Domestic waste is a by-product of human life, with the rapid development of economy and high concentration of urban population, yield of domestic waste gradually becomes more and more. Generally, domestic waste can be divided into five categories: waste paper, plastic, glass, metal, biological waste.

1) Large land occupation. Waste placed on the outskirts of the city has invaded a large amount of farmland. Waste also stays in nature world for a long time: cigarette butts and wool fabric stay for 1-5 years; orange peel stays for 2 years; painted wooden boards stay for 13 years; nylon textile stay for 30-40 years; leather stays for 50 years; cans stay for 100-200 years; glass stays for 1000 years. Therefore, we should not only make less waste, but also pay attention to the classification, recycling and turning waste into treasure. Use less disposable chopsticks, cup, lunch box and other products, use reusable products to reduce consumption of forest resource; Use shopping cloth bags instead of plastic bags to reduce harm of city “white pollution”; Buy fluorine-free refrigerators, air conditioners and other environmental protection appliances to protect the ozone layer in the atmosphere; Use phosphorous free washing powder instead of high concentration detergent to reduce water pollution.

2) Air pollution. Waste is a complex mixture. During transportation open-air stacking, decomposition of organic matter produces malodorous gas, and release a lot of ammonia, sulfide and other pollutants into atmosphere. Among them, 100 kinds of volatile gas are involved. These releases contain many carcinogenic and teratogenic substances. Plastic film, paper and dust fly in the wind, causing "white pollution."

3) Water pollution. Harmful ingredients in waste are washed into surface water by rain, a large number of acidic and alkaline organic pollutants will be generated in the course of waste stacking or filling, at the same time, heavy metal will be dissolved out. Percolate produced by waste pollution source will flow into groundwater; Directly throwing waste into rivers, lakes and oceans will lead to more serious pollution.

4) Soil residualization. Waste is applied directly to farmland as fertilizer or applied to farmland by simple processing, these will damage aggregate structure of soil, Physical and chemical properties and water retention,protecting fertilizer ability. Especially plastic bags and plastic film, if they are filled into farmland, roots of crops will not grow, farmland will be less productive, there will be less food for people to eat.

5) Fire hazards. Waste contains a lot of combustible, methane can be produced in natural stacking process, which may cause fires when exposed to fire or spontaneous combustion. With the increase of organic matter content in waste and the change from open-air dispersion to centralized storage, the use of simple cover in long-term storage causes the harm of garbage to produce biogas, and the explosion accidents continue to occur, causing major losses. 

6) Nests of pests. waste not only contains pathogenic microorganisms, but also provides food, habitat and reproduction for rats, birds and mosquitoes. It is also the source of infectious diseases.