Transport biofuels are liquid or gas fuels made from plant material, recycled elements of the food chain or waste material, for use in combustion engines.
- Biodiesel – a fuel normally derived from plant oils for diesel engines. The oils are esterified to form methyl or ethyl esters and are usually sold blended with traditional diesel.
- Bioethanol – a fuel normally derived from the fermentation of starch or sugars for petrol (gasoline) engines, usually sold blended with traditional petrol.
- Biogas/biomethane – a gas fuel derived from the digestion of organic material for natural gas engines.
- PPO – or Pure Plant Oil, unprocessed oil used in specially modified diesel engines.
This page address questions on liquid transport biofuels, for more details on Biogas please see the Natural Gas technology page.
Biofuels are fuels, which are normally produced from grown organic material (e.g. plants), and reduce green house gas emissions though the absorption released CO2 emissions, See figure 1.
The UK has significant arable land on which energy crops could be grown, such crops include.
- Rape seed which can be converted into bio-diesel
- Wheat and sugar beet which can be used to produce ethanol by fermentation
- Miscanthus and wood from short rotation coppicing, which can be burned to produce heat and power, or in the longer term potentially converted to produce biofuels.
However, for UK production the area of land available is a determining factor, with indications that about 0.8 million hectares could be given over to energy crops by 20101. In addition current exports of wheat, and waste products, could supplement production. If biofuel demand increases as anticipated (link to Q9), demand shortfalls in the UK , due to land availability or pricing, will result in supplemental import of bioethanol and biodiesel made from crops grown overseas, e.g. sugar cane, maize, palm oil and soy.
Finally a number of waste products can also be converted into energy or fuels, e.g. used vegetable oil/tallow into bio-diesel and straw and forestry waste converted into heat and power, or in the future biofuels.
Increasing quantities of biofuels are already sold in the UK, and the UK government is promoting their use, see Question 9, but care must be taken to use the right fuel and vehicle combination to avoid engine damage to fuel system degradation.
Road fuels are covered by international quality standards that ensure safe operation.
- Diesel vehicles are warranted to use BS:EN590 fuel. This standard allows up to 5% biodiesel by volume, (where the biodiesel is esterified and meets the BS:EN14214 specification).
- Petrol vehicles are warranted to use BS:EN228 or BS:7800 fuel. This standard allows up to 5% bioethanol by volume.
Work is currently underway within the European Standards Organisation, CEN, to examine if the current limits on biofuel composition of road fuels can safely be increased to 7% and then to 10% for biodiesel and to 10% for bioethanol, taking account of the operational impact upon the current and future vehicle fleet.
Pure Plant Oil (PPO) and Waste Vegetable Oils (WVO) quality can be controlled by the German rape seed oil standard DIN 51 605. However, even PPO or WVO meeting this standard should only be used in specially modified diesel engines, and it is likely that any manufacturer’s engine warranty will be invalidated.
Flexible fuel (Flex-Fuel) vehicles can run on ethanol-petrol blends of up to 85% ethanol/15% petrol (E85). Whilst Flex-Fuel vehicles and E85 are available in the UK, there is no current quality control standard to ensure consistent properties of E85 fuel in the UK. Users of E85 should discuss with the fuel provider the suitability of the fuel for their vehicle.
Today some standard vehicles and other specially modified vehicles are able to run on higher than a 5% concentration of biofuel. Generally, vehicles suitable for high biofuel concentrations are suitable for regular fuel too. Checks should be made with the vehicle manufacturer to ensure the correct fuel and blend concentration is used.
Vehicles that can use conventional petrol, high concentration of bioethanol, and any blend in between are known as ‘Flex-Fuel’ vehicles. A small network of high concentration biofuel pumps is available in the UK, mainly E85 an ethanol-petrol blends of 85% ethanol/15% petrol. For depot-based fleets, biodiesel blends like B30 (30% concentration biodiesel) may be available. See www.transportenergy.org.uk for locations of biofuel retail sites.
The 2007 EUCAR/CONCAWE/JRC Well-to-Wheel2 lifecycle analysis of greenhouse gas (GHG) emissions for a wide range of biofuels demonstrates that sustainably produced biofuels can result in an overall net reduction in carbon emissions. As shown in Question 3, biofuels can save carbon because the CO2 that is emitted into the atmosphere when they are burned is offset by the CO2 that the crop has absorbed as it grows. For biofuel produced from waste products, there is also a potential CO2 sequestration effect since organic waste produces CO2 when it decays, sometimes leading to CO2 savings of greater than 100%. In this sense they are different from fossil fuels, which emit historic carbon into the atmosphere which has been locked away under the earth's surface for millions of years.
However, the carbon savings that biofuels offer can vary widely. This is because these carbon savings are offset by the fossil energy that is used for cultivation (such as fertilisers), harvesting, processing and transportation. For example, Figure 1 which uses data from the EUCAR/CONCAWE/JRC Well-to-Wheel report of 2007 demonstrates the variations in possible savings.
Focusing on bioethanol produced from wheat, in the best case, this fuel can save as much as 80% of the Well-to-Wheel GHG’s of conventional gasoline when used neat in a passenger car, or in the worst case lead to an 8% increase in GHG emissions over gasoline.
Because of this variability in green house gas savings the UK has taken action to pursue those biofuels with the largest CO2 savings. Under the Renewable Transport Fuels Obligation (RTFO for more information see Question 9) fuel companies in the UK will be required to measure and report on how much carbon their fuel has saved over the entire life-cycle from grain to tank (including any effects of land-use change). And from 2010, when experience with carbon measurement and reporting has been established, the Government has announced its intention that the RTFO will reward fuels according to their carbon savings.
Looking forward, both the fuels industry and the motor industry are working heavy on the next, ‘second’, generation of biofuels. Fuels which can use a wider variety of feedstocks, including waste biomass, and have greater potential for greenhouse gas savings are a real possibility.
An example of a potential future transport fuel is the Volkswagen Sunfuel3. This diesel fuel is produced through synthetic fuel processing techniques (Gasification of waste biomass and transformation into liquid fuel through Fischer-Tropsch synthesis). Volkswagen life cycle analysis of the fuel, known as SunDiesel4, shows significant Well-to-Wheel green house gas reductions over conventional fuels and reductions regulated emissions.
In October 2007, Parliament approved the Renewable Transport Fuel Obligation (RTFO), requiring suppliers of road fuels to incorporate a proportion of biofuel in petrol or diesel, or pay a penalty. The Renewable Fuels Agency (RFA) was established when the RTFO Order 2007 was made and is responsible for monitoring the implementation of the RTFO by obligated companies.
The RTFO will commence on 15th April 2008 with a target of 2.5% by volume biofuel content in road fuels in 2008/9, 3.75% in 2009/10 and 5% in 2010 onwards. At the 5% level, the Department for Transport estimates that around 0.8 million tonnes of carbon emissions per year would be avoided.
Under the RTFO there will be a continued support package of 20p per litre duty incentive for biofuels (guaranteed until 2009/10) supplemented by a 15p per litre buy-out penalty for suppliers failing to meet the obligation, meaning an overall 35p per litre incentive in 2008/10 for the biofuel element but reducing to 30p per litre in 2010/11.
In 2007, UK sales of biofuels were 500 million litres, compared with approximately 49 billion litres of conventional petrol and diesel.5
As Question 7 shows the greenhouse gas (GHG) and sustainability impacts of different biofuels vary significantly. The GHG benefits of biofuels depend upon the system of cultivation, processing and transportation of feedstock. The introduction of biofuels can also lead to unintended negative environmental and social impacts. Key issues include potential competition with food crops leading to increased commodity prices. Increased pressure for land may lead to direct deforestation to make way for new plantations with biodiversity impacts and loss of carbon stocks that negate any GHG savings. Changes in land use may also occur indirectly where existing agricultural activities are displaced into forest land by crops for energy.
To encourage suppliers to source sustainable biofuels, the Renewable Fuels Agency (RFA), administrator of the Renewable Transport Fuel Obligation (RTFO) scheme, will require fuel suppliers to submit reports on both the net GHG saving and sustainability of the biofuels they supply in order to receive Renewable Transport Fuel Certificates. In January 2008 the RFA issued guidance to obligated oil companies on the reporting methodology for sustainability of biofuels supplied through the RTFO.
European Environment Agency 2006
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UKPIA – Briefing Biofuels in the UK 2008