I've read through what I can find here about this alternative technique. I put together a process to use three Corny kegs and a metering pump to slowly push through dried biodiesel, with the first two kegs containing wood chips (mixed oak, fir) and the last containing Amberlite.
The first time I pumped 45g through the tanks, all seemed to be well: by the time the BD had passed through the Amberlite, there was no detectable soap. Same with the second batch of 45g. But just for grins, I cracked the connection between the Amberlite keg and the one before it, took a sample of that fuel, and tested for soap: 320ppm. Not that great, but then I don't know what the soap content was going into the wood, either.
To give you an idea, the batch that I just made had an 8% water prewash after draining all glycerine, and it measured around 250ppm without going through any further wash.
So. I should have been sampling before/after the wood chips all along to see what the reduction was, if any. But I didn't.
My questions are: has anyone done this before/after testing with wood chips, more rigorously than a shakeup test? If so, how much of a life span are you finding that your wood chips have until their ability to remove soap is gone?
That is a question of high quality. Also, thanks for posting your results.
The testing before and after is really a key. How long the wood works is also a key as whether or not this method is the way to go. If it is single use, then it would generate lots of waste.
03 Dodge 2500 B100 homebrew
79 Rabbit B100 homebrew
All the testing I have done was the shake test and I see significant results with wood chips. I use only hardwoods, because softwoods tend to have a lot of resins that I don't want to deal with.
I test the settled BD before I run it through my column with the wood chips filter medium and then after.
The wood chips aren't good long term in my estimation, but they are free or extremely cheap and the waste product is not a problem. I pack the chips into paper sacks and burn them in my wood stove.
In a high production situation, this method would most likely be inadequate for most people.
I also filter the BD through macroporous resin after it appears to be soap free.
I wish I had the time to do some scientific testing, because I have a gut feeling that for the small producer wood chips is the least expensive and least wasteful method of filtering BD, especially if you don't want to deal with water washing.
I hope that this actually does work better than it appears to, but (like everybody else apparently) I haven't done the experiment with sufficient rigor: a shakemup test isn't sufficient. I try to get the soap content below 100ppm, and I think fuel would pass the shakemup test at 3-4 times that amount.
Doing a soap titration is not difficult if you have the right solutions for it. I replaced the wood chips today, and the next batch I run through it I'll report back what the soap measured going in, and what it measured coming out the other end. Not much point in doing this if the Amberlite is doing the vast majority of the work.
Another point that hasn't been detailed yet from what I can tell: what is your catalyst? My tests will be with KOH, FYI.
Another question is around what % of your bio is absorbed into the chips and lost?
03 Dodge 2500 B100 homebrew
79 Rabbit B100 homebrew
Having cleared the contents of my kegs once, I can answer that one: surprisingly little. The weight of the wood chips is considerably greater after than before, but out of each 5g keg that was chock full of fluid and chips, I was probably able to pump out 90% of the available fluid.
The first time, obviously, you lose a lot to filling the air in the kegs. But thereafter it will be replacing old fluid with new fuel.
I use NaOH for the catalyst.
As far as the percentage of BD absorbed into the chips and lost, my guess would be very little. The chips are filtering the impurities out of the BD, so the good part of the BD passes through.
When I replace the chips in the column, I take the spent chips and place them on a screen and allow them to drain for several days into another container. I refilter that BD. What little BD is left in the chips go into paper sacks and are stored for later use in the wood stove. It makes a nice warm fire.
Some have experimented with flushing the wood chips out with methanol and reusing. Sounds like a wasted effort to me as long as the wood chips/shavings are free.
How did you set up your Corney kegs? I just received two kegs and was contemplating 2 Eco2Pure (or equivalent), or 1 keg Eco2Pure (again, or equivalent) and 1 keg Thermax.
What are you using to push the BD through the kegs?
From my original post:
Where are you getting your kegs? I'm in Denver, Co. and cannot find any!
Proprietor of The Blunderbuss muzzle loading gun shop. Member of Denver Biodiesel CO-OP.
Try this company...
I apologize...I meant how did you build the cornery kegs (inside)? What kind of metering pump are you using?
Sorry, I misunderstood. I originally used Jeff Brandt's (Sunbreak Biodiesel) basic design, which he outlines in his thread about an inexpensive Amberlite setup. However, the rocks/marbles used underneath the 80-mesh screen at the bottom of the keg make it so that you can't easily empty the wood chips. So currently, I just have an 80-mesh filter on the output of the keg, which is at the top (plumbed backwards from stock). I am trying to find a small sock filter there, too.
The metering pump I bought off the 'Bay...Gorman Rupp, up to 5gpm but can be throttled down to 1gpm.
Well, I am in the middle of an experiment, but I figured I'd report back here. Two kegs with wood chips in them (mostly oak or cherry, some spruce and fir).
Before: 385ppm soap KOH
After a single pass at 3gpm flow rate, with basically enough flow through to fill the kegs and start getting some output: no detectable soap.
After 25g total through both kegs: barely detectable soap, between 1-2 drops of HCL solution needed to bring the solution back to yellow. Estimate 32ppm soap (.1ml HCL used), but this is very crude at this level.
So I'll continue to monitor at some intervals and see what the longevity is for the chips. If I can get 150g through them and still have a good drop in soap, I'll be happy. If not, it may not be worth the fuss compared to water washing.
greiswig, thanks for the update. what size wood chips are you using? I have a few dried oak chunks I was thinking about running on a table saw with a dado blade.
These are mostly planer chips, but it's a pretty broad mix. The only think I did was to sift out the fine sawdust with a window screen.
Posted 11 February 2009 03:40 PM Hide Post
There is a live webcast on FEB 13th (yes Friday the 13th) by Eco2Pure to show new units and how to use the media. If you are interested follow these instructions.
To join the webcast, go to
Click on the button next to "Join a web conference (participant)" and enter the following information:
Participant Code: 990377
Name, company, and e-mail and then click "Join"
To join the audio portion dial:
1-866-212-0875 (United States)
Punch in the passcode when prompted: 990377
Nathan, moderators, this same item has been posted across multiple threads. It pretty much smells like spam, although I'm sure it will be a fascinating Friday the 13th. Just one man's opinion, though...
Good luck w/ sawdust:
After running an initial test involving 25 lbs. of sawdust, not wood chips, here are the results:
Fuel Volume (gallons) Soap (ppm)
Our initial soap tested at 1622 ppm. This was a finer sawdust collected from our carpentry floor shop. The glycerin initially tested at .10. After passing through the sawdust it dropped out to .00 on all 4 tests.
Flow rate is rather slow, gallon/hour +- at gravity feed. We used a fine filter (.22 micron) on output.
Not a bad way to go for the small producer.