Dear PF Forum, I have searched biodiesel through internet. There are good answers there. And also in Physics Forum, and I come accross these two links from PF Forum, which are a very good links. http://biodiesel.org/ http://nbb.org/ And I also consulted LIPI (Indonesian Science Establishment). The pollution from Bio diesel vs petrolium oil is better. And also the carbon cycle that they explained there makes sense for me (at least I can follow their explanations if not understand them). My church wants to help the environment by converting used cooking oil to biodiesel. And that leaves me with this one question. 1. Is the pollution generated from cooking oil is less than gasoline? Actually I have other question, too Some of the internet links say that (even) pollution from biodiesel are higher than gasoline, but because of making biodiesel from plants, the plants have already converted CO2 to hydrocarbon. 2. Is it true that CO2 emission per joule from biodiesel are higher than gasoline? And the conclusion from question 2, 3. Is the pollution from used cooking oil biodiesel is higher than gasoline? 4. If it is YES, than in net, the pollution from used cooking oil biodiesel is actually lower because of carbon cycle? Thanks for any replies. I've been searching this answer for 2 months, and those are the questions that I haven't got the answer, yet.