Transportation is one of the most popular, posted-on, talked-about topics at TreeHugger, and with good reason. We all have to get around, and it’s something that most of us do multiple times every day: to and from work, school, the store; shuttling kids; meeting friends…the list goes on. While there are multiple ways to accomplish this (and we’ll talk more about the options at a later date), we’ll focus today on biodiesel.

Not long ago, biodiesel was relegated to use only by who were perceived to be backyard chemists and hippies, existing in our collective conscience somewhere between tie-dye and burlap, but not anymore. Morgan Freeman, Daryl Hannah and Julia Roberts all actively promote the fuel; Willie Nelson even makes the stuff. Bands and musicians like Pearl Jam, Dave Matthews Band, Barenaked Ladies, Guster and Gomez have embraced it and use it to fuel their tours; in short, biodiesel has arrived.

Usually derived from vegetable oils (soy is very popular these days, but animal fats can also be used), biodiesel is made through a process called transesterification which essentially splits the oil into two parts: alkyl esters and glycerine; the esters are the fuel, while the leftover glycerine is often used to make soap and other beauty products. Both virgin and waste oil (often collected from restaurants) can be used in this process with equally good results. The fuel is non-toxic and biodegradable; read more about what biodiesel is and how to make it at Wikipedia’s biodiesel entry [].

What a lot of people don’t know is that you can use it to power any diesel engine without any modifications; it’s a straight fill-up-and-go affair. The great thing about biodiesel is that, in addition to being produced domestically and not being derived from a petroleum source, is that it has 60% less carbon dioxide emissions than petrodiesel (and many people report a pleasant, French-fry-like smell coming from the tailpipe. Combined with the higher fuel efficiency of most diesel-engined passenger cars, and it’s a pretty good, pretty green combination.

It’s not perfect, though. Like its petrol equivalent, biodiesel tends to turn a little gelatinous at low temperatures, so it’s not always suitable for year-round use, depending on the climate where you live; this problem can be addressed by getting a mixture of biodiesel and petrodiesel (you’ll see it on the pumps: B50 is a 50/50 mix; B20 is 20% biodiesel, and so on). Biodiesel is still growing, and so it isn’t readily available all over the place, as gasoline and diesel fuel is, so you’ll have to pay attention to your gas gauge and a know a reliable source or two. The good news is that its popularity is exploding, and more stations are popping up every day. With the recent addition of ultra-low sulfur-emitting diesel (ULSD) in the US [], diesel engines will be available in more cars than ever, and we expect biodiesel production and popularity to follow suit. To learn more about biodiesel, including where to get it in your neck of the woods, click on over to the National Biodiesel Board [] and stay tuned for more ideas on info on greening your transportation.