Processing WVO Into Fuel

So you got your first bucket of WVO and it looks…Nasty?

I don’t know about you, but before I got started, Ienvisioned WVO to be colorless, odorless and generally cooperative.  WOW, was I wrong.  In my first experience collecting I was goingfor the Holy Grail approach.  Tocomplement the 275gallon tote in the back of my very clean truck, I had a 10gpmredline pump and a 100mesh banjo tee filter. The plan was to suck the oil out of the holding tank, through the filterand into the tote.  Voila! Cleanoil!  The real kicker is that when Iflipped the switch, it worked!...for about 3 minutes, then, nothing.  Five minutes after that, I was up to myelbows in rancid grease and literally gagging from one of the worst smells Ihad ever experienced.  The euphoria of myapparent engineering mastery was all but forgotten and replaced with more thana little bit of concern.  This was goingto be work.

That was about a year ago and things could only get better.   What hasn’t changed is my pursuit of thebetter way.  I like using WVO in mytruck, I like that it is good for the environment and I like that it costs mealmost nothing per WVO mile.  I don’tlike and can’t afford spending huge amounts of my time dealing with it. To thisend, I have always focused on reducing my time involvement.  Opinions vary but what I described below areat least food for thought before you get started and can be used in anycombination to suit your particular needs.

Time

It is ironic that for as much as I harp on about reducingtime in your system.  Letting WVO sit andsettle is by far the most effective processing technique at your disposal.  In two to four weeks, contaminants willsettle to the bottom of the container it is in. This is going to include water, most solid particles and creamyfat/shortening.   You may still see somelight bits floating  on the surface butthey are easily dealt with;  draw off thetop of your settling container taking care not to disturb the bottom andtransfer into another container through a 10-2 micron sock filter (to collectthe floaters).

Heat

Heat is your best method for accelerating WVO processing.  Hot oil pumps easier, clears filters quickerand drops contaminates/separates faster. If you are dealing with solid grease or just very cold WVO you will haveto heat it to do anything at all with it. If you are looking to accelerate a process, heat is the first place youshould look.  Keep mindful of the energyrequired, with the exception of heating a settling tank, heat the minimumamount of oil that you need to.  Thiswill consume less energy and you will achieve much higher temperatures.  One thing to consider is that heating will“melt” solid precipitates that will re-form when the oil cools.  This could cause problems in the fuel systemof your vehicle if it is not heated appropriately to deal with this.  Immersion heaters offer high power/quickheating and can be used in-line for processing or immersed in solid WVO toliquefy for collection.  Heater wraps andpads work well for filters and possibly settling drums but have much lower wattdensity and hence are slower.

Filters

Bag filters are the easiest, cheapest and slowest processingtool that you have other than strait settling to proces WVO.  Oil will run through a 100 micron filter bagat 2-5 gallons per minute however, if the oil is dirty or just creamy the flowrate will deteriorate rapidly. Pre-heating the oil helps as does larger/longer filter bags.  My advice is to only use filter bags after settling.  Cartridge filters, tee strainers ect, shouldbe used only with heated oil or heating of the filter.  Waxy precipitates in cool oil quickly clogcartridge filters and no amount of pressure will resolve this issue.  Reserve cartridge filters for finalpolishing/filtering at transfer into the vehicle or very low volume/emergencyuse.   Any mechanical cartridge filterwill require an amount of pressure to work, finding an appropriate pump,plumbing and pressure relief system can be difficult and large spills arepossible.  Plan for failure.

Centrifuges

Operating on what I call “Forced Settling” centrifuges canclean WVO to sub micron levels as well as removing heavier liquid contaminantssuch as water.  If you are looking athaving to deal with hundreds of gallons or more, a centrifuge is your onlysolution.  Until recently, the onlycentrifuges available were industrial units with capacity and price outside ofthe recreational or Coop WVOer’s scope. Early 2007, resourceful (and desperate) WVOers started experimentingwith fuel system centrifuges by Dieselcraft. These units were designed to be installed in the fuel system of largetrucks and machinery and use the fuel pressure to spin the rotor.  These units have become quite popular withthe WVO community largely due to a few very vocal proponents.  My experience with these units has led me tothe opinion that they are not worth the effort as they are both un-reliable andineffective for serious use.  Aside fromthe fact that they are fragile and the premise of using feed pressure toactivate the rotor confirms that it was never designed for serious waste oil purification.  They have minimal capacity, the jets plug,there is no ability to adjust feed rate and you never really know how fast therotor is rotating.  Quoted flow rates of50gph are very misleading as the official recommendation for WVO fuelprocessing is “multiple passes will beneeded depending on the degree of fuel contamination”.  There are other issues but suffice it to saythat there are people that do and will continue to swear by them.  A better option, in my opinion, is the basket centrifuge design of my RawPower Centrifuge, Simple Centrifuge, Interfil, US centrifuge and others.  Obviously, I am not without bias, but I chosethis direction and design because of its superior characteristics andsimplicity.  These designs allow forsuperior contamination holding capacity, robust construction, ease of cleaning,reliable operation and adjustable flow rate to accommodate feedstock.  For my part, I have gone to great lengthswith the Raw Power Centrifuge to bring the price to a point that would competeeffectively with Dieselcraft.  Also,interesting to note, Dieselcraft has recently announced its plan to re-sell theInterfil centrifuge in North America and US centrifuge is planning on bringinga WVO version to market.  Continued competitionin this market will accelerate development and give consumers a wider choice ofhigh quality products to choose from.  

Size

Processing WVO is going to be the bottleneck of your wholeoperation.  Preference should be given toautonomous operation and extended service intervals, ultimate speed is lessimportant if you can run 24/7 unattended. Avoid pumps and high pressure; these can lead to failures and extensivespills.  Ultimately you will want torefine your process to suit your climate, feedstock and requirements.

-Leon

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