What is the significance of solid waste disposal?

Solid waste treatment usually refers to the physical, chemical, biological, physical and biochemical methods to transform solid waste into a process suitable for transportation, storage, utilization or disposal, the goal of solid waste treatment is harmless, reduction, resource. Some people believe that solid waste is one of the most difficult to dispose of the "three wastes", because it contains a complex composition, its physical properties (volume, mobility, uniformity, degree of comminution, moisture, calorific value, etc.) are also very variable, to achieve the above "harmless, reduction, resource "goal will encounter considerable trouble, the general prevention of solid waste pollution methods first of all to control its generation, for example, gradually reform the urban fuel structure (including civil industry) to control the consumption of raw materials in factories, quotas to improve the service life of products, improve the recycling rate of waste products, etc.; second is to carry out comprehensive utilization, solid waste as a resource and energy treatment, really can not be The use of the end-state solid waste after compression and non-toxic treatment, and then landfill and sink the sea, the main methods used include compaction, crushing, sorting, curing, incineration, biological treatment, etc.

 

Main characteristics

From the analysis of the relationship between solid waste and the environment, resources and society, solid waste has polluting, resource and social characteristics.

(1) Pollution

The polluting nature of solid waste is manifested as the polluting nature of solid waste itself and the secondary polluting nature of the solid waste treatment. Solid waste may contain toxic, combustible, explosive, radioactive, corrosive, reactive, infectious and pathogenic harmful waste or pollutants, and even contain pollutant-enriched organisms, some substances are difficult to degrade or difficult to deal with, the quantity and quality of solid waste emissions are uncertain and hidden, and the solid waste treatment process generates secondary pollutants, these factors lead to solid waste in its generation These factors lead to the pollution of solid waste in the process of generation, emission and treatment, which is harmful to the perspective and ecological environment, and even to physical and mental health, which shows that solid waste is polluting.

(2) Resourcefulness

The resource nature of solid waste shows that solid waste is the product of resource development and utilization and solid waste itself has certain resource value. Solid waste only becomes solid waste under certain conditions, and when the conditions change, solid waste may regain its use value and become raw materials, fuel or consumer goods for production, thus having certain resource value and economic value.

It should be noted that the economic value of solid waste is not necessarily greater than the cost of solid waste disposal, and in general, solid waste is a kind of low-quality, low-economic value resource.

(3) Sociality

The social nature of solid waste shows that solid waste generation, emission and disposal have a wide range of social nature. First, every member of society produces and discharges solid waste; second, the production of solid waste means the consumption of social resources and has an impact on society; third, the discharge, treatment and disposal of solid waste and the polluting nature of solid waste affect the interests of others, that is, there is an externality (externality means that the activities of the subject of activity affect the interests of others. When the interests of others are harmed, it becomes a negative externality, and when the interests of others are increased, it is called a positive externality. Solid waste discharge and its polluting nature have a negative externality, solid waste treatment and disposal have a positive externality), resulting in social impact, which means that whether generated, discharged or disposed of, solid waste matters affect the interests of each member of society. Solid waste is a private good before discharge and becomes a public resource after discharge.

 

Classification

Solid waste is usually classified into municipal domestic solid waste, industrial solid waste and agricultural waste according to the source of solid waste.

Municipal domestic solid waste mainly refers to solid waste generated in or for the activities that provide services for daily urban life, i.e., municipal domestic waste, which mainly includes residential domestic waste, hospital waste, commercial waste, and construction waste (also known as sludge). Generally speaking, the daily incremental garbage amount of each person in the city is 1-2 kg, and its amount and composition are related to the material living standard of residents, their habits, the degree of recycling of waste materials and the situation of municipal buildings. For example, domestic garbage is mainly kitchen garbage. For some municipal domestic solid waste, the annual output is very impressive. In the mid-18th century, only 3% of the world's population lived in cities; by 1950, the proportion of urban population accounted for 29%; in 1985, the figure rose to 41%. It is projected that by 2025,  60% of the world's population will live in or around cities. With so many people living or about to live in cities, which are areas of high concentration and greatly artificialized environments, pollution from urban waste is extremely prominent. In general, the higher the level of urban living, the more waste is generated. In large cities of low-income countries, such as Kolkata, Karachi and Jakarta, 0.5-0.8 kg per person per day is generated; in large cities of industrialized countries, the waste generated per person per day is usually about 1 kg.

 

Industrial solid wastes are solid wastes such as mining waste rock, ore dressing tailings, fuel waste slag, chemical production and smelting waste slag generated in industrial and transportation production activities, also known as industrial waste slag or industrial waste, including industrial waste slag, waste chips, sludge, tailings and other wastes. Industrial solid waste according to its source and physical properties can be broadly divided into six categories. And according the toxicity of slag can be divided into two categories of toxic and non-toxic slag, where fluorine, mercury, arsenic, chromium, lead, cyanide and other compounds and phenols, radioactive substances are toxic slag.

 

Agricultural solid waste, also known as agricultural waste, refers to solid waste generated from agricultural production activities (including scientific research), including waste generated from five agricultural industries: plantation, forestry, animal husbandry, fishery and secondary industries.

 

A brief history of development

Solid waste disposal and utilization have a long history. As early as 3000~1000 BC, during the Minoan civilization in ancient Greece, the capital of Crete, Nessus, had the disposal of garbage mulch buried in a large pit. But most ancient cities were discarded arbitrarily, year after year, solid waste, and even make the city buried, and some cities were later rebuilt on the ruins. The present site of the British city of Bath is 4-7 meters higher than its original site in the ancient Roman period.

In order to protect the environment, some cities in ancient times enacted ordinances to manage garbage in ancient Rome, a sign on the platform says "garbage must be dumped far away, offenders are fined". 1384 Britain issued an ordinance prohibiting the dumping of garbage into the river. In 1874, the world's first incinerator was built in England, and after the incineration of garbage, the remaining ashes were landfilled. 1875, England promulgated the Public Health Act, which stipulates that local governments are responsible for centralized garbage disposal. The earliest disposal methods are mainly landfill or incineration.

China, India and other Asian countries have been using manure and using waste composting as disposal methods since ancient times.

After the 20th century, with the development of productivity, the population further concentrated in cities (80% of the population in the United States 100 years ago in rural areas, now 80% of the population in cities), consumption levels increased rapidly, and the amount of solid waste discharged increased sharply, becoming a serious environmental problem. Since the 1970s, the United States, the United Kingdom, the Federal Republic of Germany, France, Japan and other countries have put forward the concept of "resource recycling" due to the tight waste disposal sites and the huge disposal costs, as well as the lack of resources. In order to strengthen the management of solid waste, many countries have set up special management organs and scientific research institutions to study the sources, nature, characteristics and environmental hazards of solid waste, the disposal of solid waste, recycling, utilization of technology and management measures, as well as the development of various regulations and environmental standards, and the publication of relevant books and journals. The treatment and utilization of solid waste have gradually become an important part of environmental engineering.

 

Development trend

In order to protect the environment and develop production, many countries are constantly adopting new measures and technologies to treat and utilize solid wastes. Mining waste has evolved from being deposited in low-lying areas to mine land rehabilitation and safe damming. Industrial waste has evolved from passive stockpiling to comprehensive utilization. Municipal waste has developed from manual collection and transportation to mechanized, automated and piped collection and transportation; from uncontrolled landfills to sanitary landfills and filter leachate recycling landfills; from open-air incineration and use of incinerators to incineration for energy recovery, medium and high-temperature decomposition, etc., and from compression molding to high-pressure compression molding. Municipal organic waste and agricultural organic waste is also used to make biogas to recover energy. Industrial hazardous residues have evolved from segregated stockpiles to chemical fixation and chemical transformation to prevent pollution. The general trend is to move from passive disposal to active utilization and re-resourcing of waste.

Sorting and recycling municipal waste. According to the chemical and physical properties of waste, such as specific gravity, electromagnetism, color, resilience, combustibility, etc., sorting, and then dry, water slurry machine method, high or medium temperature decomposition and other methods to recover metals, glass, paper raw materials, plastics and other materials, as well as the recovery of heat and combustible gas.

For industrial waste residues, most of them are used as resources for comprehensive utilization. The United States since the 1970s has been discharged annually more than 40 million tons of steel slag and blast furnace slag use up. Britain, France, Sweden, Belgium, the Federal Republic of Germany, etc. blast furnace slag also in the year all get utilized. China, the Soviet Union blast furnace slag utilization rate of more than 70%, Japan is 85%. Japan, Denmark, and other countries have all the utilization of fly ash, the utilization rate of the United States is 20%, China is 10%.

 

Solid waste resource approach

1, waste recycling: including classification and collection, sorting and recycling.

2, waste conversion utilization: that is, through certain technologies, the use of certain components of waste to produce new forms of substances. Such as the use of waste microbial decomposition to produce compostable organic matter to produce fertilizer; cracking of carved plastic to produce gasoline or diesel, etc.

3, waste to energy: that is, through chemical or biological conversion, the release of energy contained in the waste, and to be recycled. Such as waste incineration and power generation or landfill gas power generation, etc.

Clean production

A practical production method and technology that uses natural resources rationally, improves the utilization of materials and energy, reduces and eliminates the generation and emission of waste, and protects the environment. Four levels of meaning.

① The goal of cleaner production is to save energy, reduce the consumption of raw materials, and reduce the number of pollutants generated and emitted.

②The basic means of cleaner production are to improve process technology, strengthen enterprise management, maximize the level of resource and energy utilization and change the product system, update the design concept, strive for the least emission of waste, and inclusion of environmental factors in the service.

③The method of cleaner production is emission audit, through which emission parts and causes are discovered, measures to eliminate or reduce pollutants are screened and product life cycle analysis is conducted.

④The ultimate goal of cleaner production is to protect human beings and the environment and to improve the economic efficiency of enterprises.

4,Cyclic Economy

Circular economy takes the maximization of resource utilization and minimization of pollution emission as the mainline, integrates clean production, comprehensive utilization of resources, ecological design, and sustainable consumption, and uses the law of ecology to organize economic activities into a feedback process of "resource-product-regenerated resource", so as to realize "low exploitation, high utilization, and low emission". It is an economic development model that "promotes the coordination and harmony between human and nature".