Among the primary needs of man on earth is energy, especially the renewable and sustainable source of energy. Humans have succeeded in the field of energy generation but have also succeeded in creating a serious problem for the existence of living organisms including humans.
[credit: Creative-commons. CC BY-SA 3.0 license. Author: Nick Youngson]
For example, nuclear source of energy possess the following threats to humans and other living things
- Cosmic rays causes skin cancer when exposed to such rays.
- Exposure to radioactive emission can also cause cell damage, leading to cancer of such cell.
- It causes weakness of the immune cells and mental retardation.
The fossil as a source of energy:
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Fossil fuels are type of fuels obtained beneath the earth crust. They are obtained as a deposit of crude oil. Crude oil is formed as a result of decomposition of decaying organic matter that died many years ago.
Fossil means the remains. The decomposition is due to high pressure and temperature, accompanied by some microbial actions.
The crude oil is useless in its state but are still called the liquid black gold, this is because it contains some valuable fractions called petroleum. Refining the crude oil through fractional distillation gives many valuable products.
Disadvantages of using fossil fuels
Fossil fuels are majorly carbon which emits a lot of CO2. It is well established that carbon (IV) oxide is a major global warming aggressor (greenhouse gas emission). Aside causing global warming, fossil fuels are non-renewable source of energy because of the period required for the formation of the fuel.
There are lots of discredits to the above mentioned sources of energy and so the need for a cleaner source of energy.
Biological source of energy seems to be more promising in terms of clean technology. Bioenergy is a type of energy sourced from biological sources such as plants and animals. Bioenergy generation is a branch of biotechnology that uses microorganisms to degrade carbon polymers, a process known as fermentation.
[A triacylglyceride compound. Credit: Wikimedia. A creative commons license. Author: Wolfgang Schaefer]
The polymers used are naturally occurring polymers such as carbohydrate polymers which may either be cellulose or starch and lipids (Triacyl glycerol). What makes it a bioenergy is that they are sourced from a biological or organic materials (biomass) and are processed using living organisms. The beauty of bioenergy is that it is the waste materials such as lignocellulosic or oil effluent biomasses that are used in the production of the energy. Bioenergy is also called biofuels and includes Biogas, biodiesel, bioethanol etc. Biofuels are classified based on their generations in the advancement of technology.
First Generation biofuels
The biomass used in this generation is mainly food crops which are grown in an arable land and specifically for the energy generation. For example, the starch foods such as cassava and sugars are harvested and fermented by yeast to yield bioethanol. Also, vegetables or palm oil generated from a farmland is converted to biodiesel by transesterification reaction using lipase or esterase as catalysts.
This generation exposes humans and other animals to food insecurity as the food meant for animals are now used in the generation of energy. Food insecurity (food scarcity) in turns results to malnourishment which will finally lead to depopulation of humans as result of death or loss of life.
Second generation biofuels
This type of bioenergy is sourced from different varieties of biomass. Biomass is a natural sources of carbon for energy production. Biomass can be sourced from plants and animal materials. Second generation of bioenergy can be sourced from lignocellulosic biomass or woody crops, agro wastes and or under-utilized starchy crops.
The major carrier of carbon here is the lignin. The lignin contains some heterogeneous poly aromatic compound, cellulose and hemicellulose. The lignin offers protection and structural integrity to the plant. It also houses the phloem and xylem which are transport vascular bundles of plants.
[Monolignol biosynthesis model for land plants showing three most common lignin monomers shown in green. Credit: Wikimedia. Creative Commons Attribution-Share Alike 4.0 International license. Author: Bjschul7]
To use the lignin as a carbon source or biomass for energy generation, it is first treated to crack the hard part or weaken the tough bonds holding the molecules together for the release of the major biomass, the polymers that contain the carbons needed for conversion to biofuels. The treatment could be chemical, physical or biological.
In chemical pretreatment, the lignin or wood is treated with an alkali (NaOH or KOH) or an acid (HCl or H2S04) to crack or break open the lignin which releases the cellulose or hemicellulose for microbial breakdown.
In physical pretreatment, heat is used to crack the lignin or wood. After the treatment with heat, the bonds of the lignin is weakened, for subsequent release of the polymers.
Chemical and physical treatment have some disadvantages in the sense that for chemical, there is a generation of some unwanted products (bye-products) which maybe poisonous to humans and the environment in general. While the heat treatment may increase the rate of global warming which we know the detrimental effects of global warming on our environment.
Biological method is the use of organic catalysts to break down or crackdown the lignin. This method involves the use lignin hydrolyzing enzymes such as lignin peroxidases, manganese peroxidases and laccases. Theses enzymes hydrolyse the bonds holding the lignin monomers leading to the release of of celluloses and hemicelluloses. These polymers are further hydrolysed to glucose and pentoses by the enzyme cellulases. When glucose is obtained from the polymers, the normal fermentation processes will then take place, and this is how the lignins or woods are converted to bioenergy.
[First and Second Generation Bioethanol Production by Alcoholic Fermentation. Credit: Wikimedia. Creative Commons Attribution-Share Alike 3.0 Unported license. Author: Ian Zammit]
Biological method of pretreatment is better than the other two in the sense that enzymes act in mild conditions and degradable and also specific in their reaction. The benchmark is that biological method of lignin degradation will not yield any unwanted products, hence will not pollute the environment. This is because of the specificity nature of the enzymes used in this process.
Enzymes are biodegradable, hence will not constitute nuisance to the environment. Enzymes act even at the room temperature, making it an ideal candidate in the control of global warming. Though second generation of bioenergy or biofuel uses other feedstock or biomass different from source of food for humans which makes them none candidate food insecurity, its production takes longer time as most woods don’t grow faster. Also, this generation of biofuel production may result to deforestation which will in turn result to increase in carbon (IV) oxide accumulation to the atmosphere, making the process unhealthy to humans and entirely the environment.
Third generation biofuels
This is majorly biodiesels. It is sourced from an aquatic algae such as chlamydomonas, spirogyra and so on. The algae is regarded as oil-rich algae. The algae is grown on algae ponds at wastewater treatment plants. The algae is processed and the oil extracted and transformed into biodiesel while the remainder which contains sugars are then dried and treated further for conversion to bioethanol.
[Carbon Intensity of different Biofuels (including biodiesels). Credit: Wikimedia. A creative commons license. Author: Mike Young.]
The first and second generation biofuels are produced from an arable land but the beauty of the third generation is that it doesn’t occupy a large portion of land. This generation is easy to handle and faster due to the fact that the biomass can easily be cultured in a plant cell culture and be induced to grow faster.
This type of biofuels has no effect on the atmosphere, hence cannot lead to global warming. Third generation doesn’t result to food insecurity because algae is not edible. Among all generations of biofuels, third generation has a lot of advantages over the first and second generation.
What future does the use of biofuels hold?
Scientific experts have predicted that in years to come, fossil fuels will be out of resources due to high usage of and dependency on the fuel. The high greenhouse gas emitting density of fossil fuels which predisposes us to many diseases and environmental challenges such as drastic climate change. Even nuclear energy won’t be the right option for energy for energy generation.
The biggest challenging question is, do biofuels hold any hope in energy generation?
It is true that biofuels have good qualities because they are regarded as clean energy and this is because they don’t emit greenhouse gases. Also second and third generations of biofuels have shown the capacity in waste management that is, converting waste to wealth. Other good qualities of biofuels have been highlighted but for the meantime, its prospect on replacing fossil fuels is rooted on a shaky foundation.
[Fossil fuel has constituted the major energy source in the world. Credit: Wikimedia. Creative Commons CC0 1.0 Universal Public Domain Dedication license. Author: Lery007]
Its possibility of production in large scale is a big problem in the scientific world. Production of biofuels costs a lot of capital due to the resources needed for the production. These resources may include an arable land that will be mapped out for the purpose of the biomass production.
I have discussed the threats of the first generation biofuels in terms of food security. From the ongoing, it is true that we need a cleaner source of energy but biofuels have a limited ability to replace fossil fuels and should not be regarded as a golden composite to combat greenhouse emission. However, availability of the biofuels will augment the fossil fuel because it will provide an alternative to fossil fuels.
Also, the biofuels can be used as an additive to fossil fuel because they have very high octane rating and this means that the fuels will undergo a complete combustion in the presence of atmospheric oxygen. When biofuels become an alternative, it means that the high price tag on the fossil fuels will be reduced.
Summary
The energy sources discussed herein have their merits and demerits but apart from the scale of production of biofuels, the fuels are very clean and should be given much attention for its sustainability and improvement in the production.
In the next article, we will look at the use of biofuels in fuel cells………..catch you then!
REFERENCES
- Fossil fuel -wikipedia
- Energy’s greatest health risk comes from fossil fuels -thinkprogress
- First generation biofuels -biofuel
- Second generation biofuels -wikipedia
- third generation biofuels -biofuel
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