Saturday, February 2, 2013

[Old MacDonald Had a Farm] EROEI

An explosion from nuclear test Operation Upshot-Knothole.  Simon, to be specific.  Source.


You have my apologies for the delay in exploration of fascinating [read: "mildly interesting"], topics.  It would seem between a laptop dying and a lack of night shifts, I don't have the large of chunks of time to properly discuss [read: "write until I get bored"] the issues which I feel you, dear monocled reader, deserve to know about.

The topic of this post is EROEI, an acronym for Energy Return on Energy Invested, also known as EREI, but if you have the extra O, it ends up being more like the Old MacDonald song.  In either case, I believe that our future prosperity as a species hinges upon our ability to effectively utilize renewable and sustainable energy sources, for reasons I will get into later.  That being the case, we need to consider EROEI when evaluating energy sources to determine their viability.

For some context, let's think about oil.  Since the first "gusher" was discovered in Texas, we have gradually been tapping all the easy oil we have been able to find.  After a while, there were no gushers left and we had to work to get the oil out of the ground.  This has continued ad absurdum because we have built an infrastructure for ourselves that runs on oil.  Those first gushers received their name for a reason.  For the equivalent energy of one barrel of oil (just above 6GJ of energy, 42 US Gallons), 100 barrels were gathered.  So we put a little energy in, and got it back one hundredfold.  In 1970, the efficiency of oil imports to the US represented an EROEI of roughly 40.  By the late aughts, it was closer to ten.  The oil from the Canadian tar sands can be extracted for an EROEI of roughly three.

This means that the efficiency of oil has decreased significantly for us.  We have gone from getting energy back one hundredfold for our efforts, down to about three times in northern Alberta.  This actually represents my biggest issue with oil going forward.  We have plenty of oil reserves from which we could draw for decades to come, but the problem is that we are approaching a point where the EROEI for oil will reach 1, and decline from there.  This would mean that it wouldn't actually be worth our time getting oil out of the ground, because the work we perform to extract the oil would be greater than the energy in the oil we extracted.

To attempt to put this in perspective, I'll talk about first generation biofuels (I provide this link knowing full well that you, my dearest top hatted reader, remember the post vividly).  In order to make ethanol out of corn in Canada, the EROEI represents between about 0.8 and 1, if I recall correctly.  That means that if you consider all the energy the farmer/factory worker spent in gas and fertilizers to grow, harvest, then convert the corn to ethanol, we would have been further ahead to just burn the gas directly and skip the ethanol fiasco.  Naturally, the legislation surrounding first-generation biofuels is really intended as a stepping stone to get to second generation biofuels, which will have an EROEI well in excess of 1, and probably greater than that of the tar sands.
You've been reading a while now, so here's a picture.  It's not switchgrass, but it sure is nifty.

In my article on switchgrass [my favourite biofuel candidate], I point out that the EROEI for growing and then burning switchgrass is roughly 20 [though I wasn't aware of the concept at the time].  For growing, converting to liquid biofuel and then burning, the EROEI is hypothetically around 5.  To put that into context, that means that in terms of energy, we would be further ahead making biofuels out of switchgrass than getting into the tar sands debacle.  Simply growing and burning switchgrass for heating purposes puts the tar sands to shame, and makes a mockery of home heating oil [in terms of energy, of course].  Why don't we do this?  Sure beats me, I assume it's some combination of an unwillingness to invest in new technology (and changing existing infrastructure), and distorted economics due to government subsidization of the oil industry.

Now, I assume at this point your are adjusting your monocle and top hat, and saying "I'm sure enjoying this talk of ratios, but could there be broad, global implications from falling EROEI?"  I'm glad you asked, dear reader.  Historians have hypothesized that a contributing factor to the downfall of the Roman Empire was falling EROEI.  The Romans, as it turns out, were not terribly good at soil conservation.  As time went on, the amount of food that Roman crops produced declined with the quality of the soil.  I am quoting a friend Paul on this, but I am told that great tracts of fertile land were reduced to desert, land which has never recovered.  Naturally, there were economic consequences to this, and the Empire declined and fell*.

It has also been pointed out that energy prices (which are somewhat reflective of EROEI in absence of ridiculous market forces), are intimately related to economic strength.  Every time there has been a sudden spike in the price of oil, an economic downturn has followed.  With falling EROEI of oil, I don't believe it's unreasonable to expect economic consequences from our continual dependence on oil.

At this point, I'm sure you're wondering what some good alternatives would be.  While nuclear explosions yield a fantastic EROEI (the picture at the top WAS related after all!), current nuclear reactors can offer an EROEI of roughly 10 and thorium reactors of the future (maybe a post-worthy topic), could yield 50.  What about wind and solar?  Well, wind offers an EROEI of 18, and solar 6.8 [though focused research is aiming to improve that figure].  I'll point out here that EROEI for wind and solar refers to the energy generated over the lifetime of the equipment divided by the energy required to manufacture the equipment.  You'll notice that even though these figures are low, they're all higher than the 3 we get from the tar sands.  That being said, it sure would be nice if we still had a sustainable power source which yielded an EROEI of 100.

Wait, hold on, there's something about that figure that's familiar...

Ah, yes.  We have an energy source like that.  It's hydroelectricity.


* - No, I'm not saying that this is the only reason that Rome fell, but I'm saying it was likely a contributing factor.  The same work producing a smaller product is bound to have consequences on that grand a scale.

P.S.  This turned out pretty messy, I'll maybe edit this later.  Hope you got this far and/or enjoyed it!

1 comment:

  1. I really liked that one. Put flesh on some bones I've been wondering about for a while. I think a worthy post in the future might be hydroelectricity. A lot of people don't like it and for probably valid reasons. On the other hand there's probably a good way to do it too.
    In terms of solar, 6.8 is low but it's not bad I'd say. It's nearly a sixfold return on your investment and they're ridiculously easy to use. All the invested energy happens at the beginning and then they just sit there. Despite having a low EROI they're probably the most user-friendly thing we have.
    In addition there are some other forms of solar power generation that are interesting. After some googling I've found out I'm talking about solar thermal energy. I saw a successful application (on TV) in Spain where they use a field of reflectors to heat steam for a turbine that looked quite promising. My favourite, though it seems to have disappeared, was a massive inverted glass funnel in Australia. The air under the glass was heated, like in a greenhouse, and then rushed up through the narrow opening. The air exited through a turbine at the peak and re-entered the system through vents at the bottom around the sides.
    There are many small return methods of gathering renewable energy. I don't think it's terrible to use small return gathering sources, it just means you need a lot of sources. The transition will screw with the economy for a while but probably won't be the end of the world. I don't think we actually need as much energy as we consume anyway.