Alice and the Red Queen illustrate ERoEI

Many people of faith, including seminarians and ordained clergy, are not trained in science or technology. They are charged with activities such as preaching, managing church finances, caring for the sick and leading spiritual retreats. These activities and responsibilities do not require an understanding of technology, systems engineering or quantification. However, as we enter the Age of Limits it will be necessary for us all to have a basic grasp of technology and its limits. Posts such as Essential Petrochemicals, Of Priests and Thermodynamics and Proper 23: The Enemy is Physics challenge such assumptions.

One technical issue that is fundamental to much of what is written at this site is the concept of Energy Returned on Energy Invested (ERoEI). This topic is discussed  in detail in the chapter entitled ‘Alice and the Red Queen’ in the ebook Age of Limits – 1. A summary is provided here.

The basic idea behind ERoEI is that all systems, including all living creatures and all human beings, need energy in order to live, grow and reproduce. But the act of acquiring energy requires the expenditure of energy. Expressed as a simple equation,

Available (Net) Energy  =  (Gross Energy  –  Energy Expended)

Gross Energy is the total amount of energy that is taken in. Energy Expended is the energy needed to find and consume the Gross Energy. Available or Net Energy is what remains. If Net Energy is positive then the system or organism flourishes. If Net Energy is negative then, once it has used up its own internal reserves, the organism will die.

Imagine a person living a simple hunter-gatherer lifestyle. He or she expends energy throughout the day gathering edible plants and hunting animal prey. That is the Energy Expended term. The person eats the food he or she has gathered, thus providing the Gross Energy. The Net Energy is the difference between these two terms.

A term that is frequently used in this context is Energy Returned on Energy Invested (ERoEI), which can be defined as,

ERoEI  =  Gross Energy / Energy Expended

If a living organism has an ERoEI of unity then it will spend all of its energy finding energy (food) just to keep itself alive. If the value falls below unity then the organism dies. Only if ERoEI is greater than one will the organism have surplus energy for growth and reproduction. Hunter-gatherers typically have an ERoEI of about 1.5. In other words, they spend 2/3 of their energy looking for and consuming new sources of energy (food).

About 10,000 years ago societies in different places started to develop agriculture. Doing so gives that society a much higher ERoEI value, probably in the 6-8 range. The surplus energy provides the foundation for civilized society, a society that can now afford luxuries such as armies, buildings, priests and writing.

Then, about 300 years ago we learned how to exploit the energy in fossil fuels such as coal, oil and natural gas. Doing so dramatically increased society’s ERoEI value. Now humans, through the use of this stored energy, have ERoEI values that can be as high as 100:1. This surplus provides the foundation for everything we take for granted in our modern way of living.

The catch is that we have used up the easy-to-find-and-extract energy sources, the low-hanging fruit. So now we are forced to spend an ever-increasing proportion of our energy simply finding and extracting new sources of energy to replace what we have used. The chart plots Net Energy against ERoEI. It can be seen that, as ERoEI falls from 100 to 20, most of the Gross Energy is available as Net Energy. But, below an ERoEI of about 5:1 Net Energy plummets. We fall off the Energy Cliff.

The ERoEI energy cliff
It is this decline in ERoEI, particularly the fact that we are reaching a point where we will soon be falling off the cliff’s edge, that is the root cause of so many of our difficulties. There are no high-density sources of energy available to use that would allow us to move back along the curve (with the possible exception of nuclear power, but that comes with its own set of problems).

It is difficult to calculate ERoEI values for various reasons. For example, government subsidies will skew any analysis. Nevertheless, we can develop some very rough ERoEI values for various energy sources.

  • Hydro                                       100
  • Oil (conventional onshore)    20
  • Wind                                           18
  • Oil imports                                12
  • Natural gas                                10
  • Solar                                             5
  • Shale oil                                       5
  • Bitumen tar sands                     3
  • Ethanol from corn                    <1 to 5

Regardless of the energy source ERoEI for society overall is declining inexorably and new technologies and sources of energy have lower values than more traditional sources (with some exceptions — the cost of solar panels has come down a lot in recent years, although even in this case there is a large amount of embedded energy in a solar panel, and that energy likely came from oil, gas or coal.)

There are also qualitative issues to consider. For example, low ERoEI projects generally impact the environment much more adversely than those with a higher value. In the “good old days” all you had to do was “stick a straw in the ground” and high quality oil flowed under its own pressure into the production pipeline. No longer — now the development of resources such as the bitumen tar sands has a huge environmental impact. And the Deepwater Horizon/Macondo catastrophe showed just how severe the environmental problems to do with deepwater drilling can be.

Political issues can also be a factor. For example, ethanol produced from corn may have an ERoEI that hovers around one, hence it does not make economic sense to bother with this activity. But the ethanol does provide a local source of fuel thus providing those countries that grow corn and make ethanol with some political independence. And the production process provides jobs for the local population.

Like the Red Queen in Alice in Wonderland, we are running faster and faster to stay in the same place.

40 Gigatons

Pilate Questioning Jesus
Pilate Questioning Jesus, “What is truth?”

In the discussions at this site we have suggested that we need to develop a theology that is suitable for the times that we are entering: an Age of Limits. We have further suggested that a foundation for such a theology is that, “We understand and tell the truth”. This is not easy. In this context, telling the truth goes beyond simply not lying — it means taking the time and effort to understand and analyze the immensely complex systems that provide the background to our modern lives. Telling the truth also means that we need to avoid wishful thinking and giving in to “hopium” — a belief that “they will come up with something”.

As an example of wishful thinking, consider the following chart. It shows the concentration of CO2 in the atmosphere. The value has risen steadily from 310 ppm in the year 1960 to its current value of 420 ppm.

CO2 concentrations in the atmosphere with overlays of dates of COP meetings and IPCC reports

Overlaid on the chart are the dates of the IPCC (Intergovernmental Panel on Climate Change) reports and the COP (Conference of Parties) meetings. These reports and meetings have been warning us for 30 years that, unless we do something to stop the increase in CO2 concentrations, we are facing a climate catastrophe. We see how effective those efforts have been. No wonder young people are angry.

So we face an uncomfortable truth: We will continue to burn fossil fuels regardless of the consequences. As we saw in the post Two Triangles, moral admonitions are of limited effectiveness.

If we are unable to stop adding CO2 to the atmosphere then the next logical step is to find some means of removing it. (Intuitively, this approach does not make sense. It is always better to avoid catching a disease than to have treatments for the disease once caught.) So we need to investigate the technologies that are grouped under the general heading of Carbon Capture and Sequestration (CCS). But that statement brings us to another uncomfortable truth, and that is to do with scalability and project management realities — an issue that we have already discussed in The Slow Train.

As is to be expected, this is a complex topic, involving many different potential technologies. But we have to start somewhere, so let’s use the following parameters.

  • Human activities emit about 40 gigatons (40 billion tons) of CO2 per annum.
    Roughly half of that CO2 comes from point sources such as power plants and industrial facilities. The other half comes from transportation (gasoline, diesel, bunker fuel and jet fuel) and from residential.
  • We need to reduce the emissions of CO2 to zero within the next 20 years.
  • There are various carbon capture technologies that can be used. Many of these have been demonstrated on a small scale, but none of them are established as an industry standard. The technology is still in the development stage.
  • CO2 can be removed either from point sources (the stacks of power plants and industrial facilities) or from the atmosphere.
  • The concentration of CO2 in the flue gas leaving a power plant stack is about 20%.
  • Currently the largest CCS facility can extract 10 megatons (10 million tons) of CO2 per annum from a point source.
  • The CO2 that has been removed is then stored in a subsurface facility, such as a depleted oil well. the power plant and a suitable geological formation in the same location.

There are lots of assumptions and simplifications in the above statements, but they do at least provide a sensible starting point in our quest for finding the truth.

Power plant stack annotated showing CO2 emission

Based on the above assumptions, we can develop the following calculation.

  • We start the program with point source emissions because that is the most cost-effective approach.
  • This means that we aim to remove 20 gigatons of CO2 per annum. This is only half of what needs to be done, but, at least, it’s a start.
  • Given a capacity of 10 megatons per annum per facility, this means that we need (20 * 109) / (10 * 106) = 2,000 facilities in operation.

But CCS technology is still in the development stage, with many unresolved issues such as, “Where do we put the CO2 once we have removed it?”. If it takes say ten years to fully develop this technology, then we need 4,000 of these facilities to be fully operational by the year 2030. Such a program would require an unparalleled, worldwide commitment of financial, engineering and project management resources.

But it becomes even more complicated. There are at least 50,000 power plants throughout the world, most of which use fossil fuels (coal or natural gas). So, maybe we need more than 4,000 CCS facilities.

There are so many unanswered questions and so many assumptions. Nevertheless, when it comes to reducing atmospheric CO2 concentrations our first-pass answers to Pilate’s question are,

  • It is very unlikely that we will voluntarily reduce our CO2 emissions.
  • The technology, financing and political will to implement carbon capture technology needs to be created within the next ten years. There are no signs of this happening.

Which leads us to the second of the theological points that we present, “Accept and adapt”.

Two Triangles

Book: Two Triangles by Ken Pye

The book Two Triangles: Liverpool, Slavery and the Church describes the trans-Atlantic slave trade that flourished in the 18th and 19th centuries. The book also discusses the church’s involvement in this terrible practice. Some church leaders provided theological justification for what was taking place, but others, including many in the Anglican church and the City of Liverpool, helped bring about the abolition of slavery within the British Empire. (Two Triangles can be purchased from the Liverpool Cathedral bookshop here.)

Although the events of the book seem now to be “just history”, the book’s message is surprisingly relevant to us now in our Age of Limits — for two reasons. The first reason is to do with the theological arguments to do with the morality of slavery, and their relevance to our use of fossil fuels. The second reason is that the slaves were needed to provide the energy needed to develop and operate the Caribbean plantations. We need the energy provided by coal, oil and natural gas if we are to maintain our current, abundant lifestyle.

The Triangle

The triangle that the book refers to was to do with trade ships that made journeys between three nodes of a trade triangle: Liverpool, Africa and the Caribbean. On the first leg a ship carrying rum, textiles and manufactured goods would sail south from Liverpool, England to ports in west Africa. Having unloaded its cargo it would be packed with slaves captured from the African hinterland. The ship would then sail west to the Caribbean using the trade winds. In the Caribbean the slaves would be sold and the ship loaded with raw materials such as sugar, cotton and tobacco. It would complete its journey by following the Gulf Stream and returning to Liverpool.

Slave triangle book Two Triangles

The descriptions in the book of the second leg of the passage — the transport of slaves from their homes in Africa to the Caribbean — were tough reading. ‘Nuff said.

Slave ship in book Two Triangles

Theological Justification

Slaves, obey your earthly masters in everything; and do it, not only when their eye is on you and to curry their favor, but with sincerity of heart and reverence for the Lord.

Colossians 3:22

The book provides an important discussion to do with theological tension between the verses in the Bible that endorse slavery and the Christian spirit of love for all human beings. We can see this same discussion playing out now with regard to climate change. There are those who want to do the right thing, i.e., reduce carbon emissions, even if that action means a reduction in our standard of living. And there are those who want to make money now, regardless of the morality of their actions.


Patrick Henry and slavery
Patrick Henry (1736-1799)

Many of the people living at the time of the slave trade recognized the immorality of what was going on, but they saw it as a necessary evil. One of the leaders of the American Revolution was Patrick Henry — “Give me liberty, or give me death!”. In the year 1773, a time when the slave trade was at its height, he wrote,

Would any one believe that I am master of slaves by my own purchase? I am drawn along by the general inconvenience of living without them. I will not — I cannot justify it, however culpable my conduct.

Do those words sound familiar?

Indentured labor of various types was needed to provide the energy that their society needed to function. Henry, and the other prosperous people of his time, needed that energy to run their society and to maintain their standard of living. They knew that what they were doing was wrong, but they could see no way out of their dilemma. The analogy with what is taking place now is stark — we know that burning fossil fuels is creating many predicaments, but we need those fuels to maintain our way of life.

For both ourselves, and for Patrick Henry, the way out of the dilemma was “alternative energy”. In his case, during the 18th century a new source of energy was coming along: coal. The energy supplied by coal was so abundant that there was less need for the human energy. Later on, we found an even better source of energy: oil.

Is it coincidence that two things happened at about the same time? In the year 1859 Colonel Drake (who wasn’t a colonel) drilled his first successful oil well. The technology that he used — a drill string inside casing — is still in use now. Just a few years later, slavery in the United States was abolished. (In the picture, Drake is the person on the right in the stovepipe hat.)

Drake first oil well source of energy

Theology and Technology

Two Triangles emphasizes the moral component to do with the abolition of slavery. This is something that is needed now with regard to climate change. One of the consequences of climate change is that the people who suffer the most from its impact are the people who are least responsible for it happening. And it is not just people. The massive fires that have recently occurred in Australia led not just to people losing their lives and their homes, it also resulted in an enormous loss of wild life.

But moral and theological pushback by itself is insufficient. We need to find new sources of energy to replace fossil fuels. This is turning out to be very difficult. Nevertheless, it is the responsibility of people of faith not only to make moral arguments, but also to understand how technology can help us find responses to the predicaments in which we find ourselves.