September 15th, 2009

The water footprint of bioenergy from Jatropha curcas L.

In an important international scientific journal (PNAS), Jatropha curcas was recently portrayed as one of the most water inefficient crops for bioenergy production (Gerbens-Leenes et al., 2009).

Wageningen University and Research centre in collaboration with Delft University of Technology strongly opposed to this conclusion, as the presented methodology was inadequately applied to jatropha. Inappropriate field data were used and the methodology neglected the remaining press-cake as energy source (Jongschaap et al., 2009; Maes et al, 2009).

The water footprint (WF) of energy crops should be calculated by relating the energy yield of a crop to its actual water use under actual climatic conditions during the growing season. The flawed methodology related optimized crop water use (of mature plantations with additional irrigation) to actual oil yields only (of younger plantations) thereby introducing bias towards inefficient WF for low-yielding crops under suboptimal rain-fed conditions, such as often is the case for jatropha. Soil characteristics that influence water availability were also neglected.

By using proper field data from 4-year old jatropha plantations in South Africa, the Water Footprint (WF) of bioenergy from Jatropha curcas L. was calculated as 8,281 L of water per L of oil and 128 m3 of water per GJ. This was 1/3 of the presented WF of soybean, comparable to the WF of cassava, and only 1/5 of the WF obtained for jatropha by using potential crop water requirements.

References

Gerbens-Leenes, W., A.Y. Hoekstra and T.H. van der Meer, 2009. The water footprint of bioenergy. Proceedings of the National Academy of Sciences 106, 10219-10223. Available online at: http://www.pnas.org/content/106/25/10219.full.pdf.

Jongschaap, R.E.E., R.A.R. Blesgraaf, T.A. Bogaard, E.N. van Loo and H.H.G. Savenije, 2009. The water footprint of bioenergy from Jatropha curcas L. Proceedings of the National Academy of Sciences 106, E92-E92. Available online at: http://www.pnas.org/cgi/content/extract/106/35/E92.

Maes, W.H., W.M.J. Achten and B. Muys, 2009. Use of inadequate data and methodological errors lead to an overestimation of the water footprint of Jatropha curcas. Proceedings of the National Academy of Sciences 106, E91-E91. Available online at: http://www.pnas.org/cgi/content/extract/106/34/E91.