I have access to a bio-fuel processor.... I have several hundreds of litres ready for use.
One of the benefits of the Delphi/Ryco fuel filters are that replacement elements are only around $6ea. They are quick and easy to change, similar to a spin-on filter. Modern stock of the filter elements now have the replacement o-rings supplied made of Viton, instead of the butyl rubber used previously, so they will be Bio-compatible.
I'm not sure of the climate you have there, but Bio-Diesel has a higher melting point than Dino-Diesel and can begin to solidify as low as 4 degrees depending on the feedstock oil used. This means that the fuel begins to turn cloudy as partially solidified fuel floats in suspension, and can even become a waxy glug if cold enough. The issue with too many filters (ie: in place of the sedimenter
plus the engine mounted one) is in cold weather is that the solidified matter can clog the filter, preventing even the liquified fuel from drawing the filter. The lift pump cannot draw enough vacuum to pull the fuel through the blocked filter. This can't happen in the sedimenter (unless well below zero temps completely solidfy the fuel), and the engine-mounted filter will receive enough radiant heat from the engine to re-melt the suspended solids to prevent a blockage. If you always intend to remain in the warmer parts of Aus where overnight temps don't drop much below 3 degwhile you're running Bio, then two filters is fine.
Hopefully your homebrew won't have any impurities to filter out! The typical solids found are bits of batter and crumb found in waste cooking oil. I really hope that your processes filter this out before your conversion process starts. The only other possible impurities come from improper batch quantities and are excesses of methanol or KOH, but these will be dissolved in the Bio and won't be removed by a filter.
That said, Bio can be a wonderful cleaner of the crud in your fuel system, and it is possible that the first 2 or 3 tankfuls will dislodge scale or gum/varnish from your fuel tanks and lines in a vehicle that has run on Dino-diesel for it's life. It is a good idea to have a spare filter or two on hand in that initial period to anticipate the crap that will fill your current filter. But once that first flush-out has occurred, you should have no need for more frequent filter changes than running on normal diesel.
The fuel change-over solenoid/motor changes over both the fuel supply AND return lines (as well as the electrical circuits to the senders/fuel gauge) , so any excess fuel will be returned to the tank it was drawn from.
