CHEN: And vegetable oil can be used in diesel car engines as a cheaper and greener alternative to fossil fuel. It is fast growing in popularity among Australians. Here is the story of a DIY biofuel user. STORY: For Sean Wright from Berowra in northern Sydney, Australia, fueling his car is not a matter of visiting his local petrol station. Instead, he fills his car up at home with an unlikely alternative --vegetable oil. With a little know-how, making the switch to vegetable oil is a relatively easy process. Wright filters his oil in barrels, then converts the filter in his engine. Wright says vegetable oil runs more smoothly and quietly than diesel. When he needs more, he simply visits his local restaurant or fish and chip shop to pick up their unwanted oil. [Sean Wright, DIY Biofuel User]: "It's cheaper so I can get the vegetable oil from the restaurants-- they don't want it so they give it to me for for free. There is quite a lot of effort involved with the...