Bioethanol: Production, Advantages, Disadvantages And Environmental Impacts
Author: Cornelius Onye Nichodemus
As biotechnology continues its pursuit to make the environment friendly for man, the need for renewable resources to be used towards achieving this goal is necessary. This resources can be agricultural wastes, industrial wastes, domestic wastes, municipal wastes etc which are processed through fermentation into bioethanol (biofuel). Biofuels are liquid or gaseous fuels that are produced from biodegradable fractions of products, remains from agricultural production and forestry, as well as biodegradable fractions of industrial and municipal wastes. Bioethanol fuel is mainly produced by the sugar fermentation process derived from crops such as sorghum, maize, sugarcane, wheat etc although bioethanol can be manufactured by the chemical process of reacting ethylene and steam. It is the principle fuel used as a petrol substitute for road transport vehicles. The primary sources of sugar required for ethanol production come from fuel or energy crops.
Bioethanol is entirely comprised of biological products and hence the combustion of bioethanol results in cleaner emissions (carbon dioxide, steam and heat). The carbon dioxide is absorbed by plants and processed via photosynthesis to help the plant grow. This cycle of energy creation and energy combustion shows that bioethanol could potentially be a carbon neutral fuel source.
Chemically, ethanol or ethyl alcohol (C2H5OH) is a clear colour liquid, it is biodegradable, low in toxicity and causes little environmental pollution. Ethanol burns to produce carbon dioxide and water.
Ethanol can be produced from biomass by the hydrolysis and sugar fermentation processes. Biomass wastes contain a complex mixture of carbohydrate polymers from the plants cell walls known as cellulose, hemi cellulose and lignin. In order to produce sugars from biomass, the biomass is pre-treated with acids or enzymes in order to reduce the size of the feedstock and to open up the plant structure. The cellulose and hemi cellulose portions are broken down (hydrolysed) by enzymes or dilute acids into sucrose which is then fermented into ethanol. Basically, there are three principle methods of extracting sugars from biomass. They are;
1. Concentrated acid hydrolysis
2. Dilute acid hydrolysis
3. Enzymatic hydrolysis.
SUGAR FERMENTATION PROCESS
The hydrolysis process breaks down the cellulostic part of the biomass or corn into sugar solutions that can then be fermented into ethanol. Yeast which contains invertase is added to the solution and then heated. The yeast acts as a catalyst and helps to convert the sucrose sugars into glucose and fructose (both C6H12O6).
The chemical reaction is shown below;
C12H22O11 + H2O ------> C6H12O6 + C6H12O6
The fructose and glucose sugars then react with another enzyme called zymase which is also contained in the yeast to produce ethanol and carbon dioxide.
The reaction is shown below;
C6H12O6 ------> 2C2H5OH + 2CO2
ADVANTAGES OF BIOETHANOL
1. Any plant can be used for the production of bioethanol provided it contains sugar and starch. And the best choice are sugarcane, maize, wheat, sorghum etc
2. It neutralizes the carbon availability in the atmosphere that is carbon dioxide released in the bioethanol production process is the same amount as the one the plants absorbed previously during photosynthesis.
3. The net effect of ethanol use results in an overall decrease in the depletion of ozone layer in the atmosphere which is of important environmental concerns. The emissions produced by ethanol combustion are less reactive with sunlight than those produced by burning gasoline has a low possibility of damaging the ozone.
4. It reduces greenhouse gases through the use of bioethanol-blended fuel.
5. The fuel spills are more biodegradable or diluted to non toxic concentrations.
6. The exhaust gases of ethanol are much more cleaner. It undergoes complete combustion
7. It comes from renewable sources that is crops and not from finite resources
8. Blending ethanol with petrol will help extend the life span of diminishing oil supplies and ensure greater fuel security around the world
9. Bioethanol is also biodegradable and less toxic than fossils fuels.
DISADVANTAGES OF BIOETHANOL
1. It leads to biodiversity do to the fact that a large amount of arable land is required to grow these crops and could see some natural habitats destroyed including rainforests
2. It may cause food scarcity because of the lucrative prices of bioethanol some farmers may sacrifice food crops for Biofuel production
3. It is quiet expensive to set-up a Biofuel laboratory
4. Bioethanol production demands strong technical knowledge for effective production and also to avoid excess emissions.
Improving the quality of air is one important function of ethanol when added to fuel. Bioethanol reduces he use of cancer-causing gasoline compounds (ethylbenzene, xylene, toluene and benzene). It also reduces the emissions of small particulates and spots from motor fuels and greenhouse gas emissions.
Water-saving ethanol plant designs. In addition, the water discharged from these plants is regulated I'm such a way that the water is environmentally neutral when it leaves the plant.
Certain plants manage and reuse the waste water generated during the ethanol process. This shows that ethanol has a positive effect on ecology, minimizes gas emissions and improves energy safety and operation of transport facilities.
About Author / Additional Info:
I am a First Class graduate of Plant Science and Biotechnology from University of port Harcourt.