OK, it seems to me that a lot of the talk about biofuels from renewable sources such as cattle waste, wheat, or cassava relies fundamentally on the amount of water available in the locations that are being farmed.
My current worry is that there may not be enough water available to grow crops or fatten the cattle, in the dryish parts of the world that are so good for these activities if we go hell for leather for biofuels. This is because much of the water we rely on in these areas is found underground in aquifers and because it may not be possible to put back the water that is extracted from the land as fast as we extract it.
It may come from underground because there is not enough surface water or rain water to successfully irrigate crops or because surface water is too polluted.
Until man came along it didn’t matter much if there was a water shortage. Plants withered in the summer, and a few of the seeds from good years managed to survive to start generations off again. One of my grandfathers, who worked the soil for a while, reckoned that you had to pull weeds up quickly because “one year’s weeding saves seven year’s seeding”.
But once you start depending on plants for food or biofuel then their performance becomes critical. And their performance depends on two main factors the amount light and heat and the amount of water that they get.
If resources are over stretched, then the results can be disastrous.
This was shown dramatically in the desertification that occurred in the US Midwest in the 1930s, and was due, at least in part to overenthusiastic farmers trying to take water out of the underlying aquifer, faster than it could flow back in.
A distance learning resource from the University of Iowa, has an interesting take on depletion of the Ogallala Aquifer which sits under a swathe of states running from Nebraska (where the Aquifer is good and big) through to northern Texas (where it is thin and skinny).
Looking at water alone, plants are more efficient converters of water to energy
According to Unesco’s report, the Water Footprint of Nations
the global average virtual water content of maize, wheat and rice (husked) is 900, 1300 and 3000m3/ton
respectively, whereas the virtual water content of chicken meat, pork and beef is 3900, 4900 and 15500 m3/ton respectively
Conveniently 1m3 water weighs one tonne so it takes 1300 tonnes of water to grow 1 tonne of wheat (but only 900 tonnes to grow a tonne of maize). It takes 15,500 tonnes of water to grow 1 tonne of beef which will produce biofuel over its lifetime. .
Now looking at Kholsa’s biofuel set up in Nebraska, you can and should argue that of that 15, 500 tonnes of water, most will be returned to the prairie as the cows go about their business. Some of it pretty directly, but the cows breathe out water vapour, and some water vapour evaporates from the surface of the prairie before it can get back into the aquifers that it came from.
Perhaps the last word should go to the editors Glantz, Michael, ed. Who produced the 1989 book Forecasting by analogy: societal responses to regional climatic change quoted by the University of Iowa
Is the drawdown a national problem? How concerned should national leaders be about the depletion of this aquifer? This question raises a dilemma for some of those immediately affected.
What do you think?