5900251

Biotechnology (Enterprise)

Dr Geoff Robson

Word count: 2616

The History and Development of Bioethanol as an

Alternative Fuel

Introduction

Bioethanol is ethanol that has been produced from or by a biological

source. The clearest way of demonstrating this production is in

fermentation of sugars in the brewing industry. In this process glucose,

along with water, is converted into ethanol, carbon dioxide and water.

It’s use as a fuel is realised by the exothermic reaction when burnt,

producing CO2 and water.

Bioethanol is used as a fuel because it is non-petroleum based, thereby

reducing our dependence on crude oil resources, and is thought to be

carbon neutral[1], thus reducing net carbon emissions that are thought to

contribute to climate change. The basis for the thought of a reduced

carbon footprint by using bioethanol as a fuel is that the biomass –

typically sugarcane or corn – used for conversion into ethanol has already

absorbed more CO2 whilst growing than is released from the production

and burning of ethanol [2]. The chemical reactions of sugar into ethanol

and burning of ethanol, respectively, are described below:

C6H12O6 + H2O 2C2H5OH + 2CO2 +H2O

C2H5OH + 3O2 2CO2 +3H2O

This usage and production of CO2 has been argued to be more beneficial

in prevention of climate change than regular petroleum fuels as the

carbon utilised and produced is part of the ‘free carbon cycle’ whereas

petroleum from crude oil is released from a ‘locked carbon cycle’ into the

free carbon cycle. The free carbon cycle involves conversion of carbon

into living organic matter by plants and animals, and it’s release back into

the atmosphere. The extra carbon released by burning fossil fuels that

have been ‘trapped’ for so long upsets this cycle. Developing fuels that

reduce the need for petroleum substances or burn with less CO2

production is seen as a major step in battling ongoing climate change.

The EU recently passed a bill whereby car manufacturers will have to

reduce the carbon emissions of their cars to 120g/km by 2012[3]. With

policy increasingly considering the effects that climate change may have,

alternative fuels are set to grow in importance and use, with more

research into increasing efficiency of production and running of these

fuels.

As well as bioethanol, industry is researching into other alternative fuels

such as biodiesel, hydrogen power, electricity, natural gas, propane,

methanol and p-series fuels[4]. These fuels all have potential as an

alternative fuel, with biodiesel and natural gas currently being used the

most, along with bioethanol. Hydrogen looks to be the fuel of the future,

eventually replacing biofuels as the main consumer fuel, but depends on

overcoming some serious technological limitations.

Current Use of Bioethanol

When examining the current use of biofuels, the obvious starting point is

to look at Brazil. Brazil has successfully been industrially producing

bioethanol since the 1970’s, when it heavily relied on foreign oil. The

Middle Eastern Oil Embargo forced Brazil to look at more sustainable

means of fuelling the nation[5]. Although it has not always been

problem-free, the Brazilian program is seen as a model success story for

sustainable development. Today all cars in Brazil run on at least 25%

ethanol mixed with petrol, with 60% of all automobiles being ‘fuel-

flexible’ (able to run on up to 100% ethanol).

Brazil produces its bioethanol almost exclusively from sugarcane. In this

model, 1 ton of sugarcane harvest yields only 72 litres of ethanol. This

ethanol may have to be refined further for blended use, or can be used as

is in a pure ethanol fuel. It is obvious from these figures that there is a lot

of waste in the conversion of biomass into ethanol. Most of this waste is

from lignin and cellulose – cellulose is the most abundant biological

compound on the planet – which are not easily converted into sugars and

then fermented.

The USA is following

the lead set by Brazil,

investing heavily in its

own biofuel

production. The USA

currently serves all

petrol as a blend with

10% ethanol, with

moves to increase this proportion. Also all new vehicles sold in the USA

must have the flexible fuel engine type. The EU has also moved to

support renewable fuels for the future by legislation stating minimum

usage for member states.

As figure 1 shows, the global use of biomass for fuel is about 10%, with a

global bioethanol production of 36.5billion litres per year[6]. Due to the

high production costs of ‘modern biomass’ it is not as widely used as

‘traditional biomass’. If the traditional biomass is replaced with modern

biomass then bioethanol as a fuel will be in good stead to take off as a

Figure 1: Current global fuel usage. New renewables refers to sustainable production, whereas tradtitional biomass refers to labour and cost intesive commercial production. Picture from: Ethanol For A

Sustainable Energy Future, Goldemburg et al.

genuine consumer fuel. This is already seen in Sweden, where Ford

produces a flex-fuel model that outsells its petrol and diesel

equivalents[7].

Advantages of Bioethanol

As an alternative fuel, bioethanol is very attractive. The need for

alternative fuels comes from the depletion of easy to access reserves of

coal, gas and crude oil within the next 150 years, with our oil reserves

being depleted before the end of the century[8]. Because of this,

industrialised nation’s governments are offering tax incentives and grants

in the commercial development and application of renewable energy in

the form of biomass. In Brazil, the government subsidises ethanol

production in order to keep the cost per gallon in line with currently

cheap petroleum. The USA is heavily funding ethanol production as a

means to reduce its future reliance on Middle Eastern oil[9].

As a fuel for automobile use, bioethanol was historically the fuel of

choice, with the first internal combustion engine designed to run on

ethanol. Ethanol has been touted as an extremely beneficial fuel due to

its higher octane rating of 113 to that of petrol’s of between 83 and 95.

The higher the octane rating, the less likely it is that ‘knocking’ will occur

– pre-ignition of the fuel – which damages engines [10].

The main advantage of bioethanol over petroleum based fuels however,

are its renewability and its supposed carbon neutrality. As will be

discussed later, there is debate over whether bioethanol is currently

carbon neutral and how it might become so. From the renewable

perspective, it is hard not to agree. Bioethanol is produced from crops,

grown and harvested every year, using the sun’s energy as the major

source of energy. The argument for it’s carbon neutrality stems from,

during photosynthesis plants absorb CO2, and the supposed amount of

CO2 produced from burning the ethanol is less than that absorbed during

growth [11]. The counter-argument states that more energy and fuel is

Figure 2: The net energy balance (NEB) of biofuels, showing a higher output than input. Source: Environmental, economic, and energetic costs and benefits of

biodiesel and ethanol biofuels,Hill et al.

used in production than is produced [12]. Hill et al find that bioethanol

has a net energy balance of 1.25 (25% higher output than input), whilst

biodiesel has an energy balance of 1.93 – see figure 2. However, they

also note that phosphorous and nitrogen used in production have negative

environmental impacts. To improve the overall benefits of they suggest

low inputs of agricultural energy, fertiliser and pesticides. These studies

focus only on corn grain and soybean however. Over a 10 year period

Hill et al [13] discovered that low-input grass (in the form of agricultural

techniques such as fertilising) can potentially reduce by 15% the global

carbon emissions if utilised as the main biofuel crop, whilst not

competing for land used for food crops.

Another advantage of bioethanol is the independence that it offers

nations. Nations that do not have access to crude oil reserves are entirely

dependent on importing their oil. If these same nations can produce crops

for energy uses then they will gain some economic independence. As

mentioned earlier, the USA is already investing in its own biofuel

programs as a means to reduce any future dependence on foreign oil.

There is an argument against the use of crops for fuel as their farming

will displace the land used for food farming[14], however many areas

currently unused for farming – either through infertility or geographically

unutilised for food farming – could be used for the production of

dedicated fuel crops. It may seem count-intuitive that infertile ground

could be used for harvesting, however switchgrass is a very robust crop

that can grow in unfertilised ground[13] and would not require intensive

farming techniques yet still producing high bioethanol yields.

Disadvantages of Bioethanol

As alluded to earlier, there is still a debate raging as to the extent of the

carbon footprint of bioethanol[12, 13]. Much of this is down to the extent

to which researchers account for labour, but also due to which source of

sugar the researchers are using. On studies focused on the USA, corn is

the major source or sugars, whereas in Brazil sugarcane is the major

source. Sugarcane has a higher energy ratio than corn. As such there is

an obvious need for further funding to both study the net energy balances

and also work towards more efficient conversion techniques. Along with

different crops having differing energy contents, not all crops can be

grown in all regions. The local geography and climate will dictate which

crops can be grown and so production may well rely on importing crops

or sugar.

As well as geography determining which crops could be grown and

harvested for fuel use, so too the land use for dedicated fuel farming. A

5% displacement of petrol with bioethanol would require a 5%

displacement of food crops in the EU[15]. In many developed nations

this does not amount to a crisis, as they are net food exporters in certain

products. However, the techniques could not then be transferred to

developing nations with large numbers of people living below the poverty

line. There is a large argument against the use of biofuels in China,

where irrigation of fields is paramount, because of this argument[14].

Bioethanol is a less efficient fuel than petroleum, having an energy

content of about 70% of that of petrol [16]. As such, when used as a fuel,

more is needed to achieve the same results as petrol. This is a problem

that cannot be changed. As consumers, the debate will be whether it is

worth switching to less efficient fuels, meaning that more fuel and

ultimately more money will be required to be spent on fuel. For public

forms of transport this might mean higher costs of travel, lowering

support for alternative fuel initiatives. Currently all new cars sold in the

USA are flexible fuel vehicles, meaning that they can run on an ethanol-

petrol blend of up to 85% ethanol. However, many older cars are not able

to run on high concentrations of ethanol and so a phasing in of ethanol

blends would be required and many classic cars would require

conversions. This would incur large costs in advertising the change of

petrol blend to ensure that everybody had sufficient time to change, with

no doubt many protesters.

These increased running costs are also seen in increased production costs

to those of petrol. This is seen in the labour-intensiveness of producing

bioethanol[8]. Again this is a factor that would increase the price of

ethanol fuel. Currently it is economically viable to produce bioethanol

due to tax breaks and government grants. However, this cannot continue

forever and will likely sway the other way with higher taxation once

bioethanol is used widely as a fuel. The most effective ways in reducing

this cost would be to utilise economies of scale, coupled with

technological innovation.

Future Developments

Bioethanol needs to become more efficient at converting biomass to fuel

if it is to become sustainable to replace petrol with. This will involve

reducing costs of conversion, increasing yields and potentially increasing

the diversity of crops used. The way in which research is currently going

for the improvements of bioethanol is by looking at ways to convert

cellulose and lignin to sugars for fermentation. An exciting prospect is

simultaneous saccharification and fermentation (SSF) as described by

Takagi et el. [17]. However this has some problems, notably with the

different optimum temperatures of saccharification and fermentation[18].

Current methods can obtain conversion of between 50 and 72% ethanol

per gram of glucose, limited by the tolerance of the yeast to the

ethanol[19]. This suggests that with engineering of yeast strains for high

tolerance even more efficiency can be achieved. In this respect

biotechnology and microbiology will be extremely useful in the genetic

engineering, not just of yeasts, but of other microbes that can hopefully

one day convert cellulose and lignin into sugars and then ferment them

into ethanol.

Increasing the efficiency will no doubt create a more sustainable fuel

technology. However, to replace petrol as a fuel major tracts of land

must be used solely for the purpose of fuel crops. As discussed earlier

this has lead to opposition of the technology in many countries. Another

possibility would be for the consumers to take control of their own fuel

supply. This would involve commercial production of small-scale

fermenters and distillers for home use. By recycling all of their

household waste and converting much of it to biofuels, the energy

demand would greatly diminish.

As our technology grows, so other alternative fuels will come to the fore.

There is a lot of research into photovoltaic (PV) energy and also

hydrogen energy is seen as a fuel for the long-term future. Figure 3

shows the predicted increase in the importance and use of hydrogen as the

prime alternative fuel. Although there is currently not a cheap way of

producing hydrogen, there is a lot of research being done in the area[20].

Of course there are many

other alternative energy

sources, such as nuclear, wind

and geothermal. It would

seem like an obvious move

for a nations geography to

play a large factor in which

alternative fuels they utilise[21]. For example Australia would be able to

take advantage of PVs more than the UK. Greenland and Iceland could

use geothermal power as an alternative source of energy. As a

replacement for petrol rather than a displacement of reliance on petrol, we

cannot rely on just one energy source for the near future.

Figure 3: Predicted use of alternative fuels until 2050. Percent of alternative fuel consumption on the ordinate axis against years. Source: Glycerol delignification of poplar wood chips in aqueous medium, Adeeb 2004 [24]

Conclusion

Bioethanol is very much a fuel of the future. It currently stands as the

leader of the pack in alternative fuels alongside bio-diesel. As a

substitute for petrol it is the obvious choice in it’s blending ability with

petrol, from which it can easily become the fuel of choice. There is a

largely positive public opinion about bioethanol[22], with California,

USA leading the way in adoption of it as an alternative fuel[23]. With

such public and government opinion, in the foreseeable future bioethanol

will be a globally used fuel with a wide user base.

There is much research ongoing into bioethanol, improving our

technology and understanding year on year. This can only enhance the

standing of bioethanol as a viable and cheap alternative fuel. With the

development now of lignocellulosic bioethanol, the efficiency of this fuel

looks set to continue to improve. Environmentally, regardless of the

current state of opinion, the carbon footprint of bioethanol will

undoubtedly decrease, helping reduce global carbon emissions. It would

not take too much to persuade the public to domesticate their own

bioethanol production, if such a project was economically and technically

feasible.

As figure 3 shows, it is projected that hydrogen will be the fuel of choice

for our long-term future. This gives bioethanol a short-term life as a

major fuel. However, it will be many years before hydrogen fuel is safe

and economic enough for its mass use. Until that time there will be a

high demand for bioethanol as an alternative fuel. Even then, hydrogen

may not be the fuel of choice for all applications, with bioethanol still

taking a role in powering our society.

References