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What are the Types of Solid Waste Disposal and Management?
‘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 :
- Reuse, and
We will now describe all these methods of getting rid of garbage in detail, one by one. Let us start with composting.
The rotted plant and animal waste (including that from kitchen) used as a manure for growing plants is called compost. And the process of converting plant and annual waste materials into manure by rotting is called composting. The biodegradable domestic garbage such as fruit and vegetable peels, left-over food and fallen leaves can be disposed of by converting it into compost which is used as a manure (or fertiliser) for growing plants. Compost is a natural fertiliser. Compost contains nutrients required for the growth of plants. So, when compost is mixed with the soil in which plants are grown, it provides nutrients to the plants. A simple method to make compost is described below.
Dig a pit in the ground about 30 centimetres deep in such as fruit and vegetable peels, left-over cooked food and fallen leaves into the pit on daily basis. The animal wastes like cow dung may also be added to the pit (see Figure). When the pit gets filled to the top with plant and animal wastes, 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. Please note that we should not dump plastics, glass pieces or metal objects in the compost pit because these are non-biodegradable waste materials which cannot be converted into compost by the micro-organisms present in soil.
Many times we see heaps of garbage consisting of dry leaves on the roadside. Most of the time these dry leaves are disposed of by burning. Farmers also often burn the agricultural wastes such as husk, dry leaves and residues of crop plants in their fields after harvesting. Burning of dry leaves (and other agricultural wastes) produces smoke and harmful gases which can damage our health. The leaves (and agricultural wastes) should never be burnt. The fallen leaves and other agricultural wastes can be converted into useful compost. Before we go further and describe vermicomposting, we should know something about redworms.
Redworms are a kind of earthworms (see Figure). The redworms have a remarkable ability to convert plant matter such as fruit and vegetable peels, left-over cooked food and green leaves, etc., into a very high quality manure called vermicompost. Thus, the very high quality compost made by redworms is called vermicompost (vermicompost means compost made by worms).
Vermicomposting is different from traditional composting because in traditional composting the kitchen waste is converted into compost by micro-organisms (such as bacteria and fungi) present in the soil but in vermicomposting, the kitchen waste is converted into vermicompost by redworms. Vermicompost is a much better manure than ordinary com-post for growing plants. We will now discuss vermicomposting in detail.
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. We can prepare vermicompost by digging a pit in the ground or by using a wooden box or a metal bin. Vermicompost can be made at home or in school as follows.
(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 cowdung 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. This vermicompost can be used as an excellent manure in the pots (having plants), garden or fields. The redworms left in the pit can be used for preparing more vermicompost or given to another person for this purpose.
Please note that only the garbage containing plant and animal wastes can be converted into vermicompost by redworms (because redworms can eat up these materials). The garbage containing plastics, glass and metal objects cannot be converted into compost by redworms. This is because redworms cannot eat plastics, glass or metal objects. We should not put the kitchen wastes containing salt, pickles, oil, vinegar, milk and meat preparations as food for the redworms in the compost pit. This is because if we put these things in the pit, then disease-causing micro-organisms will start growing in the pit.
If we are given the choice of eating food in a plastic plate or a banana leaf platter at a party then we should prefer the banana leaf platter. This is because banana leaf platter is a plant material which can be later on disposed of safely by turning it into compost (or vermicompost). On the other hand, plastic plates being non-biodegradable cannot be disposed of safely when they turn old and useless. The advantages of vermicomposting are that it helps us to dispose of kitchen garbage in a proper way and at the same time gives us a very high quality manure called ‘vermicompost’. Vermicomposting is the best way to turn kitchen garbage into compost (or manure).
It is much better to use compost (or vermicompost) as manure instead of chemical fertilisers because :
(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.
The household wastes like paper, some plastics, glass and metal objects present in the garbage are recycled. 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.
The broken and discarded plastic articles such as plastic bags, buckets, mugs, cups, plates and toys, etc., are sent to plastic processing factories where they are melted and remoulded to make new articles (All the plastics, however, cannot be recycled). The useless glass objects are sent to glass industries where they are reprocessed to make new glass objects. Similarly, waste metal articles of iron and aluminium, etc., are sent to metal industries where they are melted and recycled as fresh metal for various purposes.
In order to recycle used and discarded materials, we should first separate our household garbage properly so that the waste materials which can be recycled do not get dumped alongwith other household garbage which is to be thrown away. We do not take the wastes like used paper, plastic, glass or metal objects to the various industries ourselves for recycling. We sell these wastes to the junk dealer (kabadiwala) who visits our colony periodically. It is the junk dealer who collects wastes from all the houses in an area, loads them into trucks and sends them to the respective industries for recycling.
For example, we have all seen our parents selling old newspapers, magazines, used books and notebooks, plastic bottles, glass containers and metal articles to the junk dealer. The junk dealer then sends all these waste items for recycling. We will now describe an activity to demonstrate the recycling of paper. In this activity, we will make new paper from the old, used and discarded papers in our house.
Activity For Recycling Of Paper
(i) We take some old newspapers, magazines, used envelopes and notebooks or any other waste paper (which does not have a plastic coating on it). Tear the waste papers into small pieces and put them in a tub. 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.
(ii) 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. A sheet of old cloth or a newspaper can also be used to soak up extra water present in the layer of paper paste.
(iii) 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. Since we have done the recycling of paper by our hands (without using any machine), it is called hand-made paper.
In order to obtain coloured paper, we should add a food colour to the paste of paper before spreading it on wire-mesh. Please note that the recycled paper made by us is quite thick and coarse (rough). It is not as thin and smooth as the machine-made paper recycled by paper mills. Another point to be noted is that we cannot recycle everything present in the household garbage. For example, some types of plastics cannot be recycled.
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 later on 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. A diary can be made from old invitation cards; mats can be made from old clothes; and baskets from used and old polythene bags. The waste items which can be reused are, however, very limited.
The non-useful part of garbage which cannot be turned into compost, recycled or reused is disposed of in a landfill. Landfill is a low-lying area of ground where the garbage collected from a city is dumped (see Figure).
The part of garbage which cannot be disposed of by other methods is loaded in trucks and dumped in the low-lying open area (called landfill) inside or outside the city. This garbage is spread over the landfill and covered with a layer of soil to level the uneven ground. A big landfill site can be used to dispose of garbage (or waste materials) for a considerable time. Once a landfill is completely filled, it is usually converted into a park or a playground. 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.
In addition to all the methods of garbage disposal described above, there is a yet another method called ‘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. We will discuss this method in detail in higher classes.