A fairly recent analysis of water use in biofuel crop production finds that Jatropha uses large quantities of water, when irrigated. Researchers from the University of Twente in The Netherlands report that Jatropha requires 5 times as much water per unit of energy as sugarcane and corn, and nearly 10 times as much as sugar beet — the most water-efficient biofuel crop, according to the same study (http://ww. newenergyplus. com/bioelectricity/bioenergy-claims-more-water).

Coauthor Arjen Hoekstra says it is true that the plant can grow with little water and can survive through periods of drought, but to flourish, it needs good growing conditions just like any other plant. "If there isn’t sufficient water, you get a low amount of oil production,” Hoekstra says.

So far I agree with Hoekstra. Before a plantation is started, rainfall statistics must be assembled to get a good picture of whether the plantation needs irrigation or not. In particular, large plantations in relative underdeveloped areas of the world will only be fed by rainfall. I argue that if the plantation is large enough, the yield per hectare will indeed be much lower, but due to the size of the plan­tation the yields are still very interesting for all parties involved. Therefore, I argue that this study is very academic, and is correct on paper and in the laboratory, but far away from the real plantation management of a large operation.

Hoekstra and his colleagues assessed the water footprint of 13 different biofuel crops. Their calculations included regional estimates ofhow much rainwater each crop received and how much additional water would be required through irrigation for optimal growth. The study also considered evaporation rates during the growing season in the main production areas ofeach crop and the average yields ofeach from 1997 to 2001. The figures were then averaged by country and globally to come up with a single water-footprint figure — per liter of ethanol or biodiesel — for each crop.

"You see a big difference depending on the country where the biomass is pro­duced, different climates, different agricultural practices, the crop being used, whether it is a starch or sugar crop used for bioethanol, an oil crop for biodiesel, or a crop that is burned for electricity generation,” Hoekstra says.

My comment is that although this is a wonderful academic study, I estimate that 75% of all Jatropha plantations are rain fed and not artificially irrigated, so I think more realistic to make a study of global Jatropha yields based on rain-fed plantations.

The team calculated that Jatropha requires an average of 20 000 liters of water for every liter of biodiesel produced in India, Indonesia, Nicaragua, Brazil, and Guatemala — the only countries for which Jatropha production figures were avail­able. For all the other crops, the researchers used much more comprehensive — and thus truly global — data from the UN FAO. Soybeans and rapeseed, the two other biodiesel crops considered in the study, were next highest in terms of water consumption, each requiring roughly 14 000 liters of water per liter of fuel.

My comment is that I think that soybeans and rapeseed should never be used to produce biodiesel. These species grow on agricultural land, which should be reserved for producing food for you, our animals and me. China, the world’s

biggest producer of rapeseed along the Yangtze River, has even forbidden the use rapeseed and soybeans as a biofuel. China is miles ahead in biofuel legislation, compared to the United States or Europe.

Other experts say that Jatropha and other biodiesel crops will likely be pushed out by much higher yields of cellulosic ethanol and algae in developed countries in the coming years.

My arguments are:

1. Capital investment in Jatropha is much less than for ethanol and algae, and especially the highly technical processes of cellulosic fuels made out of wood chips.

2. I suppose we will see a large commercial algae production around 2020 produced at competitive prices, but not before. ExxonMobil and Shell are multi­million dollar investors in algae.

3. The first big Jatropha harvest will take place in 2014, so I do not think that Jatropha "will be pushed out;” on the contrary, it is just starting!

4. Research will double the seed yields per acre or hectare in the coming years. The open issue is how to manage large plantations year in year out.

Henk Joos, one of the best Jatropha scientists in Europe, contends that the EU mandates still call for large quantities of biodiesel and says that newer, higher — yield strains of Jatropha could solve many of the plant’s water-use issues. Joos is cross-breeding different strains of Jatropha to increase seed production and to maximize the seeds’ oil content, and he is developing processes that allow the remaining seed biomass to be used for animal feed.

All in all, it is essential to differentiate between rain-fed Jatropha cultivation under highly water-stressed conditions and Jatropha cultivation with irrigation or under rainfall conditions that are sufficient to grow other crops.

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