Now here's something quite a bit scarier, something that few people are talking about so far, but possibly more threatening to our way of life than any other force: EROEI.
EROEI stands for "Energy Return on Energy Invested." It's sometimes called "EROI" (Energy Return on Investment), but I'll stick with the longer, more commonly used variant. EROEI is the ratio of the energy you get from some fuel divided by the energy it took to harvest that fuel. If I have to burn 2 barrels of oil to power the oil rigs and trucks and pipelines and refineries needed to harvest 20 barrels of oil, I have an EROEI of 10.
More EROEI is better. If your EROEI is low - say, 2 or 3 - you can still produce energy, but you need a massive amount of capital to keep production going. "Capital" is stuff like trucks, rigs, refineries, etc. And capital wears out and has to be replaced. So if your fuel has a low EROEI, you have to maintain a huge stock of capital, which means it costs you a ton of energy just to maintain and replace that stock, leaving less energy for you and me to consume. If you have an EROEI of less than 1, you're screwed - no energy for you.
For non-renewable resources like oil, EROEI decreases over time, because we take out the easy-to-reach stuff first, and the stuff that's left is buried deep. When we first started using oil - when it was gushing and bubbling right out of the ground - oil had an EROEI of 100, the most of any fuel in history. But now oil's EROEI is down to around 10, and falling. Coal used to be at 30, and is now down to around 9 and falling.
Ethanol? Don't make me laugh. You get out less energy than you put in! It's like those robots in The Matrix trying to use humans as generators - stoopid.
So as fossil fuels run out, we're going to need to go to alternatives. Assuming we can store and transport energy - which I'm fairly confident we'll be able to do, with improved battery technology - we can switch to "backstop technologies" like solar, wind, nuclear, biofuels, etc. But these things all have much lower EROEI than fossil fuels did in their heyday. Just take a look at this chart:
| Fuel Source | EROI | |
| Nonrenewable | ||
| Oil and gas (domestic wellhead) | ||
| 1940's | > 100.0 | |
| 1970's | 23.0 | |
| Coal (mine mouth) | | |
| 1950's | 80.0 | |
| 1970's | 30.0 | |
| Oil shale | 0.7 to 13.3 | |
| Coal liquefaction | 0.5 to 8.2 | |
| Geopressured gas | 1.0 to 5.0 | |
| Renewable | ||
| Ethanol (sugercane) | 0.8 to 1.7 | |
| Ethanol (corn) | 1.3 | |
| Ethanol (corn residues) | 0.7 to 1.8 | |
| Methanol (wood) | 2.6 | |
| Solar space heat | | |
| Flat-plate collector | 1.9 | |
| Concentrating collector | 1.6 | |
| Electricity Production | ||
| Coal | | |
| U.S. average | 9.0 | |
| Western surface coal | | |
| No scrubbers | 6.0 | |
| Scrubbers | 2.5 | |
| Hydropower | 11.2 | |
| Nuclear (light-water reactor) | 4.0 | |
| Solar | | |
| Power satellite | 2.0 | |
| Power tower | 4.2 | |
| Photovoltaics | 1.7 to 10.0 | |
| Geothermal | | |
| Liquid dominated | 4.0 | |
| Hot dry rock | 1.9 to 13.0 | |
Even the upper estimates of renewable EROEIs are around 10 (Wind is actually around 25, but only in very windy places). Is that good enough to power our society? Remember, with low EROEI it takes a ton of energy just to maintain the capital stock, much less build more as world population increases. Energy efficiency can help us maintain a higher level of consumption, but it can't solve the problem of low EROEI.
Low EROEI is much more threatening than peak oil - it's peak everything.
You may reply: "Well, oil only has an EROEI of about 10 now, and we're doing OK now, aren't we?" But we're now pumping and refining oil with capital built in the 1970s, when oil had a much higher EROEI. As those rigs and refineries and tankers decay, they'll be a lot more expensive to replace than they were to build. We're living on borrowed time.
Provided world population stabilizes, renewable energy should be able to keep us from collapsing into a new Dark Age (knock on wood). But with all our energy and effort just going into maintaining what we have, where will we have the surplus energy (i.e. surplus time and money and wealth) to invent new stuff? I think it's no coincidence that productivity - a loose measure of technological progress - seems to be correlated with world energy prices. When oil was bubbling up out of the ground, it was easy to sit around inventing airplanes and TVs and rockets. Twenty years from now, when you have to build another giant solar tower to power every new housing development, there won't be as much room to play around.
There is no possible economic solution to the EROEI problem. And, with renewables only at 10 or worse, there's no technological solution yet either. Last time we faced this threat was 100 years ago, when coal was failing to meet our needs. Oil bubbled up out of the ground and rescued us. What hidden source of massive abundant free energy will jump up to rescue us next time? Maybe nothing. And next time is now.
Now sleep tight.
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