Making Bio-diesel

Making Bio-Diesel - it's a great alternative fuel that is 70% cheaper than diesel and lowers your carbon footprint by 50%, or so I am told.

Legally the government will allow any person to make 2,500 litres per year as long as it is for their own personal use. Please make sure you don't go over that limit - the penalty is you have to pay the Revenue 30.5p tax per litre back over the whole amount you have made. That would hurt big time!

This is Bio-diesel, made my way. Collect used vegetable oil. It usually comes in 20 litre cans. Do not use palm oil - it's too soapy. Leave your oil to settle out for about a week. Then carefully pour out the oil into another container leaving about 25mm or so dirty oil in the bottom of the can. This is waste and cannot be used.

As you are pouring the oil into the reactor you should filter it through a sieve lined with a nylon stocking or similar. This takes out any small food particles like pips, seed and chips, etc. The cheapest type of reactor is a 45 gallon/205 litre oil barrel (see how to build a bio reactor). Close the outlet tap/valve on the reactor and fill with 130 litres of filtered used vegetable oil. Turn on the circulating pump - if you have a speed setting on the pump use slow or speed 1 as it flows around the system. Turn on the heater, at 3 kilowatts. The time taken to heat the oil to 65°C will be 2 hours.

The next stage is to make your Methanox. I use two 25 litre clear plastic drums, and I have made a mark at 16.5 litres on each one. Now safety - please be careful to cover yourself because these chemicals are very dangerous. Use mechanics rubber gloves plus heavy duty rubber gauntlets over the top of your hands. Use light grinding glasses and over the top is a perspex shield for your eyes and face, wear a long plastic apron, skull cap and leather boots. Use a Paint-sprayer's mask with chemical type filters. This sounds over the top but it's a must, wear it now, remember prevention is better than cure! You cannot breathe this stuff: it's too dangerous.

Now fill each container with 16.5 litres of methanol. Methanol vaporises at 60°C so make sure NO ignition sources - e.g. naked flame, cigarette - are anywhere near. As methanol burns with no flame, so great care has to be taken!

You will now need 124 grams of caustic soda - I use the granule type, a 1 litre measuring jug, and weigh the caustic out in 62 gram quantities per container. Slowly pour the caustic soda into the methanol through a small funnel, and when all the caustic soda is in, seal the container by screw-down cap and turn off the tap. Now the methanox - it needs to be mixed. To do this, rock the container back and forth: as you do this a chemical reaction will be taking place and you will notice the liquid heating up and expanding the containers so you will need to vent them by opening the tap on top of the container from time to time as you continue to mix the chemicals. 15 to 20 minutes mixing time should be ok.

Check the temperature of the oil in the reactor: if at 65°C turn the heater off, turn the pump to fast or speed number 3 and allow the temperature to reduce to 50°C. This temperature is important to get right. Now lift the methanox onto the top of the reactor, supporting the methanox container with two wooden planks.

Make sure that the outlet tap is over the point where the oil is pouring in the reactor. Repeat this with the second container of Methanox. Now with all 33 litres of Methanox mixing in the reactor cover it with a ply board sheet keeping heat in, and mix with the pump on fast speed or number 3 for 60 minutes. Mixing longer than this makes no difference to the quality, its just a waste of electricity.

You need to stop the reaction now, by adding 7 litres of warm water. Just pour it into the top of the reactor, allow it to pump around and mix in for 15 minutes then turn off the pump.

Take a sample from the top third of the reactor in a pint glass, leave it to settle for an hour. You should see a small line about 25% up the glass, black at the bottom, amber at the top.

This is the good part, the black stuff is soap or glycerine waste. We don't use this stuff so after 3 hours or so you can drain off the glycerine from the extreme bottom of the reactor (slowly!) - as the reactor will still be warm, this helps the glycerine to flow out. I measure the amount of it that comes out of the tube - it holds 15 litres each. The first two tubes can be quickly filled, the last one is best to fill slowly as when the thick black changes colour to a light golden colour it is time to stop - this is your bio-diesel.

Put two bubblers in the bottom of the reactor: this sends a small bubble up through the bio-diesel. This is very important as you filter out any Methanol that is left in the bio-diesel. It's a slow job, but just requires you to leave it bubbling for 48 hours. You may see a residue line around where the oil left was - prior to the bubbling. This reflects how much has evaporated out - the top of the reactor should be vented when bubbling is taking place.

After 48 hours turn the bubblers off, turn the pump on to slow, turn the heater on and heat up to 70°C which should take 2 hours. Turn the heater off, turn the pump off and turn bubbler on for 3 hours.

Turn the bubbler off leaving the bio-diesel to stand for as long as possible - at least 24 hours. Now you can enjoy motoring at a sensible cost!

Taking the finished bio-diesel from the reactor: use the tap about 50mm off the bottom of the reactor. I filter the finished bio-diesel through a filter cloth, about 5 microns. You will be amazed at how clear and pure it looks.

In the winter I use bio-diesel 50-50 with pump diesel because the pump diesel has anti-waxing agents in the fuel for very cold conditions - in the summer you can use just bio-diesel. I have made over 2,000 litres now and have used it in a variety of motors with no problems. The key is getting the entire Methanox out and that is about it.

Clean all equipment with water. When you have used the reactor, you will have a small amount of glycerine left at the very bottom forming a skin. Scoop it out and wash down the reactor before your next batch.

The only problem with manufacturing bio-diesel is sourcing the starting product of old used vegetable oil. Chip shop oil is not good as they tend to use palm oil and that goes solid at 5 degrees, so definitely not good!

The old vegetable oil needs to be liquid at -5°C. Hotels, pubs and clubs are the best, but don't expect to get it for free. I pay £2 for a 20 litre can and that is good for all. I tell them about the carbon footprint reductions because it all helps our planet. The waste product is glycerine which is green waste, so next time you are at the recycling centre it goes in with green waste.

Of course there are other recipes, but this one works and is easy to do. Remember be safe, and follow ALL safety instructions!

Mike Chubb, August 2010