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Drive a Greasecar - DIY Biodiesel
TinyTim writes "Sure, you could buy expensive biodiesel for you car - or you can hack your diesel to run on filtered vegetable oil. Kits take a few hours to install and cost about $800, but you can get your fuel free from restaurant deep-fryers (the filters are ~$10/2000mi). Supposedly no loss of performance or mileage, and you can change between diesel and veggie oil with the flick of a switch. A previous article mentioned the theoretical possibility, but it looks like kits are now available from greasecar.com."
I remember reading that running on vegetable oil smells more or less like french fries. Anyone who has worked fast food can imagine the smell of burned grease-trap fuel. *wretch*
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Exactly how much used vegetable oil do we have lying around to convert into biodiesel? If there's so much waste veggie oil, there must be some other industry that takes it and uses it for another manufacturing process. It's a great idea, but I don't see this displacing the oil industry anytime soon.
I can't run my truck off vegetable oil. I'd be too tempted to cook chicken in it as I drive. Then again, I'm already tempted to drink the diesel for the ethanol, so it's really a toss-up.
Bart: When you want grease, go to the source. Good old Krusty Burger.
Homer: Oh, I'll say. Look at that red-headed kid. There must be twenty dollars worth of grease on his forehead alone.
Bart: I was thinking more of the deep-fryer.
Homer: All right, we'll try it your way.
J
Most restaurants with friers, dump the old oil into a large bin out back. Every few months a tanker truck comes and picks up the oil. Then they make crayons and other shit out of it. Point is, restaurants get money for their old oil. Why would they give it away?
The most critical part of the diesel is the fuel pump and injectors. They run at 3000-5000 psi with very low volume per stroke, so leakage cannot be tolerated. The fuel has to be filtered extremely well (sub micron). My worry with biodiesel is that it might plug filters due to microbial growth [always a problem in diesel], or the vegatable oil hydrolyze into organic acid plus glycerol. The organic acids will cause corrosion of the injector pump plungers and injector tips. Not good at all. The fuel will also have different rubber swell characteristics, so you may get fuel leaks. I'd try this first on a imetal-to-metal Mercedes with simple to replace rubber rather than a Peugeot or VW with a fuel-lubricated pump and that main O ring soaking in fuel.
I expect vegatable oil could be made to work with additives: a biostat, acid neutralizer plus seal swell control. But it would have to remain a separate product becauase petroleum oil and vegatable oils aren't miscible. If you wanted a blend, you'd need an emulsifier, and the results might be too viscous.
Having worked with the development of high-pressure direct-injection diesel engines at both Volkswagen and Volvo, I am quite critical towards any replacement fuel that has not been widely and thoroughly tested.
To begin with, some links for self study:
- Dieselnet.com has a great glossary and provides some excellent links
- Delphi has some nice PDF's on Unit Injectors and Common Rail
- Here some information from Bosch - Siemens has some nice pictures of injection systems, mainly common rail
Due to the very high pressures (up to 2100 bars) and therefore high temperatures with modern fuel injection systems, you really go to the limit of what diesel fuel can do: You use it simultaneously as fuel, coolant and oil and it takes a good blend to fulfill all these requirements! The chemical formula is important as well as the physical properties. The DOE has a webpage about diesel fuels. Have a look at their online diesel fuel property database and see which properties are essential for characterizing fuel. Other important factors are
- durability
- particles/filtration
- compressability/resistance against cavitation
Not to forget resistance of all sealings etc against the fuel. Think RME and you know why almost everybody in the industry (e.g. SCANIA) only approves blends with max 5% alternative fuels...
Don't get me wrong, but if those fuels are ruining the car, we really can't talk about environmental advantages then, now can we? On the other hand, serious life cycle analysis like this one and field studies will hopefully help to develop cleaner cars. If those are then driven by gas engines, diesel engines or fuel cells... who knows?
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Caveat: Although I have friends who run diesels on various fuels, I myself do not. So I'm a friend of experts, not an expert myself.
Rudolf Diesel designed his engine to run on vegetable oil. That's how it was originally supposed to work, and it was originally demonstrated at the World's Fair running peanut oil.
Modern diesel engines are slightly modified to optimally burn the refinery waste products we call "diesel fuel". But only slightly...
If you want to efficiently burn vegetable oil in an unmodified modern diesel, you should use biodiesel (easily home-made, see Tickell's site for details).
If you want to run straight veggie oil, you need to preheat the oil (no problem when the engine is running, plenty of heat easily available, but you will need a preheater or a small tank of "starter fuel" at startup time). You also need to make sure that your filters are very efficient, and that you have bacteria/fungi controls, and that you have a water trap. These are the same considerations with regular "diesel fuel", but since the latter is nasty hostile petrowaste and the former is edible bio-friendly fryer grease you will have to be much more careful and vigilant.
Most people running straight vegetable oil are uber-geeks. They like to tinker and they aren't afraid of breaking things, because they know they will be able to get something to work if they need to. If you don't feel like that is a description of you, try biodiesel instead, and you won't have to make any modifications to your vehicle at all. You can even mix biodiesel and petrodiesel with no problem.