Biofuels - An explanantion

What are biofuels?

They are biodiesel and bio-ethanol; liquid fuels made from plant material and recycled elements of the food chain. To a large extent, they are renewable and sustainable. Biodiesel is a diesel alternative. Bio-ethanol is a petrol additive/substitute. They are produced from crops such as cereals, oilseeds, sugar beet and fodder beet.

What are the advantages of biofuels?

They can cut emissions of carbon dioxide, a greenhouse gas, by 50%-60% compared to fossil fuels and so can contribute to meeting UK targets for alleviating climate change.

Biodiesel is biodegradable and non-toxic.

How can they be used?

Biodiesel can be used either as a blend with mineral diesel (5% biodiesel is common in France and has been introduced into the UK) or as a straight fuel. Vehicle manufacturers' warranties cover use with 5% biodiesel blends. 100% biodiesel must meet the EU quality standard EN 14214. No engine modifications are required and biodiesel can improve engine lubricity when blended with ultra low sulphur diesel (ULSD)

Bio-ethanol can be used as a 5% blend with petrol under the EU quality standard EN 228. This blend requires no engine modification and is covered by vehicle warranties. With engine modification or a vehicle purpose built bio-ethanol can be used at a higher levels, for example E85 (85% bioethanol) is common in the USA.

What are the disadvantages with biofuels?

Producing biofuels costs (pre tax) about twice as much as fossil fuels does to produce.

Several of the outstanding ethanol fuel issues are linked specifically to fuel system materials. Fuels with more than 10% ethanol are not compatible with non E85-ready fuel system components.

Certain materials commonly used in the storage and dispensing of existing fuels can be affected by ethanol blended fuels, such as

Aluminium
Brass
Zinc
Lead and lead based solder
Cork gaskets
Polyurethane
It will be essential that a full survey of the existing site be carried out to identify any components that may be incompatible with bio-fuels.

The largest concern to bio-ethanol is water. Ethanol and water are simply not compatible. It takes a small amount of water to cause what is known as "phase separation".

 When water does contaminate ethanol blended fuel, the water dissolves into the ethanol and disperses throughout the tank. Once it exceeds its maximum tolerance, the alcohol/water mixture will separate from the fuel. As little as 50mm of water in a 38,000 litre tank can start phase separation.

Depending upon the conditions, up to 80% of the ethanol will separate from the fuel, forming two separate layers in the tank: petrol on top of ethanol-rich water. Phase separated product cannot be re-blended on site and will need to be removed for reprocessing or disposal.

Debris or particulates create similar problems in tanks containing ethanol blended fuels. For this reason it is critical that all tanks receiving ethanol fuels should be carefully inspected prior to the first introduction of fuel to ensure that there is no water or debris present.

The ethanol in bio-ethanol is ethyl alcohol and will act as a cleaning/scouring agent when introduced into existing UST's therefore any remaining debris will be held in suspension within the new fuel. Biodiesel is a better solvent than existing diesels, and has been known to break down deposits of residue and sludge in UST's.