The only problem, is that getting from the oil (let alone the bean and the non-greenness associated with it's production) is quite a series of steps. Consider this:
"Castor oil is converted to methyl ricinoleate by treatment with methyl alcohol. Methyl ricinoleate is pyrolysed at high temperature yielding heptaldehyde, methyl undecylenate and a small amount of fatty acids. Methyl undecylenate is hydrolysed to produce undecylenic acid. When undecylenic acid is treated with hydrogen bromide in a non-polar solvent in the presence of peroxide, reverse Markownikoff addition occurs and the main product is x-bromoundecanoic acid. This is then treated with ammonia to give x-aminoundecanoic acid, which is a crystalline solid. Aminoundecanoic acid is the starting material for nylon-11."Source
So after getting the oil, you add 1) methanol, 2) heat, 3) a purification step, 4) water, 5a) HBr and 5b)an unspecified solvent and 5c) peroxide, and finally 6) ammonia. But after all that, you're still not done - you still have to polymerize the aminoundecanoic acid and remove the water.
And somehow this is considered a renewable polymer!
As we all learned in multivariable calculus, you don't find a global optimum by optimizing each individual variable, you optimize the systems as a whole.