Q. What cars can use biodiesel? Return to top

Interest in biodiesel has greatly increased over the past few years due to the increase in popularity of diesel cars, the increase in price of conventional fuels and the realisation that low percentage biodiesel blends (B5) can be used in place of mineral diesel without any engine modification in many diesel engines (a 'B5' blend is 5% biodiesel mixed with 95% mineral diesel). Indeed, with the correct fuel specification, many diesel engines run more smoothly on biodiesel, which have good lubricating properties. Some (though certainly not all) diesel cars will also run on straight vegetable oils (SVOs) or pure plant oils (PPOs).

However, several practical issues concerning the use of pure, or high percentage biodiesel blends have emerged from real-world use. First, ester-based biodiesel degrades rubber products. Engine parts and equipment with rubber seals and piping are usually therefore replaced with non-rubber alternatives. Second, as biodiesel is more viscous than mineral diesel, biodiesel can clog fuel lines, fuel filters and fuel injectors when cold - one solution is to use a heated fuel filter and/or tank (standard in some cars) - see below. To reduce these problems, national and EU standards have been developed. Users of ester-based biodiesel should therefore ensure the fuel's compliance with EN14214 as well as with EN590 (conventional diesel standard). The other option is to only use low percentage blends and is the reason that most car warranties are only valid up to B5.

With these issues in mind, a few (mainly German and French) manufacturers have designed a range of vehicle engines that can operate on high quality B100 - one example is the VW Golf TDi Mk4 (though, confusingly, not the Mk5). That said, a number of research reports suggest that many 'conventional' diesel vehicles may tolerate biodiesel blends of up to 20% without reporting significant problems. To check whether a particular car can use high percentage biodiesel blends, read your vehicle manual, ask your dealer and (for new cars) check the wording on the vehicle warranty. You may also find advice on models that can use B100 listed on Biodiesel Filling Stations. However, it is likely that you may have to take responsibility for any damage to your engine.

What are biodiesel cars like to drive? Return to top

In general, unmodified cars running on pure biodiesel may be difficult to start in cold weather. However, this can be alleviated through the use of fuel blends or heaters located on the fuel lines or in the tank (see above). That said, driving on biodiesel is virtually indiscernible from using mineral fuel with the exception (for SVOs) of the occasional smell of frying food!

How do I refuel a biodiesel car? Return to top

As biodiesel is a liquid at room temperature, it is dispensed from fuel pumps in the same way as conventional diesel. Although to be confirmed, it is likely that future biodiesel hoses and fuel nozzles will be colour coded in orange, the percentage of biodiesel also being displayed.

For locations of UK biodiesel stations, see Where can I buy biodiesel in the UK?

How is biodiesel produced? Return to top

Biodiesel is commercially produced by the esterification of energy crops such as oil seed rape (producing RME) or from waste vegetable and animal oils (from the food industry). The oils are filtered and pre-processed to remove water and contaminants and are then mixed with an alcohol (usually methanol) and a catalyst. This breaks up the oil molecules, which are first reformed into fatty acid methyl esters (FAME) and glycerol, before being separated and purified. The industrial production of biodiesel has two valuable by-products: glycerine (used in the manufacture of pharmaceuticals and cosmetics) and cattle cake made from the remaining plant material.

Almost three quarters of European biodiesel is commercially produced by the esterification of oil seed rape, the remainder being produced from sunflower, waste vegetable and animal oils. There are currently approximately 40 processing plants in the EU mainly located in Germany, Italy, Austria, France and Sweden.

One possibility for the DIY enthusiast is to make your own biodiesel using waste cooking oil. In principle, anyone with access to a supply of used oil, a multi-gallon drum, some basic kitchen utensils and a storage area can manufacture their own biodiesel. Several organisations, such as Bio-Power (UK) have been set up to advise DIYers on how best to source and mix the ingredients. A process has been developed which eliminates the use of methanol. Advice is also given on how to make a fuel line heat exchanger, and keep your fuel use legal through accurate record keeping and by paying of the appropriate tax per litre of biodiesel produced. Note that many small producers have received unannounced visits from Customs & Excise! However, before you rush off and gear up for commercial production, it is worth noting that producers of WVO fuels are required to formally register as a substitute fuel producer and must comply fully with regulations pertaining to the processing and storage of fuel and waste substances.

Are biodiesel cars better for the environment? Return to top

The great promise of biodiesel is its potential to be 'carbon-neutral' on a life cycle basis; all the carbon dioxide emitted during use of the fuel being balanced by the absorption from the atmosphere during the fuel crop's growth. However, in practice the process of growing the crop requires the input of fossil fuels for fertilisers, harvesting, processing and fuel distribution. The actual extent of total life cycle greenhouse gas emissions is therefore strongly dependent on the crop grown and the fuel processing employed.

Taking into account emissions of carbon dioxide and nitrous oxide (associated with agriculture) for RME, biodiesel studies show that life cycle greenhouse gas emissions (per mile) can be reduced by up to 60%. Proportionately, this means that a 5% RME blend would result in a carbon reduction of around 2.5%. If waste oils are used, larger reductions are likely - this is because the source material, which would otherwise be thrown away, essentially replaces its petroleum-derived equivalent.

For regulated emissions, estimates based on a number of comparative tests suggest that biodiesel particulate emissions are lower than for mineral diesel. Biodiesel's low sulphur content also increases the efficiency of exhaust emission control systems, which reduces emissions of carbon monoxide and hydrocarbons. However, without an emission control system, NOx emissions are often slightly increased for biodiesel as compared to mineral diesel fuel.

How much do biodiesel cars cost to own? Return to top

Vehicle ownership costs are unaffected by switching from conventional to low percentage biodiesel blends as no engine modifications are required. However, additional costs may be incurred if pure biodiesel or high percentage blends are used - the replacement of rubber components could cost several hundreds of pounds depending on the vehicle model. A DIY heat exchanger used by some proponents of SVO and WVO fuels, on the other hand, can cost as little as £100 to make and fit to your own car (see above). A further consideration is the assurance offered by car warranties, which may be rendered invalid by the use of higher than 5% biodiesel blends. In a worse case scenario, this could result in significant repair costs that would have to be paid by owner of the car.

If low percentage blends are used, depreciation and insurance costs are likely to remain unchanged as is vehicle excise duty ('road tax') which costs the same as for a diesel car running on conventional diesel fuel (there being little change to the vehicle CO2 emissions).

How much do biodiesel cars cost to run? Return to top

Due to economies of scale, commercially produced biodiesel tends to have a high production costs. This is partly offset by tax benefits as the UK government has reduced fuel duty on biodiesel for the next three years by 20p/litre (to stimulate production). Despite this, the retail fuel price of biodiesel is often higher than mineral diesel, with forecourt prices starting from around £1/litre - the exact price depending on whether the biodiesel is a pure or blended formulation. Note that as biodiesel has lower energy content than conventional fuels, slightly more fuel is required - a car running on pure biodiesel typically uses around 10% more fuel per mile (by volume) than it would using mineral diesel.

In contrast, making your own biodiesel could offer significant fuel cost savings. In theory, DIYers could produce their own fuel using waste oils for as little as the cost of the fuel duty alone. In practice, if labour costs are factored in, it is likely to be somewhat more than this figure suggests. Also, sourcing high quality waste oils may involve paying a small amount to a supplier.

If low percentage blends or good quality pure biodiesel is used (such that the car's warranty remains valid) other running costs, including servicing, maintenance and repair costs are likely to remain the same as for a conventional car using mineral diesel. (It is however recommended that, a short time after switching to high percentage biodiesel, the fuel filter is replaced - this is due to the cleaning action of biodiesel fuels.)

Where can I buy biodiesel in the UK? Return to top

Commercially produced biodiesel is becoming increasingly available in the UK. Over 140 fuel stations now supply biodiesel with most regions having at least one retail outlet. Given the warranty issue already discussed, most of these stations supply B5 as this can be used by most diesel cars without any engine modification being required. However, it is likely that as the fuel's popularity increases, so will the number of suppliers of B20, B50 and B100.

See the Energy Saving Trust website for locations of UK biodiesel stations or go to BiodieselFillingStations.co.uk for a list of retail biodiesel outlets across the UK.

For bulk fuel buyers, several companies are now supplying blended and pure biodiesel to order. One of the largest is Greenergy whose main product is GlobalDiesel, a B5 blend. The company are also able to supply any ratio of biodiesel/diesel blends (a popular order is for B20), and pure RME as part of a 'Field to Forecourt' scheme (in which the carbon balance is independently audited). Rix Biodiesel also manufacture, distribute and supply a range of pure and blended biodiesel fuels - their website also provides information about biodiesel retail locations across the UK.