This instructable has a lot of great advice on making your own biodiesel. You should learn as much as possible about the process since it can be dangerous. However, it’s a great way to use waste vegetable oil (WVO) and reduce pollution.
This type of Processor is called an appleseed processor. It uses an old (or new if you feel like dropping the money) water heater. The amount of fuel you can make will depend on the size tank you use. My first prototype uses a 10 gallon tank. Not too efficient if you plan on making large quantities, but great for figuring things out.
Learn how to make a Biodiesel Processor