March 18, 2006

Energy, and why you should care

Posted in Uncategorized at 9:19 pm by Chris

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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