There is a very good reason why no environmental and bio diesel scientist /engineers considers  hemp as viable bio-diesel material,hemp is a terrible plant for  for bio diesel production.The yield is pathetically low when compared to other candidates,the fact is there are plants that easily outclasses hemp both in oil production(via hemp seed) or plain biomass production readily available in every growing climate and region.Furthermore large scale  hemp cultivation  is just as damaging to the soil as   corn and cotton .