There is a considerable number of energy sources which have been mooted as alternatives to fossil fuels. These include wind power, nuclear power, waves, tides, solar and biofuels derived from plants. The key data for these alternatives is given on Basic Data for:- Energy and Emissions, but one fundamental fact must be born in mind.
This is that the first four of these sources must reach the consumer as electricity. At the moment fossil fuels account for 92% of UK energy consumption and only one-sixth reaches the end-user as electricity. Thus any significant shift from fossil fuels must involve a huge extension to the National electricity grid with all that means in terms of cost and disfigurement of the landscape.
But the alternatives are not all equal in these respects. This page will consider alternatives to fossil fuels from their cost, environmental, and availability points of view, starting with biofuels.
BIOFUELS
by S F Bush[1] (18 July 2008)
- Section 1: Present Position
- Section 2: What are the current biofuels for transport?
- Section 3: Purpose of this paper
- Section 4 Assumptions
- Section 5: Results
- Section 6: Processes involved in making biofuels”
- Flow Diagram 1: Sugar beet to Bio Ethanol
- Flow Diagram 2: Fats to Biodiesel
- Flow Diagram 3: Hydrogen
1 Present Position
As part of its EU “Renewable Transport Fuel Obligation (RTFO)[2], the UK government with no serious opposition in Parliament, has agreed that biofuels shall be added to standard petrol (octane) and diesel fuels at the following levels:
2.5% from April 15 2008
3.75% from April 15 2009
5% from April 15 2010
Though supporting this scheme originally, the Green lobby has recently put pressure on the government to reduce or abandon its commitments on biofuels on the grounds of their adverse effect on world food production. Accordingly Ruth Kelly, the Transport Secretary, has announced that the Department of Transport would not support the EU proposals to increase the level of biofuel addition from 5% to 10% by 2020 without further study.
This paper is designed to examine the implications for the UK of biofuels as replacements or additives for the current oil-derived petrol and diesel fuels.
2 What are the current biofuels for transport?
These are:
(a) “bioethenol” (chemically the same as ethyl alcohol as found in spirits, wines and beers) designed to be added to or replace petrol (basically octane).
(b) “biodiesel” – a mixture of compounds, like diesel fuel itself, which meets a specific combustion standard (BSEN 14214) as shown on the forecourt pump.
Under the 2004 Energy Act, in order to contribute to meeting our RTF obligation, biofuels must show a minimum of 60% saving on CO2 emissions over a “full life cycle” compared with their fossil fuel comparators (i.e. petrol and diesel).
3 Purpose of this paper
This is to calculate or estimate the implications for the United Kingdom of meeting the 5% RTF obligation and further extending it to the limits which British agriculture could achieve with a wholesale switch away from growing food.
4 Assumptions
4.1 People and Business will want to make the same number of journeys per vehicle per year as in 2005. The national statistical office (NSO) data for 2005 published in August 2007[3] gives a UK total of 513 billion kilometres per year of which private cars account for 409 billion.
4.2 Petrol (octane) and diesel engine efficiencies (kilometres per litre or miles per gallon) will be unchanged from 2005 at an average over all vehicles on the road of 1690 litres per vehicle per year (for private cars the data gives around 10 km per litre or 27 m.p.g.)
4.3 Car Ownership will increase from the 2005 figure (26 million) at the current rate of 3% per year to around 32 million in 2013, and all vehicles from 33 million in 2005 to 40 million in 2013. Fuel consumption will increase in the same proportion[4].
4.4 As well as manufacturing inefficiencies, the energy used and CO2 emitted in converting biomass to fuels suitable for internal combustion engines will be taken into account when calculating biofuels’ advantage or disadvantage in these two respects.
4.5 The analysis below concentrates on bioethanol (for cars) where the manufacturing process (from sugar beet) is well-defined[5], but also looks at biodiesel and also processes for producing hydrogen as a substitute for petrol or means of upgrading biofuels. The economic implications of using wheat as a biomass feedstock are also noted.
5 Results
5.1 The 20 pence fuel duty rebate on 5% biofuels added to petrol and diesel will cost the exchequer in 2010, around 54 x 1.15 billion litres delivered x £0.20 x 0.05 = £620 Million.
5.2 If the whole UK acreage of sugar beet were used to make ethanol, it would yield “octane equivalent” fuel per annum for around 380,000 vehicles or 1.2% of 2013 car population.
5.3 If all UK “set aside” land was used, as proposed by the British Association for biofuels and oils (BABFO) at the sugar beet yields assumed by BABFO for this land, namely 1,000 litres per acre, this would yield octane equivalent fuel per annum for a further 600,000 vehicles or 1.9% of the 2013 vehicle population, making 980,000 vehicles or 3.1% in all.
5.4 If the whole of the UK sugar beet acreage at present day yields (as in 5.2) and the whole of set-aside at the yields in 5.3 were employed, this would still only provide around 90% of the 2010 5% Renewables Transport Fuel Obligation.
It would also mean:
(1) importing all the 1.3 million tonnes of refined sugar presently used in the UK food production;
(2) converting all four of British Sugar’s factories to exclusively ethanol production and constructing another 15-20 similarly sized factories besides;
(3) constructing the road and rail links needed to bring sugar beet to the new factories from scattered areas of set-aside land.
5.5 If, as has been suggested by BABFO, 3 million tonnes of wheat exports were converted to biofuels, this would yield at most octane or diesel equivalent biofuel of 1 billion litres or enough for a further 600,000 vehicles, bringing the total of UK sugar production, UK wheat exports and UK set-aside used for fuel for around 1.6 million vehicles or 4% of the 2013 vehicle population.
It would also cost the balance of trade £500 Million in lost exports in addition to the cost of importing all our sugar (£300 Million).
5.6 If all current UK wheat production for our home market, 4.6 million tonnes per annum, were diverted to biofuels this would provide fuel for a further 920,000 vehicles approximately.
This would add a further £800 Million to our import bill at current world grain prices, that is additional to the £800 Million given in 5.5.
5.7 Viewed simply as alternative fuels, for every gigajoule (GJ) of energy released on combustion, octane (petrol) emits 70 kg of CO2 while bioethanol emits 71.4 kg.
5.8 The claim that biofuels are “carbon neutral” rests on the assumption that the process of growing their feedstocks on the land absorbs at as much CO2 as is emitted on combustion and in the manufacturing process. This claim ignores the fact that even land used as set-aside absorbs CO2 growing weeds at rates which may be comparable with those growing sugar beet – or trees for that matter.
5.9 For every tonne of hydrogen produced as a fuel by one of the proven steam reforming processes used around the world, at least 5.5-11 tonnes of CO2 are co-produced, depending on the hydrocarbons used.
Unless the hydrogen is produced by the unproven (on the industrial scale) electrolysis-of-water process, with the electricity required produced entirely by non-fossil fuels, hydrogen cannot therefore be counted as a “green” fuel.
5.10 In the short term from 2010 signing up to the Renewable Transport Fuel Obligation will cost the UK well over £1 Billion per annum in imported biofuels.
6 Processes involved in making Biofuels
These are best seen in flow diagrams:
(1) Sugar Beet to Bio Ethanol
(2) Fats To Biodiesel
There are a number of companies selling equipment to convert vegetable oils to diesel fuels which meet the octane rating required by the fuel standard BSEN14214.
(3) Hydrogen
Though not strictly a biofuel, hydrogen is often cited as a “green” or environmentally friendly fuel. It is also an essential component for any biofuel or indeed oil-based fuel requiring “sweetening” by increasing its hydrogen content and therefore its energy release per kg.
About 50% of hydrogen made is converted into ammonia and thence into nitrate fertilizer. Diversion of hydrogen for fuel uses would thus also have a major impact on agriculture for food.
Hydrogen is predominantly made by a “reforming” process using methane as feedstock, and where 5.5 tonnes of CO2 are produced for every tonne of hydrogen. If coal were used with steam as a feedstock (the original process) 11 tonnes of CO2 would be co-produced for every tonne of hydrogen.
Starting with methane (the commonest feedstock) we have in highly simplified form:
Thus the claims, by its proponents, that hydrogen is in some way a low or zero emission fuel are thoroughly misguided. It seems even more misguided to use hydrogen to run fuel cells in cars which have not only to carry about heavy cylinders of compressed hydrogen and oxygen, but also the fuel cell itself, and in its current form an electrical battery stack as well. Every fuel conversion process means energy loss. It would be much better to burn the gas or oil or coal directly as now in specifically designed boilers and engines.
In practice, this is a highly complex catalytic process which has been the subject of intensive optimisation over 8 decades.
References
[1] Professor Emeritus of Process Manufacture and of Polymer Engineering, University of Manchester
[2] EU directive 2003/30/EC
[3] Annual Abstract of Statistics table 15.5 increased by 2.9% to account for Northern Ireland
[4] This may be unduly pessimistic because of down-sizing, but car ownership may increase more than assumed in 4.3.
[5] British Sugar operate the only full-scale biofuels plant in the UK producing 70 million litres per annum (55,000 tonnes).
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