The Oil Drum

Virtual Water, Real Profits

"A typical meat-eating, milk-guzzling Westerner consumes as much as a hundred times their own weight in water every day," says Fred Pearce, former New Scientist news editor and author of When The Rivers Run Dry.

That's because it takes between 2,000 and 5,000 litres of water to grow one kilogram of rice, 11,000 litres to grow the feed for enough cow for a quarter-pound hamburger, 50 cups of water for a teaspoon of sugar and 140 litres of water to produce just one cup of coffee. The world today grows twice as much food as it did in the 1960s, but uses three times as much water to grow it. Two-thirds of all the water taken from the environment goes to irrigate crops. "This is massively unsustainable, and has led many people to conclude that the apocalypse wasn't averted, only postponed," says Pearce.

And the over-use of water doesn't just apply to food production. Every T-shirt you wear will take 25 bathtubs of water to produce. Every small car uses 450,000 litres. If what you wear or drive is imported, you in the West are helping to empty rivers across the world. Water used for growing food and making products is called "virtual water". Every tonne of wheat arriving at a dockside carries with it, in virtual form, the 1,000 tonnes of water needed to grow it, explains Pearce.

The global virtual-water trade is estimated at around a thousand cubic kilometres a year, or 20 river Niles. Two-thirds is in crops, a quarter in meat and dairy products, and just a tenth in industrial products. The biggest net exporter of virtual water is the US, which exports in grain and beef around a third of all the water it takes from the environment; Canada, Australia, Argentina and Thailand are all net exporters too.

In posting about oil shale, one of the points that needs stressing is that the oil is not really oil. And this creates a problem when it comes to getting the kerogen (or oil for simplicity) separated from the rock around it. As I said in the first post on this, the oil can be separated in a retort, after being mined. The retorting can be self-energized and, by heating the oil it can be transformed into a form of butumen that can then be further refined into a commercial grade of shale oil that can be similar to a more conventional crude.

Mining shale, however, is fairly expensive, both in terms of energy, and hard dollars. At the same time, once the oil is extracted, the spent shale has to be disposed of. That costs more money. Considering all these potential expenses and potential problems, it is therefore not surprising, from the beginning, that the idea of trying to create the initial retort in the rock, and making that transition to oil in-place looked as though it might be a winner.

Grin - well Yankee has suggested that we need more information on coal gasification and so, after threatening to do this a couple of times, today, having talked a little about surface gasification I thought I would move to the subject of in-situ gasification of coal. That would allow, if successful, that we would burn the coal in place, underground. This might have the advantages of not requiring the surface plant and impacts that a conventional coal mine would need, and it might also provide some useful way of getting to otherwise unavailable deposits such as those under the North Sea. Most particularly it would remove the need for all the grimy gas works that were dotted over Europe and North America until natural gas came along to clear the air. It is a subject that the Chinese are looking into

The Chinese government has authorized an underground coal-gasification project in Lineng of Shandong Province recently. This is a model project combining in-sit-coal gasification and gas-fired power generation.

, as well as being of interest to the British, the Australians and ourselves, to name but a few.

This is another in the weekend technical talks that pop-up at frequent intervals on this site, It fits in with a series on coal technology that is listed at the end of the post, and more particularly is related to other ways of generating fuel from coal other than just burning it in a boiler to generate steam. As with a number of ideas that are getting more discussion (such as the injection of carbon dioxide back into the ground, and the use of pulverized coal in diesel engines) it is not particularly new, but since it is now getting more attention, the post will attempt, in a relatively simple manner, to explain what it is all about. For those more knowledgeable please do comment, as should those who find the explanation not totally clear.