What cars can use bioethanol? Return to top

Being a liquid at room temperature, bioethanol can be handled in a similar way to conventional gasoline. The fuel's high octane rating enables the use of a high engine compression ratio so increasing engine efficiency. Bioethanol can be used in spark-ignition engines with little or no modification as a low percentage alcohol-gasoline blend ('E10' is 10% ethanol; also known as 'gasohol') or as pure alcohol fuel in modified vehicles. The suitability of ethanol as vehicle fuel is demonstrated by its use as a high performance motor-racing fuel.

To convert a conventional spark-ignition engine vehicle to run on pure bioethanol requires the adjustment of the ignition timing, and the fitting of a larger fuel tank due to the fuel's low energy density. As alcohol fuels degrade certain types of rubber and accelerate the corrosion of several metals, some engine components may also need to be replaced. Pure bioethanol is difficult to vaporise at low temperatures - E95-E100 vehicles can be therefore difficult to start in cold weather. For this reason, the fuel is usually blended with a small amount of gasoline to improve ignition (E85 is a common high percentage blend).

Globally, bioethanol is the most widely used green car fuel due to its popularity in Brazil (where most cars are fuelled by sugar cane ethanol) and the US. Most North American manufacturers now produce 'Flex-Fuel' Vehicles (FFVs) that run on any percentage gasoline-ethanol blend (up to E85) or on conventional gasoline – the engine management system automatically detects which fuel is being used and adjusts the timing accordingly making the vehicles fuel-flexible.

What are bioethanol cars like to drive? Return to top

In general, vehicles running on pure bioethanol may be difficult to start in cold weather. However, this can be alleviated through the use of gasoline-ethanol blends. That said, cars modified to use pure ethanol have improved performance, as the compression ratio is often increased to take advantage of its high octane rating. Hence the use of bioethanol as a motor racing fuel.

How do I refuel a bioethanol car? Return to top

As bioethanol is a liquid at room temperature, the fuel is dispensed from fuel pumps in the same way as conventional fuels.

It is likely that you have already driven on ethanol as it is routinely added to gasoline (as a 5% blend) to improve octane ratings and as an oxygenate additive (to reduce carbon monoxide emissions). Ethanol reacted with isobutylene to form ethyl tertiary butyl ether (ETBE) is also used as an oxygenate additive in the US.

For locations of bioethanol stations in the US, visit the US DoE Alternative Fuels Data Center website.

How is bioethanol produced? Return to top

The production of bioethanol first uses enzyme amylases to convert a feedstock crop into fermentable sugars. Yeast is then added to the mash to ferment the sugars to alcohol and carbon dioxide, the liquid fraction being distilled to produce ethanol.

The choice of crop used to produce bioethanol depends on the prevailing soil and climatic conditions. For example, in Brazil, sugar cane is the preferred feedstock due to its very high sugar content and fuel yield. In the North America, over 50 production plants produce fuel ethanol from starch crops such as corn. Most European ethanol is produced using sugarbeet and grains (egs wheat and barley).

Are bioethanol cars better for the environment? Return to top

The great promise of bioethanol 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 extent of 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 sugar cane ethanol, studies show that life cycle greenhouse gas emissions (per mile) can be reduced by up to 90%. This represents the best-case scenario as sugar cane processing is one of the most energy-efficient methods of making ethanol - large amounts of bagasse (the woody fibres remaining after the juice is extracted from the cane) are used to provide the process heat energy. For current EU production using sugar beet or wheat, the reductions are less dramatic though still highly significant - life cycle greenhouse gases being reduced by 35%-65% (depending on processing method used). Corn based ethnaol, howeverm is not not so favourable from a lifecycle CO2 perspective, and in some cases may lead to an overall increase in carbon emissions.

Regarding regulated emissions, for high gasoline-bioethanol blends, carbon monoxide, particulate emissions and tailpipe hydrocarbons are generally reduced. In theory, bioethanol vehicles should emit fewer nitrogen oxides (as alcohol fuels burn at a lower temperature than gasoline). In practice the compression ratio is often increased to improve engine efficiency, which raises the combustion temperature and offsets any NOx emission benefit.

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

Ownership costs are unaffected by switching from conventional to low percentage bioethanol blends as no engine modifications are required. However, it is important to note that most car warranties are likely to be rendered invalid by the use of more than 5% bioethanol blends. In a worse-case scenario, this could result in significant repair costs that would have to be paid by owner of the car.

For cars converted to use pure bioethanol or a high percentage blend, additional costs will be incurred - as the use of pure alcohol requires engine recalibration, the replacement of engine components and the fitting of a larger tank and fuel lines - all of which can cost several hundred pounds. Having said that, the purchase prices for new FFVs are very competitive and are similar to the prices of similar conventional gasoline models.

Vehicle excise duty ('road tax') payable on FFVs that can use high percentage blends is marginally lower than for conventional gasoline cars (by around £10). As FFVs are new to the UK, depreciation and insurance costs for these cars is unknown and may take some time to become established. If low percentage blends are used, depreciation and insurance costs are likely to remain unchanged as is road tax which costs the same as for a car running on conventional gasoline (there being little change to the vehicle CO2 emissions).

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

Due to economies of scale, commercially produced bioethanol tends to have higher production costs than gasoline. These are partly offset by tax benefits as the UK government has reduced fuel duty on bioethanol for the next three years by 20p/litre (to stimulate production).

Despite this, the retail fuel price of bioethanol can be higher than conventional gasoline - the exact price depending on whether the bioethanol is a pure or blended formulation. Having said that, the first supermarkets selling E85 in the UK are offering the fuel at 2p below the price for conventional gasoline. However, as bioethanol has lower energy content than conventional fuels, significantly more fuel is required - a car running on pure bioethanol typically uses around 50% more fuel per mile (by volume) than it would using conventional gasoline.

If low percentage blends or good quality pure biofuels are 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 gasoline.

Where can I buy a bioethanol car? Return to top

Commercially produced bioethanol is still new to the UK and, depending on where you live, difficult to find with only around a dozen stations selling high percentage bioethanol fuels (usually E85). Many more stations, however, already supply E5 as this can be used by the majority of gasoline cars with no engine modification being required. However, it is likely that, if bioethanol’s popularity increases, so will the number of suppliers of E85.

See the Energy Saving Trust website for locations of UK bioethanol stations.

The use of bioethanol as a vehicle fuel is being promoted through the European 'BEST' Project (Bioethanol for Sustainable Transport). During the project more than 10,000 bioethanol cars and 160 bioethanol buses will be introduced across the EU and E85 and E95 fuel stations will be opened for fleet and public use.

In the UK, the BEST project is likely to be instrumental in increasing the popularity of bioethanol as a green car fuel. The main focus of activity will be in Somerset where a network of fuel stations selling E85 has already been established (and is why most of the first E85 stations are in this region). A number of supermarket chains (in particular Morrisons) are supporting the project and now offer E85 on a small number of their fuel station forecourts.