WVO Cleaning Basics
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[edit] 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 going for the Holy Grail approach. To complement the 275gallon tote in the back of my very clean truck, I had a 10gpm redline pump and a 100mesh banjo tee filter. The plan was to suck the oil out of the holding tank, through the filter and into the tote. Voila! Clean oil! 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 my elbows in rancid grease and literally gagging from one of the worst smells I had ever experienced. The euphoria of my apparent engineering mastery was all but forgotten and replaced with more than a little bit of concern. This was going to be work.
That was about a year ago and things could only get better. What hasn’t changed is my pursuit of the better way. I like using WVO in my truck, I like that it is good for the environment and I like that it costs me almost nothing per WVO mile. I don’t like and can’t afford spending huge amounts of my time dealing with it. To this end, I have always focused on reducing my time involvement. Opinions vary but what I described below are at least food for thought before you get started and can be used in any combination to suit your particular needs.
[edit] Time
It is ironic that for as much as I harp on about reducing time in your system. Letting WVO sit and settle is by far the most effective processing technique at your disposal. In two to four weeks, contaminants will settle to the bottom of the container it is in. This is going to include water, most solid particles and creamy fat/shortening. You may still see some light bits floating on the surface but they are easily dealt with; draw off the top of your settling container taking care not to disturb the bottom and transfer into another container through a 10-2 micron sock filter (to collect the floaters).
[edit] Heat
Heat is your best method for accelerating WVO processing. Hot oil pumps easier, clears filters quicker and drops contaminates/separates faster. If you are dealing with solid grease or just very cold WVO you will have to heat it to do anything at all with it. If you are looking to accelerate a process, heat is the first place you should look. Keep mindful of the energy required, with the exception of heating a settling tank, heat the minimum amount of oil that you need to. This will 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 system of your vehicle if it is not heated appropriately to deal with this. Immersion heaters offer high power/quick heating and can be used in-line for processing or immersed in solid WVO to liquefy for collection. Heater wraps and pads work well for filters and possibly settling drums but have much lower watt density and hence are slower.
[edit] Filters
Bag filters are the easiest, cheapest and slowest processingtool that you have other than straight settling to proces WVO. Oil will run through a 100 micron filter bag at 2-5 gallons per minute however, if the oil is dirty or just creamy, the flow rate 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, should be used only with heated oil or heating of the filter. Waxy precipitates in cool oil quickly clog cartridge filters and no amount of pressure will resolve this issue. Reserve cartridge filters for final polishing/filtering at transfer into the vehicle or very low volume/emergency use. Any mechanical cartridge filter will require an amount of pressure to work, finding an appropriate pump, plumbing and pressure relief system can be difficult and large spills are possible. Plan for failure.
[edit] Centrifuges
Operating on what I call “Forced Settling” centrifuges can clean WVO to sub micron levels as well as removing heavier liquid contaminants such as water. If you are looking at having to deal with hundreds of gallons or more, a centrifuge is your only solution. Until recently, the only centrifuges available were industrial units with capacity and price outside of the recreational or Coop WVOer’s scope. Early 2007, resourceful (and desperate) WVOers started experimenting with fuel system centrifuges by Dieselcraft. These units were designed to be installed in the fuel system of large trucks and machinery and uses the fuel pressure to spin the rotor. These units have become quite popular with the WVO community largely due to a few very vocal proponents. My experience with these units has led me to the opinion that they are not worth the effort as they are both un-reliable and ineffective for serious use. Aside from the fact that they are fragile and the premise of using feed pressure to activate 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 the rotor is rotating. Quoted flow rates of 50gph are very misleading as the official recommendation for WVO fuel processing is “multiple passes will be needed depending on the degree of fuel contamination”. There are other issues but suffice it to say that 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 chose this direction and design because of its superior characteristics and simplicity. These designs allow for superior 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 lengths with the Raw Power Centrifuge to bring the price to a point that would compete effectively with Dieselcraft. Also,interesting to note, Dieselcraft has recently announced its plan to re-sell the Interfil centrifuge in North America and US centrifuge is planning on bringing a WVO version to market. Continued competition in this market will accelerate development and give consumers a wider choice of high quality products to choose from.
[edit] Size
Processing WVO is going to be the bottleneck of your whole operation. Preference should be given to autonomous operation and extended service intervals, ultimate speed is less important if you can run 24/7 unattended. Avoid pumps and high pressure; these can lead to failures and extensive spills. Ultimately you will want to refine your process to suit your climate, feedstock and requirements.
