Do not bust this myth at home
A favorite show, Mythbusters, is not exactly my favorite example of science on television, but it is entertaining none the less. But watching this episode recently reminded the me of the danger of a little bit of knowledge.
Adam and Jamie show that it’s possible to run a diesel-powered car using nothing more than used, filtered, cooking oil (sometimes called yellow grease) that they obtained from restaurants.
And strictly speaking, yes, it is true that a diesel engine can be run on straight vegetable oil–for a while. In an unmodified engine, continued use of vegetable oil as a fuel will eventually cause engine failure, typically by a buildup of carbon or polymer deposits on the piston rings or fuel injectors. The engine will eventually seize. No kidding.
Although there are some after-market systems that can be installed in the car’s fuel system to help eliminate the risk of engine damage, these are not for the faint of heart.
In short, vegetable oils are not the same as biodiesel. Vegetable oils typically consist of three fatty-acid molecules linked to a glycerol molecule. In a nutshell, to create biodiesel from vegetable oil, the oil is mixed with an alcohol (typically methanol) and lye, which cracks the fat molecules, replacing the glycerol molecule with an alcohol molecule, and thereby yielding methyl esters (biodiesel) and glycerin.
Without making use of this process, called transesterification, straight vegetable oils do not make a good substitute for biodiesel. Mythbuster-generated myth, busted.
Posted: Tuesday, Jun 3, 2008 6:18 pm by adam
File as: Biofuels; Energy
Comments
Comment from Sara Zoe
Time: Wednesday, Jun 4, 2008, 2:10 pm
I don’t know a lot about this process so I was wondering if you could tell me - how “environmentally responsible” is the process of turning used veggie oil into biodiesel, ie are the methanol and lye used generally ok in their own production processes? I like the idea of re-using the resource, and there is actually a company in Seabrook that has or is about to start doing that on a scale and selling for home heating biodiesel: http://smartfuelamerica.com/Smartfuel_Home.html
Comment from adam
Time: Thursday, Jun 5, 2008, 11:14 am
Sara, thanks for your comment, and for the information about the company in Seabrook.
I don’t know very much about the production of either lye or methanol. Both are hazardous materials. My guess would be that overall, the production of biodiesel is more environmentally benign than the refining of fossil fuels.
But I will still caution that biodiesel production itself is not without environmental risk. The glycerin byproduct requires disposal, or further processing to be made useful (such as for soap), and some producers are clearly jumping on the biodiesel bandwagon without proper permitting or respect for the existing regulations.
Some smaller-scale plants are attempting to make use of the glycerin by composting it. However, I don’t know of any industrial-scale producers that dispose of the glycerin in this way.
I’m very curious what Smart Fuel in Seabrook plans to do with their wastes and byproducts. I plan to contact them and ask, and suggest you do the same. If enough people ask, they will realize that the community is concerned about their plans.
Thanks.
Comment from Sara Zoe
Time: Friday, Jun 6, 2008, 5:26 am
Actually, they emailed me and asked me if I had some ideas for composting their waste material after I emailed to find out if their product was for sale to the general public (not yet, but soon, and to larger operations, yes). But I was a bit confused about what the waste material actually was (I was assuming vegetable solids and things like that from vegetable oil) and have been asking around about the compost-ability of that kind of thing. They definitely have the proper disposal of waste on their minds! So is glycerin actually compostable?
Comment from adam
Time: Friday, Jun 6, 2008, 7:23 am
I do believe that glycerin can be composted. If you Google “compost glycerin”, you’ll see many pages of claims that it can be done. However, I don’t know of it being done on an industrial scale.
One concern is that the glycerin is often contaminated with traces of methanol, which is toxic. I don’t know if the glycerin can be composted without removing the methanol first.
Piedmont Biofuels is a good source for biodiesel information.
Write a comment