The reuse and recycling of solid wastes can also serve as a means for conservation of energy. In the light of this, let use see, what are the principles guiding the management of solid wastes. Recognizing that our resources are finite and continued pollution will be difficult to rectify in coming times, the management of solid wastes has become important.
Before disposal, a waste should be considered for the following possibilities:
- Reduction in raw materials and solid waste quantities
- Reuse of waste materials
- Materials recovery
- Energy recovery
i) Reduction in Raw Materials and solid Waste
Solid wastes are generated at the start of the process beginning with the mining of raw material. Thereafter, solid wastes are generated at every step in the process of conversion of goods into products. The products are then used by the consumer whence again wastes are generated. Clearly if a reduction in the usage of raw materials is to occur the quantity of waste must be curtailed. This can be achieved by
(a) Reducing the amount of materials used in the manufacture of a product,
(b) Increasing the life of the product, and
(c) Reducing the amount of materials used for packing the consumer goods.
ii) Reuse of Waste Materials
Reuse of waste materials now occurs most commonly in those situations where a product has utility in more than one application. For example, the paper bags used to bring home groceries are used to store household wastes prior to placing them in containers used for storage for collection. Soup and vegetable containers are used to store cooking medium, like ghee or oil.
Newspapers are used to start fires in fireplaces; they are also tightly rolled and used as logs for burning. While all the above reuses are important, their impact on generation of solid wastes is minimal. A much larger impact would occur if this habit is encouraged on a large-scale, in urban and town communities.
iii) Material Recovery and Recycling
A number of materials present in municipal and industrial waste are suitable for recovery and recycling about 10-15 percent of solid waste are recoverable. Most suitable candidates are the wastes generated by paper, cardboard, glass, ferrous metals, metals (mostly aluminum) and rubber. On the country, plastics, leather, textile and food wastes are unsuitable candidates for materials recovery. This is why; it is advisable to save on the number of polyethylene packets, when purchasing consumer goods.
Fly ash, which is a dust like by-product of the thermal powder plants, is produced in huge quantities. Over 22mt of fly ash from thermal power sector was available for utilization in 1985-86. It appears that the fly ash can be compressed into bricks as such or in combination with cement etc., that can be used for building houses.
iv) Energy Recovery
Alter segregation of wastes in the above-mentioned categories, the remainder is considered for the recovery of heat by burning (incineration). Because about 70 percent of the components that comprise solid waste are organic, the potential for recovery of heat energy is high. The energy content in the waste matter is converted to a form that can be used more easily. The remainder (ash) is also more compact and weighs less, occupying a smaller volume.
A wide variety of waste construction materials, municipal sewage and industrial by-products, forestry waste and urban waste (like rags, plastic bags, newspapers, etc.) are generated by modern human activities. Such wastes can be used for incineration to recover their heat energy. For instance, about 10 percent biomass produced in paddy fields forms rice grain, the remaining 90 percent is usually burnt but can be put to good use. If burnt in skillfully managed incinerators, paddy straw turns out to be far cheaper (about one third) than local as fuel for power generation. It has substantial energy value ranging from 3,200 to 3,500 kcal/kg. The availability of paddy straw is also good. In Punjab alone, bout 5 Mt paddy straw is available. In remote areas, for power generation through small and medium units, the bulk of power needs of the farm sector can be easily met by using paddy straw.
Conservation of Physical Resources
Man is integral part of the biosphere and therefore, is totally dependent on its recourses. His future and even his survival, depends upon the rational use and conservation of the resources available to him.
If the environment is to continue to sustain life, it must be protected from the consequences of our own actions. Breathable air, clean water, fertile soil, and innumerable life forms, are all important resources that are vital to our own survival. This is particularly important because physical resources are limited.