stoutdog wrote:
Okay, so here is what it boils down to:
1) Should I use B20 or B99? Right now, straight B99 is $0.30 less than ULSD. But, will I see less mileage with B99 over B20? I'm seeing multiple opinions here.... I'm not worried about gelling, I live in AZ
2) Given that the rubber in my fuel line is safe for bio (thanks geordi) are there any other concerns that I should have about running B99?
Also, this place is ASTM certified. I assume that means they make quality bio?
Thanks again.
I'll answer all of these for ya:
Like I said previously, unless you have ridiculously low mileage, you will want a spare fuel filter in the truck with you for the first few tanks. Trying to do it slowly with B20 is OK, but probably will just prolong the inevitable. I would go with the B99, especially since it is cheaper than the ULSD. Yay for that, ya lucky bastage!!!! Drop down to B50 or B20 in the winter, and you will probably maintain the summer mileage while everyone else is suffering with suckful winter fuel.
You might be concerned with not having a lift pump, but since you said this place is ASTM certified, the fuel actually should be chemically the same viscosity of dino. The molecular specific gravity of GOOD biodiesel is only about 1 point heavier than Dino. Water has a SG of 1, it is the baseline. Dino is like 85, so it is 85% the weight of water, which is also why it floats on water. Good bio should be 85 to 86, my homebrew was usually 86, once in a while I got 87. Heavier means it can be thicker, and possibly have leftover oil that didn't react or settle out. This would be VERY unlikely in ASTM fuel.
I think I've gotten your third question already, but here it is again: If this place is certified, they are already selling better fuel than any of the dino places around, b/c they can probably tell you where the original feedstock came from and how it was processed. Even if the cashier doesn't know, the certifying process isn't easy. They have to have good stuff.
As far as someone else's comment about incomplete reactions and methanol-laden fuel... Not very likely. The reaction is a feeding process and the settling process relies heavily on gravity. To make bio, you are dealing with substances that have WILDLY differing specific gravities. The NaOH (Lye) is EXTREMELY heavy at over 2.1 The oil is about 1.3~ or so (IIRC) and the glycerin closely matches that. The methanol is much lighter, I can't recall an exact SG, but I believe it is in the 50-60 range. Add to that, it evaporates VERY easily, and you are unlikely to have much at all remain in solution once the reaction stops.
The reaction is a feeding frenzy on a chemical level. The oil contains very long molecular chains, which is part of what makes it so thick - these chains don't want to break. The Sodium methyl hydroxide mix uses the catalyst NaOH to sever the chain, and the alcohol to "plug the hole" in the chain so it can't recombine. The result is two chains: A glycerin chain and the Methyl Ester chain. The glycerin is the longer one, hence why it is heavier and settles to the bottom. This reaction will continue until one of the two reactants is exhausted. If the alcohol runs out first, the lye will drop out of solution (since the alc is gone) and the reaction will come to a screeching halt. The lye will settle out with the glycerin, but the mix may be too thick with unreacted oil to be usable. If the lye runs out , the remaining alcohol will separate to the top and either evaporate off or it can be captured and distilled for re-use. Unreacted oil in this case is usually less, b/c it really doesn't take much lye at all to complete a mix. The SG of the mix will be a bit heavier, but still usable with good filtration
I let mine evaporate off any excess, because I was running a process that involved ZERO added energy. I did it at ambient temperatures, triple gravity filtered, final polish filtered before going into the car, and NO WATER WASH. Like I said, over 1000 gallons produced. I've had some sample containers aging in my garage in Florida (non insulated, HUMID SWAMP conditions) for the last 5 years or so since I stopped making the stuff. Two of the containers are open to the air, the rest are sealed. ALL are still clear. Cloudy would indicate algae growth. I can back up my observations of the reaction behaviors from my own experiments. I was able to refine the process down to about a 12% methanol mix, a VERY low percentage, considering that most of the recipes call for a 20% mix. The resultant drum at 20% REEKED of methanol vapors 2 hours after mixing, and continued to stink for hours afterward. The 12% mix would smell strongly of methanol for about 30 minutes or so, then the smell would almost vanish in seconds. To me, this was the completion of the reaction. At a 12% mix, I was still getting a SG of 86-86.5, and NOTHING would separate out from a centrifuge spin after 12 hours sitting in an open-topped drum.
I would let the glycerin-and-oil-and-bio slurry drain from a bottom valve into an open 5 gallon pail, then leave that alone for a few weeks until the glycerin compacted into a disgusting Jello. I could then usually pour off about another gallon of biodiesel from the top, and have 4 gallons of glycerin from a 40 gallon batch. Good stuff. Restaurants LOVE the stuff for cleaning their back door areas where the grease collects in the asphalt and makes things hazardous. Cleans around the dumpsters too, and removes the smell.
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His numbers (as best I can remember):
4/11)..Bus gone to Scarp 8/23/11 
I like the better lubricity, lower cost, and I tell myself I'm blocking some investment in the mid-east madness. B20 runs about the same as dinodiesel for me as far as mileage and power. From what I've read anything over B2.5 will more than compensate for the lubricity lost by switching to ULSD.
I wouldn't want ANY of whatever it was they were making.
