Thursday, 20 March 2008

EROEI for doomers debunked

The EROEI myth debunked.

The concept of EROEI.
It stands for Energy Return on Energy Invested.

The party line:
The original oil get an energy return of one hundred barrels of oil for each barrel of oil equivalent that was put in. Since oil is getting harder and harder to extract we are now down to one barrel of oil equivalent gets twenty barrels of oil out.

The reader is invited to extrapolate all the way down the curve and conclude that we are sliding down the curve till it will take more than one barrel of oil equivalent to get one barrel of oil out.
When we hit that stage it will not be possible to get any more oil out and we will leave it in the ground.
There is nothing wrong with the mathematics there, but let's examine the assumptions.

Barrels of oil and Barrels of oil equivalent.
There is a difference between barrels of oil and barrels of oil equivalent.
On the one hand we have barrels of oil equivalent sitting in the ground that when they are used up they are gone. (Oil, Natural Gas, Tar Sands, Nuclear fuel etc).
On the other hand we have barrels of oil equivalent that are not sitting in the ground but are replenished every day. Sunlight is one such barrel of oil equivalent and it is the basis of all of the other barrels of oil equivalents like wind, wave, oil, natural gas and tar sands. Only nuclear does not come from the sun.
The problem with this definition is it invites us to think of energy as barrels of oil instead of just energy. Thus we are led to the idea that you need to burn up barrels of oil equivalent to get some more barrels of oil equivalent back.

In the case of oil, natural gas, tar sands and nuclear this is indeed exactly the case.

The Second Law of Thermodynamics
Some people over at TOD quote quite correctly that Net Energy = Energy In - Energy Out. In the context of barrels of oil to get barrels of oil it looks like we have a dimishing resource and once it's gone we have no energy left. They then go on to say that the second law of thermodynamics says we will run out of energy because we need to use up barrels of oil to get more barrels of oil. This is part of the same fallacy propounded by Jay Hansen all those years ago. In fact the second law of thermodynamics says that "in the absence of energy being added to the system, the amount of energy in the system always runs down". This is a more helpful way of describing Net Energy = Energy In - Energy Out because it makes you realize that we're not living in a closed system with a limited stock of energy. Sunlight is continually pouring in. We have a full tank of sunlight and every morning it is refilled. This new tank of energy is added to the system every morning.

The final part of the fallacy is where they do an EROEI calculation on windmills and other forms of energy harvesting infrastructure but only using barrels of oil as an input. This is fundamentally wrong headed.
The reason is that if you artificially constrained the system to use only barrels of oil to get barrels of oil instead of barrels of oil equivalent to get barrels of oil equivalent you'd conclude that you need to burn up energy to get energy. In the case of the oil to get oil this is true. Thus saying "I burned a barrel of oil to get 20 barrels back" would make sense. The net result is 19 barrels of oil after one is used and it's a continual processing of burning barrels up till you have none left.

In the case of a wind turbine, however, you build the windmill and then it provides energy. If you use that energy to build another windmill, the first windmill is still there. So let's use EROEI in the correct context for a windmill.

Taking the ridiculously low extrapolation of a 20% return on energy invested what that means is that for every four barrels of oil you burn you get one back. This is equivalent to spending the principal.
Obviously not good as your supply is diminishing at an every increasing rate and a inversely corresponding larger amount of your economy has to go towards creating energy.

In the case of a windmill, though, what it means is fundamentally different. For every four windmills that are built, you get one free one and the other four are still there. Now you have five. Using the concept of EROEI here means that the interest is compounding. This is equivalent to investing the principal and growing it. The economy here would be growing, not contracting and an ever diminishing share of the economy would be going towards producing energy unlike in the case of using oil to produce oil.
Anyone who has studied compound interest knows that there is a doubling time. Let's look at that.
In the case of the ridiculously low EROEI of 1.2 quoted on the oil drum, that's a 20% rate of interest. The doubling time is about four years. Now even if you had to use half of that, you would still be left with 10% interest on your original principal. That means that your installed base of energy doubles every ten years and ultimately, this will result in many windmills.

These two concepts are related but opposed to each other but it's important to include them here because they apply in opposite ways to renewable energy and fossil fuels.
Economies of scale is where the bigger the manufacturing facility you build the more efficient it becomes. With windmills, the bigger the windmill is the more power you can get out of the wind due to it being a power cube rule. This means that the bigger the factories are to produce the windmills, the compounding effects means we get a higher and higher EROEI as we go. The economy can thus grow quicker and quicker.
Diminishing returns means that the more effort you put into something the less return you get back out. Oil is like this. The harder you suck it out, the faster you use it up. In an economy dependent on oil, more and more of the economy is used up to get the oil out faster and faster and ultimately it will collapse if there is no alternative to oil.

What is the conclusion?
Jay Hansen did us all a big disservice by propounding the myth that we need oil to get oil. He did us a worse disservice by inviting us to measure EROEI in barrels of oil equivalent leading us to think that the ability to extract energy was diminishing. This is the same myth that is being propouned on the oil drum. They claim that ultimately we will get down to 1 or less whereas in fact we will never even get down to the 1.2 I used for the argument. There is no possibility except perhaps in the case of nuclear war that declining eorei of conventional oil is going to lead to cannibalism as per "The Road". Even solar panels are better than that (1.2 factor return), and though the EROEI of oil is decreasing if we mistakenly use only the diminishing quantity remaining barrels of oil to calculate it, we still have that full tank of sunlight every morning to use up so we have a floor under us of the lowest EROEI of renewable energy devices (solar PV) which is more like 4.0-8.0 depending on whose calculations you use. So if we have renewable energy to create more renewable energy devices we can still have a growth economy up to the limits of resources on this finite world. But we have no problem of for ever diminishing returns on EROEI waiting for us up ahead. One day we will in fact find that it's pointless using electricity to pull oil out of the ground or make syncrude out of the tar sands, but way before we reach that point we will have already clued in to the fact that we can get by on electricity by using it directly instead of wasting it digging up or making oil.