Know your veggie oil from your grease
What is vegetable oil? Vegetable oil is usually the cooking oil you purchase at a retail store. It’s a domestically produced renewable resource, and can be made from a variety of seeds and plants such as soybean, corn, canola, and sunflower, to name the most common. It’s used in large quantities by many restaurants for cooking, and when used to fry food, much of it can be recovered and reused to make other products such as fuel for vehicles.
What’s the difference between high and low quality used cooking oils and compost? Vegetable oil is used for cooking and frying. It’s liquid at room temperature and can be many shades from a light yellow to a dark brown. High quality used vegetable oil is a clear liquid, light in color with no water or particles; it is the kind that can be most easily used to make biodiesel. Low quality used cooking oil refers to lower grade lipids including animal fats and pan grease. This product is often dark brown in color and highly contaminated with food particles. It’s very difficult to recycle for biodiesel production, but can be turned into other industrial biofuels. Compost in this context means food scraps. Griddle scrapings, animal carcasses, breading, and other food particles are often mixed with cooking oil. They should be strained and separated from the oil and disposed of with the rest of the compostable materials.
What about shortening and lard? Shortening is another term for partially hydrogenated oil, which contains transfats. We strongly recommend against the use of partially hydrogenated oil. For more information on hydrogenated oil and transfats, visit the San Francisco Department of Public Health website at www.dph.sf.ca.us/. Lard is animal fat. Both are not ideal for biofuelcollection because they solidify at room temperature, requiring special fittings and expensive modifications to existing collection equipment. They cannot be recycled at the residential drop-off sites. For more information on different types of grease and their use as biofuel feedstock, visit our FOG Facts page.
What is biodiesel? Biodiesel is the name of a clean-burning alternative to diesel fuel, which can be produced from vegetable oil. Biodiesel contains no petroleum, but can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.
