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Reader Question: What’s the cost of homemade biodiesel?


biodiesel - various biodiesel blends

Various blends of homemade biodiesel.

photo © Adrian Gable

While the instructions were very clear (regarding homemade biodiesel making), I didn't understand the part about the 20 - 100%. I live in California in a mild climate. I have a '77 300 D and diesel prices are killing me, as everyone else.

Do you add your biodiesel to regular diesel fuel, or are you running pure biodiesel without mixing it with regular diesel? Would you first fill your vehicle half full at the service station and then add another half a tank of bio? Also, approximately what is your final cost for a gallon of bio using your recipe? Final question. What are the waste by-products and how do you dispose of them?

Thank you very much for your input.

Hi Rich,
With the age of your car, 100 percent biodiesel (aka B100) may be a problem with your fuel system. The injectors and tank should be fine, but the rubber hoses and rubber seals inside the injector pump could be compromised. Mercedes had most of their diesel fuel system components converted to synthetic rubber by the mid 80’s (those are the years of our cars), but we’re not sure how soon that started—it’s quite possible that your system has natural rubber parts. The reason for the concern is the caustic nature of methanol in the biodiesel degrading non-synthetic natural rubber.

In all likelihood, you’d be perfectly fine with a 20 percent biodiesel, 80 percent diesel blend (B20). The only way to know for sure is by experimentation—run several tanks of B20 regularly checking the fuel lines for softness or swelling. If that doesn’t appear to be happening, you can probably bump it up in 5 or 10 percent increments. The choice is yours regarding how aggressive you want to get. Time will tell how high a percentage of biodiesel you can run.

We recommend that you start with B20—depending upon how much accumulated diesel sludge is in your tank and lines, you may have to change the fuel filters several times over the course of a few months. You’ll be able to tell the filters are becoming clogged when the car slowly starts to lose power. We run B100 in the summertime and dilute that down to B20 in the winter. You can add diesel fuel to bio, or vice versa—they blend perfectly well and there’s not a particular order they have to be put into the tank. As far as the cost, we’ve found that with purchasing the methanol and lye, the cost for homemade biodiesel rings in between $1 and $1.50/gallon. In the winter time months, we run a 20 percent maximum blend here in central PA (due to cold weather and biodiesel issues). The price of methanol is climbing, as with all other fuels, so it’s constantly changing.

The only real waste product is glycerin which is biodegradable and can be composted—be sure to read our article about how to dispose of waste. If you haven’t already, we recommend reading all of these articles we’ve written before getting started—it will help you understand the entire biodiesel making process.

Thanks for writing, and please let us know if you have any more questions.
Christine & Scott

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