So, we just made 1 liter of biodiesel. Now it's time to see if this is something that can save us money- that's one purpose of this project- to see if replacing some our weekly fuel consumption with what we just did will lower fuel costs. Let's start off by figuring how much our biodiesel costs to make:
Our bottle of Heet cost $2.29 for 355 mL, so that turns into $1.29 for the 200 mL we used.
The bottle of Drano cost $5.78 for 510 g, that turns into about $.06 for the 5.5 g we used.
The vegetable oil was $2.50 for the 1.42 L bottle, which turns into $1.76 for the 1 L we used.
Adding this up makes our biodiesel cost $3.11/L or $11.78/gallon!Clearly, this is not a viable economic choice at all. So, now what? Can this be economically feasable? Perhaps on a large scale. Looking aroung on the internet, I found a purchasable large-scale (relatively speaking of course) biodiesel reactor from Northern Tool for the price of $3500.
This is an 80 gallon capacity batch processor- so we can make up to 80 gallons of biodiesel at a time. Now, we need to figure out how much to scale up our chemical raw materials. I'll spare the nitty-gritty unit analysis, but to make 80 gallons of biodiesel, we'll need roughly:
17 gallons of methanol
80 gallons of vegetable oil
~2 kg lye
I was able to find prices for the methanol and lye in bulk from Oakwood Chemical Products (http://www.oakwoodchemical.com/). Unfortunately, I found that vegetable oil only comes in sizes of 1-10 L or sizes on the scale of 1 metric ton (1000 kg). So, I figured that investing $3500 in a biodiesel maker, we'll be making a lot more than just one 80 gallon batch. Re-scaling everything to make 1 metric ton of biodiesel (using 1 metric ton of oil as the basis- or ~320 gallons), and using prices from Oakwood, our raw materials will cost us:
$480 for four 18 L jugs of methanol at $120 each
$110 for a 15 kg container of lye (we'll only need ~8 kg, but there's not a big choice in size here)
and $1000 for the oil (metric ton)
This leaves us with a fuel cost of $1590/320 gallons, or $4.97/gallon. That is a lot more economical, but we're not including the whopping $3500 up front cost to make this. Including that in our calculations for 320 gallons makes our biodiesel cost $15.90/gallon! Ouch! That's even more expensive than the home-brewed variety we made.
Something that is very important to understand now, is that most diesel engines can only handle around 20% biodiesel. So our 320 gallons would be good for around 1,600 gallons total. If we have a Volkswagen Jetta that holds 15 gallons in its tank, and averages 40 mpg, our 320 gallons of biodiesel would last us around 64,000 miles! Most people only drive around 10,000 miles a year, so 320 gallons of biodiesel would last us over 6 years! Since biodiesel is, well, a bio-based fuel, there is some serious breakdown and deterioration of the fuel over the course of 6 years.
No matter how we slice it, on a backyard/garage-sized setup, we wouldn't be able to make biodiesel less expensive than regular diesel that currently costs $3.98 on average in the Midwest (http://www.eia.gov/petroleum/gasdiesel/).
Well, we learned how to make a biofuel known as "biodiesel" which is really just a (slightly) complicated class of organic molecules known as fatty acid methyl esters. It's really simple to do, and can be done with household products. Economically, this process is not viable- for now. This is a classic example of where the chemistry is pure awesome, but the real-world economics say, "I don't think so."
The whole concept of biofuels leaves plenty of room for improvement- one of the big downfalls is figuring out how to make stuff like biodiesel and corn ethanol for a fraction of the current cost. That's why it takes teams of research scientists to figure out processes for making biofuels, and engineers to figure out how to make it big and cheap. I hope you followed along in this series of posts, and that you learned a thing or two about biofuels. Thank you also to Paige Hancock, who assisted with picture-taking and moral support. Finally, thank you to Professor David Schmidt who assigned this project and helped me learn a plethora of things in the process. Now, go out and make a gallon or two of biodiesel! Or better yet, switch to an engineering major and help figure out how to make a billion gallons!