factsheet

biodiesel

what is it?

Biodiesel is a biofuel – that is, a renewable source of energy made from plants. It is very much like diesel that is used in cars, buses and lorries, but instead of being drilled from under the ground it is made from plant oils such as peanut, sunflower or rape seed – in fact any plant oil can be made into biodiesel. It can also be made from waste cooking oil. Scientists who have tested biodiesel in vehicles have found it to be cleaner burning than normal diesel with only a very slight loss in range (how far a vehicle can go on a full tank) of 3-5%. No engine conversion is necessary, so you can use it in any vehicle with a diesel engine; either neat, or in a mix with mineral diesel. Biodiesel can also be used for generators, boats, or as a heating fuel.

what are the benefits?

climate change: use of biofuels can help to slow down global warming. Most scientists now agree that the earth’s temperature is rising much faster than would naturally occur, because of human activity. Even a small rise in average temperatures could melt polar ice caps and raise sea levels, increase the rate of desertification and soil erosion, threaten the habitat of species such as the polar bear, and cause human misery due to famine and flooding. A major cause of global warming is the build-up of greenhouse gases in the atmosphere, which allow the short-wave radiation from the sun to pass through the atmosphere, but absorb the long-wave radiation reflected back from the earth, preventing the heat from escaping. The most important greenhouse gas is carbon dioxide (CO2), which is emitted by the burning of fossil fuels such as petrol, diesel, gas and coal. Burning biodiesel also emits CO2, but this is offset by the fact that the crop used to produce it uses CO2 from the atmosphere to grow. For this reason, biofuels are often called ‘carbon neutral’.
However, there is not enough land to grow crops to replace all diesel with biodiesel. It has been estimated that for Russia to replace all its diesel use with biodiesel, it would have to use 7% of its land to grow the crops needed – a huge land area, but feasible. However, this figure rises to 30% in the USA, and over 100% in the UK. Biofuels will have to be used in combination with fossil fuels, and with other renewables as fossil fuels run out.
emissions: other pollutants, such as alkanes, carbon monoxide (CO) and particulates are also reduced; only nitrous oxides may stay the same or increase, but can be reduced with a catalytic converter, and / or by altering the engine timing. Sulphur is almost completely eliminated. As well as being good for the atmosphere, this can increase operator safety on vehicles such as waste collection trucks, and the smell is much more pleasant than with conventional diesel vehicles. Also, biodiesel is more lubricating than mineral diesel, and so increases engine life.
waste reduction: it can reduce waste by recycling used oil. (100,000 tonnes of waste cooking oil are produced each year in the UK).
spills: it reduces the risk of oil spills from tankers. Small spills and leaks from vehicles are harmless, as it is biodegradable.
energy balance: biodiesel has an energy balance of 3:1, i.e. it provides 3 times the amount of energy used to produce it. (compared to around 1:1 for mineral diesel).

IMPORTANT NOTE: when we talk about biodiesel, we are really only talking about biodiesel made from used cooking oil, or possibly from oil grown locally and sustainably. Some companies are now producing biodiesel from palm oil grown in huge plantations in West Africa or SE Asia. We think that biodiesel from these sources is at least as environmentally damaging as mineral diesel, and possibly more so. For more information on this, see Biofuel Watch.

what can I do?

buying biodiesel: biodiesel is not yet available at most petrol stations; it can, however, be delivered in IBCs. Also, see Biodiesel Filling Stations for more places to buy biodiesel.
The tax on biodiesel was reduced by 20 pence per litre in April 2002. The government hopes that this reduction will encourage the use of biodiesel on a larger scale.
NB: the duty was removed completely for small producers (2500 litres or less per year) from 30 June 2007, and also, medium-sized producers now have to send in returns quarterly instead of monthly. See here for more details.
making biodiesel: biodiesel can be made on the home or farm scale. You can buy used cooking oil cheaply (or maybe get it for free from local restaurants) as well as the other chemicals that are needed, and make biodiesel in a simple reactor. An off-the-shelf home reactor might cost a few thousand pounds, but if you are at all handy, it's possible to make one with a couple of oil drums, a pump, filter, copper pipe and plumbing fittings. Oil is mixed with alcohol and potassium hydroxide (KOH), which acts as a catalyst. When the mixture settles the biodiesel is poured off the top, leaving a layer of glycerine (which can be used to make soap and other useful products). The biodiesel must then be very finely filtered and de-watered. If you make biodiesel you have a responsibility to declare the usage to HM Revenue & Customs and to pay tax to them (unless you produce less than 2500 litres a year - see above).
Extreme care must be taken when making biodiesel, as the process requires the use of potentially hazardous materials.

resources

more - information, books, links, courses, online shop etc.
 


printable version
of this factsheet (pdf)

 


ingredients and by-products: from left – methanol, potassium hydroxide, wash-water, glycerine, finished biodiesel

 

 

 

 

 

 

 

 


participants on a LILI ‘how to make biodiesel’ course carry out a titration test to calculate how much catalyst to use to make biodiesel from this batch of waste cooking oil

 

 

 

 

 

 

 

 

 


biodiesel is a biofuel, made from plant oils, not fossil fuels. Biofuel crops absorb the carbon dioxide emitted when biofuels are burnt

 

 

 

 

 

 

 

 

 


a home-made biodiesel reactor