WVO Filtering Settling Process

Beyond a doubt, the greenest option when it comes to running on Veg Oil is to use Waste Vegetable Oil (WVO). Thankfully this is also the most affordable running option as well.

There are a variety of ways of filtering WVO, but my preferred method is Settling. Essentially this means that rather than using a variety of pumps, valves and filters to force the impurities out of the WVO, we allow gravity and time to do all the work for us.

Waste Veg Oil is invariably contains all manner of debris, like batter, crumbs, chips. etc, as well as fats and water. It's essential that ALL of these impurities are removed from the WVO before its used within your vehicle. Failure to do this will result in expensive motor repairs!

I use a two stage process to clean my WVO. Firstly I rough filter / settle my WVO, then Secondly I fine filter it down to 1 micron.

My WVO Filtering Set Up - Stage One - The Settling Tank

Below you'll see a sketch of my Settling Tank (click here for full details about my filter system). The tank is a small shipping container purchased from eBay that has already been used to transport foodstuffs around the globe. I say small, it's actually a 220 litre barrel, but that's small when you think of many shipping containers...

The WVO Filtering Process

For those of you like me who don't like to read all the waffle, here's a quick breakdown of the process. For those of you who do like the detail, there's links to the relevant bits:

• 1 - Stockpile your WVO until you have enough to fill your barrel.
• 2 - Rough filter the oil into the barrel using large sieves to 100 microns
• 3 - Discard the sludge that fouls the rough filters
• 4 - Seal the barrel and wait 4 weeks
• 5 - After 4 weeks, drain the settled oil, but NOT from the bottom, rather from three-quarters of the way down the barrel. 6 - Similarly do not empty from the top of the barrel, but rather from at least 1 inch below the surface.
• 7 - Fine filter to at least 5 micron (I prefer 1 micron) and use.

I bought my sieves from eBay and I include this link in the hope that this guy is still providing these excellent products.

(1) I stockpile my WVO until I've got enough to add to my Settling tank. (2) When I'm ready, I "rough filter" it by pouring the oil into the barrel through 3 sieves. These aren't the sort of sieves you'd find in your kitchen draw, they're approximately 12 inches in diameter and stack one with the other. The upper filter is 600 microns (the roughest filter to pull out the biggest chunks), followed by a 400 micron and finally a 100 micron filter. The trick is to pour slowly to allow the filters to do their work. It's surprising how quickly they fill up. In fact, it's very rare for me to be able to pour more than 20 litres before I have to empty the contents of the 100 micron sieve.

(3) Invariably the bottom of any WVO container holds the thickest, sludgiest oil (because the thick stuff sinks), so I keep an empty container close at hand. When the 100 micron filter fails to drain, I empty the contents into this spare container then repeat the process. Depending on the WVO sourced, I can lose up to 20% of the volume as it's unusable fats and debris.

Eventually after a couple of hours of pouring (oh yes, it takes time to get through 200 litres or so), I find myself with a full barrel and a couple of full containers containing thick fatty WVO. At this point I seal my barrel (and the spare containers) and forget everything for a while.

(4) Commonly most folk leave their WVO to settle for 2 weeks. Personally I prefer to leave mine 4 weeks (better safe than sorry). During this time gravity pulls the heavier content of the WVO to the bottom of the barrel. (5) Consequently you NEVER want to empty your barrel from the bottom as that's where all the sludge is. Instead draw off around three-quarters the way down your barrel where the oil is cleaner.

(6) Not all impurities sink to the bottom, some float on the surface. Consequently you do NOT want to use the top WVO either, but ideally want to remove oil from around a inch or so below the surface.

This completes the rough filtering stage

After you've allowed the WVO time to settle, you can draw of oil for (7) fine filtering. Within this website I've described this process as Stage 2 - Fine Filtering and to read more about that, just follow the link here.