Ethanol and Methanol as Biofuels for Internal Combustion Engines in Motor Vehicles
Ethanol & Methanol can replace Petrol (Gasoline) with minor vehicle & fuel-storage modifications
By Gordon Shaw
|Ethanol (ethyl alcohol) and Methanol (methyl alcohol aka wood
alcohol) can be used to fuel internal combustion motor vehicles,
either as sole fuels or, more usually, when mixed with petrol (gasoline). As a
warning, in case you think these alcohols are a cheap way of fuelling
your cocktail cabinet, note that this ethanol is of a
dangerously high proof and contains additives which make it poisonous (it is referred to as denatured
alcohol). Methanol is well known to be a dangerous
poison in its own right.
There are two generic sources of biofuels (for both biodiesel and methanol) referred to as biomass feedstock . They are 'first generation' which comprise grain and other vegetable crops grown for their sugar, starch and oil content. Then there are the 'next generation' sources which comprise cellulose rich sources including wood, tall grasses, crop residues and municipal waste organics. The latter are dependent on developing technology to improve yields. Two technologies are favoured: gasification and hydrolysis using enzymes. These methods should enable next-generation to become competitively priced with first-generation sources but with the big advantages of offering the potential to dramatically increase the amounts of biofuels produced and with far less impact on the environment and ecology.
Most contemporary petrol cars will run on E10, a 10% mixture of ethanol to petrol, although warranties may state that a mix of 5% is the maximum allowed. Many major car manufacturers have developed cars which run on fuels containing higher proportions of alcohol, typically E85. Ethanol has some properties which are different from petrol; for example, in car engines, it has a higher octane rating, is more corrosive and abrasive, cleans the old deposits away (hence fuel filters, in converted vehicles, may need changing after a short time, initially), may create minor flow problems and can make starting more difficult. The national distribution network will also require modifications to some of its components, mainly because of the corrosive properties of alcohol and its ability to mix with water.
In the UK, in 2005, tax concessions for ethanol encouraged a minor shift and a 5% ethanol mixture entered the retail market. A firm called Greenenergy pioneered this and Tesco have been reported as the retailers (mainly in SE England), the ethanol source being Brazilian sugar cane. The real motivation may be cost (although the reduction in price to the UK customer is small) but even so that is no bad thing. In 2006 another supermarket, Morrisons, started selling E85 bio-ethanol in East Anglia. The 5% mix can be used in most petrol vehicles but the 85% mix is limited to a very small number of current vehicles. It is hoped that the trend continues with a significant expansion of the use of bio-ethanol in the UK, and other sources will be created, prodded by expected government policies. These are needed if vehicle manufacturers are to be tempted and oil companies are to be 'persuaded'. The way that the fuel distributors work means that they all need to cooperate for a substantial conversion to take place.
|The estimated energy densities* for ethanol and methanol.
When compared to diesel, the energy densities are about 56% and 46% respectively, when compared with petrol (gasoline) the ratios are about 64% and 53%.
The design and adjustment of a Flexible Fuel Vehicle (an FFV will run on petrol and ethanol) must take these differences into account although the basic technology is not necessarily more advanced. Of course, if you don't have an abundance of suitable filling stations around the country then you can't expect the car manufacturers to supply the cars. Brazil is a country which well known for using alcohol based fuels but there are others too. It appears that in the USA, farmers can brew their own licensed supplies.
How are they produced?
It is fairly common knowledge that the alcohols can be made from organic materials such as grains, fruit and wood. In practical and commercial terms the sources may be quite varied and sometimes surprising.
For example, waste from fields (used in food production) can be a useful source. The waste, traditionally, may have been burned but using the residue instead to create fuel gives a two-pronged environmental benefit. Firstly, the burning of the waste that would have fed dirt and toxic compounds into the atmosphere is obviated, and secondly, the use of the new byproduct as a renewable fuel means that less fossil fuel is consumed in vehicles.
There is also a potential for the extraction of alcohols from domestic rubbish or trash. We suspect that the yield might be small and wonder what emissions would be produced by whatever process is used. To some extent the advantages are as described above but additionally the amount of waste going in to landfill is reduced.
Sugar Cane is a good example of a raw material which can be cultivated for the purpose of producing alcohol and therefore is different in principle from using already existing material. Other food crops such as corn and potato can be used to produce alcohols but none seem to have the potential of sugar cane. Dr Andre Faaij at the Utrecht University describes it as a 'Wonder Crop' (Ref: 'Sugar Rush', Engineering and Technology, Feb. 2007). Sugar Cane has a very efficient cropping habit and the fibrous waste (bagasse) can be used to power the plant and evaporate the cane juice. This is a prime instance of industrial cogeneration or CHP. Where the cogeneration is efficient it is even possible to sell excess electricity to the the grid. The world's largest producer of ethanol from sugar cane is Brazil but other countries include India and Mauritius and there are more with considerable potential.
The main argument in favour of the process is that the growing of the crops absorbs carbon and so compensates for the eventual emissions. That argument has its doubters but certainly there can be little doubt that this is far preferable to the use of fossil materials. The same reasoning can be applied to all similar processes where the fuel is sourced by live cultivation, even though it may be used in an entirely different way, such as, for example, coppicing.
Other raw materials which are commercially viable are fossil fuels such as coal and (especially) natural gas. However, since the extraction process involves freeing sequestered carbon-rich compounds it is difficult to expect any benefit in the reduction of the greenhouse gases by using alcohols derived this way.
The processes by which alcohols are produced are environmentally relevant. For example in the US, corn mash may be fermented to produce alcohol and the dried residue used for animal feed. In the States, the Environmental Protection Agency (EPA) argues that some of these production plants are releasing carbon monoxide, methanol and some carcinogens at unacceptable levels. Methanol is classified as a hazardous pollutant if it is allowed to contaminate the environment, and the emitted carcinogens include formaldehyde and acetic acid, released as volatile organic compounds (VOCs). It would appear that processes that are not properly controlled could create serious pollutions; so we conclude that control is important.
There are clearly pros and cons in greenness when sourcing and producing alcohols. What we deduce is that if the sources are materials which are being cultivated or would normally be created anyway (eg waste from food production) there are substantial benefits to be gained. On the other hand if the raw materials are fossil extractions they will release sequestered carbon and that is as bad as it gets. Also we note there is a need for scientific monitoring and control of the production processes.
If alcohols are used instead of petrol is there less tail-pipe pollution?
Here again we don't find an easy answer. Although cars can run on pure alcohol, road vehicles normally use a mixture of petrol and alcohol. The ratio of the mixture makes a difference to the pollution potential. In general when alcohol is added there appear to be less carbon monoxide and other toxins but there are greater emission of VOCs (see above): localised pollution is not only about carbon emissions.
On balance we do believe that the optimum mixture will be slightly greener at the point of exhaust.
Economic and political arguments in favour of ethanol and methanol?
Economic advantages are perhaps most evident to the producers of the raw materials, but the populace in general can benefit too.
Where the basic material would normally go to waste, such as residues from harvesting then there is a clear option for the producers to turn an expense into a profit. Additionally the whole community may benefit if there are less toxic and anti-social emissions, such as those produced by burning field waste. In the case of urban waste conversion, everyone can benefit because of the potential reduction in landfill investment or the cost and unpleasantness of dedicated waste incinerators, even though the conversion costs in isolation might not appear to be economical.
Farmers might find it profitable to grow crops which are designed to produce alcohol as their prime objective. A notable example is in Brazil where the crops of sugar cane could be used either for sugar or alcohol production; the country is exceptional in its ability to produce large quantities of either. The decision of which end product to aim for may rest with individuals and any aggregate trend could lead to volatility in supply and prices. This suggests a national strategy and good leadership are vital and that thought conveniently links us to the next paragraph.
Politics, indeed, are intimately entwined with economics because politicians want to be elected or re-elected and that often depends on their control of the prosperity of their constituents. This is true for both local and national politicians. For example a law allowing the production of alcohol from field waste might be a good move for a local politician in a farming community.
On a national basis, politicians might worry about the volatility of oil prices and thus there would be a pressure to look for home produced fuels but as the example of Brazil shows this line of action can create its own volatility.
There are international political pressures of other kinds too. Nations have reacted differently to the principles enshrined in the Kyoto Protocol. Where a populace is dedicated to its habits of car worship then it is likely to be in the forefront with its carbon emissions and that is counter to Kyoto. A leader of such a community who took global warming seriously (and, for example, tried to limit the consumption of oil) would not increase his or her popularity. On the other hand this could contribute to the reduction of dependence on a foreign nation and possible international strife.It is worth noting that we have seen some evidence of national support for the production of alcohols from biomass in the US and the UK.
However, in the UK the advancement of ethanol as a motor vehicle fuel has so far been pathetic. In Q1 of 2006 we were looking forward to having tens of flex-fuel cars on our roads, unlike in Sweden, for example, where numbers are measured in thousands. The Swedish tax concessions and other perks have been a significant driving force and indeed their motor industry (eg Saab and Volvo) has embraced the relevant, if not advanced, technology. In Europe, he Ford motor company has a welcome production vehicle with its Flex-Fuel Vehicle (FFV), in its Focus range which is specified to run on any combination of alcohol and petrol. To be generous to the UK, there are slight movements in the right direction but much more needs to be done by a government which had a mandate to tackle climate change and it would not do badly to emulate Sweden as an exemplar with its' energy policies.
If ethanol-from-crops was adopted as a motor fuel on a vast commercial scale then there would be serious problems caused by reduced biodiversity, deforestation and the disrupted supply of other vital agricultural products. It would be completely impractical to assume that petrol (gasoline) could be completely replaced by bio-derived ethanol or methanol.
Summary: we believe that there are significant green benefits in the use of alcohols to replace, or complement, the consumption of petrol, however, these benefits depend on not using fossil fuels as the raw materials and they also depend on adequate process control and a strategy of efficiency.
On economic grounds there can be considerable benefits especially, but not only, for select groups of the community such as specialist farmers; that is particularly true in the Americas.
Politically there is a potential benefit where countries might achieve some independence from the main oil producing nations. In Q1 2006, after a year when the volatility of prices and national threats have emerged from oil- and gas-producing countries, western leaders seem to have realised at last that there is more to renewable energies than environmental factors. Needless to say, the conversion from petroleum- to bio-based products could contribute to the achievement of Kyoto targets.
Set against this there is a danger, to the environment, of excessive expansion of fuel crops and there should be international monitoring and control, both in the growing and manufacturing stages. Nevertheless if ethanol and methanol could replace a proportion of petrol as a vehicle fuel then that could be good for our environment.
As a final note we should add that in concentrating on fuels we should not forget that there is a need for consumers world-wide to move towards more efficient vehicles and more efficient use of these vehicles.
our estimates of energy densities are derived from a pdf article: "Fuels of the Future for Cars and Trucks", Dr. James J. Eberhardt, Energy Efficiency and Renewable Energy, U.S. Department of Energy, 2002 Diesel Engine Emissions, Reduction (DEER) Workshop, San Diego, California, August 25 - 29, 2002. That pdf link no longer works but some comparable material may be found here on Energy Density: Wikipedia.
: "Fuelling the Dilemma", Mark Venables, Engineering & Technology, 10-23 May 2008.
Footnote: in a very different technology, alcohol may be used as a source in fuel cells; this option is not discussed here. You can access our summary of Fuel Cells from the Renewable Energy Menu above