Help: article Science - biofuels

[jones123]

Hi,

 

I was asked to evaluate the following article, concerning the disadvantages of biofuels: http://faculty.ucmerced.edu/ecampbell3/duane/Fargione-carbondebt-2008.pdf

 

But there are some things about figure 1 that I do not completely understand:

 

1) In the text it says: "Converting lowland tropical rainforest in

Indonesia and Malaysia to palm biodiesel would result in a biofuel carbon debt of ~610 Mg of CO2

ha−1 that would take ~86 years to repay (Fig. 1D)"

while the figure shows 702?

2) Figure 1C and D: "Number of years after conversion to biofuel production required

for cumulative biofuel GHG reductions, relative to the fossil fuels they displace, to repay the biofuel carbon debt"

Does this mean while continuing biofuel (and so CO2) production (then there would be more CO2 released during these years which accumulates to the initial release...) or after it stopped 50 years earlier? And what does this 'relative to fossil fuels they displace' mean?

Thanks a lot!

Edited March 14, 2013 by jones123