China's urban garbage disposal started very late, in the 1980s. Before that, garbage was piled up in the open.
According to information from the Municipal Domestic Waste Disposal Committee of the China Environmental Protection Industry Association (CEPIA), China's municipal waste disposal rate was less than 2 percent before 1990. It was only after entering the 1990s that China's urban garbage disposal improved continuously. in 1999, China's municipal cities were 668, *** there were 696 garbage treatment plants (fields), including less than 200 harmless treatment plants, the garbage disposal rate was 63.4%, and the harmless treatment rate was only 20.3%.
Currently, there are more than 700 harmless treatment sites for domestic waste alone in Chinese cities, and the national rate of harmless treatment of urban domestic waste is 52%.
Waste disposal in Chinese cities first goes through collection. At present, China's urban garbage collection method is basically mixed collection, although the Chinese government advocated separate collection in 2002, but the separate collection of garbage currently accounts for only 16%.
There are three main ways of mixed collection, one of which is to place collection containers in fixed locations, such as residential neighborhoods, on both sides of the street, and in other public **** places. Specialized sanitation personnel are responsible for collecting garbage from these containers every day. Second, there are fixed garbage collection stations in residential neighborhoods where residents can throw their household garbage to the garbage station every day. Thirdly, there are garbage lanes. In high-rise residential buildings in China, the garbage lanes are already designed when the building is constructed, from the first floor all the way to the top floor, so that residents can throw their garbage into the garbage lanes and the sanitation staff will take it away from the bottom floor. Collecting residents' garbage through garbage tunnels used to be the most common way of collecting garbage in residential areas. However, after the SARS outbreak in 2003, it was banned in many cities because it was conducive to the spread of bacteria. Cities such as Beijing, Guangzhou, and Shanghai have mandated that new residential buildings do not have garbage lanes, and some cities have also closed garbage lanes in already-built residential buildings and stopped using them.
The collected garbage is transported to the garbage transfer station by special garbage trucks. The garbage trucks are completely sealed. After the garbage is transported to the transfer station it undergoes the first step of processing. It is first classified by a sorting machine into organic and inorganic materials, as well as utilizable and non-utilizable. Bulky waste is also compressed. After that, the waste is sorted and transported away.
From the transfer station, some of the garbage is transported to sanitary landfills, where the garbage is filled into pits that have been prepared, covered and compacted, so that it undergoes biological, physical, and chemical changes to decompose organic matter, and to achieve the purpose of reduction and harmlessness. Special pipes and impermeable layers are laid in these pits to collect the gas and leachate produced by the fermentation of the waste. The gas is combusted, part of the leachate is purified and processed into water, which is used to clean garbage trucks and ground dust, and part of the leachate is filtered to meet the national level standards before being discharged, so that it does not pollute the environment.
Others are transported to a composting plant, where they are composted and turned into hygienic, odorless humus, which is used as fertilizer for plants.
Another portion is sent to incinerators for burning to fully oxidize the combustible components of the garbage, and the heat generated is used to generate electricity and heating. There are currently 140 waste-to-energy power plants built, under construction and in the process of being approved in China. One ton of garbage can generate 300 degrees of electricity, and the waste heat can also be used for heating. The Tianjin Shuanggang garbage power plant, which handles 1,200 tons of garbage a day, generates 120 million degrees of electricity a year for 50,000 households, which is equivalent to saving 48,000 tons of standard coal.
For recyclable garbage, it will be recycled and reused.
In the process of dealing with garbage, China has formulated a number of relevant standards, such as the standards for controlling agricultural use of urban garbage, the standards for harmless sanitation of feces, and the standards for emission of incineration exhaust gas.
Among the current methods of garbage treatment, incineration is slower to develop in China, mainly because of the lack of funds. The initial investment in incineration is large, the construction of a 1000-ton daily waste incinerator and ancillary heat recovery equipment, about 700-800 million yuan. Moreover, because incineration produces dioxin gases when treating waste, many cities do not use incineration much except for the need to treat medical waste. Many cities are more likely to use sanitary landfills, a method that environmental officials say is better suited to China's national conditions.
According to the China Environmental Protection Industry Association's Municipal Waste Disposal Committee, 70% of China's municipal waste is disposed of in landfills, 20% is composted, 5% is incinerated, and the rest (including open piles and recycling) accounts for 5%.