I get my used vegetable oil from local Chinese or Vietnamese restaurants. It feels a little awkward at first, but when first approaching a restaurant, ask to talk to the manager, and then simply explain what you want. Tell them you'd like to pick up their oil (or some of it) every week if they don't mind. Once they see that you're reliable, they may even cancel their contract with the rendering company that usually picks up their oil (which costs them around $40 per month!). This has happened with most of the restaurants where I get oil. Technically, if the restaurant has a contract with a rendering company to pick up their oil, the oil belongs to that company once it's in the waste barrel.

The oil from my sources is soybean, canola, and peanut. Ask to look at the box that the oil came in; you want plain "salad oil" if possible, with no additives (which are often added to extend the life of the oil. One called dimethylpolysiloxane (yuch!) will make the oil thicken in the winter. Also stay away from hydrogenated oils, which will make biodiesel that gels at higher temperatures). It's also a good idea to titrate the oil before agreeing to take it. The more the oil is used for frying, the more free fatty acids will be in the oil, which will generate soap when you make biodiesel. If the oil titrates above 3, I usually won't take it. You can bring your titration kit with you and decide on the spot. My better oils titrate at 2 or below (see titration section).

Some restaurants put their waste oil in 5 gallon plastic containers (which is great cause it won't allow water to get in), others in a 55 gal drum, and some in a 400 gallon tank. Check to make sure you are not getting any water along with your oil. Some drums are not covered well and water gets in; my sources always have good lids. If they do not have a good lid or their drum is bent, buy them a new drum with a good cover (if they don't have a contract with a renderer). Also, it's a good idea to put a piece of window screening on the drum under the lid to catch food chunks so they don't accumulate in the drum.

To transfer the oil from a drum to 5 gallon containers, I use a 12V diesel transfer pump (10 gal per minute- also check out this oil pump that is probably better) that clips to my car battery (see video), or can be used with a battery charger set at 15 Amp. I use the battery charger at one restaurant where I can't get my car close to the oil, but where they do have an AC outlet. The charger acts like an inverter, allowing he DC pump to run on AC. You could also use a lot cheaper hand pump. Be sure to put a piece of window screening on the end of your sucker hose, so you don't clog your pump with french fries or beans.

When you get the oil in plastic containers, you might also get some water; you should see it as a layer at the bottom, especially if you let it sit for a day or two. Heating also helps separate the water from the oil. Just pour off the oil and leave the water. Sometimes the oil and water don't separate and the oil looks a bit milky. In this case, it's best to dispose of the oil, rather than risk using it to try to make biodiesel (it will produce bad biodiesel and too much soap).

Let the oil sit in the carboys for a couple days to allow water to settle out; this will allow you to see any water that might be present, cause it'll show up as a light layer on the bottom. Water in your oil will cause you to get a fluffy soapy middle layer when you do the reaction, and that's not a good thing! If that happens, you can still successfully wash it out, but it's trickier and more time consuming (see wash section). You can also try pumping the oil into your processor, heating it up as much as possible for an hour or so, and then just letting it sit for a couple days- then drain any water out the bottom.

Pour the oil through another 200 or 400 micron mesh filter/strainer just to catch any additional food bits. You don't really want that stuff getting into the plumbing of your processor.