http://www.oilgae.com/energy/sou/ae/re/be/bd/po/hem/hem.html
"Hemp plants can produce about half a ton of seeds per Acre but such production is currently relatively expensive. Hemp seeds contain 30% oil, compared to 18% for soybeans, 30% for canola, and 40% for flax. Thus hemp’s Oil content is comparable to that of any other common oil crop. But hemp oil has its problems—the oil degrades even more quickly than other vegetable oils and it is much more expensive than current oil crops. Hemp Biodiesel theoretically can a source of energy. However, it does not appear to offer any significant advantages over other biodiesel sources"
Also, here in Canada, there is a huge regulatory aspect. Only certain (Low THC)varieties can be grown, and then only under Govt license, Moving viable seed requires bot shipper and receiver to be licensed. If you are processing it you need a license.