Les partisans des agrocarburants sont de doux rêveurs. C’est ce qui ressort de solides travaux publiés dans Environmental Research Letters par un quintette de chercheurs américains. (...) Le verdict: la capacité de production annoncée par les partisans des agrocarburants est largement surévaluée, parfois le double de ce qu’elle est réellement (...)

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Resetting global expectations from agricultural biofuels
Matt Johnston et al 2009 Environ. Res. Lett. 4 014004 (9pp)   doi: 10.1088/1748-9326/4/1/014004 

Abstract. Aggressive renewable energy policies have helped the biofuels industry grow at a rate few could have predicted. However, while discourse on the energy balance and environmental impacts of agricultural biofuel feedstocks are common, the potential they hold for additional production has received considerably less attention. Here we present a new biofuel yield analysis based on the best available global agricultural census data. These new data give us the first opportunity to consider geographically-specific patterns of biofuel feedstock production in different regions, across global, continental, national and sub-national scales. Compared to earlier biofuel yield tables, our global results show overestimates of biofuel yields by ~100% or more for many crops. To encourage the use of regionally-specific data for future biofuel studies, we calculated complete results for 20 feedstock crops for 238 countries, states, territories and protectorates.

Version intégrale HTML:

http://www.iop.org/EJ/article/1748-9326/4/1/014004/erl9_1_014004.html

Les valeurs étaient sur-estimées d'un facteur 2 pour: blé, sorgho, betterave sucrière, maïs, Jatropha, noix de coco, tournesol,  colza, etc. !


Rendements avec l'éthanol (moyenne mondiale), en fonction du type de plante
Barres orange et rouge: valeurs qui étaient retenues jusqu'à présent, mais complètement remises en cause par cette étude globale. Barre noire: moyenne obtenue avec cette étude.
Gris: monde entier - Pays développés: vert -  Pays en développement: bleu

Rendements avec les filières huile (moyenne mondiale), en fonction du type de plante:

Figure 2. Revised estimates of global biofuel crop yields. (a) Global ethanol yields, (b) global biodiesel yields. (Box plots represent the variation of yields for common biofuel crops. Here we show results averaged for the entire globe (gray), developed countries (green) and developing countries (blue). The horizontal black bars represent median yields, and the boxes are bound vertically by 25th percentile yields on the bottom and 75th percentile yields on the top. The whiskers (in light gray) represent the absolute minimum and maximum yield values recorded in the M3 cropland datasets. The red and orange bars offer comparisons to two previous examples of biofuel feedstock yield estimates, reported by Worldwatch Institute [18] and Brown [16] respectively. Please note, the M3 results for sorghum are compared to Brown's estimate for sweet sorghum, which is a different variety with higher sugar content than is normally grown and traded commercially.)