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ENERGY

ENERGY IS THE ABILITY TO DO WORK AND IT IS ALL AROUND US If you notice anything moving, growing, heating up, creating light or producing a sound, energy is what is making it happen.

Almost all energy originally comes from the sun. Plants are special because they can harness the sun’s energy. They use a unique process called photosynthesis, which means ‘producing from light’. It uses the energy in sunlight to take carbon dioxide which they get from the air, and water, from the ground, to produce biomass. Oxygen is also produced – the same oxygen that we people and animals depend on! When a herbivore (a plant-eating animal) eats a plant, solar energy that the plant collected and used to create biomass passes to the animal. The herbivore digests the food it ate, uses some of the energy and stores some. When a carnivorous (meateating) animal eats the herbivore, so the energy is passed on again. At each stage, energy is lost as heat from the animal’s body as it undertakes all sorts of chemical reactions in order to live.

You can read about food chains, food webs and ecological communities in the PACE Wildlife booklet Like animals, humans get energy to move and to keep their bodies functioning from eating food.

But unlike animals, humans have found ways to harness extra energy to use as fuel for things that make their lives easier. We burn wood to cook food and heat water, we make electricity to light our homes and towns at night, listening to the radio, charging a mobile phone, airconditioners and fans, keeping food and medicines fresh in a refrigerator – all these activities need energy.

Universal access to electricity Some people are unable to access or afford enough energy to meet their basic needs - cooking food, lighting their homes and neighbourhoods. Other people have unlimited electricity, use banks of air-conditioners, fridges, freezers and can splash large properties with light. This inequality is not only to do with wealth, it is about finding the right technology and sustainable ways to meet everybody’s energy ‘needs’ and as many energy ‘wants’ as possible.

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This chapter explains different kinds of energy, with advantages and disadvantages. It looks at sustainable technologies that you can use to supply your own energy in your homes and communities. There is general information and examples from different countries, cities and communities across Africa. The chapter also looks at ways your community could manage the energy sources you already have in more sustainable ways. It explains different sustainable technologies that you could use to supply your own energy.

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PEOPLE NEED ENERGY

Energy can reduce…

• Extreme poverty, by freeing up time spent gathering fuel and increasing income and employment through enterprises that depend on energy: workshops, sawmills, welding and metalworking, food processing, IT, manufacturing, etc.

• The number of people living with hunger: approximately 95% of the food we eat has to be cooked, and most foods need energy for processing of some kind. Hunger is related to poverty, so efforts to eradicate poverty should help eradicate hunger.

• Gender inequality, by reducing arduous tasks like collecting and carrying heavy loads of firewood and the drudgery of food preparation that is mostly done by women and girls.

Energy provides opportunities…

• For enterprise and for evening education as people have lighting by which to read and write.

• For communicating – powering our telephones, computers and access to internet.

• For people to live healthier, longer lives, by reducing indoor air pollution from household smoke, providing cool air when it is hot and warmth when it is cold. Fans, air-conditioners and heaters need power.

• For better health facilities, with vaccine refrigeration and modern hospital equipment, scanners, lab testing, operating facilities etc.

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Electricity Most people want electricity. An easy source of energy, it is invisible, and silent, it does not smell although if you touch it, it can burn or shock you. It can light up a house at the flick of a switch, warm us in cool weather, cool us in hot weather, keep crucial food and medicine cool, drive our computers and mobile phones. Electricity has mostly been generated by burning coal, natural gas or oil (known as fossil fuels) in a power station or generator. Now, renewable technology is starting to take over from fossil fuels. Photovoltaic or solar panels convert energy from the sun into electricity. Special turbines use the energy in wind and moving water to generate electricity. Other systems use gas produced from organic waste to fuel generators and the heat from incinerated refuse to produce electricity. Renewable energy is the future, especially in Africa which has sun, wind and big rivers!

Most electricity comes from large power stations which supply whole towns and regions.

Power lines can run all over the country carrying the energy on a national grid - this is called a ‘grid’ supply.

Many governments have made universal electricity supply a priority. More and more people are being provided. However, especially in places far away from towns and cities, grid supply is still non-existent, or poor. In 2017, 96% of Kenya’s rural population lacked access to grid electricity. If national supply fails people are suddenly in the dark, unable to run their businesses, equipment is damaged, produce wasted and security jeopardised. A back-up system is valuable, and the best source may be within your own town or village.

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WAYS TO ACCESS ENERGY

Batteries Batteries store energy and release it when needed. The chemicals used in many batteries are toxic and also very expensive (lead, cadmium and mercury are examples), so it is important that old batteries are recycled whenever possible.

If the components are reused or disposed of safely then the dangerous chemicals will not get in the soil or food-chain.

The metal called lithium is used to make the rechargeable batteries for mobile phones, laptops, digital cameras and electric vehicles and also for medical devices like pace-makers and hearing aids. Lithium batteries hold a lot of power, have a long life, and can be very, very, small, but they are expensive.

Solar powered lanterns and wind-up radios are two popular ‘clean’ and affordable devices that have improved many lives.

They both use rechargeable batteries.

ACTION SHEET - 68: Solar lanterns

FUN FACTS • Lithium is a soft silvery metal, which has the lowest density of all metals.

• The chemical symbol for Lithium is Li. • Most lithium comes from Chile in South America and from Australia.

• Electric cars run on batteries. They are re-charged at home or at charging points on highways.

• After 2035 diesel and petrol cars will be forbidden in the UK - all vehicles will be electric!

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Fossil Fuels Fossil fuels are literally made of fossils – the dead bodies of trees and other organisms that died during the Carboniferous Period (about 354 – 292 million years ago). Coal is the remains of forests and swamps that covered the earth hundreds of millions of years ago. As the trees died they were buried under layers of soil and weighed down as more fell on top.

Gradually over time, pressure and high temperatures turned it into coal.

Oil and natural gas was made in a similar way from the bodies of marine plankton: tiny plants and animals which floated in the sea millions of years ago and sunk to the sea floor when they died. Their prehistoric remains were buried in sedimentary rocks, where they were changed by heat and pressure into gas or oil. The bodies of plants and animals contain a lot of the chemical element carbon. Burning fossil fuels, just like burning wood, releases the carbon, as gases, into the atmosphere. This has consequences for the climate, as explained on page 140 and in the Booklet on Energy and Climate Change.

Fossil fuels are not renewable because they were made slowly over a long period of time and we are using them up, very fast. All the world’s oil and most of the gas could be finished by 2050. Most countries currently depend on fossil fuels and buying them from countries where they occur naturally or are processed.

Producing energy locally from clean renewable sources can save a country money and protect our planet. Zimbabwe and Zambia started a project like this in 2018, a new joint hydro-electric project that will generate 1600 Megawatts of electricity, enough to meet their own needs and export! It will use energy from the Zambezi River, below the Victoria Falls. Africa has a lot of energy in its sunshine, wind and great rivers waiting to be harnessed.

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Nuclear Power Nuclear energy is the energy inside atoms. Atoms are the tiniest particles of things and there is enormous energy holding them together. This energy can be used to make electricity.

The process is called nuclear fission and it takes place inside massive machines called nuclear reactors housed in nuclear power stations. They use uranium. Uranium atoms are split releasing energy as heat. The heat is used to boil water, producing steam that drives turbines to produce electricity.

Some countries favour nuclear power, others do not. About 17% of world electricity is produced in this way. Seventy percent of France’s energy comes from nuclear power, about 20% for the UK and USA. Less than 2% of Africa’s energy comes from nuclear power.

South Africa has the only nuclear power station on the continent, it is at Koeberg, 30 km north of Cape Town and has two reactors that generate 5% of South Africa’s electricity.

FUN FACTS • The chemical symbol for uranium is U. • Uranium is a heavy metal.

• Uranium is naturally radioactive. It is found in rocks in the earth’s crust.

• Many African countries have uranium reserves.

• Niger, Namibia and South Africa together mine up to 18% of annual global production.

• Most uranium is mined in Kazakhstan (39%), Canada (22%) and Australia.

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GooD To KNOW Renewable and Non-renewable energy Solar, wind, water - these are all renewable sources of energy. Unlike fossil fuels (oil, coal, gas) which take millions of years to form, renewables are ever-present or can be grown or made again and again. Renewable sources of energy include the sun, the wind, water, human and animal waste. You have to buy or build equipment to harness energy from the sun, wind or water in order to make household energy.

But, once this is paid for the only cost is maintenance. No bills! and locally produced renewable energy is more reliable than grid power in many areas.

Solar energy: Get on the sunny side The sun is a huge ball of fire, a mass of energy, of material burning up in outer space, 93 million miles away. It takes 8 minutes for light from the sun to reach us here on Earth. In the centre of the sun, it is 15,000,000°C and it’s been burning for the last 4.6 billion years. This energetic star can be used to make household energy. Solar energy is in many ways the perfect power source. It won’t run out for another 5 billion years! Sitting in the sky sometimes it seems friendly, sometimes too hot and deadly, but it is always there for free.

Humans have been slow to take advantage of the sun’s energy. You can’t hold the sun in your hand or put it into a tin can or a petrol pump so it’s difficult to sell. You can use solar power to cook food on a solar cooker, heat your water and home, even to make electricity with photovoltaic technology. The Botswana government have made it a legal requirement for all their buildings to have solar water heating systems installed. Solar energy systems for homes and renewable energy village power systems are now common and widely available in many countries across Africa.

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Wind Power The movement of air can be used to make electricity.

Wind turbines are used to convert the kinetic energy in wind to mechanical (electrical) energy. Turbines are like windmills but with blades, as the blades are rotated by the force of the wind, they turn a generator which produces electricity. Small turbines are used to power a single device, larger ones make electricity for a single house or building and commercial turbines, often arranged in large numbers as a ‘wind farm’ are usually connected to a grid that carries the electricity to whole regions.

Wind turbines work most efficiently when they are 30m or more above ground, where the blades can capture faster, less turbulent air.

For this reason, commercial wind turbines can be up to 100m above the ground.

The amount of wind we get each year is usually about the same, but it varies at different times of the day, on different days and between seasons. The amount of electricity produced depends on the strength of the wind. If you have a turbine for your house, business or community it can be connected to a battery that will store electricity made when there is plenty of wind so that it can be used when the wind is light.

• In Africa big wind farms are commonest on the coast and hilly areas, where there is more strong wind, more often.

• Egypt, Tunisia, Morocco, Kenya, and South Africa have big wind farms. Kenya built the biggest in 2017: 365 turbines, covering 40,000ha, employing 200 people.

• Namibia’s power plans include wind. A new wind farm was built in 2018 and two more are on the way.

• Senegal, Ghana and Mozambique are installing wind farms.

• Denmark in northern Europe generates 40% of its electricity using wind power - 31,000 people work in its wind industry.

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Water Power If you stand in a river or the sea or just pour some water on your hand you can feel the energy in moving water. It is called hydro power and can be turned into electricity using turbines and generators, using a similar system to wind energy.

Water passes through the turbines making its blades spin. The turbine is connected to electromagnetic generators which produce hydroelectricity. When the water is falling, by gravity it has potential energy; when it is flowing, in the sea for example it has kinetic energy. Hydroelectricity is ‘renewable energy’ because the water cycle which provides the moving water is continuous, fuelled by the sun and by gravity.

Hydroelectricity is an important source of energy, especially in Africa where most countries have built very large hydro-electric plants on big rivers. The Zambezi, Nile and Congo are great sources of energy. Some countries make more than 90% of their electricity from hydro, examples are Ethiopia, Malawi, Mozambique and Zambia.

Hydroelectric plants come in all different sizes. Small scale equipment that use water from a river or stream can be set up locally at little cost and are not difficult to use.

• Pico hydro uses turbines that produce up to 5 kilowatts of electricity, enough for one or a group of houses or a workshop.

• Micro hydro units produce 5-100 kilowatts.

This picture shows a micro-hydro system, which produces energy for a community in Kenya. 18 kilowatts of power is produced to provide light and power to 180 homes. They set up, own and manage the plant themselves.

Can you think of the advantages and disadvantages of hydroelectricity?

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Biomass – Energy from life Wood, charcoal, dung, agricultural and human waste, even bacteria and algae – anything that grows or is produced by living things is known as ‘biomass’ and can be used to make energy. Biomass energy is created from the carbon stored in the bodies of plants and animals.

Like fossil fuels, biomass produces carbon gases when it is burnt or digested, however there are technologies that allow us to capture these gases, and even to make them work for us. Using modern technology, biomass can be used to generate electricity, provide fuel for vehicles, gas for cooking and heating and powering machinery.

While Biomass is considered to be a renewable or so-called ‘Clean’ source of Energy, it needs to be used sustainably. We must ensure that it is renewed, that means when wood is cut, burned for fuel or used to make charcoal WE MUST plant more.

DON’T FORGEt

IF YOU BURN WOOD, PLANT A TREE! Burn Dung Animal faeces or dung is waste material, but we can get energy from it, and make it work for us. It is one of the fuels of the future. Cow dung that is left to decompose naturally produces methane, a smelly gas which is 21 times as bad for the climate as carbon dioxide. Capturing and using this gas is a clever way to stop methane getting into the atmosphere and to solve energy problems at the same time. The PACE Climate Change booklet explains how African countries are providing power for factories and cities using this kind of biogas.

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Biogas Biogas is gas made from the breakdown of organic matter, including dung, by bacteria in the absence of air (the process is called anaerobic digestion or fermentation). A smelly pond or marsh producing methane or a cow’s wind – are all biogases.

Biogas factories use special sealed digesting chambers to speed up the process of breaking down the waste. The chambers have two products - biogas which is captured and bottled to burn for lighting and cooking and other uses, and slurry which is used as fertiliser on farms.

Digesting chambers can be made by local artisans. As the material breaks down it gets hot.

The high temperatures kill any dangerous bacteria (similar to the process of making compost).

Methane can also be made using municipal garbage, from waste foodstuff and other organic remains that are usually discarded on rubbish dumps and landfill sites. Biogas can be made in people’s homes, by schools, farmers or by businesses.

Human waste can also be used to make biogas. If toilet waste is channelled into a biodigester you’ll end up with cooking gas for free, safe fertiliser – free, better sanitation and healthier kitchens.

FUN FACTS • 1m3 of biogas can cook 3 meals for a family of five or six.

• Biogas can fuel power stations. It is burned to heat water, producing steam that powers turbines which generates electricity.

• There are 880 biogas plants in Kenya.

• Tanzania uses biogas from municipal and industrial waste to produce grid electricity and make fertliser.

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Biofuels Biofuels are liquid or gas fuel made from processed plant material. Bioethanol and biodiesel are common examples. They are used instead of petrol or diesel in cars, trucks, generators, even aeroplanes.

Biofuel is big business in some parts of the world. Large bioreactors use waste from sawmills, waste cooking grease and old cooking and motor engine oils, even crop residue.

It is broken down into sugars and fermented into alcohol. Brazil makes 16 billion litres a year. There is a more complicated chemical process that is used to make biofuel from algae. But the simplest method uses sugars like sugarcane and vegetable oils like palm, sunflower, groundnut, soya, corn and coconut. The oils and sugars can be extracted using a hand press like the ones used to extract oil to eat. Then it is fermented, the same as making wine or beer, to produce ethanol, which is the alcohol in wine and beer. Glycerin which is also useful is a by-product. Locally made biofuel can be used in an ordinary diesel engine, in fact it will make your engines last longer!

You may be starting to realise that there are good jobs for people who have studied biology, microbiology and chemistry and lots of opportunities to make more use of the resources around us!

Biochar Biochar has been central to life on John and Anna’s small holding in north western Kenya for more than twenty years. At Spencer’s Farm biochar has provided clean energy and clean drinking water for local households, halted deforestation, improved soil and helped fight climate change. Biochar is a fantastic way to use the energy in wood, at no cost and actually reduce CO2 emissions at the same time. What could be better?

Biochar is similar to charcoal, but is actually made while cooking, it is a by-product of a simple model of improved cook stove. Biochar stoves make very little smoke, require only twigs of wood and cook well.

Biochar is wood that has been ‘burned’ with very little oxygen present. The process is called pyrolysis. The presence of just some oxygen causes the tars and oils in the wood to burn away. As they burn heat and a clean, hot flame is created. A light, brittle structure like charcoal, remains. This is biochar, it is made up of carbon. It can be used to filter water to make it safe for drinking. It is added to compost to reduce odour and to soil to increase productivity, especially poor soils.

ACTION SHEETS - 68: Solar Lanterns, 60: Solar Cooking, 64: Solar Water Heating, 67: Planting Trees for Fuelwood, 66: Biogas

Watch the films Energy, Biogas and Water Energy

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SMALL CHANGES MAKE BIG IMPROVMENTS

The type of cooking stove you use needs to suit you and your family, but its design can affect your health, wealth and happiness too! There are models of stove that use less fuel and produce less smoke. They often reduce cooking time as well.

To be efficient a stove must suit the way fire works! Fire needs air, circulating under and up and through. A grate and a door on the stove help air enter. Walls around your stove contain and shield the fire directing more heat into the cooking pot. In Western Kenya, the Jiko Kisasa stove is built by local potters. It halves the amount of fuelwood needed to cook, and can also be fuelled with straw, sawdust and farm waste. The stoves are so popular that a hundred thousand are now sold every year.

FUEL SAVERS • Reduce the amount of fuel you need by two thirds! Put a lid on your cooking pot!

• Use a pressure cooker - a special pot which cooks food much faster than a normal pot • Soak lentils, beans and grains and chop vegetables small to reduce cooking time.

More ideas for cough-free cooking Houses need to be well insultated but also well ventilated. Insulation keeps the temperatures comfortable, ventilation lets fresh air enter, and lets stale air and smoke get out.

ACTION SHEETS - 62: Cook stoves, 69: Energy Efficient houses

Watch the films Fuel Efficient Stoves 137

Use the sun instead! Solar cookers and stoves use the sun’s energy to cook and heat water.

Dry wood is crucial! Wet wood, like green grass or damp paper, contains moisture.

The fire has to work hard to drive away the water. Less heat energy is produced, so food takes longer to cook. Try the fuelwood experiment, Energy activities page 145.

ACTION SHEETS - 63: Smoke Hoods, 59: Make a Fireless Haybox Cooker, 61: Make your own Solar Cooker

Watch the film Energy: Solar Energy - Solar Cookers

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Put a smoke hood and chimney over the stove and make holes between the roof and the walls of your house to allow air to circulate through the house. In Kenya, this reduced indoor air pollution by up to 80%. Smoke can drive away insects, so it has some advantages, but it is better that we can use smoke when we need it rather than living with it all the time.

Cut wood into small pieces.

Smaller pieces of firewood have more surface area exposed to air. Air makes the wood burn hotter and more efficiently, so you can cook more quickly and with less fuel. Cooking with smaller pieces also means that you use just the right amount and not more.

Cook without fire! Heat the food up in a pot until it’s bubbling, then transfer it to a haybox and leave to cook!

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GLOBAL CLIMATE CHANGE

The atmosphere, the air we breath, is naturally made up of several gases, including carbon dioxide, oxygen and nitrogen.

Burning carbon (the carbon in wood, charcoal, fossil fuels, etc) creates carbon dioxide and other carbon gases that collect in the atmosphere, high in the sky. There they act like a glass roof around the earth, trapping in heat that would otherwise escape into space. This is referred to as the ‘greenhouse effect’ and is explained in the Energy and Climate Change booklet.

This is a good thing, because it keeps the heat in. If it wasn’t for gases like carbon dioxide, the temperature of our planet would be on average -18oC, very cold!

A big source of greenhouse gases is the smoke from fires when we burn trees, crops and fuelwood. This along with burning more and more fossil fuels, is making the planet warmer and warmer.

The climate is changing and climate change is affecting the whole planet, not just Africa.

Weather is becoming unpredictable; droughts, heatwaves, floods and cyclones are now more frequent.

Extreme changes in temperatures create health problems for people and animals. Drought and floods disrupt farming, creating food insecurity.

Humans, plants and animals will perish if temperatures become too hot or too cold. We all need to adapt to the changes and we need to reduce our carbon emissions. Which of the ideas in this book could you use? There are many more in the Energy & Climate Change booklet.

Learning how to use fire was one of the discoveries that set humans on their path of development. Another brilliant human invention was using the combustion of fossil fuels to drive engines. Sadly, they could destroy our own planet if we are not careful.

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OUR ECOLOGICAL FOOTPRINT

An ecological footprint can be big or small. It measures the impact we have on the natural environment. To minimise climate change and to keep the planet as healthy as possible we need to use energy with the smallest footprint, and to use as little as possible.

Energy efficiency Efficiency is when a task is done in the best possible, least wasteful way – using minimum resources, and time. Energy efficiency is all about the amount of fuel used to do things.

To cook food efficiently means to do it properly, with as little fuel as possible. We can adopt efficient behaviours, like turning off devices when they are not needed, and efficient technology, using equipment or energy sources that are least wasteful.

Efficient cooking technology A three-stone fireside is less efficient than a metal improved wood burning stove, which is less efficient that an improved clay or cast iron stove. A kerosene pressure burner is more efficient than all of these, and a LPG gas stove is even better. A solar cooker is fuel efficient but takes a lot of time to cook food.

‘Clean’ ‘Eco-friendly’ electricity We have seen how electricity can be produced using many different sources: using solar, fossil fuels, nuclear, wind, batteries or biomass. Each one has a different impact or footprint on the planet.

DID YOU KNOW? What is the ecological footprint of different sources of electricity?

BEST: Renewables: solar / wind / hydro MIDDLE: Biomass and biofuels WORST: Fossil fuels, nuclear.

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DON’T FORGEt

KEEP YOUR FOOTPRINT SMALL!

Save energy! Turn off the lights!

Get switched on to switching off! Leaving TVs, computers and hi-fi equipment on stand-by uses 1% of all the electricity in many industrialised countries. Leaving your mobile phone charger switched on at the wall when you are not charging your phone wastes energy disconnect it! Half of a school’s fuel bill is often lighting! Turn off the lights when rooms are empty. If a classroom is empty for more than one minute, turn the lights off.

• If you have electricity there are lots of ways you can reduce the amount you use, to save the planet!

• If you use a fridge keep the back of it clean with space for air to flow then the cooling coils work efficiently.

• Open fridge and freezer doors as little as possible – if the cold comes out the motor has to work more.

• Fill empty space in a fridge or freezer - even ice, paper, bread or rice will reduce fuel consumption.

• Don’t use fans or air conditioners if you can manage without.

• Turn off lights when nobody is in a room.

• Turn off gadgets when you are not using them and cook beans and stews in a slow cooker to save gas or wood.

• Get an electric car!

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Insulation When it is cold shut the curtains to stop precious heat escaping. Curtains and blinds will also keep heat outside when the sun is burning! How hot or cold your house gets and the amount of energy needed to keep it cool or warm enough depends on INSULATION. Insulation stops heat from passing through. Buildings can be insulated with cotton, grass, straw, sheep’s wool, paper, clay bricks or straw. Build thick walls with layer of insulation in the middle.

If your roof is made of zinc think about putting layers of insulation in the loft. Include an insecticide, one that is biodegradable and safe.

Energy self-sufficiency Most countries import their oil and gas. When producers increase the price it’s difficult to pay the bill. We struggle to pay our household fuel bills and countries have the same problem, making life harder for everyone. Increasing the amount of renewable energy produced in a country reduces import bills and helps stabilise the economy. During its economic crisis Zimbabwe used locally manufactured equipment to make 50 million litres of cheap biofuel every year: without it cars would not have moved - imported fuel was too expensive.

Think about installing a biogas or solar system to power your own house, school or business.

It won’t create greenhouse gases like a diesel or petrol generator, is more ‘climate friendly’ than grid electricity, and will give you electricity with no bills.

The activities on the next few pages demonstrate how you can save fuelwood, cooking time and reduce kitchen smoke – win for you, win for the planet.

REFLECTIONS • Have you noticed climate change in your area?

• What has changed?

• Can you remember any rivers that used to always flow with water but now dry up?

• Can you still plant your crops on a certain date knowing the rains will come within a week?

• How are people adapting to climate change in your area? Do you think they need to?

• How can we help prevent negative effects of climate change?

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ENERGY

ACTIVITIES

The activities on the next few pages demonstrate how you can save fuelwood, cooking time and reduce kitchen smoke – win for you, win for the planet.

ACTIVITY 1 Fuelwood Experiment How does size, moisture content and type of wood affect how fuelwood burns?

What you need for the experiment: • Two three-stone fireplaces in a safe outdoor area • Wood (as described below) • Matches • Water • Two equal-sized cooking pots

Preparation Collect wood for three experiments as follows: 1. Wet and dry wood Find two pieces of wood the same size. Soak one of the pieces of wood in water for one day or get one freshly cut piece of wood, and one piece of dry wood.

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2. Logs and twigs Take some dry wood from the same tree and weigh out two equal amounts — one in the form of logs and one in the form of twigs. You can use the technique shown in the picture to get two piles of wood that are the same weight. Tie a bundle of logs to one end of a pole, and then tie a bundle of twigs to the other end. Keep adding twigs until the pole is balanced when hung from a rope tied to its middle. When the pole is balanced, you will have bundles of twigs and logs of equal weight.

Experiment 1. Build two three-stone fireplaces. Use the pile of logs and the pile of twigs to make two separate fires. Compare the way the fires burn. Which pile of wood ignites and burns faster? Time how long it takes to light each fire and how long it takes to boil a pot of water with each fire.

If you have a thermometer, you can measure the temperature at ground level at a given distance from each fire. Explain your results. (Hint: Which wood has a larger surface area exposed to the air?)

2. Get the two fires to burn at the same intensity. Then add the wet piece of wood to one fire and the dry piece to the other. Compare how they burn.

How long does it take to light the two pieces of wood? Which gives off more smoke? Which gives off more heat? Explain your observations.

3. Don’t forget to make some tea with the water when it has boiled!

SOURCE: Outreach hands on Science: Wood it burn?

Burning Wood Efficiently

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ACTIVITY 2 Compare the efficiency of different cook stoves What you need for the experiment: • A 3-stone fireside and three or four different types of improved woodburning cook stove, eg. metal, clay, mud, cement.

• Firewood and matches.

• Four sets of cooking utensils: pots, knives, spoon, etc.

• Ingredients for a simple everyday meal: enough to prepare the same meal on each stove.

• A balance to weigh the wood ( a butcher or grain merchant may be able to help with this).

Experiment Each person or group prepares the same meal, each using a different stove.

Each uses exactly the same quantity of ingredients.

Record the time taken from start to end of cooking.

Weigh the wood before cooking and when complete.

Record your results Stove

Wood Consumption (kg)

Cooking Time (Hours/Minutes)

a) 3-stone b) Improved 3-stone c) Metal d) Clay e) Other

Discuss!

SOURCE: UNAFAS, BP 307, Yaounde. www.unafas.org

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