John,
I wondered about the same thing, and this is what my research
kicked-up: you can run a diesel on Straight Vegetable Oil (SVO) but
you can't start a diesel on SVO, you can start a diesel with either
Bio-Diesel (Transesterified VO), blended VO (RUG/VO) or 2# diesel
then switch to SVO after the diesel is running.
Vegetable Oil will cause carbon build-up problems in diesels if you
don't first equalize its viscosity and volatility to the same levels
as #2 diesel, there are a lot of people experimenting with blending
and equalization, but right now Bio-Diesel is the only sure-fire
replacement for #2 diesel.
The transesterification process requires either methanol or ethanol
and since methanol is currently a fossil-fuel derivative,
transesterified VO made with it is not really a bio-fuel and is still
tied to the fossil-fuel market, requiring ethanol for
transesterification of true bio-diesel. For me anyway, since either
process would require ethanol, there are other considerations that
just made ethanol a better option.
The EPA (in the US) has cracked down and banned the importation of
most listeroid type small diesel engines so finding engines to suit
particular purposes is difficult and more expensive. Still the diesel
route would make more sense for many, but at $1650 for just a small
screw-press
http://www.woodnstuff.ca/oil_presses.html this option
isn't as simple as it first might seem.
Growing the feedstock are just about a wash, and the rough comparison
looks something like this:
Crop yields:
Sunflowers for oil, about 100 gallons per acre.
JA or sorgum for ethanol about 400 gallons per acre.
At 4 to 1 yield ratio it seems an easy choice, but next you need to
account for fuel value.
SVO about 125,000 btu per gallon.
Ethanol about 75,000 btu per gallon.
SVO 100 (gallons per acre) x 125,000 (btu per gallon) = 12.5 million
btu/per acre.
Ethanol 400 (gallons per acre) x 75,000 (btu per gallon) = 30 million
btu/per acre.
The gap narrows form 4 to 1 to 2.4 to 1 in favor of ethanol.
Next we need to account for production energy, any energy used in
production which is subtracted from the total.
SVO about 12,000 btu per gallon (screw press)
Ethanol about 40,000 btu per gallon (chopping, cooking, fermenting, &
distilling)
SVO 100 x (125,000 - 12,000) = 11.3 million btu/per acre.
Ethanol 400 x (75,000 - 40,000) = 14 million btu/per acre.
Again the gap narrows yet further form 2.4 to 1 to 1.25 to 1 in favor
of ethanol but SVO is getting close.
Lastly we look at the cost upgrades to the equipment and the learning
curve (mechanical vs thermal dynamics) and crop spoilage for both
seeds (which can be processed into oil for many months) and stalks or
grass (which must be fermented quickly, requiring larger
stills/equipment) so the decision has a lot to do with personal
variables.
In my view, that 40,000 btu bite for ethanol energy usage can be
reduced by solar to both eliminate cooking & fermenting energy usage
and augment distilling energy usage to bump
ethanol's advantage back up to a 2 to 1.
Curbi
