power the global economy at today's levels - and we should reach this goal as soon as possible. It needs to be a national and an international priority. We have reached a point, on planet earth, where energy is everything! We can conserve, and find ways to do more with less, but even so, the demand for energy will grow, and the supply must keep pace, or our great great grand children, all 10 million of them, will be subsistence farmers, telling fanciful stories of ancestral technology that couldn't possibly exist, powered by mysterious fuels mined from the ground. Most people don't believe these tall tales, but how else can we explain those strange plastic cups and lids and straws, found all over the earth? Nobody knows how to make that material, and frankly, nobody understands it. And what does "AAAAH, SO TASTY!" mean, anyways? That is our future, unless we can wean ourselves off of fossil fuels in the next 200 years.

It is difficult to overstate the good fortune we experience today, living in the one and only industrial age on planet earth. If humanoids had developed the internal combustion engine, and supersonic aircraft, and the internet, two million years ago, and then crashed, there would be no archiological evidence of that civilization today. All technology, even plastic, succumbs over geologic time. However, we would know that such a civilization existed, because all the coal and oil would be gone. That precious storehouse of captured sunshine would be plundered. Therefore, we currently live in a 300-year window that is unique to the history of life on earth. Fossil fuels are a one-time gift; we need to use them wisely. It is vital that we take the next step, and advance in our technology. A thousand years from now, we will power the globe with renewable energy, or we will be back in the bronze age, never to rise again.