Apologies to those on multiple lists for all the cross-posting.
I spammed a couple of the biofuel-related lists last week with some
complaints about trying to make biodiesel in the midst of some dramatic
local weather. We got the first real winter storm, serious rain- the
Northern California version of winter is lots of rain and 60F. Not too much
to complain about considering I've lived in Leningrad and in New York. But
this weekend I wasn't too happy about the timing: my biodiesel equipment is
all outside, and I had a lot of fuel that I had JUST finished washing, and
it was time to let it 'dry' or 'settle'. But the weather out there was
pounding down rain (the remnants of a Typhoon that hit Guam a few days
earlier, it turns out).
I'd just recently found some info, re-reading a couple of the the U of
Idaho biodiesel reports, about bubble drying fuel. It somehow didn't make
it into common homebrewers' practice, everyone I've talked to said, yeah, I
remember reading that, but I didn't think about applying it to my
situation. So I tried it out under the worst possible conditions- ran a
bubblestone into a tank of hazy biodiesel that was carefully swathed in
tarps (therefore no real opportunity for the moisture in the biodiesel to
excape outside the now-closed tank)- and ran some severely humid air
through it.
People have different techniques and theories about 'drying' biodiesel
after washing. Some people leave it in an open container, and claim that it
clears up any water haze in anything from a day to a week. It sounds to me
that the people doing this live in dry regions. We don't.
Others (like Aleks Kac' published acid-base two-stage directions) say to
let fuel settle for three weeks or so until it clears water haze.
Other options include heating it to drive off water. There are some
problems with this- among them, the fact that the MSDS for biodiesel says
that biodiesel fumes are not harmful to health- unless heated. I was
prepared to do this as I really needed some finished fuel, but I feel like
it's not something to take lightly, besides the obvious unnecessary energy
input.
At our biodiesel coop, we do the 'settling' technique after washing fuel.
Sometimes it takes 10 days, but quite often it is still hazy after that point.
I was getting frustrated about having all of these drums of settling fuel
sitting around at the co-op, taking up storage space, not clearing in the
humid weather. It was the bottleneck that was messing up fuel production
capacity- we store fuel to settle before washing, then we wash for three
days and then we store it some more. And this is a 12' x 8' space in which
we are trying to produce fuel for about 15-25 drivers (not very
successfully). Sheesh. Seems like a common problem for small-scale homebrewers.
So back to the wet weather bubbledrying- it worked to clear haze in that
fuel, humid air and all. The 'technique' is to chuck an airstone into a
tank of hazy fuel, and bubble for 24-????? hours. It doesn't seem to make a
really HUGE difference how much fuel you're working with- around here (in
the humidity) Kenneth Kron cleared 3 gallons in 12+ hours, Mr.Biosmell
cleared 55 gallons in similar conditions of humidity in under 24 hours,
which seems about average for the several experiments with this so far
(though in Nevada, Rainer Busch dried some fuel this way in 2-3 hours, in
the dry desert air)... In the storm, buried under a thick lid of plastic
tarp, my Wet Air treatment seemed to clear up a drum of hazy fuel in
something like two days. (I didn't check after the first 24- I eventually
got sick of wading outside to see whether the entire site was going to go
airborne or to float away in the storm, and of babysitting the flapping
tarps at my house. I threw a bunch of wood on top of the tarps to hold them
down against all the wind, and ran away to the boyfriend's house where I
could observe the storm from the comfort of a decadent California hot tub
where I still spent too much time worrying that my biodiesel site was
floating away).
48 hours into the bubbledry I got back home to some clear fuel and more
cloudy skies.
Some thoughts and questions:
So the big question for me is, does clearing fuel 'haze' actually remove
water content? Most homebrewers consider 'clear' fuel to be dry fuel. three
weeks of settling will do this. The drylands(?) Infopop people say that
'letting it sit outside in open drums exposed to drying breezes' does this
in 24 hours to a week.
After prolonged settling, there will also be various crud at the bottom
of the settling tank, and often some hazy fuel near the bottom of the
settling tank. I haven't observed it closely enough to see if there's also
visible free water.
My local chemist friend Rainer confirmed (??) that the amount of interface
between air, and the water content of the biodiesel would be much greater
with bubbling than with just blowing air over the surface (which is
something two or three people on the Maui/infopop site advocate cause it
works for them in their climate). But it doesn't entirely make sense to me
that bubbling the severely HUMID air through would do much for evaporating
away water.
Also, it seems to me that in 'settling' fuel to clear it, it takes
different amounts of time for different batches to clear. Obviously you
can't account for things like ambient air humidity if these different
batches were settling at different times. But what I've asked on these
lists before is, is there some other chemical mechanism at work in making
some of these batches clear quicker than others? I think I've heard people
say that inadequate washing (ie there's still soaps or catalyst in the
fuel) can lead to persistent fuel haze, but I don't remember where this
came from exactly. It does make sense that residual soaps would bind water
somehow.
I suppose the test would be like that for water content in oil: to bring
a weighed sample to the boiling point of water for a while, then weigh it
again and see how much disappeared. I did get a hazy sample for a reference
before starting the entire operation. Those of you with lab equipment might
have access to a better way to do this (moisture meter). If I do this, I'll
post something later.
Mark the longwinded
t
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