Sorry I mean that with the current availability it will not be used in the long term. I am pretty sure KL will fly a few routes now, and after a while switch back to regular kerosine.
You are right that frying oil is wasted all over the country...but to collect it at one place is expensive. Just think about collecting the stuff at various restaurants, a few litres at a time. Crazy expensive compared to current kerosine prices.
When production of vegetable-based oils becomes higher, with lower prices, I am sure airlines will start using it. Especially with the taxes you mention. Because that has the potential to be cheap and available in large amounts. I don't think frying oil will ever be available on the cheap in large amounts.
It is funny to think you fly thanks to all the fries you ate. You don't have to feel guilty anymore.
Dont forget that the extra weight you gained by eating fries will cost more fuel for take off! ;-)