FUELS AND ENERGY

FUELS

GENERAL USES OF FUELS

• Wood, coal and charcoal are used domestically as heat sources for cooking, boiling and Ironing.
• Petrol, diesel and LPG are used for running industrial plants and means of transport such as buses cars and planes
• Kerosene is used in kerosene stove for cooking and source of light in the kerosene lamp.

Some Sources of fuels

1. Forests and bushes
This is the main source of fuels in most areas. From these sources we get firewood and charcoal. Firewood is a common source of energy in rural areas whereas charcoal is abundantly used in urban areas.
2. Fossils
From fossils, fossil fuels which are coal, oil and natural gas are obtained

1. Coal mines – from this source coal is obtained.
2. Oil wells – from this petroleum (crude oil) is obtained. Petroleum can be refined to get fuels such as diesel, petrol, kerosene and liquefied petroleum gas (LPG).
3. Gas wells – natural gas is obtained from this sources. Natural gas is mainly used for cooking and running machines.
3. Biomass
1. Bioethanol – obtained by fermentation of sugar from sources such as waste wheat starch and molasses, which is a by-product of sugar production.
2. Biodiesel – manufactured from vegetable oil such as soya bean, sunflower, coconut and cotton seed animal fats such as beef tallow, sheep tallow. The oil or fat is combined with an alcohol in the presence of catalyst.
3. Biogas – it is combustible fuel that is produced when animal waste or other organic material rots in the absence of oxygen. Example of animal waste is faeces.

Categories of Fuels

1. i. According to the physical state in which they exist in nature – solid, liquid and gaseous fuel.

Physical state	Primary (natural)	Secondary (artificial)
Solid state	Wood Coal	Charcoal Coke
Liquid state	Crude oil (petroleum)	Petrol Diesel Kerosene
Gaseous state	Natural gas	Coal gas Producer gas Liquefied petroleum gas Acetylene Hydrogen Producer gas Water gas

2. Basing on efficiency Gaseous fuels have high efficiency, liquid fuels have medium efficiency and solid fuels have low efficiency.

FOSSIL FUELS

1. Coal – the remains of trees, ferns and other plants that lived millions of year ago in the swampland. They were pressed down by layers of earth and rock very high pressure, heat and anaerobic bacteria slowly changed these into coal.
2. Oil and gas - crude oil (petroleum) and natural gas are the remains of millions of tiny plants and animals that lived millions of years ago in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains turning them into oil and gas. Meanwhile the silt was slowly compressed into rock. The oil and gas seeped into the porous parts of the rock, and got trapped like water in a sponge.

Advantages of fossil fuels

1. They release high amount of heat.
2. The products formed after being processed have variety of uses (versatile).

Disadvantages of fossil fuels

1. Acid rain. The release of sulphur dioxide gases contribute to occurrence of acid rain.
2. Global warming. Fossil fuel is carbon-containing compound. When burnt, carbon from these compounds is oxidized to carbon dioxide. The accumulation of carbon dioxide in the atmosphere is the main cause of greenhouse effect.
3. Incomplete combustion of fossil fuels lead to liberation of carbon monoxide. Carbon monoxide is harmful gas to both animals and human being.
4. Air and land pollution. Fossil fuel when burnt releases harmful gases and residue of burning contribute to land pollution.
5. Environmental degradation. Fossil fuels are found deep on the earth’s crust. To obtain these, the holes are dug. These processes lead to environmental degradation and destroy the landscape of the area. Displacement of animals from their natural habitats.

SOLID FUELS.

Processes involved in preparation of secondary solid fuels

DESTRUCTIVE DISTILLATION

1. Destructive distillation of coal
2. Destructive of wood

Destructive Distillation of Wood

1. Wood is cut into small pieces.
2. Pit is dug in the ground
3. The wood pieces are covered with grasses following by soil. Few air holes are left at the bottom.
4. The wood pile is lit at the center from one end.
5. The air holes are closed .when the fire goes off, the charcoal is ready and is left to cool.
6. The soil and the remaining unburnt grasses are removed after two or three days. The charcoal is packed for use.
7. The wood pieces are piled in the pit.

Negative effects of using both firewood and charcoal as fuels:

1. Air pollution: The combustion of firewood and charcoal produces smoke and pollutants like particulate matter, contributing to air pollution and poor air quality.
2. Greenhouse gas emissions: Burning charcoal and firewood releases carbon dioxide, a greenhouse gas that contributes to global warming.
3. Loss of biodiversity: Deforestation which occur due to the demand for firewood and charcoal, disrupts habitats of plant and animals, leading to a decline in biodiversity. Many species lose their homes and food source, resulting in ecosystem imbalances.
4. Soil degradation: The removal of trees and vegetation can lead to soil erosion. Trees play a crucial role in maintaining soil structure and fertility; without them the soil loses essential nutrients and becomes less productive.
5. Reduced rainfall: Trees play a vital role in water cycle through a process called transpiration. Removing trees can reduce local rainfall (disruption of local climate patterns), which can affect agriculture and water supplies.

Destructive Distillation of Coal

1. Coke
• It is a tough and porous black solid substance.
• It is pure form of carbon. It is about 98% carbon.
Uses of coke
1. It is mainly used as a reducing agent in the extraction of metals e.g iron and zinc.
2. It is used in the manufacture of steel.
3. It is used as fuel.
4. It is used for making industrial gases such as water gas and producer gas.
Why coke is considered to be better fuel than Coal
• It produces higher energy value than coal. Coke produces more heat than coal of the equal mass.
• Coke does not produce smoke on burning.
2. Coal gas
• It is prepared by destructive distillation of coal.
• It is a mixture of methane, hydrogen and with some carbon monoxide.
• All the gases present in coal gas can burn to produce heat, due to which coal gas is an excellent fuel ( having high calorific value)
• It is used as a fuel in industries. These days however coal gas is used as a source of heat rather than light.
3. Coal tar
Coal tar is a thick, black liquid having an unpleasant smell which is obtained by heating coal inabsence of air.
• Coal tar is a mixture of about 200 carbon compound (organic compound).
• The various compounds present in coal tar are separated by the process of fractional distillation.

Uses of products of coal tar They are used in preparation of synthetic fibres , drugs (medicines ) , plastics , synthetic dyes , perfumes , paints , varnishes , pesticides , roofing materials explosives etc.

LIQUID FUELS

Examplespetrol,kerosene,ethanol,diesel.

Advantages	Disadvantages
They possess high heat content per unit mass than solid fuels.	The cost of liquid fuel is relatively much higher as compared to solid fuel
They burn without leaving residues.	Most are highly flammable they are responsible for explosion of fire.
They are easy to transport through pipes	They give bad odour.
They require less space.	They are expensive, because special storage tanks are required for storing liquid fuel.

GASEOUS FUELS

Gaseous fuel a gas, (methane, ethane, propane, butane) natural gas, coal gas water gas.The most important gaseous fuels used in industries are water gas and producer gas.
1. Producer gas
Producer gas is a mixture of carbon monoxide and nitrogen (CO +N2)


How producer gas is manufactured

Producer gas is prepared by passing air over red –not coke .the nitrogen in air is not affected during the process and the carbon monoxide and nitrogen is formed
C (red hot coke) + O₂(Limited) → (CO + N_2­)(producer gas)

2. Water gas
Water gas is a mixture of carbon monoxide and hydrogen with a small amount of carbon dioxide.

How water gas is manufactured.

It is manufactured by passing steam over red –hot coke at 11000c because reaction is endothermic when temperature decreases CO2 begins to form.
C (red hot coke) + H₂O (steam) → (CO + H₂)(Water gas)


Advantages and Disadvantages of Gaseous fuels

Advantages	Disadvantages
Need the least storage space.	They are highly inflammable so chances of fire hazards in their uses is high
Easy to transport through pipelines.	They are more expensive than liquid/solid fuels.
They have high heat content.	Very large storage tanks are needed
They are clean in use.They burn without any smoke and ashes
Easy to control when burning.

QUALITIES OF GOOD FUELS

1. They should be easily stored and transported.
2. They should have low content of non- combustible material.
3. They should not give off poisonous gases during combustion.
4. They should be readily available in large quantities.
5. They should be affordable to most people.
6. They should not have harmful effects on the environment during its production and its use.
7. They should have an average ignition point Ignition point – the temperature to which the fuel must be heated before it starts burning.
8. They should burn with a moderate velocity for a continuous supply of heat.
9. They should have a high pyrometric effect. Pyrometric burning effect –the highest temperature that can be reached by the burning fuel.

ENERGY

Energy is the capacity or ability of a body or system to do work The SI unit for energy is the Joule (J). Energy exists in two major forms:-

1. Potential energy.
2. Kinetic energy.

Potential energy is the energy in matter due to its position or state.
Kinetic energy is the energy possessed by a body due to motion.
Mechanical energy = kinetic energy + potential energy

Some forms of kinetic(KE) and potential energy(PE):-
1.	(KE) Electrical energy is energy possessed by electrical charges in motion.
2.	(PE) Chemical energy is energy possessed by matter due to its chemical make-up e.g. Bios mass , petroleum and natural gas.
3.	(KE)adiant energy is electroma gnetic energy that travels in a transverse. Radiant energy include visible right, x- rays, gamma rays radio waves and solar energy.
4.	(PE )Elastic potential energy is the energy stored in objects by the application of a force .e.g. compressed springs and stretches) rubber bands.
5.	(KE)Thermal energy is the internal energy in substances caused by the vibration and movement of atoms and molecules within the substance. geothermal energy is an example of thermal energy.
6.	(PE)Nuclear energy is energy possessed by an atom in its nucleus. Nuclear energy holds the nucleus together. The energy is released when nuclear are combined or split apart.
7.	(KE)Sound is the movement of energy through substances in longitudinal waves. Sound is produced when a force causes an object or  substance to vibrate.
8.	(PE)Gravitational energy is the energy possessed by a boy due to its position or place. When an object is lifted or suspended in air, its possesses grantational energy due to its position.

Principle of conservation of energy state that:

“Energy can neither be created nor destroyed it can only be transformed from one form to another”

Transformation of energy

Transformation of energy is the process of changing energy from one form to another.

Example of transformation of energy
1.  Water in a dam has a potential energy.
2.  If this water flows downhill and is converted to kinetic energy
3.  The falling water turns the blades of a water wheel so that kinetic energy is converted to mechanical energy.
4.  The water wheel tums  a generator to convert methanical energy into electrical energy
5.  Electrical energy may be converted into light energy , sound energy and heat energy in the home

ENERGY VALUE OF FUEL

The energy value of any fuel is the total amount of heat liberated by the complete combustion of a unit mass of the fuel in air (oxygen) .
Energy value = total energy liberated (J or kJ)÷ Mass of the fuel used (g/kg) The unit of energy value is joules per gram (j/g) or kilojoules per kilogram ( Kj/Kg)
Heat = mass of a substance x specific heat capacity x change in temperature.

ENERGY SOURCES

Sources of energy can be divided into renewable and non-renewable sources.
Non-renewable source of energy are sources that cannot be replenished within short periods of time.ources They include fossil fuel and nuclear energy. Non-renewable sources are not being replaced at the same rate as they are being used up.

Renewable sources of Energy (Alternative sources of energy)

Renewable sources of energy are those which are continually being replaced within short periods of time.

1. Hydroelectric energy

The potential energy stored in the water held in dams is made to drive a water turbine and generator which in turn produces electric power. This form of energy generation is called Hydroelectric Power (HEP).

Advantages

1. Water used for power generation can be put to use again.
2. No chemical process involved in the power production process, therefore the power generated is clean and does not harm the environment
3. The source of hydroelectric power generation that is water is free of cost.

2. Solar energy

This is the energy which the earth receives from the sun. As long as the sun exists, there will always be solar energy reaching the earth. Solar energy can be tapped in various ways. These include the following
• Generating electricity using photovoltaic solar cells.
• Generating electricity using concentrated solar power
• Heating and cooking using parabolic mirrors that focus the sun’s ray to a central position.
• Heating and cooling using solar chimneys.

Advantages

1. The source of energy is absolutely free.
2. It is clean there is no harmful gases released.
3. Can be used to generate power in rural and remote areas where there is no reach of the conventional form of energy.

Disadvantages

1. Initial cost of cells.
2. The sun does not shine all time.

3. Wind energy

The power of the wind is harnessed to propel the blades of wind turbine attached to an electric generator which produces electricity. Wind energy is an effective alternative source of energy in areas where the velocity of wind flow is high.

Advantages

1. It is a clean form of energy
2. The source of power generation i.e. wind is free of cost.

Disadvantages

1. Require vast amounts of land as machines have to be carefully arranged so that their operation is not impaired.
2. They produce a lot of noise. They cannot be used near residential areas
3. Can only be used in areas which experience high winds, which mean that it cannot be as a source of energy anywhere.

4. Geothermal energy

This is the energy tapped from the heat inside the earth. Hot rocks residing in the core of the earth heat water which emits on the surface of the earth with pressure and as steam This pressurized steam can be used to run steam turbines to generate electricity.

Advantages

1. It is free of cost.
2. With a proper power generation system in place, no harmful by-products are produced.

Tidal energy

The surface of the earth is 75% covered by water bodies especially oceans. The tides in water rise and fall due to gravity of sun and moon. Since we know about how the position of moon changes we can predict the rise and fall of tides.

Advantages

1. It is free of cost.
2. No harmful gases released during its operation.

Disadvantages

Not all areas have water bodies.

Biogas

Biogas is a renewable energy source that is produced through the anaerobic digestion of organic matter, such as agricultural waste, animal manure, and municipal solid waste. Here are some key points about biogas fuel:


Composition: The main component in biogas is methane. Other gases which can be present in biogas are carbon dioxide, hydrogen sulphide and water vapor.

Production: The organic matter is broken down by anaerobic bacteria in the absence of oxygen, producing biogas as a byproduct. This process takes place in an airtight container called a biodigester.

What is a Biodigester? A biodigester is a sealed tank or container where anaerobic digestion takes place.

Structure of a Biodigester:
Inlet: This is where the organic materials (feedstock) like food scraps, animal manure, and agricultural waste are added to the digester.

Digestion Chamber:
The main body of the digester where anaerobic digestion occurs. This chamber is designed to be airtight to create an oxygen-free environment needed by anaerobic bacteria to break down the organic matter.

Gas Holder:
A section or component of the digester where the biogas is collected after being produced during the digestion process. Some digesters have a separate structure for gas storage.

Outlet: The point where the digested material, often called digestate, is removed. This material can be used as a nutrient-rich fertilizer for plants.

Mixing Mechanism: Some biodigesters have a system to stir or mix the contents, ensuring that the bacteria evenly break down the organic material.

Uses of Biogas

Biogas can be used for various purposes, including:
• Electricity generation: Biogas can be used to power generators and produce electricity.
• Heating: Biogas can be used directly for heating homes and buildings, or for industrial processes.
• Transportation fuel: Biogas can be purified and used as a transportation fuel, similar to natural gas.
• Cooking: Biogas can be used for cooking, similar to liquefied petroleum gas (LPG).

Advantages:

• Renewable and sustainable: Biogas is derived from organic matter, which can be continuously replenished.
• Waste management: Biogas production helps in the disposal and management of organic waste.
• Environmental benefits: Biogas production reduces greenhouse gas emissions and potential methane release from the decomposition of organic matter.
• Cost-effective: Biogas production can be a cost-effective source of energy, especially in rural and agricultural areas.
• Reduces reliance on fossil fuels
• The remains after biogas plant has extracted all the methane they can be used as fertilizer.
Challenges:
• Requires a constant supply of organic feedstock for continuous production.
• Purification and upgrading: Biogas may require purification and upgrading to remove impurities and increase the methane content for certain applications, which can be energy-intensive.
• Initial setup costs for biogas plants can be high
• Odor emissions and potential air pollution from biogas plants
• Methane leakage during production and utilization can contribute to global warming

Biomass

Biomass refers to organic matter in living plant material. This type of energy is made up of organic compounds that are produced in growing plants.

• Biodiesel fuels are alkyl esters manufactured from vegetable oil such as soya bean, sunflower, coconut and cotton seed.
  Also from animal fat such as beef and sheep tallow. The oil or fat is combined with alcohol in the presence of a catalyst.

Disadvantages

1. pollutes the air by emmiting sulphur dioxide.
2. Require vast land for planting fuel crops.
3. Leads to the destruction of natural habitats of some living organisms.
• Bioethanol
It is obtained by the fermentation of sugar from sources such as waste wheat starch and molasses (end-product of sugar production).

Advantages

Reduces pollutants.

Disadvantages

1. The cost of processing is high.
2. Produces less energy per gram.

THE CONCLUSION

Advantages of Renewable Sources of energy	Disadvantages of Renewable Sources Energy
Reliable/sustainable (inexhaustible and can be replenished naturally)	Vulnerable to changes in weather conditions.
Stable energy prices.	High initial costs of installing renewable energy systems
Low cost operation. Manufacturing, maintenance, research and development, installation	Require a large space to set up. This competes with other land uses such as agriculure.
Job creation and economic benefits.	Limited supply of energy
Energy independence. Dependence on foreign fossil-producing contries will greatly be reduced.	Not available in all areas.
Reduced greenhouse gas emissions.

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Further studies on the Renewable Sources of Energy

You may prefer to revise the renewable sources of energy by clicking Renewable sources of energy, the page which was submitted by Kipepeo B.

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Form Two topics

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