What follows is not a guide to manufacturing Biodiesel but is intended to illustrate how I built a simple biodiesel processor. If you want to know detailed information on all the methods of manufacture and alternative processor designs, refer to the links included earlier in this thread posted by Stickboy.
In order to manufacture Biodiesel you will need to construct or buy a vessel for holding your oil (either new vegetable oil or Waste Vegetable Oil - WVO). You will need to be able to drain from the vessel so it will help if it has a conical bottom. You will need to heat the oil contained in the vessel. You will need to add a mixture containing Methanol and Caustic soda (Lye) to create what is referred to as Methoxide. You will need to mix the methoxide with the oil. Finally, after draining the byproduct, you will need to filter and wash your brew.
After toying with various ideas, I settled on a domestic water heater (A). It already had all the holes in the right places, the rounded top (when turned upside down) gave it a conical bottom. It has a heater element for warming the oil and… most importantly, cost me just $120
After making a wooden stand, I then plumbed in a water pump (B) this is just a pump used in a central heating system and cost me $40 from eBay.
The pump serves three purposes, it allows me to circulate the oil when heating and is powerful enough to mix the methoxide with the oil at that stage of the process. Finally, by shutting off one valve and opening the other (valves cost $10 each) I can divert the oil into the filter (C)
The filter cost me $30 and the filter cartridges (5 microns and 1 micron) are about $3 each. I generally recirculate the oil thru the filter and then back into the tank thru the hose (D) several times. When I am happy the oil is cleaned I take the hose out of the tank and pump the biodiesel into a holding tank to dry.
There is another valve, that you can't see in the picture, that is at the base of the tank. This is used for draining the by-product from the process (glycerine) into a bucket.
The final stage in the process involves 'washing' the biodiesel. I have a length of hose connected to a tap and use a garden 'mister' to add the water to the BD which then forms droplets that gently washes out impurities (methanol and soap) from the BD. This water is drained from the bottom in the same way as the glycerine.
Like I said before, I don't want to go into the details of the process, just share an idea on how to build a processor. I am new to biodiesel and have only made 2 batches (of about 50 litres each) but this system works.
One improvement would be to use a sealed container in order to keep the poisonous (methoxide) fumes contained. I turn on several powerful fans and keep out of the garage until all is clear - be aware that methoxide is a nasty, toxic liquid/gas that you should take all necessary steps to avoid contact with.
Jim