Sunday, September 18, 2005

Testing the Biodiesel Bandwagon - Part II

In my previous posting, I showed a mathematical equation to estimate how many gallons of biodiesel are needed to recoup the initial investment cost of the biodiesel kit:

[$400+($3.46+$0.50)*x]/x = $2.847

What I forgot to mention is the vegetable oil cost ($3.46/gallon) should be a variable, y. This is because if the ingredients’ cost ($3.46/gallon for vegetable oil, plus $0.50/gallon for lye and methanol) is already close to $4 per gallon, there is no way the average biodiesel price would be below petrodiesel’s price ($2.847/gallon).

I have since then modified the equation to:

[$400+(y+$0.50)*x]/x = $2.847

What it means is that depends on the vegetable oil’s cost, number of gallons of biodiesel needed would vary in order to be economically competitive with petrodiesel’s price.

Since the equation has two variables in it, the best way to determine the result is to set the vegetable oil’s price at a fixed value and then slowly increase it:

In the plot above, the horizontal black line is the current petrodiesel price of $2.847/gallon. If the vegetable oil cost is at $0.00/gallon, then it would take about 170 gallons to recoup the initial investment cost. The numbers of gallons increase along with the vegetable oil’s cost.

When the vegetable oil’s cost is above $1.50/gallon, it would take more than 500 gallons. For an average driver with a vehicle that gets mileage of 20 mpg, 500 gallons of fuel would last 10 months.

Jason Younker of emailed me a photo of current B20 grade (mixture of 20% biodiesel with 80% petrodiesel) biodiesel price in Denver is $2.909/gallon. For B100 grade (100% biodiesel), it would cost $3.049/gallon.


  1. Last Thursday I was able to listen to author Greg Pahl, Biodiesel: Growing a New Energy Economy. He said that the feedstock for biodiesel accounts for 70% of the production costs (read the full notes that I took from his presentation here).

    Another thing to consider is skipping the biodiesel process all together and run SVO (straight vegatable oil). That will eliminate all the work associated with processing it, if thinking about a homebrew option. Running SVO doesn't make sense in some situations, but if in a warmer climate year around, very viable option. There is a conversion kit required to allow a diesel to run on SVO, but it might not take to long to make it worth while.

    Jason Younker
    Alternative Fuels Awareness Organization

  2. Glad to see you opened the formula up for cheaper vegetable oil. You have to take into account that you are buying off the shelf cooking oil.

    If you were converting water into hydrogen at home for a fuelcell you wouldn't use brand name water in a bottle off the supermarket shelf.

  3. This is an apples and oranges comparison. When was the last time your made Petrodiesel in your back yard? Ever herd of economy of scale. Please go find a kit to distilled your own Petrodiesel from crude oil. Then see how much that would cost and compare it to home made Biodiesel. Until you do that I don't think you can make a meaningful cost comparison.

    I doubt anybody has seriously suggested replacing manufactured Petrodiesel with Biodiesel made in your back yard. While it is cool you can make it your self, it's a novelty at best. As with any product mass production is the only way to go. Why buy 4.5 gallons of oil at a time when you could buy a rail car, or a whole train full. At that volume you would pay a small fraction of the price. Say you paid $1 a gallon in bulk, then you could recover your investment in 300 gallon, according to your chart. As you pointed out it would take you a while (about 1 year) to recover your investment. Please go talk to a banker, ask him how long commercial equipment is expected to take to pay for its self. Hint, it a lot longer than a year.

    I think it very cool you took the time to do this analysis, but please take a little more and refine you criteria. You may draw a different conclusion, and will bake a much better argument no matter what your conclusion is.