Unfortuantely, it is a bit more complicated than Marjorie makes it sound. You cannot seperate cooking oil into biodiesel and glycerine buy simply heating it up. Biodiesel is a compound know as methyl-esters or ethyl-esters, the distinction coming from which alcohol you use with your catalyst. In order to produce biodiesel you have to break the chemical bond in the oil. Below I will outline the process. If you want more specifics, please email me and I will be happy to send them to you.

1 Collect used oil
2 dry the oil- Heat to a temperature greater than 212degrees.
3 Titrate the oil. you will need to know the ph of your oil in order to use the right amount of catalyst
4 Mix Methanol or Ethanol with Cataylst (NaOH). Produce Methoxide
5 Mix with oil for aprox 1-2 hrs.
6 pump into seperating tank takes aprox 24 hrs to settle out.
7 pump the biodiesel into a water wash tank. let settle again.
8 pump into storage tank or your fuel tank.

I have been making biodiesel for the past 8 years with various rigs that I have made myself. The simplist was 3) 55 gallon drums, and old water heater and 2) water pumps from habor frieght. I use 100% in my truck and then mix a 55 gallon drum into my heating oil tank.

My final cost per gallon is about $.50 per gallon not counting my labor and the propane I use to dry the oil.