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Saturday, 28 April 2007

No Silver Bullets (re Peak Oil)

My previous post was about the tension between the growing demand for oil and predictions of declining availability, and the relationship of oil consumption to global warming.

I expect that many people reading that post would quickly reassure themselves by thinking about one or more of the following:
- biofuels (especially ethanol for use in existing cars)
- electric, hybrid or hydrogen-powered vehicles
- coal liquefaction (literally converting coal into a fluid form similar to oil)

Here's why none of those make me worry much less, if at all.

1. Biofuels

The basic idea is neat: instead of giving carbon a one-way trip from oil to the atmosphere, lets grow plants to take CO2 out of the air then convert it to fuel which when burned puts the carbon back where it came from. The overall amount of CO2 in the air stays constant and we don't need oil.

But already we've hit a fatal flaw with biofuels: in fact the production of ethanol from, say, corn requires massive inputs of oil in the form of fertilisers, pesticides and fuel for agricultural machinery and transport. It also requires significant electrical input which - especially in Australia - basically means burning coal. So we're still consuming oil and adding CO2 to the atmosphere even before the ethanol gets into our petrol tanks.

Fatal flaw #2 is so obvious I'm stunned we are even bothering to attempt growing fuel. Our cars and trucks and planes and ships consume enormous amounts of fuel. Even if we dedicated all the productive land on the planet to growing fuel crops we would only manage to produce a fraction of the fuel we need to keep everything running at the current pace - let alone meet the exponential demand predicted for the future.

There is some research being done into growing algae in tanks or ponds as an alternative to land-based fuel crops. This may lead to a significant, sustainable biofuel industry and I'd be encouraged by that. But from what I've read it's still not likely to ever be enough to match our current appetite for oil.

2. High tech cars

It's true. We can make cars which don't need to burn oil.

Some people are keen on cars similar to the ones we have today but which burn hydrogen gas (H2) instead. There's no "C" in hydrogen, so when you burn it you just get H2O. Water vapour. But hydrogen gas is highly explosive (can you say "Hindenburg"?) and it's very difficult to handle. Oh yeah, and water vapour is a much more powerful greenhouse gas than is carbon dioxide.

So there's a lot of attention on using hydrogen in fuel cells - basically little modules of hardware that generate electricity through chemical reactions and which you'd either swap in and out of your car like rechargable batteries in a camcorder, or top up with additional hydrogen. Fuel cells are real enough (they're used in the Space Shuttle, for example) but the technology needs a fair bit of development before it's suitable for use in everyday transportation.

Sounds good, huh? Uh-oh, here it comes.

Hydrogen's fatal flaw when it comes to the global warming / peak oil dilemma is that it generally isn't a source of energy but a carrier of energy. Hydrogen can't be mined*, it has to be produced. The simplest way to produce it is to push an electric current into water so that you give the hydrogen atoms the energy they need to escape their bonds to the oxygen atoms. That's how it acquires the energy which we want to use later on when we burn it in an engine.

Fuel cells and electric vehicles get lassoed with the same rope now. All these vehicles depend on large inputs of electrical energy. Hopefully you recall that our electrical consumption is already a major concern because of the CO2 we emit when we generate it. Unless we come up with a revolutionary large-scale way to produce electricity, these cars would simply drive us from the peak oil frying pan into the global warming fire.

3. Coal liquefaction

I only learned about this one recently, but it's old technology. During one of the Great Wars the British were astonished that their attacks on the German sources of oil didn't bring the Nazi machine to a halt. The Germans had prepared by switching to production of liquid hydrocarbons from coal.

The world does have heaps of coal (though calculations for "Peak Coal" are already being debated) and I get the impression that it's relatively simple and efficient to convert it to a liquid. On the positive side, this may help alleviate the shortage of raw material for plastics and fertilizers etc. But of course burning the stuff in cars is just as bad as burning it in power stations. As a greenhouse-friendly replacement for oil, coal is also fatally flawed.

Three bullets: shiny-looking, but definitely not silver.

* I am simplying things a fair bit with regards to hydrogen as an energy carrier but it's generally true that getting usable H2 on a very large scale would require massive energy input and that would predominantly come from coal at this point in time.

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