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Biodiesel 101

biod6.jpgBiodiesel seems too good to be true. Substituting processed vegetable oil for petroleum-based diesel is as much a political act as a technical one, and tends to inspire thoughts of being able to say goodbye to Big Oil. Plant-based fuels are inherently close to carbon-neutral, and biodiesel is non-toxic, as well. It's especially appealing to those worried about being able to shift to new vehicle technologies before oil runs out, too, since we already know how to make diesel engines. There has to be a downside, right?

Well, yes. Commercial biodiesel is still pretty expensive, where available, and questions remain about just how energy-efficient the whole process is. Biodiesel has some disadvantages as a fuel, such as a higher "gel" temperature than regular petro-diesel, meaning that your car will stop working in colder weather. On top of this, in the US, at least, diesel cars are actually pretty hard to come by these days.

But let's say you do have a diesel car, live where it's still relatively warm, and want to give this whole biodiesel thing a try. While some truck stops may have biodiesel/petrodiesel mixes available (usually "B5," 5% bio, or "B20," 20% bio), most biodiesel aficionados actually make it themselves. And that remains one serious advantage of biodiesel: it's the only fuel for your car you can make at home in the kitchen.

Instructions for making biodiesel at home aren't too hard to find online, but one of the better recipes comes from a site that's rapidly becoming one of my favorites: inhabitat, a site which mixes innovation, design and sustainability. Inhabitat writer Sarah Rich gives a detailed DIY guide for "brewing biodiesel," using a process that she uses herself. It's a good mix of science and straightforward step-by-step instructions, and makes me long for an as-yet-unavailable diesel hybrid.

How many of you use biodiesel in your own vehicles? Tell us your stories...

Comments (19)

Good spy! The more sites with interesting environmental stories to tell the better, and Inhabitat looks like a good one. Organic concrete (the most recent post) has interesting applications for greening cities etc.

I recently graduated from a university and there were a couple of students who retro-fit their VW's to run off of vegtable-based oil. There are kits you can get to modify your diesel car, and the setup seems relatively easy. The best part was that the students were able to obtain relatively large amounts of used oil free from the dining halls. It was a great concept, yet seems like a niche solution for a few. Dependability of the vehicles was also a possible issue, especially in cold weather.

Steve Andersen:

Commercial biodiesel is still pretty expensive...

It's all relative. In Seattle, commercial biodiesel is now cheaper than petroleum-based diesel. I pay $3 for b-100, and I saw diesel for $3.09 at the pump.

People need to distinguish between biodiesel and "greasel".  "Greasel" is filtered waste grease (triglycerides), which is rather viscous and must be heated to flow well enough to be atomized and burn properly in a diesel.  Triglycerides can be converted to biodiesel by transesterification:  the glycerine backbone is detached from the 3 fatty acid chains on it, and the fatty acids are converted to methyl or ethyl esters (the glycerol is a byproduct).  The esters are much less viscious and flow at much lower temperatures than grease, though they do have a high cloud point compared to petroleum diesel.

Biodiesel and greasel are good ways to make use of a waste product, but there is not enough production of vegetable oils to replace more than a small fraction of petroleum diesel.


Go to your search engine and punch in urieli alpha stirling turbine and you will find a machine that will be able to burn hay, nut hulls, grass or whatever, and do the same work as a diesel, while leaving behind (or storing in a little bag) a whiff of biomass ash and recycled carbon dioxide.

This thing lasts a very long time, does not take any magic to make it happen (unlike fuel cells) and will burn just anything at all pretty cleanly.

Diesels are great, and biodiesel even more so, but why bother when you can turn into real power all sorts of trash old hay, and all the stuff that goes to landfills and turns into wasted methane?

The real power of biodiesel is its low barrier to entry. You don't need to wait for some giant corporation to decide that it makes sense to manufacture biodiesel cars, and you don't need to wait for a nationwide network of fuel stations, service stations, parts distributors, etc. to spring up supporting them. You just find a diesel car, slap on the (relatively simple) conversion kit, and start running. You can burn as much or as little biodiesel as you like. This is the way to make a major change happen!


I don't buy the theory that biodiesel is climate neutral, especially when you consider all the petroleum inputs necessary to get that liter, gallon or whatever of oil to market. In any event, this will always be a niche product because we don't have the farmland necessary to make it available on a mass basis.


All the talk of biodiesel is great...a friend of mine and I are scaling up to manufacture the stuff in 100 to 200 gallon scales in the home, all from greasel. But the talk of using soy beans to make biodiesel is nuts! A better plant material would be jathropta or rapeseed, which do not need the high inputs of fertilizer and pesticides. Also, the oil content of the plants is much higher than soy, 20% for soy vs. 70%-80% from jathropta. As we start facing oil shortages, both from weather, infrastructure and geological depletion, energy return on investment will be a major filter for all sort of energy projects. Diversity of fuel will result in a more stable, sane, just and healthy society. Recycling waste vegetable oil may be niche now, but in about 5 years it will occupy a larger sector of the energy pie...how many McDonald's, Burger Kings, Dairy Queens, Burger Shacks and Chinese restaurants dot the landscape in North America? That's a lot of greasel...

Digging through my archives I found that I'd read (somewhere) that the US uses about 3.5 billion gallons (833 million barrels) of cooking grease per year.  If you converted all of it to biodiesel at 1:1, you'd replace a mere 5.6% of US distillate oil consumption and about 1.1% of US oil consumption (see the data).

It's a big problem and small measures won't fix it.  (On the other hand, it fixes the low-sulfur lubricity issue.)

Whoops, that's 83.3 million barrels/year (need to use scientific notation in my calculator).

What E-P said. Still, even that tiny contribution will might help in small ways.

Many years ago I used to work as a dishwasher at a restaurant. One of my tasks was to empty and clean grease traps and otherwise collect all the grease that accumulated during my shift. The sanitation department wouldn't let us dispose of this grease in the trash, so we had another company come in and "do something with it." I never figured out what happened to all that grease. Maybe that company converted it to fuel or something.

Anyway, greasel sounds like a good way just to keep that grease out of the waste stream even if it's woefully inadequate as massive petroleum replacement scheme.

O'Reilly's Make magazine volume 3 has an article on a detail recipe on making biodiesel (http://www.makezine.com/03/biodiesel/). No online edition, have to buy the zine though. It has an interesting comment that the production process feels more like cooking that refining :)


Here's an interesting article entitled "Widescale Biodiesel Production from Algae":


The author claims that you could replace all petroleum used in the U.S. with biodiesel from algae grown on 15,000 square miles of flooded desert.


As the discussion shows (and sometimes does it indirectly), any attempt at conservation and material recycling will have benefits for society. Removing waste grease from the waste stream may have other beneficual effects that have not been accounted for in the discussion.

And thanks to E-P for the quick calculation on the WVO output in this country. Even though, after the correction, this accounts for less than a percentage of total US oil consumption, it may have a comparatively large effect on diesel users (a minority fuel in transportation in the US).

That's what I love about this site, a great mix of dreamers, doers and engineering-types. Maybe the world isn't so bad after all.


Here's a great site on how to make your own Biodiesel. They use an old water heater.


The fraction of demand which can be satisfied from waste grease is a hint as to how useful it is to ramp up production to make more:  not very.  It would take only a small boost in economy to offset a complete loss of all biodiesel.

While it is only too sensible to make use of every process byproduct we can instead of throwing them in landfills, we ought to oppose tax preferences for crop-derived biofuels because we can achieve better results for less money in other ways.  Every dollar we spend on e.g. ethanol subsidies is a dollar we don't have for something else (or a dollar of debt), so we should watch them all.

Luisa - chemist wannabe:

All this discussion is extremely focused on the first world. Although clearly it is the main consumer of fossil fuels, perhaps another discussion could be started if we focused on poor and developing countries.
Here in Brazil the first biodiesel plants have just been opened by president Lula, but all is woefully inadequate. By focusing the production on soy biodiesel, he privileges only those who are already privileged, the powerful rural elite and its also powerful group of congressmen. However, if serious investment was made in researching local plants, such as dendê, babaçu, cupuaçu or açaí (can anyone translate these?), serious development could be brought to our poverty-struck Northern and Northeastern areas. These plants seem quite promissing, since even with very little investment results nearly as good as the ones found with soy have already been reached.
The plus side of Lula's policy is mandatory addition of 2% of biodisel to diesel in the next few years, and then 5%...

The downside of mandatory biodiesel content is that the providers can soak the buyers for a great deal of money and there is little the buyers can do about it.  The US sees this with ethanol, where the subsidies jack the net cost of the biofuel well above the price charged at the pump.


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