First lets get straight what making Bio Diesel (BD) means.
There are sites that claim to make BD by adding some secret chemical plus gasoline and/or other ingredients to vegetable oil. That is NOT Bio Diesel.
Bio Diesel is produced by a transesterification process in which the vegetable oil molecule is torn apart producing 1 molecule of glycerol and 3 molecules of BD. While there is more than one way to accomplish transesterification the most common is the base (NaOH or KOH) alcohol (MeOH or EtOH) reaction in some kind (and there are several) of reactor vessel.
The site below will provide you with a good education in how to make BD and give you plans for an Appleseed processor (reactor).
so with an appleseed processor you can only make what the waterheater will hold in gallons at one time and that takes a few days to process. how do you make it in bigger quantities? can you?
Right. the conversion / processing tank size is your limitation in batch size. So, you can use a larger tank, or, run parallel tanks. Also, if you seperate your processing, washing and drying tanks, you can increase your rate of production since you can have one batch processing, another washing, and a third drying.
Once you are thru the reaction cycle all you have to do is move the batch to a settling tank and you can begin another batch in the reactor.
The total volume you can have in various stages will be limited by available room and the number of tanks you have that is a settling tank, a methanol recovery tank, a wash tank, etc.
I would recommend you consider methanol recovery and dry washing instead of the water wash methods found on most How To sites.
Methanol recovery saves money.
Dry wash gives a better quality product and reduces problems.