Saturday, March 18, 2006


Energy, and why you should care

I've been meaning for some time to write something about energy, in particular its relationship to climate change and associated issues. In a radical breach with blogging custom, this is something I have some professional knowledge about and I hope to bring in some facts.

If you know that my profession is that of biologist and ecologist, you might be forgiven for wondering exactly what I have to contribute to the realm of public knowledge about energy. In actual fact, ecologists spend a great deal of time thinking about energy; how it moves through ecosystems and what organisms do with their finite energy budget. The comparison is rather more cogent than that, because human ecosystems ultimately get most of their energy from the same place as most natural ecosystems: the sun.

Fossil fuels are of course at the heart of this matter, seeing as they're the primary source of the extra atmospheric CO2 that's causing global warming. Fossil fuels are very handy things, being as they are the concentrated remains of very old plant matter. They also represent energy that came from the sun millions of years ago, and was locked up in plant tissues. Those plant tissues became in time the handy long-chain carbon molecules that burn so easily and are so easy to carry around in cars and ships.

The world's food supply is also the result of energy from the sun being trapped by plants. The interesting thing about food crops is that they represent what some call a subsidised ecosystem. The productivity of an ecosystem is defined by the amount of carbon fixed per square metre over some set time period. The most productive natural ecosystems of all are coral reefs, for reasons that aren't important here. On land, the most productive ecosystems are probably temperate grasslands; they're made up of fast-growing plants that fix carbon very efficiently, and they generally get good rainfall and plenty of nutrients (despite the popular image, rainforests aren't all that productive, because of the slow growth rates of trees and the high level of competition all the vegetation in a forest experiences).

Modern, selectively bred crops grown in an intensive manner can fix at least twice as much carbon as a temperate grassland, and probably more like 4-5 times as much. This is also more than a coral reef, if you're wondering. I'll dig up the exact figures if I remember. This sounds like a great thing -- we can get 4-5 times as much energy out a piece of ground than if we were harvesting a natural ecosystem. Unfortunately, this is where the "subsidised" bit comes in. That high productivity figure is a result of intensive crop and soil management. It comes at the expense of burning quite remarkable amounts of fossil fuels. Some of this is used in machinery, of course: tractors, harvesters, water pumps and their ilk. The rest? Fertiliser. Modern agriculture requires lots of fertiliser; the plants are bred to expect it, and we turn them over too fast for natural soil fertility to last long.

Fertiliser is horrendously energy expensive and the production of it uses lots of fossil fuels. Some of this is actually used directly as part of chemical reactions that incorporate nitrogen into compounds that plants can absorb (making nitrogen compounds other than N2 is like pushing water uphill with a stick -- it's the breakdown of nitrogen compounds that powers most explosives). The rest creates electricity to power other energy-intensive processes, up to and including transporting raw materials and the finished product around. In many ways fertiliser is fossil fuels.

Subsidised? Without a doubt. Only everyone can currently ignore the source of the subsidy, because it's the same discounted, concentrated energy we already pump out of the ground for so many other purposes.

Believe it or not, I do have a point here. I want to talk about biofuels. Biofuels are the great white hope of alternative energy, and not without reason. To summarise a diverse field, biofuels are stuff produced by living things, stuff that burns well. In general they're refined into some form that's similar to existing fuels; bioethanol and biodiesel are the two main one, although they come from different sources. Biofuels produce CO2 (y'know, the greenhouse gas) when burned, of course. The trick is that this is new carbon, not the old carbon that's in fossil fuels. Cut down a crop in April, burn it in September and the net change in the carbon balance of the atmosphere is zero -- especially if that CO2 is then absorbed by next April's crop.

Astute readers may see where this is going. If agricultural crops are subsidised by fossil fuels, and you replace fossil fuels with biofuels, which are an agricultural crop themselves... Some of the energy from your crop needs to go straight back into the production process. Efficiency drops immediately, and the price of your produce probably rises -- an inevitably consequence of your energy no longer being almost free.

Depending of the efficiency with which you can produce your biofuels, the situation could be grim indeed. Some people have calculated that it takes more energy to grow the crops that can be fermented to ethanol than what you can get from burning the ethanol itself. Fortunately I don't think we should believe them, and not just because of the power of wishful thinking. Like Yoda, my reasons I shall below explain.

Firstly, it depends a great deal where your calculations are done. In many developed countries agriculture is already, realistically, not economic. I'm referring of course to agricultural subsidises and the "toy farm" industries that they encourage. I strongly suspect that no crop is energetically or economically sustainable when farms are run as an extended tax-fiddle. Show me figures based on New Zealand farming practices (no subsidies, no tax breaks, nothing) and I might be more inclined to believe you. I can't bring myself to care about the probable fate of subsidised, trade protected European and American farms if the effective cost of energy rises. I'm sure someone will find a way to keep them employed, maybe in a museum where they belong.

Secondly, the production of biofuels is fast-changing business. Take ethanol, one of the more widely touted biofuels because you can make it from a range of crops and burn it in petrol engines with trifling modifications. Ethanol is produced by fermentation, involving our old friend the yeast. Ordinary yeast can only grow on fairly sugar-rich mediums, and by sugar I mean sucrose, table sugar. This means you need to either grow crops like sugar cane, or break down things like wheat to release sugar. Taking it up a step, you can use industrial processes to liberate sucrose from most plant material, including the woody waste from fast-growing crops like wheat, or from a crop like buffalo grass chosen specifically to grow like buggery. Having digested such a crop though, you're left with about 40% sucrose and whole lot of funky sugars like xylose. Yeast can't normally break down xylose, but there's no theoretical objection to xylose being broken down. Clever people like Microbiogen have bred a yeast that can break down xylose. Impressed? I certainly am, and ideas like that are receiving a lot of attention at the moment. Expect this kind of thing to only get better. Improving the availability of the raw materials and increasing the efficiency of the production process obviously reduces the costs of producing fuel and takes less of a chunk out of agricultural production. I'm making an example of ethanol, but there is plenty of work going into the production of other biofuels.

[Time for an aside on organic foods. Tree-hugging type people tend to like organic food. I doubt that any of them have ever been to a proper organic orchard and seen the big scary "chemicals in use" signs permanently bolted to the fence, but that's a grumble for another day. Organic farming makes a great deal of taking care of the soil and not using fertilisers. Laudable aims, but the brutally simple upshot of this is that for high-yield crops like wheat, an organic farm produces about half the food of a conventional farm of similar size (that's why organic flour and so on is so expensive, apart from the snob value). If all the world's crops were organic, we would need far more farmland. As a ecologist the idea of even more farmland fails to appeal to me, and depending on whose figures you trust there wouldn't be enough arable land in the world to feed the projected peak human population, if all food was grown organically. Even with minimal fertiliser use, organic farms still need energy input from machinery and transport and to refine all those chemicals they spray around. Inefficiency at growing crops would also translate into inefficient production of energy crops. I've never seen any figures for organic farms in this regard, but I suspect they would be pretty shabby.]

OK, aside over. The prospects for biofuels are actually pretty good, especially if we can arrange to extract them from plants that grow fast and utilise sunlight efficiently, rather than whatever food crop we happen to already have in the ground.

I want to say a something about hydrogen while I'm in an energy frame of mind. There's a lot of noise and light surrounding the idea of hydrogen economy, and that's all it is -- noise. I don't even see much evidence of light at the present time, that's how empty all the idea is. The problem, minor as it may seem, is this: gaseous hydrogen is vanishing, infinitesimally, get-out-a-very-small-jar-I-might-have-some-here rare on earth. There are many many compounds that contain hydrogen (water is the one that everyone knows), but you need to apply energy to actually get the hydrogen out, normally quite a lot of energy. Where do you get the energy from? Not hydrogen...

Leaving aside this minor but pressing issue (I think nuclear power often assumed. I might deal with nuclear power later, but let's be charitable and assume some sort of solar power). Once you have hydrogen in your hand, few fuels are more of a nuisance. It burns very nicely of course; you can even persuade a piston engine to run on it, and boilers will run on anything you can shove under them (the recovery boilers in paper mills do very well burning wet, green bark). The real problem with hydrogen is transport and storage. Gas pressure is mostly a result of kinetic energy in the molecules. Being very small, hydrogen molecules move very fast. At a given pressure a given volume of hydrogen contains far fewer molecules than most other gases. In other words, it's bulky. You need big tanks to store it and big pipes to transport it (some piston engines designed to run on hydrogen have one intake valve that's solely for the fuel). On the other hand, being such a small molecule hydrogen also makes its way out through seals and so on very easily. That means it leaks. In fact hydrogen is such a nuisance to transport and store (even if you like dealing with liquids at minus lots and lots of degrees Celsius) that the most sensible solution is probably to attach it to some carbon molecules, to make something like ethanol... (or sugar, which is basically what plants do). Not to put too fine a point on it, the "hydrogen economy" is utter bollocks.

You could possibly argue on the basis of all this that energy in general, and transport in particular, are liable to become more expensive if and when we switch to biofuels. You would quite possibly be wrong, not because biofuels are cheap but because fossil fuels are expensive. Thanks to the dubious joys of the free-market economy, what's likely to happen is that consumers (that means you) will switch (if the choice is available) when alternative fuels become cheaper than the dimishing fossil fuel supply. For ethanol that point was reached and passed in the aftermath of Hurricane Katrina. You can buy ethanol-based fuels in Australia already, albeit manufacturers won't guarantee their cars to run on it (although the same manufacturers do make that guarantee in Brazil). The future is now...

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