At last I've managed to get some hardwood sawdust - mahogany this time - not enough for a large batch but enough to experiment with.

The result is very good..not just good, VERY good. I got crystal clear biodiesel and the sternest shake-up test was clear. So as was expected the greater surface area of the sawdust brings faster clearing than the shavings.

There is a minor drawback; the sawdust has about 30% very fine dust which will clog most filters. The solution will be to riddle it thru a seive. That will take a bit of time but its well worth it.

I've been promised as much ofg the stuff as I like, but I can only get it at certain times because its from a furniture factory and their sawdust is vacuumed straight from the machinery into a large skip, ie its all sealed in and I can only get it when the plant is down for maintenance.

If you want low cost low labour reliable filtering this is it.

Interesting. I haven't tried Mahogany yet, but like Red Oak & Walnut, it is high in tannic acid. Could be something to the tannic acid angle.