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.
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
| Cetane number
| Octane number
| Auto-ignitation temperature (K)
| Latent heat of vaporization (MJ/Kg)
| Lower heating value (MJ/Kg)
Table 1: Properties of ethanol, compared to other alcohol fuels (source: Balat, 2007)
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
Feedstocks for biofuel production are e.g.
- plant oils
- sugar beets
- 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.
|| Bioethanol production potential (L/ton)
| Sugar cane
| Sugar beet
| Sweet potato
| Sweet sorghum
| Bagasse and other cellulose biomass
Table 2: Different feedstocks for bioethanol production and their comparative production potential (source: Linoj Kumar et al. 2006)