The keyword is 'cellulase'

One of the main barriers to widespread production of biofuel from biomass (corn stover, switchgrass, etc.) is breaking down cellulose.  But as this video notes, it's something that the gut bacteria in major consumers of biomass - in this case the panda - do quite readily.  So the key to biofuels is finding the bacteria with the cellulase -- the enzyme that breaks down the cellulose -- in the guts of the consumers.

So you collect panda poop and analyze the DNA of the bacteria.  Simple.