Oil and doomsday

Recently, I provided an estimate of the amount of oil that was formed in the Earth—about 18 trillion barrels.  It's always good to tackle these kinds of problems from different angles, and before using the composition of the atmosphere to do the calculation, I had planned to re-purpose the doomsday argument.  It seems much better suited to this type of problem.  After all, there is a finite amount of oil—or, rather, a finite number of barrels of oil—that we are drawing from.

However, before we are able to apply the doomsday argument, we need to know how many barrels of oil have already been consumed. Using data from Energy Trends Insider, it appears that approximately 1.4 trillion barrels have been produced in modern history.  That being said, reliable verifications of this estimate are hard to find.


Using the doomsday argument, we find that we can be 94% confident that there are at most 16.6 trillion barrels of oil remaining, given that we have already consumed 1.4 trillion barrels.

Peak oil, part II

"It is sunlight in modified form which turns all the windmills and water wheels and the machinery which they drive. It is the energy derived from coal and petroleum (fossil sunlight) which propels our steam and gas engines, our locomotives and automobiles." ― John Harvey Kellogg

In a previous post, I wrote about peak oil—particularly that answering the question of how much oil is left is not easy.  That said, a new approach has occurred to me.  Oil and coal are the remains of ancient plants, formed 300 million years ago in the carboniferous period—C on the horizontal axis of the chart below.  The periods leading up to this saw the proliferation of plants, which removed massive amounts of carbon from the atmosphere.  At its peak, carbon dioxide made up 7000 parts per million (ppm) of the atmosphere, but today makes up only 180 ppm.  This carbon went somewhere, and for the most part it was sequestered in rocks as coal and oil.  A simple calculation puts the weight of this carbon to be 10 trillion tonnes.

How much is oil and how much is coal?  Consider the proven reserves of oil versus coal.  There are 190 billion tonnes of oil reserves, but there are 860 billion tonnes of coal reserves.  Assuming that this reflects their natural abundance, we'll assume that oil and coal are in a ratio of 5 to 1 of sequestered carbon.  This implies that there have been 3.6 trillion tonnes of oil and natural gas—18 trillion barrels—and 11 trillion tonnes of coal.

How long will this last?  As of 2015, 93 million barrels of oil are consumed per day—about 34 billion per year—which has grown by about 1% per year since the 1980s.  If this continues, there are 185 years of oil.  That being said, consumption must eventually stop growing and begin to decline—that is the notion of peak oil.  Instead, oil rations will eventually be put into effect, which could mean that oil will be here for centuries.  As for coal, 7.5 billion tonnes are consumed per year, growing by about 2% per year since the 1980s.  This implies a 170 year supply.  The same caveats apply.  Many things can change in this time, too.  It's still hard to say how long we will burn fossil fuels.

Peak oil

"Life without oil, in fact, would be so different that it is frightening to contemplate. We are addicted, and it is no comfortable addiction. Like other drugs, oil comes with a baggage of greed, crime and filth. Worse, it is smothering the planet."  ― James Buchan

Petroleum is a non-renewable resource. The question we need to ask is just how much is left?  A 2013 OPEC report estimated that there are 1.5 trillion barrels of oil in proven reserves in the world.  At the rate the world consumes oil, this will be gone in only 44 years.  In 2014, BP released a report putting the figure at 1.7 trillion barrels, claiming that this will last 53 years.  New oil is continually being discovered, though—oil companies have an incentive to find these new resources.  How long we can keep discovering new oil, however, isn't clear.

Source data via OPEC.

Understanding this chart is difficult—not what it says, but why it says it.  This requires a more detailed study of the history of oil production and the technologies that have driven discovery.  In the past, intermittent bursts of discovery seem to have been the norm.  This appears to have changed in the 1990s, with a lull that has lasted until the present—I am most interested in finding out why.  However, the size of the earth is finite.  The oil we have already found is low hanging fruit—the remaining oil will be difficult to find.  In addition to slowing rates of discovery, the oil industry will also face increased competition from alternative energy and—one may hope—increased pressure from the public for environmental responsibility.  It is likely that the end of oil will not come from dwindling supplies, but from these other causes.

Computers vs. peak oil

Computers have become entwined in our daily lives.  Imagine, if you can, a day in which you didn't interact with a computer in some form or another.  Media, communication, personal finance, and commerce have become reliant on these technologies for success.  Will personal computers remain so readily available to everyone indefinitely?  It is easy to extrapolate form past experiences.  Computers have become steadily cheaper and more powerful for decades, but there is no real guarantee that this trend will continue.  This has also been confined mostly to Western Europe and the Anglophone nations, with computers remaining widely unavailable in developing nations.

Petroleum is very important in the manufacturing of electronics.  Over 40% of the chemicals used for creating semi-conducting devices rely on petroleum in some aspect of their manufacturing.  It is true that in most of these cases substitutes exist, but we don't rely heavily on these substitutes for a reason—either they are more expensive or cannot meet current demands.  Without cheap petroleum, manufacturing of semi-conductors will also rise in price, which will adversely effect the supply of these machines.

The energy requirements for producing electronics is enormous.  For example, one study found that manufacturing a laptop requires between 3000 and 4000 megajoules of energy—the equivalent of 24 and 32 gallons of gasoline, respectively.  Furthermore, these products often contain plastic components, in an effort to reduce costs.  Plastic can be replaced with metals, such as aluminium—many high-end models already use these materials.  But, this increases the price of products, as metals are harder to shape than plastics and are more expensive, in general.

Personal computers will remain available, even as petroleum supply dwindles; however, it is reasonable to expect that the price of these machines will likely increase.  Businesses will continue to rely on computing to run efficient operations, and the wealthy may have access to personal computers.  However, the poor may have to rely on publicly available machines—such as those at libraries.  This may have the effect of widening the gap between these groups of people, contributing to greater levels of wealth inequality.

Hydrogen fuel cells

How much energy is needed to make each kilogram of gasoline?  This may sound like an unusual question, because we tend to think of gasoline as a source of energy.  When one kilogram of gasoline is burned it releases about 45 megajoules (MJ) of energy in the form of heat, that can then be converted into other forms of useful energy.  However, 9 MJ are needed to produce a kilogram of fuel.  Though this number is non-zero, the important point is that less energy goes into the fuel than is recovered from it.  This feature makes petroleum good as a fuel source, among other properties.

In a previous post, I wrote about the energy requirements of producing hydrogen.  Every kilogram of hydrogen contains roughly three times as much energy as a kilogram of petroleum—about 140 MJ.  Steam methane reformation requires 135 MJ per kilogram of hydrogen; this represents a net gain in energy, but a very small net gain.  Furthermore, it relies on the same non-renewable resources that it is meant to replace.  However, even if we rely on electrolysis to manufacture hydrogen, the fuel cells extract energy by performing the electrolysis reaction in the opposite direction.  That is to say, the energy recovered by fuel cells is the same as the energy used in manufacturing the fuel.  At best, this only allows electricity to be converted to a more portable form.

There are difficulties in making hydrogen portable, as well.  Because gasoline is relatively dense, it can carry a large amount of energy in a compact space.  Hydrogen pressurized to 5,000 psi, would occupy over eight times as much space as the equivalent amount of gasoline, at room temperature.  Instead, hydrogen is typically cooled to about −400 degrees Fahrenheit.  At this temperature, the same hydrogen would occupy a similar amount of space as gasoline, but this temperature would need to be maintained.  Gasoline can sit for years before being used, but hydrogen would likely need to be used shortly after it is brought to temperature.

Crossing an ocean

“There is nothing more enticing, disenchanting, and enslaving than the life at sea.” ― Joseph Conrad

Despite the fact that most people travel by air, the majority of trade still travels by sea— as much as 90% of it.  Most commodities have long shelf-lives to begin with, but cargo ships are also one of the most fuel efficient modes of transportation.  But how much energy is needed to cross the ocean?  This is a simple physics problem.  Most fuel will be used to work against the drag of the water against the ship.  The required energy, in horsepower-hours, is $$E \approx \frac{1}{10,000,000} \times \frac{\Delta x^3}{\Delta t^2} \times \text{WSA},$$
where Δx is the distance in nautical miles, Δt is the travel time in days, and WSA is the wetted surface area of the ship in square feet.

The real usefulness of this equation lies in it's ability to estimate the fuel requirement of these vessels, as one tonne of fuel carries 17,000 horsepower-hours of energy.  In general, the numbers will be enormous, especially over long distances and short travel times.  Pull out a calculator, and see how much energy certain trips might cost—use your imagination or use real shipping routes.

The moral of this story is that as our supply of fossil fuels dwindle and their costs rise, it is highly likely that the age of sail will return.  After all, wind was able to supply all the energy needed during the 19th century to transport goods and will supply our electricity during the 21st century.

Replacing fossil fuels

"The future is already here—it's just not very evenly distributed." ― William Gibson

It is trivial to say that wind and solar will replace fossil fuels, because in many places they already have.  Given that these sources produce less pollution and provide more autonomy in energy production, why haven't we been using them all along?  The simple answer is that fossil fuels are just easier to use.  They store a large amount of energy per pound and can provide energy consistently to the grid.  Most of all, they are easy to transport.

via NREL.

There are approximately 48,000 wind turbines in the U.S., supplying 4% of our electricity.  To supply our full electricity demand would require on the order of 1 million wind turbines. However, building these turbines would require a large amount of steel and copper, and they would need to be replaced every twenty to thirty years.  Wind farms also require more space than conventional power plants, and may not provide power with the same consistency.

via NREL.

Solar energy has experienced fast growth, recently, though it suffers from a similar set of disadvantages as wind.  There are other problems with the availability of the materials needed to make more efficient solar panels—though, we will visit this issue later.  We may have to settle for relatively inefficient silicon-based solar panels.



However, this entire discussion ignores that electricity generation is only 40% of our energy usage.  Almost none of the energy used for transportation is electric.  The question then becomes
"How will we provide transportation without petroleum?"

How is energy made?

"It is important to realize that in physics today, we have no knowledge what energy is.  We do not have a picture that energy comes in little blobs of a definite amount.  It is not that way." ― Richard Feynman, The Feynman Lectures on Physics

It is a myth to say that we produce energy.  It is impossible to create—or destroy—energy.  Instead, we extract it from energy-rich sources, like coal or petroleum.  The problem then becomes how to make it do what we want.  In the 18th century, engineers were able to build machines that could turn chemical energy into motion.  In the 19th century, engineers were able to build machines that could turn motion into electrical energy.  And in the 20th century, engineers were able to build machines that could turn nuclear energy into heat.  However, at this point, most methods of extracting energy are in place.

via LLNL and DOE. (Full size).

Above is one of the best infographics I've seen.  It shows the energy sources and uses for the United States—by far, the largest energy consumer in the world.  Let's begin the controversy.  Fossil fuels are, undoubtedly, a limited resource.  The notion that we will reach—or have reached—a point where we are no longer able to increase the available supply of petroleum is called the peak oil hypothesis.  Looking at this chart, though, we see that over 80% of our total energy needs comes from fossil fuels, and over 95% of energy used for transportation comes from fossil fuels.  Tomorrow, we'll look at what sources may replace fossil fuels in the future.