What is it?
Biodiesel or Methyl Ester as it's also known is a clean
burning renewable fuel made predominantly from vegetable oils.
Its physical and chemical properties are very similar to mineral
diesel, so it can be used either as a blend with mineral diesel
or in its pure form.
is it being used?
Pure Biodiesel (referred to as B100) is manufactured to a
European Standard EN14214. It is the grade used by commercial
vehicle and bus operators across Germany.
of 20% Biodiesel manufactured to the US Standard ASTM D 6751
and mixed with mineral diesel (referred to as B20) is the
fuel preferred by American truck and bus operators. The B20
blend currently provides commercial vehicle operators in the
US with the optimum cost vs benefit balance.
in a 5% blend with mineral diesel is now allowed within the
EN590 mineral diesel specification across Europe and is the
grade most readily available in the UK today, particularly
in the retail network.
note that the benefits, storage and handling considerations
and other precautionary measures covered in this guidance
note relate to the use of pure Biodiesel (B100). These effects
are diluted with the use of blends such as B20. A 5% blend
can be handled and used as normal mineral diesel.
should I use Biodiesel?
Better ignition and combustion
Biodiesel has better ignition and combustion characteristics
(due to a higher Cetane Index), which allows the engine to
run more smoothly with less of the "knocking" sounds
typical of diesel engines.
Reduces exhaust emissions
Biodiesel substantially reduces exhaust emissions (unburned
hydrocarbons, carbon monoxide and particulate matter). It
contains naturally occurring oxygen, which enables the fuel
to burn more completely and all but eliminate the black smoke
normally associated with diesel engines. There may be a slight
increase in NOx emissions but this is dependant on the engine
type and its operating environment.
Improves lubricity & reduces engine wear
Biodiesel has very good intrinsic lubrication properties.
Even blends as low as B1 (1% in ULSD) can improve the lubricity
in highly de-sulphurised mineral diesel. In engines approved
for operation with B100 Biodiesel, the engine wear is significantly
Although there may be a slight increase in fuel consumption
when using B100, the effects are mitigated by the improved
ignition and combustion qualities of Biodiesel. B20 on the
other hand has no effect on fuel consumption; some operators
claiming it actually improves fuel consumption.
Safer, biodegradable and non toxic
Biodiesel has a higher flashpoint than mineral diesel. It
is also readily biodegradable and non toxic, which makes it
a safer and more environmentally friendly fuel to handle,
particularly in sensitive areas.
Biodiesel is naturally free of sulphur and so produces no
sulphur dioxide, considered to be one of the main precursors
to acid rain.
Carbon dioxide neutral
Biodiesel is made from renewable resources, which means it
reduces the contribution of carbon dioxide (one of the main
greenhouse gases) to the atmosphere.
about quality issues?
Biodiesel, like its mineral diesel counterpart, has certain
characteristics that may be affected either during manufacturing,
or subsequent storing and handling.
Standard: EN14214 has been adopted throughout Europe for the
manufacture of Biodiesel to ensure it consistently meets the
strict quality parameters established. This is the Standard
that all reputable manufacturers and suppliers will meet up
to the point of sale.
all fuels however, the continuing quality of the Biodiesel
is dependant on steps taken to safeguard it during storing
and handling, right up to the moment it is combusted in the
it invalidate my engine warranty?
All motor vehicle manufacturers have accepted that a 5% biodiesel
blend in EN590 may be used in all diesel engines regardless
of age or mileage.
addition, a number of motor vehicle manufacturers such as
Mercedes, MAN and DAF Trucks, recognising a growing interest
in B20 (20% Biodiesel in mineral diesel) and B100 (pure Biodiesel),
have carried out tests to check the suitability of Biodiesel
for use in their engines.
positions adopted by the vehicle manufacturers vary widely
with approvals for Biodiesel ranging from 5% in DERV all the
way through to full approval for B100. For a vehicle operator
to be certain that a particular vehicle or engine type is
suitable for a B20 blend or B100 Biodiesel, the vehicle manufacturer
should be consulted directly.
a vehicle may be suitable to run on B20 or B100, there are
still certain considerations that must be taken into account
before using Biodiesel for the first time.
and handling pure (B100) Biodiesel
The same properties which give rise to the benefits of Biodiesel
such as biodegradability and cleaner running engines are those
which need to be considered for storage and handling.
As a mild solvent, Biodiesel has excellent cleaning properties.
It will loosen and dissolve any accumulated sediment left
by mineral diesel in fuel tanks, fuel lines and fuel systems
whether in bulk storage or in the vehicle itself. The extent
of sediment build up will depend on the age and condition
of the storage tank or vehicle, but fuel filters are likely
to clog up with these mineral diesel deposits if the fuel
tanks and systems are not cleaned before using Biodiesel.
same cleaning qualities may affect paintwork and the adhesives
fixing graphics or signs to a vehicle or tank, so if Biodiesel
is spilled, it must be wiped up immediately.
with other materials
In older vehicles, Biodiesel may not be compatible with certain
polymers and rubbers found in hoses and gaskets that typically
form part of the fuel system. Materials such as Nitrile, Fluorosilicon,
Polypropylene, Polyvinyl, Tygon and natural Rubber may soften
and degrade. Any sediment formation resulting from the degradation
of these materials could lead to blocked filters, damaged
fuel pumps and so on.
is however compatible with many seals, gaskets and adhesives
in use today. Materials such as Teflon, Nylon 6/6, Viton A401-C,
Viton GFLT and Fluorinated Rubber are resistant to the effects
of Biodiesel and are standard fittings in many approved vehicles.
The vehicle operator should check with the vehicle manufacturer
to be certain.
Fuel stability and quality maintenance
As a biodegradable material, Biodiesel will age faster than
mineral diesel and so current best practice is not to store
it for any longer than 6 months.
is affected by water, oxygen and direct sunlight, so any storage
tank previously used for mineral diesel should be cleaned
thoroughly to remove any sediment and water. Tanks for Biodiesel
storage should be selected to minimise water contamination,
air contact and exposure to direct sunlight.
with mineral diesel, Biodiesel is produced to meet summer
or winter specifications. If a summer grade is used incorrectly
in the winter months, and the air temperature drops to ~5
deg.C, Biodiesel is likely to become viscous with reduced
flow rate qualities. This may cause problems with pumping,
cold starting and increased stress in fuel systems and injectors.
Consequently, the correct specification of Biodiesel should
be used at all times.
I use Biodiesel in my vehicle right now?
Providing the following precautionary steps are taken, Biodiesel
can be used straight away.
Check with the vehicle manufacturer to see if the vehicle
or engine type has been approved to run on Biodiesel. Certain
manufacturers such as Mercedes, MAN and DAF Trucks have granted
full approval for the use of B100 in their vehicles. However,
the releases only apply to vehicles of a certain age, engine
type or chassis number, so it is important to check carefully.
Make sure the vehicle tank is clean and free from loose rust
particles, sediment and water. If not, flush and drain the
tank with either mineral diesel or Biodiesel. The dirty fuel
must be disposed of in accordance with the appropriate regulations.
Depending on the age and mileage of the vehicle, and the build
up of mineral diesel sediment in the fuel system itself, the
frequency of the following fuel filter changes may need to
be increased to ensure the fuel system is thoroughly cleaned.
After the first full tank of Biodiesel, change the vehicle
fuel filter. (Note: For older trucks, it is suggested that
a spare fuel filter is kept in the vehicle, as it may need
changing anywhere between 100 and 300kms).
b. After the second full tank of Biodiesel, change the fuel
c. After refuelling for a third time, the fuel filter will
need to be changed anywhere between 1,000 and 5,000kms.
d. Thereafter, revert to manufacturers recommended servicing
intervals for fuel filter changes.
note, every vehicle and its operating conditions will differ,
so the above fuel filter change intervals are only given as
a guide. There are no standard procedures for this activity,
so each truck will need to be monitored individually to ensure
fuel filters are changed as appropriate.
It is considered to be good practice to keep the vehicle fuel
tank topped up, particularly if the vehicle is left standing
for any length of time. This will help to prevent the build
up of moisture in the tank through condensation. Note
6 month limit still applies.
As with all other fuels, Biodiesel is manufactured and supplied
to a European Standard EN14214. Where a vehicle operator has
used Biodiesel incorrectly and the fuel itself is found to
be within specification, the operator must retain responsibility
for any loss or damage caused to the vehicle.