By the time you've grown crops, transported, processed, etc any sort of biomass - is it still an efficient source for biofuels?
Your question is excellent. You don't want to spend more $$ or fuel on transport than the price of the material itself! A decentralised model is necessary for the biorefinery concept to work. The plant needs to be close to the source of waste. I stress the term waste, the process to work must turn a waste into a commodity. Also the single product paradigm will not work, as you mention in your question. A biorefinery, however, extracting all the value from the material, may work. The biorefinery concept is that we should never only make one product, but a combination of production of different values. For example, coupling bioethanol synthesis with the bacterial production of biodegradable plastics.
Answered By: Dr. Richard Sparling