A recent editorial written by Fred Pearce in points out the alarming possible repercussions of growing biofuels for the world’s water supply. As the policy makers seriously consider this option as an apparently climate change-friendly method of fueling the world, we have to consider what affect this might have on other, already stretched, natural resources such as water.

George Bush has announced that he wants to turn corn into ethanol to fuel America, but a lot of energy would be needed to produce fertiliser and pesticides to grow the corn and the process of conversion is very inefficient, resulting in greenhouse gains of probably only 10-20%. So, should we follow the example of the Brazilians and grow sugar for ethanol? Sugar produces bigger greenhouse gains as agricultural inputs are often lower and it avoids the process of conversion of plant starch to sugar to produce ethanol. However, as Fred Pearce explains in his editorial, "Sugar is one of the thirstiest crops in the world… It takes a great deal of water to grow. Sometimes that comes from the rain, but in many parts of the world it comes largely from expensive irrigation schemes that are already, as we have seen, drying up great rivers. Sugar, moreover, takes a great deal more water than most other crops to process. Typically, more than 100 tonnes of water for every tonne of sugar, though there are ways of reducing that."

If biofuels really are going to be used to the scale that some people are predicting, this could have huge implications for water use in agriculture. Whilst well-off sugarcane farmers divert water to their fields, the poor farmers will be left to fend for themselves. This may already be the case in Maharashtra where big landowners are scrambling to grow more sugarcane to meet expected demand for biofuels, resulting in water tables being lowered by hundreds of metres in some places. According to the editorial "the International Water Management Institute reckons that world water use in agriculture could almost double if biofuels took even a quarter of world energy requirements."

This extra pressure on the water supplies could cause a water shortage for growth of food crops. According to Rijsberman, director general of IWMI, there are two types of water shortages: those observed in regions such as North Africa, northern China or parts of the southwestern United States where water is over-exploited, causing a lowering of groundwater levels and rivers to dry up; and those in countries where water is available in rivers and aquifers but where people lack infrastructure to exploit it, such as in large tracts of sub-Saharan Africa or northern India. A report by IWMI released at the 2006 "World Water Week" conference in Stockholm and compiled by 700 experts, suggests that better irrigation, rainwater harvesting from roofs or use of simple water pumps, operated manually, could help poor countries in Africa and Asia.

So if we are going to grow biofuels in large quantities we need to start thinking about improving irrigation systems and/or finding alternative biofuel crops that provide a balance between carbon efficiency and water requirements, otherwise we may have the climate change-friendly fuel to power our cars but not enough water to grow food to feed ourselves!

Fred Pearce, "Can the planet irrigate the world’s ethanol demands?", 12 January 2007.
Alister Doyle, "Food, biofuels could worsen water shortages-report". Reuters, 20 August 2006.

For more information on biofuels, irrigation and/or climate change, subscribers of CAB Abstracts, Biofuels Abstracts or Irrigation and Drainage Abstracts can search these databases for similar publications.

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