I hope that this message gets to you, as a somewhat belated reply to your response to my enquiry about using biodiesel, back in September 2010! I have been running several Skodas over the years since, and my current car is a 2010 Octavia Scout 2.0 TDI. I’m still making biodiesel from used chip oil, at about 21 pence per litre, and I have had no problems, not even with waxing in the cold weather. I add a product called Bioboost all the time, and when I make my diesel in the summer, I add Coldflow additive and keep that for the winter. One of the plus points of using biodiesel is that nobody tailgates me now, once they get a good whiff of fried fish from my exhaust! Over the years I have, at a guess, saved around £12,000, which I feel is enough in hand to carry out any repair work if there should be a problem. Keep up the good work,
Richard Hogarth

Nearly every week Richard (it’s been five years and three months since our correspondence appeared in Issue 278), I’ve been sitting here at my PC wondering how you were getting on. I’m also a fibber! But I’m really delighted to read of your long-term success with the old bio stuff, and that it apparently hasn’t screwed up your engine. I’m going to stick my neck out and guess that your Octavia Scout 2010 is an early 2010 car with the PD Pumpe Düse engine, and not from later that year when the common rail (CR) diesel engine came in. I would be careful about using your brew in any CR engine, as they are so sensitive to fuel and any impurities, although I do know about your one micron filter. Are you an industrial chemist, by any chance? All the very best. I look forward to hearing from you – before another five years pass!
Doctor D

P.S. Any chance of a few details of your production methods?

Richard then came back to me with a description of his process, which I have described below, along with his comments, which I think may be a great interest to many readers, even if they are not tempted to bravely follow his cost-saving route!
Doctor D

I get my used chip oil (liquid, not solid) from pubs that don’t over-use the oil, and who don’t put all the solid scraps from the griddle into it – or any other kitchen waste either. I generally let the oil stand for around a week when I get it home, in order to allow any sediment to settle, so that when I decant it to the heating tank (filtering it through a pair of my wife’s old tights!) it is reasonably free from lumpy bits and other contamination. My batch size is usually 50-litres, since that is the size of my reaction vessel. 

In my heating tank, the oil is heated to 80 degrees Celsius and circulated to thoroughly mix it. The waste oil comes to me in 20-litre containers, and varies in quality and colour according to its usage. The next task is to carry out a titration (that’s a chemical test) to establish how much caustic soda has to be added to the methanol to make sodium methoxide with which to carry out the “transesterification” that converts the oil into biodiesel. At this point the hot oil is transferred to the reaction vessel, a circulation pump is started and, using a vacuum lift, sodium methoxide is introduced to the oil over a 10 minute period – the watchword here is gradually – and the mixture is circulated for half an hour. With the circulation pump then turned off, the whole thing is left to stand for a couple of hours.

There is a complete and irreversible chemical change taking place, and after two hours a separation line becomes visible in the reaction vessel. The dark liquid at the bottom is glycerine, which must be drained off and disposed of. It is biodegradeable and can be put into any domestic compost. So there is now a fairly clear liquid, golden in colour, and this is the biodiesel. At this point I add the Bio Boost, which is a cetane improving additive, and for winter fuel, Cold Flow additive as well.

My storage is in 20-litre plastic containers after the product has first been filtered through a ten micron filter, which is cheap) and a one micron filter, which is expensive. I don’t “wash” my bio diesel, as many people do, but I do let it stand for two or three months before I use it to let any glycerine etc. sink well to the bottom. My winter fuel, which I make in the summer when the ambient temperature is higher, stands for up to eight months before I use it.

To refuel the car, I use a submersible 12-volt electric pump to transfer it from container to fuel filler. Regarding Fuel Duty, Customs & Excise allow the home manufacturer of biodiesel to produce up to 2,500 litres per year, as long as it is for for personal use only. Beyond that, it should be declared and duty paid at the appropriate level. My production has peaked at under 2,500 litres every year. I understand, though, that if you were to put any excess into your central heating kerosene tank, then no duty would be due on that either.

My cars have all been pumpe düse (PD) engined, except for a 2003 1.9 TDI which used the old-fashioned rotary pump. I make a point of changing the fuel filter every 10,000 miles. When I bought my current car, the Octavia Scout, it had 57,000 miles on the clock, and I found myself changing the filter twice in 5,000 miles, due to the cleansing effect of the bio diesel. There is no reason, as far as I can see, why bio diesel should not be used in a CR engine, as you asked. The seals in the fuel systems are the usual failure point and, if the material used is the same in PD and CR engines there ought not to be a problem. (You may well be right Richard, but I still don’t think I would take a chance on using it in any still-in-warranty new car! Doc.)