Earth is our home, which provides us with the necessary environment and space for living; but with the rapid development of social economy and the urban population of highly concentrated, the output of waste is gradually increasing, our home is surrounded by garbage from day to day. In densely populated cities, waste disposal is a vexing problem. Common practice is collected and sent to landfills, or use incinerators; but both would create environmental problems, and excessive consumption can further reduce termination landfills saturation level. Improper waste disposal in landfills can contaminate groundwater and odour, and many cities have been available for less and less landfill area. Produce poisonous gas, harmful organisms is inevitable forIncineration. Most of the cities are studying ways to reduce waste, and encourage recycling. Research Methodology
3.Collect the needed information.
The definition of waste
Waste is also known as rubbish, trash, refuse, garbage, junk and litter; which refer to unwanted or useless solid, fluid substance.
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Merriam-Websterdefineswaste is the trash from places of human or animal residence; The World Book Dictionary also say that waste is the useless or worthless material, stuff to be discarded. Unfortunately, these two definitions reflect a common attitude that does not admit waste as a resource.Nevertheless, Zero Waste America defines waste as “a resource that is not safely recycled back into the environment or the marketplace.” This definition considers the value of waste as a resource, as well as the threat of unsafe recycling could present to the environment and public health. The word ‘waste’ and the act of ‘wasting’ actually does not exist in nature, they are human inventions due to human behaviour.In nature, everything has a purpose. Waste was created by humans for short-term convenience and short-term profit.Meanwhile, this leads to long-term harmful consequences for humans, nature, and the economy.
Waste classification, recycling and processing
Waste classification means according to different composition, properties, use value of waste as well as the impact on the environment, andthe requirements of different disposal methods, divided into a number of different types of properties.Its purpose is to bring convenience for resource recovery and subsequent disposal. The meaning of the classification of waste
People are faced with the situation of the growing waste production and environmental deterioration. How to through the waste classification managementto maximize waste resource utilization, reduce the amount of garbage disposaland improve the living quality of the environment is currently the world’s pressing problems of common concern. Waste classification is the reform of the traditional way to garbage collection disposed; it is aneffectivescientific management methodfor waste disposal.Waste classification is put waste classificationat source, and through the classification of the pickup and recycled back into a resource. The benefit of waste classification is obvious. After being classification, waste was sent to a factory instead of landfills, not only save the land, but also avoids the pollution produced by landfill or burned. Waste classification
They are mainly five categories which include waste paper, plastic, glass, metal, and cloth. Waste Paper: mainly includes newspapers, periodicals, books, all kinds of wrapping paper and so on; But should pay attention to paper towels and toilet paper because of their water soluble is too strong, cannot be recycled. Plastic: plastic waste containers, plastic packaging and other plastic products. Such as various plastic bags, plastic bottles, foam, disposable plastic lunch boxes cutlery, hard plastic and so on. Glass: mainly includes all kinds of glass bottles, pieces of broken glass, mirror, light bulb debris, and thermos bottle, etc. Metal: mainly includes cans, cans and so on.
Fabric: mainly includes the abandoned clothes, tablecloths, towels, bags, shoes and so on. Kitchen waste
Kitchen waste is refers to catering units, enterprises, institutions, schools, canteens and other food scrapswaste, commonly known as swillor pigwash. The main component of kitchen waste are starch, food fibre, animal fats and other organic substances; it have a high moisture content, fat, high salt content, perishable smelly fermentation characteristics. Hazardous waste
Toxic and hazardous waste refers to the solids that could be harmful to human body health or toxic substances or cause real harm to the environment or potential hazards wastes. Including batteries, fluorescent tubes, light bulbs, mercury thermometers, paint bucket, home appliances, expired drugs, expired cosmetics. If the battery is burned, after the blast will be killing hundreds of people; Fluorescent tubes and bulbs are just like the battery, radiation is also large; Mercury is more dangerous, it is toxic substances. Therefore, the hazardous wastes take the way of landfilling. Other rubbish
Includingin addition to the above-mentioned categoriesgarbage, such as ceramictile, muck, toilet waste paper, paper towels and other difficult to recycle waste, usually based on the characteristics and take the way of burning or burying garbage processing.
Waste materials by kind, composition and sources.
GarbageWastes from preparation, cooking, and serving of food; market wastes; wastes from handling, storage, and sale of produce
Households, restaurants, institutions, stores, markets
Flammable: paper, cartons, boxes, barrels, wood, tree branches, yard trimmings, wood furniture, bedding, dunnage
Inflammable: metals, tin cans, metal furniture, dirt, glass, crockery, minerals AshesResidue from fires used for cooking and heating and from on-site burning Street refuseSweepings, dirt, leaves, catch basin dirt, contents of litter receptacles
Streets, sidewalks, alleys, vacant lots Dead animalsCats, dogs, horses, cows Abandoned vehiclesUnwanted cars and trucks left on public property Industrial wastesFood-processing wastes, boiler house cinders, lumber scraps, metal scraps. shavings Factories, power plants Demolition wastesLumber, pipes, brick, masonry, and other construction materials from razed buildings and other structuresDemolition sites to be used for new buildings, renewal projects, expressways Construction wastes Scrap lumber, pipe, other construction materialsNew construction, remodelling Special wastes Hazardous solids and liquids; explosives, pathological wastes, radioactive materialsHouseholds, hotels, hospitals, institutions, stores, industry Sewage treatment residueSolids from coarse screening and from grit chambers; septic tank sludgeSewage treatment
plants; septic tanks Waste recycling and processing
In the process of urbanization, the waste was once the burden of city development as the product of urban metabolism; many cities in the world have been besieged by garbage before. In now days, waste is considered to be the most potential, inexhaustible”urban mines” for development; it is the “misplaced resources”.Waste all have the corresponding recycling technology, make it can be used as “secondary sources” into the new production cycle, thus reducing resource consumption and environmental pollution.
This is not only the in-depth and deep understanding of the waste, but also is the inevitable requirement of urban development. General city garbage can be divided into the followinggroups: 1.Wet garbage (organic waste): processed into organic compound fertilizer and used for landscaping or agricultural fertilizer in organic waste processing factory. 2.Dry waste (inorganic waste): further refined classified as waste paper, waste plastic, glass, scrap metal and other recyclable componentsin the garbage sorting centre, and then recycling plant for recyclingby thecorresponding. 3.Hazardous waste: recyclable materialssent to recycling after sorting in the hazardous waste sorting disposal station and the residue are safely landfill or incineration. Currently, there are several ways of waste disposal:
1.Landfill Method: Fill trash in the pit that has been ready for, make it automaticallyhappen biological, physical and chemical changes, decomposition of organic matter, to achieve reduction and harmless purposes; but for a long time, most cities are carried out with open dumps and natural filling ditch without any protection. This leads to a lot of rubbish sewage from the surface into the ground and cause serious pollution of groundwater sources and the urban environment. Therefore this waste disposal method has gradually been eliminated. 2.Incineration method: incineration method is to put thegarbage into high temperature furnace; make one full oxidation of combustible ingredients; the heat that generated can be used for power generation and heating.The biggest shortcoming of this method is generatedof dioxin gas during the incineration; thereforefor achieving environmental protection, Therefore only on the incineration of toxic and harmful gases through a series of processing,this method can realize environmental protection.
3.Composting Method: piles of garbage accumulation, heat up to 70 ℃, storage, fermentation, with the ability of microbial decomposition in garbage, to decompose organic matter into inorganic nutrients.After composting treatment, garbage becomes hygienic, odourless humus. Not only way to solve the garbage, but also to achieve the purpose of the resource; but the large amount of solid waste composting, nutrient content is low, long-term use could easily lead to soil compaction and deterioration of groundwater quality, so the scale is not easy to compost too. 4.Treatment resources: Careful classification of urban living garbage, Then according to the different nature of classified garbage after respectively adopt appropriate methods to deal with, make all the different types of waste can be utilized, thus to be truly achievereduction, harmless and resource of waste. Waste power generation
From the 1970s onwards, some developed countries have started to use the heat generated by burning garbage to generate electricity. Some country in Europe built a garbage power plant, a U.S. garbage power plant generating capacity up to 100 MW, processing 600 thousand tons of garbage per day. Now, garbage power plant in Germany is spendinga huge sum of money from abroad to buy rubbish every year. According to statistics, currently there are nearly a thousand types of waste disposal plant; all kinds of garbage utilization facility will be increased to 3000 or more in three years. Scientists measure that the garbage in the secondary energy, such as organic fuelcontains high calorific value, the heat of burning 2 tons of wasteequivalent to about 1 tons of coal. Confrontingproblem
The reason that why waste power generation is developing slowly Is mainly due to some technical problems or process constraints; Such as generating toxic gas during the combustionpower generation, which cannot be effectively solve for a long time. Japan has been promoting a super waste power generation technology, by using new gas furnace; rose the furnace temperature to 500 ℃, increase the power generation efficiency from 10% in the pastto around 25%, reduced toxic emissions to less than 0.5%, below the international standard; But, of course, the cost of waste power generation is still higher than the traditional thermal power.Some experts believe that withthe technology development inwaste collection, handling, transport, utilization and other aspects, waste power generation is likely to become one of the most economical power generation technologies. From the long-term benefits and the comprehensive index, it will be superior to the traditional electric power production.