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  • Biodiesel pH

    I was wondering whether anyone has reliable information about an acceptable pH range for biodiesel. Everywhere I look it says the pH should be neutral (7) but is there an acceptable range that it should be within? For example 6 - 8, or 5.5 - 8.5? Any information is welcome!

  • #2
    Re: Biodiesel pH

    Paul - a good question. One that I am not really qualified to answer, but I guess that the higher or lower you go off neutral, then the more likely you are to get corrosion in your fuel system. As for how much is acceptable... maybe someone like Terry might know? Anyone else with some more experience in this have a better answer for Paul?
    Robert.
    Site Admin.

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    • #3
      Re: Biodiesel pH

      You can't measure the ph of biodiesel accurately, liquids of low conductivity such as biodiesel give erroneous readings. However, you can measure the ph of the water wash very easily.

      The infopop forum has dealt with this issue many times. You can put 'biodiesel ph' in the "Find" function and come up with lots of discussions.

      Here is about the best sysnopsis of what you might want to do -

      http://biodiesel.infopop.cc/groupee/...5487#374105487

      You might have to cut and paste that URL into your browser to get it to work.

      I note that the water in my area has a ph of 8.5, I could water wash 'til the cows came home and the wash water would never get below 8.5. However all the water soluble constituents in the biodiesel would have been washed out.
      Terry Syd
      Senior Member
      Last edited by Terry Syd; 23 November 2005, 01:44 PM.

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      • #4
        Re: Biodiesel pH

        Thanks Terry and Robert for your replies.

        The pH readings I've got from my biodiesel vary from 5.2 to 6.5 - all on the acidic side. I havent been washing my biodiesel, but have been letting it sit for several weeks before I use it. It seems to get more acidic the longer I leave it(??). I'm measuring the pH with a small, reasonably good, electronic pH meter so I think its accurate, but perhaps not.

        Would you recommend washing to get the pH more alkaline?

        thanks again
        paul tyndale

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        • #5
          Re: Biodiesel pH

          If you have not been washing then I doubt if your biodiesel is acidic as you mentioned. The residual soap in the biodiesel would be alkaline, not acidic. In order to get the glycerine to seperate from the triglyceride you have to neutralise the FFAs in the WVO. After they are neutralised, then the reaction can occur. Therefore, the biodiesel reaction is not an acidic reaction (unless you are using a two stage acid/base reaction). As I mentioned in the previous post, biodiesel by itself gives inaccurate ph readings.

          Here is a something to try. Let a little water trickle down through the biodiesel. This will pick up some of the alcohol and soap/glycerine in the biodiesel - now check the ph of that yucky white water. It should have a alkaline ph.

          In some literature it is recommended to use a bit of acetic acid in the wash - do not do this. The acid in the wash water will clear up the soap, but it does it by converting the soap back to FFAs - which is what you were trying to get rid of in the first place. Biodiesel produced with that method will create a biodiesel that is acidic, simply because there are FFAs floating around in it.

          If you are going to wash, then do as Neutral suggests in the above link. Just wash until the wash water is still a bit cloudy. Most of the glycerine will have been removed at that point and you shouldn't have problems with clogging a fuel filter, however the biodiesel will still remain on the alkaline side and not present corrosion problems to the steel components in the fuel system.

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          • #6
            Re: Biodiesel pH

            This may not relate to this thread, but how long can you store biodiesel before is goes off or gets growth in it, thats if it does react like petro-d. I have 15-5m motor sailer with 671GM (2stroke). She has a fuel capacity of 3200lt and sits on her mooring for months sometimes, does it react to salty air or the huge ranges in temperature we have here in Tas. Can you put growth inhibitors in it like petro and would it be better to make it as needed or make and store.

            I am just starting out with this and so far have only made a very small batch that went wonderfully in my 1984 3.3lt turbo nissan patrol. I took her on a trip to Hobart, 240klm round trip, with big hills and changing terrain. A couple of times she blew large amounts of black smoke, which made me stop, but it just went away. On the return trip I noticed the engine was running cooler, it was quiter and had suddenly lost the smoke puffs when accelerating. So I assume that it may have cleaned out my engine somewhat, is this normal or a sign that something may be going wrong. Sorry for all the questions, finally has anyone actually made a processor. My aim is to make a small seed crusher processor for those that want to grow their own. I looked around my property (25acres) and noted the amount of seed bearing plants. What about wattle seed oil, can you use any plant oil, just specific ones

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            • #7
              Re: Biodiesel pH

              I don't know how long you can store it. I've had stuff sitting around for six months without any problems. We had a discussion about this over on infopop and one of the issues that came out with storage is that unwashed was a better option.

              It seems that the growth in a tank of fuel, whether it is diesel or biodiesel occurrs at the boundry layer of any water in the tank and the fuel. If you use unwashed biodiesel, then any water in the tank will have too high of a ph for anything to grow. In other words, you are putting in your own biocide.

              In regards to the boat, take a look at Robert's recent problem with a clogged fuel filter. This is the most common problem when someone starts using large percentages of biodiesel (if you are only using B20 or less then you may never have the problem).

              It is not the biodiesel that is at fault, it is the dino diesel that allowed the plaque to form in the tank. The biodiesel only cleans it out, unfortuately it gets the blame. When the plaque loosens up, it has to go somewhere - that somewhere is the fuel filter.

              Now, lets say you are motoring into a rough section where the waves are crashing up on the rocks. At about this time the fuel filter decides it has enough of the dino plaque diet and says 'no more'.

              My suggestion is that it would be prudent to work out some sort of parallel filter system, or a quick filter change system so that you don't end up on the rocks. In a truck when the engine starts to starve of fuel, it is easy just to pull over and change the filter.

              Regarding the smoke, when you use biodiesel the oxygenating fuel tends to reduce the visable smoke. B20 reduces emissions by about 50%.

              You can use any vegetable oil or animal fat to make biodiesel. All you need is a triglyceride.

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              • #8
                Re: Biodiesel pH

                Thanks terry, we have 7 different fuel tanks and 4 filter systems, as well as 3 water traps so we can change filters and switch tanks with relative ease. We can also drain filter bowls whilst underway, you need as many backups as you can. The smoke has stopped and I did instal a water trap and drainable filter in the patrol when I got it. I do this with all my vehicles. The 671gm runs on just about anything, she has even run on a mixture of water and diesel when we had a bad fuel contamination. But she chugged through it trailing a huge plume of white steam and smoke, they thought we were on fire until we could clear it. Thats when we put in the multiple filter system.

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                • #9
                  Re: Biodiesel pH

                  Alga, sounds like your boat would be a candidate for some poorly settled biodiesel. The extra glycerin in the fuel would settle out into the residual water under the existing fuel and would create a biocide to prevent any growth (and prevent the tank from rusting). The water traps would pick up any of the milky white water that got into the fuel line.

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                  • #10
                    Re: Biodiesel pH

                    Thanks Terry for the information and advice. I will try what you suggest and see what the pH of the wash water is.

                    If it is alkaline as you say, then do you think washing is necessary? I imagine the only potential problems with having soap, glycerine and alcohol in the biodiesel are clogged fuel filters and perished rubber hoses. Am I right? If so, then regularly replacing the fuel filter and having a vehicle with no rubber hoses should negate these.

                    I would prefer not to have to wash, but obviously do not want to damage my engine either.

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                    • #11
                      Re: Biodiesel pH

                      Sometimes the decision to wash is made for you by the fuel. If you have a really nuked WVO (especially with lots of animal fats) there will be so much soap trapped in the biodiesel that you have to wash to prevent filter clogging.

                      Other WVO can simply be set aside to settle a bit more after being processed. Usually, a week of further settling can be enough to avoid problems.

                      A lot depends on the vehicle and the filtering system. If you have a seperate water seperator, like with a clear glass bowl to see if any glycerin is building up, that can prevent the glycerin from reaching the paper filter element.

                      Getting a water seperator and installing it in the fuel line is not a big job and is great insurance.

                      If you have to wash, or just decide to wash, then it comes down to how much washing is necessary for your fuel to prevent problems. There a heaps of different ways to do it. Some people will use just a gentle static wash where the water lays on the bottom of the biodiesel overnight and by the process of osmosis the glycerin moves to the water. This technique does not remove all of the glycerin (maybe only about a third), but does save time on drying of the biodiesel.

                      Another technique is to add 5% water to the biodiesel/glycerin after processing and then remix the whole thing and let it settle overnight. This removes about 75% of the glycerin. The biodiesel will have minute water droplets in the fuel and it will take a few days in an open container for the droplets to either evaporate or settle to the bottom. (or you can add a bit of alcohol to keep it all in solution)

                      Then there is the 5% mix, and then afterwards any number of 'bubble stone' washes, or mist head washes, or turbulent washes - different strokes for different folks. After which there is drying which can also be assisted with mechanical pumps to spray the biodiesel (to increase surface area), or heating to 120C, or bubble stone air drying - different strokes....

                      Most people start out trying to produce the highest conversion biodiesel with the clearest water wash water. After they realise that the fuel works, they start modifying the process to make it easier and cheaper.

                      If your filter ever clogs because of glycerin - do not throw it away! Simply flush some water through the filter. The glycerin contains soap, it is water soluable. When you flush the water through the filter it is actually going to become cleaner (soap, remember). You can then flush the water out with some menthylated spirits or methanol and put it back on the vehicle. You can even just put it back on without flushing with alcohol and it will still work (the engine might miss a few times, but that's all that happens).

                      Therefore, a clogged filter from glycerin is not a big deal. If it happens to you and you don't have a spare handy and your out on the road - just flush it out with some water and get back to the journey.

                      The perished rubber hoses are related to natural rubber hoses. Biodiesel itself (washed or unwashed) will degrade the natural rubber hose over time. This is only a problem on some pre-1995 vehicles, after that the hoses were converted to synthetic (although you might want to check with your manufacturer). I have a 1984 Toyota Hiace van and have never had any trouble. My brother has a 1982 Mecedes he has run 100% unwashed biodiesel through for four years and still does not have any problems. The "hose problem" is over rated.
                      Terry Syd
                      Senior Member
                      Last edited by Terry Syd; 28 November 2005, 10:47 AM.

                      Comment


                      • #12
                        Re: Biodiesel pH

                        I've got a 1998 Hilux so dont have rubber hoses. I've been running unwashed biodiesel for a year now without problems - I use the settling for a week technique which seems to remove nearly all the glycerine. I carry a spare fuel filter in the car, but also change the filter every 5000km or 6 months as per the recommendations. Its not that expensive and as you say is good insurance. On Filters that I have removed there is glycerine, so I'll try your flushing technique. I'll also check the pH of some waste water as you suggested when I make my next batch, but it sounds like I can get away with not washing (which I'm happy about!). Thanks again for the information and advice.
                        regards
                        Paul Tyndale

                        Comment


                        • #13
                          Re: Biodiesel pH

                          Hi all,
                          I have started making up small batches of bd from wvo my ph levels have come out at 8.5.
                          From fryer to fuel states this is acceptable if not normal.
                          Since this is the only reliable info i have found in a book form i will accept his advice.
                          I bought a new fangled electronic ph meter and also some new oil testing strips from a chemical suppliers in moonah, he said they were a new product as litmus paper tends not to work properly.
                          The meter is all over the shop even when titrating the oil.
                          As i said my batches are coming out at 8.5, i bought some dino diesel today it measured 5.5.
                          The question being i suppose is, what is right and does it really matter.
                          I cannot find any info on the correct ph for dino diesel any where on the web.

                          Comment


                          • #14
                            Re: Biodiesel pH

                            I don't think electronic pH meters work in oil. They are only reliable for water based solutions. The best you can do is test your wash water. Keep washing until the pH matches that of your source water.

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                            • #15
                              Re: Biodiesel pH

                              Yeah I'd have to aggree with you Geewizztoo,

                              PH testers don't give accurate measurements with oil based products, only water. So measuring the washed water is the best and probably only method. This very point is being hotly debated in other forums at the moment. And some of the older and well respected users/producers are ademate about the uselessness of measuring the ph of bd.

                              Joe
                              Joe Morgan
                              Brisbane Biodiesel Site Admin
                              http://www.brisbanebiodiesel.com

                              Searching tips using Google - SVO Dual tank systems
                              SVO, Common Rail and Direct Injection - Vehicles converted to Used Cooking Oil

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