No Time For Complacency: The Immense Task Of Decarbonization

“With infinite complacency, men went to and fro about the globe, confident of our empire over this world.”

So begins the book “War of the Worlds” by H.G. Wells.  The menace in his story, of course, was hostile aliens.  The menace today is a climate that is becoming too hot and too unstable to support our global civilization.  The characters in Well’s story may be forgiven for not anticipating the sneak attack of the Martians, but we deserve no such clemency because the signs of the growing danger of manmade climate change have long been evident for all to see.

One of the morals of Wells’ story is that technology is no cause for complacency.  As our day-to-day lives have become less connected to the natural world, we imagine that we are its master.  For example, at an ExxonMobile shareholders’ meeting in 2015, Rex Tillerson, then the company’s CEO, rebuffed requests by concerned shareholders who wanted to see the company begin to shift away from fossil fuels and invest in renewable energy.  His comment was “I choose not to lose money on purpose.”

One argument Mr. Tillerson gave for this solipsistic remark was that he was confident that we would “engineer our way out of whatever crisis might arise as a result of climate change.”  Was he right?  Let’s consider the facts.

The planet is now out of thermal equilibrium because human activity has put an additional 1.6 trillion tons of carbon dioxide into the atmosphere, and in the next thirty years will add another 1.2 trillion tons for a grand total of almost 3 trillion tons by 2050.  It’s enough to push the concentration of carbon dioxide in the atmosphere up from 280 parts per million (ppm) to 500 ppm which will, in turn push the global temperature up by 2.4 degrees Celsius (4.3 degrees Fahrenheit) over the preindustrial average.  This will produce catastrophic climate changes.  (For information about how these numbers were derived, see the article “Dance Until the Music Stops”.)

In order to avoid a climate catastrophe, we must do two things.

1. Stop burning of fossil fuels and replace them with clean sources of energy – nuclear and renewables. (There is a debate over whether nuclear energy should be part of the solution, but that is the subject of another discussion.)
2. Reduce the concentration of carbon dioxide in the atmosphere to 350 ppm, the highest level that many scientists today say that we can tolerate without heating the planet to an unacceptable level.

Replacing Fossil Fuels

First, let’s consider the elimination of fossil fuels.  This is a fairly straightforward math problem. We determine how much energy is being produced by fossil fuels and then calculate how many nuclear and/or renewable power plants would be required to produce this amount of energy.

Here is the US Environmental Information Administration (EIA) energy consumption forecast for 2050:

The EIA energy data is provided in quadrillions of Btus (QBtus).  It has been converted to Terawatt-hours (TWhrs) because it is a measure of electrical energy, and since electrical energy is the only type of energy that nuclear and renewables produce, in order to do the required calculations, all energy terms must be expressed in TWhrs.

The first step is to strip out the energy already being produced by nuclear and renewable sources.  That leaves us with 621 TWhrs.

The next step is to reduce the energy consumption by the amount of energy wasted in producing electricity.  The EIA forecast estimates that the energy wasted in 2050 will be 279 QBtus.  This leaves us with 342 QBtus.

And finally, we need to account for the fact that all vehicles will be powered by electricity.  An electric car motor is 3 ¾ times more efficient than an internal combustion engine.  The EIA forecasts that transportation demands in 2050 will require 164 QBtus.  When the global fleet is converted to electricity, this demand drops to 44 QBtus – a savings of 120 QBtus.  This leaves us with 222 QBtus, which converts to 65,000 TWhrs.

Next, we need to determine the power generation capacity of wind, solar, and nuclear plants.

• A typical commercial wind turbine today is rated at 2 MWs (MW = megawatts = one million watts), operates at an average efficiency of 40%, and can produce 3.5 GWhrs of electricity per year. (GWhrs = gigawatt-hours = a billion watt-hours.)
• A typical one-acre solar farm is rated at 2 MWs, operates at 20% efficiency, and produces 1.75 GWhrs of electricity per year.
• A typical nuclear power plant is rated at 1 GW (one billion watts), operates at 90% efficiency, and produces 8 TWhrs (trillions of watt-hours) of electricity per year.

Now we can calculate the number of installations required to replace fossil fuels, but before doing that, let’s put the situation into perspective by looking at the following graph based on EIA data.

In this business-as-usual scenario, by 2050, nuclear will fill 1% less of the global energy demand, renewables will fill 11% more of the global energy demand, and fossil fuels, at 68%, will still be meeting the lion’s share of energy demand.

At this rate, even if energy demand did not increase after 2050, it could take to the end of the century to eliminate fossil fuels.  The IPCC has said that, unless we eliminate fossil fuels by 2050, climate change will be out of our hands and climate conditions will continue to worsen for the foreseeable future.  Some scientists believe that even this deadline is to loose and that more drastic action is required.

Now let’s calculate the number of nuclear, solar, and/or wind installations we will need (in addition to the ones that this scenario assumes will be built by 2050) in order to produce the 65,000 TWhrs of energy we will need to replace all fossil fuels by 2050.  To recap, here are the annual production capacities of each type of installation described earlier:

Wind:  3.5 GWhrs

Solar:  1.75 GWhrs

Nuclear: 8 TWhrs

To obtain the number of each type of facility required, we divide 150,000 TWhrs by the annual production capacity of each, as follows:

• Wind: 65,000 TWhrs/3.5 GWhrs =   18,571,000   2-MW wind turbines
• Solar: 65,000 TWhrs/1.75 GWhrs = 37,142,000   2-MW solar farms
• Nuclear: 65,000 TWhrs/8 TWhrs = 9,750   1-GW nuclear power plants

The result of each calculation shows us the number of each type of facility required if all energy requirements were to be met through that individual source alone, but a combination is obviously going to be the case.  So, for example, total energy demand could be met through a combination of 18 million solar farms and 9 million wind turbines.  But we need not and cannot be specific about the number of each type of facility that will be required.  The point is that, whatever the combination, the magnitude of the task is epic in its proportions.  It would be an engineering feat on a scale far beyond anything mankind has done before.

As staggering as these numbers are, they only represent the requirement to meet projected global energy demand in 2050.  If demand continues to increase past 2050, these numbers will increase.  Doubtless as technology improves the number of facilities required will go down, but the starting numbers are so enormous that even a 25% reduction would still leave a challenge of unprecedented proportions.

And since renewables are not dispatchable (on-call), we also need to consider energy storage.  (Nuclear power, like fossil-fuel electrical generation, is dispatchable – one of its significant advantages over renewables.) As of 2018, the largest battery storage power station in the world was the Hornsdale Power Reserve which provides 70 MW with a 10-minute capacity and 30 MW with a 3-hour capacity.  The plant is designed to kick in when the wind slackens or when demand exceeds capacity.  These are not expected to be protracted periods of time.

Solar installations, on the other hand, will produce no electricity at all at night, so all nighttime energy demand from solar plants will need to be provided by batteries or some other form of stored energy.  The technological breakthroughs and infrastructure demands required to build the energy storage capability that renewables will require will be on a par with that required to build the renewable plants themselves.

Removing Carbon Dioxide from the Atmosphere

Now let’s consider what it will take to remove the carbon dioxide that has already been emitted into the atmosphere.  We’ll make the following assumptions:

1. By 2050, atmospheric carbon dioxide concentration will reach 500 ppm and
2. There will be no further carbon dioxide emissions after 2050.

By 2050, human activity will have produced 2,867 billion tons of carbon dioxide emissions and the atmospheric concentration of carbon dioxide will have increased from 280 ppm to 500 ppm.  The ppm difference is 220.  The difference between 280 ppm and 350 ppm (our target) is 70 ppm.  Seventy ppm is 32% of 220 ppm.  This means that we will need to remove 68% (1 – .32) of the total carbon dioxide emissions from the atmosphere to get back to 350 ppm.  This amounts to 1,950 billion tons.

The process of removing carbon dioxide from the atmosphere is called Carbon Capture and Storage (CCS).  What will it take to remove 1,950 billion tons of carbon dioxide from the atmosphere?  Nature has an exquisite carbon capture process called photosynthesis.  Plants and phytoplankton (microscopic algae – in the oceans) absorb carbon dioxide and combine it with water to make glucose which provides energy.  The destruction of forests and other land habitats, and the acidification of the oceans not only  reduce the ability of the biosphere to extract carbon dioxide from the atmosphere, but the decay of the dead plants returns the carbon dioxide they captured back into the atmosphere.

By restoring our damaged land and ocean ecosystems, nature can absorb more carbon dioxide.  The amount of carbon dioxide it can absorb, however, is not enough to remove the excess manmade carbon dioxide, which is why we find ourselves in this position in the first place.  Restored and revitalized ecosystems will reduce the amount of carbon dioxide being produced by the degradation of the land by human activity, but it will not restore the energy equilibrium of the planet.  But the survival of the human race, not to mention all the other species on the planet, depends as much on stable, healthy, life supporting ecosystems as it does on maintaining a global temperature at which life can survive, and so this is something that we must do anyway.  Humans put the extra carbon dioxide into the atmosphere, and only humans can remove it.

CCS is not a new technology.  The oil industry has used it since the 1950’s.  Virtually all CCS today starts in the smokestacks of fossil fuel power plants where carbon dioxide is scrubbed from the exhaust of the power plant boilers and sent to oil fields where it is pumped into tapped out wells to liquefy the sludge so that it can be recovered.  It’s called Enhanced Oil Recovery (EOR).

The oil industry rather disingenuously advertises EOR as an environmentally friendly activity, but a process that is designed to produce even more oil to be burned can in no way be considered environmentally friendly.  For every ton of carbon dioxide it prevents from reaching the atmosphere, the additional oil recovered puts another .83 tons into the atmosphere when it is burned.  At a time when we must not just curtail but altogether stop carbon dioxide emissions, this is not helping.

Capturing carbon dioxide at the point of emission is more efficient than capturing it from ambient air, but this is what we must do if we are going to reduce the concentration of carbon dioxide to a safe level.  Carbon capture from ambient air is a new technology and is still in the early stages of development.  The process is simple to understand.  Fans are used to pull air across an “air contactor” (filter) that contains a substance (called a “sorbent”) that binds to the carbon dioxide molecules.  The carbon dioxide is then separated from the sorbent and stored, and the sorbent is recycled through the air contactor.

There are two challenges with this process.  First, because carbon dioxide is present in only a trace amount (about four molecules per every million molecules of air), a lot of air must be moved just to get a little carbon dioxide. Second, because the carbon dioxide is so rarefied, carbon dioxide molecules may not pass close (at the atomic scale) to the sorbent molecules as they cross the air contactor.  This means that the sorbent must exhibit a strong attraction to the carbon dioxide molecules in order to capture them.  In order to reuse the sorbent (it would be prohibitively expensive not to recycle it), this bond must be broken, and because the bond is so strong, it takes a lot of energy to do this.  In fact, more energy is required for this than for running the fans.

The point is that CCS requires a lot of energy.  If that energy comes from renewables and/or nuclear sources, fine.  But if the energy comes from fossil fuel plants, we will be emitting carbon dioxide to capture carbon dioxide (just the reverse of EOR) and will be fighting ourselves.  The deployment of an efficient, wide-scale CCS system must therefore await the build-out of a robust renewables/nuclear infrastructure.

How big is the task?  Let’s consider this hypothetical scenario:

Let’s say we have a carbon dioxide removal plant with one thousand typical 48” industrial fans each rated at 19,500 cubic feet per minute (CFM).  Operating 24 hours a day, seven days a week, this plant could process 10.3 billion cubic feet of air in a year.  Each cubic foot of air contains .0807 pounds of carbon dioxide, so 10.3 billion cubic feet of air would contain .83 billion pounds of carbon dioxide or .000415 billion tons of carbon dioxide.

One thousand plants like this could capture .415 billion tons of carbon dioxide per year.  In order to remove 1,950 billion tons of carbon dioxide, these plants would have to operate 7×24 for 4,700 years! Needless to say, we can’t afford to wait that long.  If we wanted to remove the 1,950 billion tons of carbon dioxide in 50 years, we would need 940,000 plants.

Conclusion

It should be evident by now that the challenge of restoring the energy balance of the world before the climate slides into a permanently unstable condition is a far more difficult task than Mr. Tillerson’s glib remarks to his shareholders suggest.

The magnitude of the task is so vast that in some circles, consideration is being given to implementing stopgap measures which, while they won’t solve the problem, could buy us time to do the things we need to do to save the planet.  One of these stopgap measures is solar radiation management (SRM) –artificially increasing the Earth’s albedo (reflectivity) to offset the warming effect of the increasing amount of carbon dioxide in the atmosphere.

Critics fear that SRM could cause unexpected and undesirable side effects, and that it could be used as an excuse to continue to burn fossil fuels.  These are both valid concerns, but if we are facing catastrophic climate change within a few decades, a hail Mary pass, as this type of last-ditch effort can aptly be described, may be our only shot.

One day our children and their children will look back in consternation and, perhaps, bitterness at the decisions made by this generation – decisions that destroyed the Eden that we enjoyed.