Transport is not just driving to work in the morning: it is also needed to deliver goods. The Department for Business Enterprise and Regulatory Reform (BERR) has researched the energy consumption of the UK, and transport forms part of this study. The whole point of their report was to look at trends and patterns within the UK’s energy consumption. It’s uses include identifying where a sector has been increasing or decreasing, and from these statistics and studies, create assumptions, i.e. is a sector likely to carry on increasing? This report was written in 2001 and looked at the energy consumption of the last 30 years. ¹

Overall the report shows that there has been a 15% increase in the UK’s entire energy consumption since 1970 to 2001, and of this, there has been a 10% increase since 1990 (taking into account the cold winters or hot summers)¹. Interestingly, transport has increased 95% between 1970 and 2001. In 2001, 54,932,000 tonnes of oil equivalent (toe) was consumed by the transport sector, of which, approximately three quarters was consumed by road transport.²

Today, the rate at which we consume oil is not only a concern, but the amount of carbon emissions being emitted from our day to day usage is also an issue. By finding an economical alternative to oil, oil consumption and carbon emissions can simultaneously be reduced.

Alternatives for diesel and petroleum fuels that are fast becoming economical to the user are ‘Biodiesel’ and ‘Bioethanol’. With some slight engine modifications, these fuels may be used to replace or offset fossil fuel consumption and carbon emissions.

World Ethanol fuel production currently (2009) stands at 4,067 million (UK) gallons, the USA producing over half and Brazil a third of this total.

How Biodiesel  and Bioethanol is made

Biodiesel

Biodiesel is made from natural fats, a typical source is vegetable oil which occurs naturally in seeds from many plants. Crushing these seeds is the basis of extracting these oils. Vegetable oil is made up of triglycerides which are compounds made up of three strands of fatty acids and a strand of glycerol. By processing these triglycerides with an alcohol (methanol) and a catalyst (sodium hydroxide or potassium hydroxide), two products can be made: crude biodiesel and crude glycerol. Later refining of the products and recovery of methanol will leave methyl ester (which is a pure biodiesel) and a purer glycerol. So let’s now look at the process in more detail. The diagram below illustrates the biodiesel process.

The first stage is to mix the alcohol and catalyst together. The raw vegetable oil is added to the mixture and heated. This is known as the ‘transesterification’ process. There is always a surplus of an alcohol added to ensure that all of the vegetable oil has the chance to react.

After a reaction has taken place, there will be two products, crude biodiesel and crude glycerine with other impurities from the reaction. The glycerine mixture has a higher density than that of the crude biodiesel and so rests on the bottom. Tapping this off from the bottom will leave the crude biodiesel remaining. This is the separation step.

Both products of the transesterification process will contain excess amounts of alcohol (as it was used in excess!). This will be taken out by distilling, or flash evaporation, and reused within the process again.

Catalyst that hasn’t been used during the process, as well as any soaps and water, are removed from the crude glycerine. This can now be sold on as crude glycerine or purified further by distillation. The glycerol is a useful by-product as it can be sold to pharmaceutical or cosmetic industries.

The crude biodiesel is also purified (if it needs to be) to take out impurities. Biodiesel essentially is produced from a renewable resource. It is biodegradable and is not toxic to the environment. Therefore, the impact from a biodiesel spillage is relatively low in comparison to that of fossil fuel diesel. Biodiesel also has a higher flash point than fossil fuel diesel and is safer in the event of a car crash due to the nature of its flammability.

Waste vegetable oil is often used as opposed to pure oil as this is a cheaper supply. However, as a result it will more often require filtration in order to take out impurities. Impurities are not just remnants of fish and chips, but also will include water which will need to be taken out of the raw vegetable oil. Water is unhelpful in the process as it combines with the fatty acids producing soaps.

Bioethanol

Ethanol (ethyl alcohol) is the same alcohol found in alcoholic drinks! Bioethanol is simply ethanol made from biomass. The feedstock for bioethanol can come from any crop that can be used as a carbohydrate source. Common crops are sugar beet, sugar cane, miscanthus, maize, sorghum, potato, wheat and corn. In brief, the feedstock is converted into sugars. These sugars are then fermented which forms a by-product, ethanol. The process of making Bioethanol is outline in the diagram below.

Bioethanol differs from biodiesels in regard to the fact that bioethanol requires the feedstock to be grown, whereas biodiesel can be made from used vegetable oils.

Milling is required as this creates a greater surface area for the third stage, hydrolysis, to take place.

The hydrolysis process breaks down carbohydrates, i.e. starch, into simple sugars such as glucose

The fermentation process breaks down the sugars using yeast. The ethanol is a by-product of the fermentation process, and is toxic to the yeast if it exceeds 15% of the total volume. Therefore, the ethanol must be continually siphoned off so that the yeast can continue to work. As the siphoned ethanol has high moisture content, the water will need to be removed.

This purification stage involves distilling the liquid. By heating the liquid up, the ethanol boils before water (as it has a lower boiling point than water) and so can be allowed to vaporise, condense and be collected.

Work is being done on using the waste products of the milling process to make Bioethanol. This involves breaking down biomass slowly using enzymes (much like cattle digestion), to form glucose. This is production of ethanol from cellulose, and is still being researched.

Advantages and Disadvantages of Biodiesel and Bioethanol over Fossil Fuel Diesel and Petroleum

Advantages of Biodiesel

• A Renewable Source (N.B. tends to use ‘waste’ oil as opposed to growing ‘new’ vegetable oil for economic reasons).
• Environmentally friendly: 78% less Carbon emissions than fossil fuel diesel³.
• Non-toxic: It is up to 98% biodegradable within 3 weeks, and is immiscible (does not mix) with water.
• Often only a slight engine modification is needed due to the nature of the biodiesel that eats away at plastic seals within the engine. Older diesel engines tend not to have any plastic within the engine!
• Prolongs the life of an engine: it has better lubrication properties than normal diesel, this reduces system wear.
• Combusts more completely: fuel economy is up 8% over diesel.
• High flash point, making it safer to transport and safer in case of a road traffic incident.
• Generally cheaper by 20p/litre than diesel.

As you can see it is much more environmentally friendly than diesel! It has no Sulphur Dioxide content, around 50% reduction in soot and other particulates, anywhere between 10 and 50% reduction in Carbon Monoxide, and a reduction in Poly Aromatic Hydrocarbons (PAH’S). PAH’s’ are organic pollutants and also, more crucially, are also formed from incomplete combustion of fossil fuels.

Disadvantages of Biodiesel

• Has a lower energy content (around 8-9% lower) than diesel. However it makes up some of this by the lubrication properties and its more complete combustion than diesel.
• Few outlets sell biodiesel, and there are only a small number of manufacturers.
• If the biodiesel is poorly made (i.e. its water content is higher than it should be) then it could cause engine problems.
• Some manufacturers now account for blends of biodiesel in modern cars.  This will need to be checked when purchasing a new car.

Advantages of Bioethanol

• Is a Renewable source, providing it is sustainably managed.
• Exhaust gases are much cleaner than fossil petrol.
• Almost any plant can be used, as long as it contains starch and can be converted into sugar.
• Has a lower taxation in the UK. This reduced fuel duty offsets the higher production costs.

Disadvantages of Bioethanol

• During the processes of making Bioethanol, the amount of CO₂ released almost matches that which has been taken in during the feedstock growth, making little ecological difference as an entity. However, the production of petrol will release much more CO₂ than Bioethanol production.
• Sustainability issues: Brazil is a good example of the environmental impact caused from growing fuel crops. Huge amounts of rainforest were destroyed in order to grow sugarcane for Bioethanol production.
• Energy content is much lower than Bioethanol. Weight for weight, it could contain up to a third less energy than petrol-all dependent on the feedstock used, and quality of the process and fuel.
• Older cars will struggle to accept even a 10% Bioethanol mix (B90).

Implementation of Biofuels for the UK

Distribution within the UK of biofuels is extremely limited in comparison to other countries. Unlike many other countries that have been incentivised to produce and distribute biofuels, the UK has been in a more comfortable situation in the past few decades, and as a result biofuels have not been needed. However, since the UK has gone from being a net exporter to a net importer of oil (from the North Sea), transport fuel is now an issue.

Biofuel implementation is going to be a gradual process unless a sudden incentive to produce and distribute biofuels happens. It is also a ‘chicken and egg’ situation: do you build the infrastructure needed to distribute and consume the biofuels, or grow the crops first and hope that the demand for them becomes apparent? As it stands at the moment, the Government has a target for biofuels that it wants to achieve and this comes under the ‘Renewable Transport Fuels Obligation’ (RTFO). The RTFO denotes that all transport fuel suppliers ensures that 5% of all road vehicle fuel is supplied from renewable sources by 2010.

The UK is at a disadvantage in comparison to the USA due to the lack of space available for, or land able to be converted into growing biofuels. Biofuels are not only used for transport fuel but also for combustion in biomass plants (generating electricity). Miscanthus is a suitable crop to be grown in the UK, but there is competition here for who will use the fuel, do we use it for transport fuel, or burn it in a biomass plant? Cereal crops could also be used for biofuels. The total area that is used to grow crops within the UK in 2009⁴ equated to 4,695,000 hectares. Cereals constituted 3,133,000 of these hectares. There are many uses for these crops (such as beer!), but would anybody be happy to accept a straight swap for beer crops to biofuel crops?

1. Department for Business, Enterprise and Regulatory Reform [BERR]. Energy Consumption within the UK. [2001]. Introduction. Available [Online] at: http://webarchive.nationalarchives.gov.uk/+/http://www.berr.gov.uk/files/file11250.pdf

2. Department for Business, Enterprise and Regulatory Reform [BERR]. Energy Consumption within the UK. [2001]. Section 2.1. Available [Online] at: http://webarchive.nationalarchives.gov.uk/+/http://www.berr.gov.uk/files/file11250.pdf

3. USA Biodiesel Board. Available [Online] at: http://www.biodiesel.org/resources/faqs/

4. Department for Environment Food and Rural Affairs, DEFRA. DEFRA Economics and Statistics –Agriculture in the UK 2009. Table 3.1. http://www.defra.gov.uk/evidence/statistics/foodfarm/general/auk/latest/excel/index.htm