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As the use and combustion of fossil fuels is responsible for 73 % of the CO2 production in the atmosphere and therefore extremely contributes to global warming, the interest in the development of methods, reducing green house gases, has been increased enormously.

In order to control such emissions, many advancing technologies have been developed, which help in

  • reducing energy consumption
  • increasing the efficiency of energy conversion or utilization
  • switching to lower carbon content fuels
  • enhancing natural sinks for CO2
  • capture and storage of CO2
  • reducing the use of fossil fuels, in order to decrease the amount of CO2
  • minimizing the levels of pollutants.

In the last few years, the research for renewable energy sources, that reduce CO2-emissions, has become very important. Since the 1980s, bioethanol has been recognized as a potential alternative to petroleum-derived transportation fuels in many countries.

Bioethanol (ethyl alcohol, grain alcohol, CH3-CH2-OH or EtOH) is a liquid biofuel, produced from several biomass feedstocks and different technologies.
Bioethanol is a renewable bio-based resource. Additionally, it is oxygenated (35 % oxygen), providing the potential to reduce particulate emissions in compression-ignition engines.

Advantages of bioethanol

Bioethanol as alternative fuel has, compared to gasoline,

  • a higher octane number
  • broader flammability limits
  • higher flame speeds
  • higher heats of vaporization
  • a higher compression ratio
  • a shorter burn time

Some properties of ethanol, compared to other alcohol fuels are shown in Table 1.

Fuel property
Isoctane
Methanol
Ethanol
Cetane number
-
5
8
Octane number
100
112
107
Auto-ignitation temperature (K)
530
737
606
Latent heat of vaporization (MJ/Kg)
0.26
1.18
0.91
Lower heating value (MJ/Kg)
44.4
19.9
26.7

Table 1: Properties of ethanol, compared to other alcohol fuels (source: Balat, 2007)

Disadvantages of bioethanol

compared to gasoline, bioethanol has

  •  lower energy density
  •  its corrosiveness
  •  low flame luminosity
  •  lower vapor pressure (difficult for cold starts)
  •  miscibility with water
  •  toxicity to ecosystems

Bioethanol feedstocks

Feedstocks for biofuel production are e.g.

  • plant oils
  • sugar beets
  • cereals
  • organic waste
  • processed biomass

All feedstocks, which contain amounts of sugar, as well as materials, that can be converted to sugar (e.g. starch or cellulose) can be used in a fermentation process to produce bioethanol.

In Table 2, numerous feedstocks, which can be utilized for bioethanol production as well as their comparative production potential are shown.

Feedstock
Bioethanol production potential (L/ton)
Sugar cane
70
Sugar beet
110
Sweet potato
125
Potato
110
Cassava
180
Maize
360
Rice
430
Barley
250
Wheat
340
Sweet sorghum
60
Bagasse and other cellulose biomass
280

Table 2: Different feedstocks for bioethanol production and their comparative production potential (source: Linoj Kumar et al. 2006)

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