photo: Mike Locke via flickr
You’ve undoubtedly seen estimates about the crop yields of various plants for use as biofuels. Indeed, when comparing the potential of different crops you need these numbers to make informed agriculture and renewable energy policy decisions. The problem is, according to a new report published in Environmental Research Letters the estimates we’re currently using are way too high. Here’s why:Published Tables Don’t Distinguish Between Locations
It’s really a problem of over generalization: Most current yield estimates are based on data from the US and Europe and don’t take into account local variation in climate, soil, technology, etc. What’s more, the widely quoted and circulated tables of biofuel crop yields don’t always cite the original sources of their data, often listing only one figure for a particular crop whether it’s grown in Iowa, India or Brazil.
Happens in Both Developed and Developing World
The greatest gaps were often found (not surprisingly) to be between the published yields and those in developing countries. Citing the figures for corn production, it was found that the difference between developed nations and developing ones was severe: While crop yields in developed nations corresponded well with published tables, in developing nations the yields were often overestimated by nearly 100%.
But even in developed nations there were discrepancies. Looking at Canada, it turned out that average yields of rapeseed for biodiesel were about 50% lower than widely accepted figures.
New Yield Range Tables Determined
To rectify the situation researchers looked at a global agricultural database which took data from 238 countries on the yields of 20 different biofuel crops. These numbers were compared against published yield tables, and new averages were calculated: A global average, one for the developed world, and one of the developing world.
I'd reproduce the graphs here, but reducing them enough to fit here would just result in a squiggle of lines. Those wishing to view these averages (given as a range of yields, not a single number) should view the original article: Resetting global expectations from agricultural biofuels
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