Class 6 Science Chapter Notes
Chapter 16 Garbage in Garbage out
The waste materials especially household wastes, are called garbage.
Some examples of garbage are: The peels of fruits and vegetables, left-over cooked food, fallen leaves of potted plants, packing materials, waste papers, old or broken glass articles, old and useless metal objects, used aluminium foils, rusted iron grills, door handles, old clothes, discarded shoes and slippers, etc.
The garbage collected in dustbins in our homes, shops, offices and schools is taken away by sanitary staff (ragpickers) of our area and put into big garbage dumps constructed by the Municipality at various locations. From the garbage dump, garbage is loaded into trucks and disposed of in a number of ways depending on the nature of garbage.
Components of Garbage
Garbage has two types of components in it: useful components and useless components.
(i) Those things present in garbage which can be converted into useful products, recycled or reused are called useful components.
(ii) Those things present in garbage which can neither be used in any way nor recycled are called useless components.
The useful components of garbage are also of two types:
(a) Fruit and vegetable peels, left-over cooked food (called kitchen waste) and fallen leaves, etc., which can be converted into compost.
(b) Used paper, some plastics, glass and metal articles which can be recycled or reused.
Biodegradable and Non-biodegradable Garbage
The part of garbage which can rot or decompose in nature to form harmless substances is called biodegradable. All the garbage from plants (such as fruit and vegetable peels, leftover food, leaves, paper, cotton, jute etc.) and from animals (such as wool, silk, leather and cow dung) is biodegradable. Biodegradable garbage is also known as organic waste.
The part of garbage which does not rot or decompose in nature is called non-biodegradable. The garbage which consists of plastics, glass and metal objects is non-biodegradable. All the garbage which is not derived from plants or animal sources is non-biodegradable.
Activity: Separating Biodegradable and Non-biodegradable wastes
We can collect the garbage from our house and separate it into two groups as follows:
(i) In the first group we take garbage from the kitchen (called kitchen wastes) such as fruit and vegetable peels, left-over cooked food, tea-leaves and egg-shells, etc. We also include dry leaves, paper bag, cotton cloth, wool, jute bag and an old leather belt in this group.
(ii) In the second group we take a plastic bag (polythene bag), broken plastic toy, synthetic cloth, broken glass and metal objects such as aluminium foil and iron nails.
(iii) We dig two pits in the ground about 30 centimetres deep. In one pit we place garbage from the first group and cover it with a layer of soil. In the other pit we place garbage of second group and also cover it with a layer of soil and leave these materials buried in the pits for about a month.
(iv) After a month, we dig up the buried waste materials or garbage from both the pits and observe them.
(v) We will find that the garbage made up of fruit and vegetable peels, left-over cooked food, tea-leaves, egg-shells, dry leaves, paper bag, cotton cloth, wool, jute bag and leather belt buried in the first pit 'rots' completely to form a black looking substance resembling soil. This means that all these waste materials present in the garbage have been decomposed by the micro-organisms present in soil, so they are biodegradable.
(vi) The garbage containing plastic bag (polythene bag), broken plastic toy, synthetic cloth, broken glass, aluminium foil and iron nails does not rot at all. It remains as such. This means that the waste materials present in this garbage have not been decomposed by the micro-organisms present in soil, so they are nonbiodegradable.
Colour Coded Dustbins
The green dustbins are used for collecting kitchen wastes and other plant and animal wastes, which can be used to make compost.
The blue dustbins are used for collecting waste materials such as plastics, glass objects and metal articles which can be recycled and used again.
Disposal of garbage
'Disposal of garbage' means 'to get rid of garbage.' There are different methods of disposal of garbage. The method to be used depends on the nature of garbage. Some of the important methods (or modes) of garbage disposal are:
(i) Composting
(ii) Vermicomposting
(iii) Recycling
(iv) Reuse
(v) Landfill
(vi) Incineration
Composting
The biodegradable garbage such as rotted plant and animal waste and the waste from kitchen are used as a manure for growing plants. This manure is called compost. Compost is a natural fertiliser.
The process of converting plant and animal waste materials into manure by rotting is called composting.
When compost is mixed with the soil in which plants are grown, it provides nutrients to the plants.
Activity: To Prepare Compost
We can dig a pit in the ground about 1 foot deep in an unused field.
We dump the plant wastes such as fruit and vegetable peels, left-over cooked food, cow dung and fallen leaves into the pit on daily basis.
When the pit gets filled to the top, a few buckets of water are added to the pit.
The pit is then covered with a paste of soil and left undisturbed for about 3 months.
The micro-organisms present in soil decompose the plant and animal waste materials buried in the pit to form compost.
The compost formed can be dug up from the pit and used as manure in the garden to grow plants.
Vermicomposting
The method of making compost from kitchen wastes (or kitchen garbage) by using redworms is called vermicomposting. The compost made by using redworms is called vermicompost. Vermicompost is a very high-quality manure.
Only the garbage containing plant and animal wastes can be converted into vermicompost by redworms (because redworms can eat up these materials).
Activity: To Prepare Vermicompost
(i) Dig a pit about 30 centimetres deep in the ground (or keep a wooden box) at a place which is neither too hot nor too cold. The place should also not get direct sunlight. Spread a chicken mesh (or 1 to 2 cm thick layer of sand) at the bottom of the pit.
(ii) The kitchen garbage containing fruit and vegetable peels, left-over cooked food, tea-leaves, etc., is now spread over the chicken mesh or sand layer. Other waste plant materials such as green leaves, dried stalks, husk, pieces of paper or newspaper, and cardboard can also be added. However, plastic coated paper (laminated paper) should not be added. The animal waste such as dried cow-dung can also be used for making vermicompost.
(iii) Sprinkle some water in the pit to make the layer of garbage wet. Do not use excess of water. The layer of garbage in the pit should not be compressed. The layer of garbage should be kept loose so that it has sufficient air and moisture.
(iv) Buy some redworms from the market and put them in the pit (or box) containing kitchen garbage and other such wastes. Cover the pit loosely with a gunny bag or an old sheet of cloth or a layer of grass. Once in a few days mix and move the top layers in the pit.
(v) Redworms eat the rotting (or decaying) garbage of the pit as food. Redworms do not have teeth. They have a structure in their body called 'gizzard' which helps in grinding the food which they eat. Powdered egg-shells (or sea-shells) are usually mixed with the kitchen waste in the pit. The hard particles of egg-shells (or sea-shells) help the redworms in grinding their food in the gizzard. A redworm can eat food equal to its own weight in a day. The excretions of redworms keep on collecting in the pit. These excretions of redworms make up vermicompost. Observe the contents of the pit after 3 to 4 weeks. We will see loose, soil-like material in the pit. This is vermicompost.
(vi) Put some fresh kitchen waste (such as left-over food) in one corner of the pit. All the redworms will shift towards the corner of the pit containing food. Remove the vermicompost from vacated part of the pit and dry it in the sunshine for a few hours. Vermicompost is now ready for use.
Advantages of manure or vermicompost over fertilisers
(a) making compost (or vermicompost) is quite cheap whereas chemical fertilisers are very expensive and hence a lot of money is spent in buying them.
(b) compost (or vermicompost) is a natural manure which does not harm the soil but chemical fertilisers are man-made which may harm the soil in the long run.
Recycling
Recycling means that we should collect and separate the used and discarded items made of paper, plastics, glass and metals, and send them to the respective industries for making fresh paper, plastic, glass and metal objects. For example, the waste papers such as old newspapers, magazines, books and notebooks, etc., are sent to paper mills where they are reprocessed to make new paper or cardboard.
For recycling the waste material, we sell these wastes to the junk dealers who visit our colony. Junk dealers load them into trucks and sends to the respective industries for recycling.
Activity for Recycling of Paper
(i) We take some old newspapers, magazines, used envelopes and notebooks or waste papers, which do not have plastic in it.
(ii) We tear the waste papers into small pieces and put them in a tub.
(iii) Now, we pour some water into the tub. Let the pieces of paper remain submerged in water for a day. Then make a thick paste of paper by pounding it.
(iv) Take a fine wire mesh fixed to a frame. Keep this wire mesh on a table. Now, take the thick paste of paper from the tub and spread it on the wire mesh. Pat it gently to obtain a uniformly thick layer of paper paste. Wait till all the water from paper paste drains off.
(v) We now remove the layer of paper paste from the wire mesh carefully and spread it on a sheet of newspaper kept in the sunshine. Keep the corners of the newspaper pressed by putting some weights so that they do not curl up. The heat of sunshine will remove all the water left in the layer of paper paste and make it completely dry. This dried and thin layer of paper paste is the recycled paper.
It is called hand-made paper. To obtain coloured paper, we can add a food colour to the paste of paper before spreading it on wire-mesh.
Reuse
Reuse means that, if possible, we should use the same things again. For example, the plastic jars in which we buy various food items such as jams, pickles, oils and ghee, etc., can be used for storing things like salt, spices, sugar, tea-leaves and pulses, etc. The paper envelopes can be reversed inside out and used again. We can reuse old chart papers to make files or greeting cards. Mats can be made from old clothes; and baskets from used and old polythene bags.
Landfill
Landfill is a low-lying area of ground where the garbage collected from a city is dumped.
No building is constructed on the landfill site for at least the next 20 years (because it has loose ground). Most of the solid garbage from a city which cannot be disposed of by other methods is got rid of by dumping in landfills.
Incineration
In this method, the non-useful garbage is burned at a high temperature in a special kind of furnace called 'incinerator'. This reduces the large amount of garbage into a small amount of ash. This ash is then disposed of in a landfill.
Plastics – Boon or a Curse?
Plastic can be considered as a boon as numerous items used in our daily life, such as, plastic bags (polythene bags), water bottles, buckets, mugs, water tanks, water pipes, pens, combs, tooth-brushes, toys, shoes, tea strainers, cups, plates, chairs, tables, insulation of electric wires, covers of electric switches, plugs and sockets, parts of radio, television, refrigerator, cars, buses, trucks, scooters, trains and aeroplanes, etc., are made of plastic.
Plastics become a curse when we use the things made of plastics excessively but do not dispose of their wastes properly. This is because all types of plastics cannot be recycled (only some kinds of plastics can be recycled) and plastics do not rot (or decompose) when buried in soil. The articles made of plastics are non-biodegradable, so they cannot be disposed of easily. Even burning of plastics produces extremely harmful gases.
Harmful Effects of Plastics
(i) Plastics do not rot (or decompose) in nature on their own. So, the plastic bags (polythene bags) thrown away carelessly on roads and other places get into drains and sewers (sewers are underground dirty water pipes). These plastic bags block the drains and sewers causing the dirty drain water to spill on the roads. During heavy rains, the choked drains and sewers are not able to carry away all the rainwater quickly and hence a flood like situation is created in the city areas.
(ii) Some people fill household garbage in plastic bags and throw it away. When stray cattle look for food in this thrown garbage, they also eat up plastic bags alongwith the garbage food (such as fruit and vegetable peels, left-over cooked food, etc.). The eating of plastic bags harms the cattle. Sometimes the cattle even die because of eating plastic bags.
(iii) Sometimes the plastic bags which have been used earlier for storing poisonous substances and then thrown in garbage dumps are picked up by ragpickers, washed and sold to shopkeepers in the market. The use of such plastic bags for packing and storing cooked food materials can harm our health. For carrying and storing food products, we should use only new plastic bags or containers which are approved for such a use.
(iv) The burning of plastic waste materials gives out extremely harmful gases which can cause many health problems. The gases given out during the burning of plastics can even cause cancer disease in humans. We should, therefore, never dispose of plastic waste materials by burning.
Steps to Minimise the Overuse of Plastics
(i) We should reuse the plastic carry-bags for shopping purposes (whenever it is possible to do so without any adverse effects). This will minimise the number of plastic bags used by us.
(ii) We should carry our own cloth bag or jute bag when we go out for shopping. This will cut down on the number of plastic bags used.
(iii) We should use paper bags wherever possible to reduce the use of plastic bags.
(iv) We should reuse the plastic containers which come with jams, pickles, oils and other packed food materials for storing salt, spices, tea-leaves, and sugar, etc., in the kitchen.
(v) We should give away old plastic toys to others who can use them.
Steps to Reduce the Generation of Garbage
(i) We should dispose of our kitchen garbage by vermicomposting to obtain high quality manure for our plants. We should never put kitchen garbage in polythene bags and throw it away.
(ii) We should not throw plastic bags here and there after use. The plastic bags and other plastic containers should be reused wherever possible. We should, however, never bum plastic bags or other plastic items.
(iii) We should make full use of paper in our notebooks, etc., by writing on its both sides. We should use a slate to do rough work and hence save on paper.
(iv) Used newspapers, magazines, and notebooks, etc., should be sent for recycling.
(v) We should give old clothes and books to others who can use them.
(vi) We should use cloth handkerchief instead of paper tissues to save paper and reduce the generation of garbage.
(vii) We should choose and buy products with the least packaging.
(viii) We should use cloth bags, jute bags and paper bags for shopping instead of plastic bags to reduce the generation of plastic garbage.
(ix) We should recycle the old and useless objects made of glass and metals instead of throwing them away.
(x) We should recycle plastics wherever possible.
End of Notes
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