If Rudolf Diesel used hemp oil in the engine he originally invented and assumed we'd be doing the same then why is that information kept from the public?

If Rudolf Diesel used hemp oil in the engine he originally invented and assumed we'd be doing the same then why is that information kept from the public?
In Diesel's original US patent, there is no evidence for the truth of the first part of the question. In fact, the patent specifically makes the point that you could use many different kinds of fuels; vegetable oils are mentioned, but there really aren't any particulars of which ones. There are also no indications of redaction in the patent. At the time the patent was issued growing hemp was entirely legal in the US, so there's no real reason for him for him to have left it out if he thought it was important.I don't believe there is a conspiracy, crops grown for fuel remove land from food production. I think given a choice between food and fuel,food is a better use of agricultural resources. Recent shifts of corn to ethanol production drove up food prices because of greater demand for corn and less availability.As an example of the point made in the previous post, George Monbiot contends that if Britain were to switch to bio-deisil entirely, It would take twice the amount of total arable land it currently has.