Because of its length I divided this subject into three parts:
Part one: ERoEI
Part two: Net Energy
Part three: some general remarks
Maybe the subject is a little bit boring for a lot of people, but in my view the subject is important enough to write about it (especially in ‘Overthepeak’). And excuses for my bad English. I hope that my English is sufficiently clear.
A negative spiral. The knife cuts along several sides.
Not only the gross production of oil is important, but also the amount (units) of energy produced (extracted) per unit of energy input. Also the quality of the oil is important. Per barrel of good quality oil a relatively higher amount of important petroleum products can be made then per barrel of lesser quality oil.
EROEI: “The amount (units) of energy produced (extracted) per unit of energy input.”
A certain amount of energy (energy input) is needed to extract a certain amount of oil and transport it to the (nearest) refinery.
The energy input is often expressed in ‘barrels of oil_equivalents’. How many barrels of oil_equivalents are needed to extract a certain amount of barrels of oil.
Sometimes the BTU (a thermal unit) is used as an energy unit. How many btu’s are needed to extract a certain amount of btu’s (contained in the form of oil).
When, by example, 10 barrels of oil_equivalents are needed to extract 100 barrels of oil, the EROEI is 10 (100 : 10). One unit of Energy Input (EI) input returns 10 units of Energy output (ER).
When, by example, 6 barrels of oil_equivalents are needed to extract 100 barrels of oil, the EROEI is about 17 (100 : 6).
Difficulties in measuring EROEI:
The amount of oil extracted from the ground is relatively easy to measure.
But how to calculate the exact amount of energy input?
Mostly a certain amount of natural gas, coal or even other forms of energy input are needed to extract a certain amout of oil. But besides the direct energy input in the form of natural gas, coal, oil or whatever, there is also indirect energy input. By example how much indirect energy input was needed to make, transport and maintain the materials that are needed to extract the oil?
For many analists ERO(E)I is a very important concept:
Because it is very difficult to calculate the exact number of “EROEI”, it doesn’t mean that het EROEI concept is meaningless. On the contrary, for many analists it is a very important concept even if there is disagreement on how to calculate the exact value of EROEI.
Declining trend of the “ERO(E)I”:
“ERO(E)I of oil and natural gas decreased from 35:1 in the 1990’s to 20:1 in 2005”.
If I remember correctly, at this moment (2010) the ERoEI of oil is about 17 (17:1). This means that for every 85 million barrels of oil daily extracted, about 5 million ‘barrels of oil equivalent’ a day are needed to produce 85 million barrels a day.
Some analists claim that in the next decades there will be a 5% growth in energy input per unit of production per year (for oil, gas and coal!). If the latter becomes true, this means that the energy input per unit of production in the year 2020 will be about 1,6 times higher (1,05^10) then in 2010. If in 2010 an energy input of 5 million barrels of oil equivalents per day are needed to extract 85 million barrels of oil per day, in 2020 about 8 millions barrels of oil_equivalent per day will be needed to extract 85 million barrels of oil per day.
So, from an ERoEI perspective, in 2020 the gross production has to be about 3 million barrels a day higher then the gross production in 2010. (85 million a day in 2010, 88 million a day in 2020) to stay even in the available amount of energy for society.
Same story for other fuels and (from a RO(E)I perspective) for minerals.
The same story goes for other fossil fuels (Coal, Natural gas) and for a lot of important minerals, because the highgrade mines of many minerals are almost depleted and it costs (even with better and more efficient technology) more and more energy to mine a certain amount of an important mineral.
More and more oil, coal and natural gas are needed to extract a certain amount of oil, natural gas and coal. More and more energy is needed to mine by example 1000 ton of a mineral.
More about energy in PART 2 and PART 3.