"Tim Lamb" wrote in message
...


Now for the arithmetic.... Most arable crops need to be grown as part of a
rotation to reduce the build up of pests and diseases. Let us say you grow
it one year in four. That is 1.8tons x 0.4 /4 = 0.18 tons of oil/ha.

A bit too simple.. you can grow other oil plants in the rotation, like rape.