China attaches great importance to the disposal and utilization of solid waste, and has issued relevant laws and regulations one after another, witnessing rapid development of the industry of collaborative disposal and utilization of solid waste by various industries.

Annual Report on Prevention and Control of Environmental Pollution by Solid Waste in Large and Medium-sized Cities in China in 2020 shows that in 2019, the output of general industrial solid waste in China’s 196 large and medium-sized cities was 1.38 billion tons, in industrial hazardous waste 44.989 million tons, and in urban domestic waste 235.602 million tons, adding greater pressure on disposal and utilization of solid waste. The CPC Central Committee and the State Council attach great importance to the prevention, treatment and utilization of solid wastes to pollute the environment. With the implementation of “Law of the People's Republic of China on the Prevention and Control of Solid Waste Pollution”, “National Catalogue of Hazardous Wastes”, both of which were revised in 2020, and the promotion of the pilot construction of a "waste-free city", the industry of coordinated treatment and utilization of solid wastes by various industries is developing rapidly, and a new development pattern with many ways and high added value is being formed.

1 Collaborative Disposal and Utilization in Cement Industry

The technology of collaborative disposal of solid wastes in cement kilns uses the unique high-temperature environment and alkaline atmosphere of cement kilns, which can effectively prevent the harmful substances in incineration wastes from dissolving out, neutralize hydrogen fluoride, hydrogen chloride and sulfur dioxide, and avoid the re-synthesis of dioxins and furans. It uses solid wastes to replace some raw materials or fuels, so that cement production enterprises can save raw material demand, reduce energy consumption, and completely realize resource utilization. At the same time, the carbon dioxide released by decomposition of calcium carbonate is reduced, and the waste landfill is greatly saved, which meets the requirements of energy saving, consumption reduction and emission reduction, featuring obvious economic and environmental benefits. At present, the solid wastes for cooperative disposal and utilization in China's cement industry mainly include domestic garbage, hazardous wastes, sludge, etc. The main types of disposal and utilization are alternative raw materials, alternative fuels and waste disposal.

2 Collaborative Disposal and Utilization in Concrete Industry

At present, more than 80% of the materials used in buildings, roads, pipelines, bridges, high-speed railways, subways, airports, etc. are concrete. The concrete industry should mainly utilize solid waste from three aspects: aggregate, admixture and cement containing about 30% of industrial solid waste. Take ready-mixed concrete as an example, every 1m³ of ready-mixed concrete weighs about 2400kg, most of which contains about 500kg of construction waste and about 80kg of fly ash.

Currently waste glass, waste rubber powder, steel slag, part of tailings, slag, incineration ash, waste rock and so on have been proved to be applicable to concrete. China produces about 10.4 million tons of waste glass every year, accounting for about 5% of the total solid waste.

In the future, relevant departments will intensify research efforts, formulate technical documents such as relevant standards for preparing concrete from solid wastes to guide and standardize the application of solid wastes in the concrete industry, and constantly explore solid waste concrete materials with wider application types of solid wastes, excellent product performance and appropriate price.

3 Collaborative Disposal And Utilization In Ceramsite Industry

The main components of ceramsite raw materials are silica and alumina, and the main components of some solid wastes such as fly ash and sludge with small particle size are compatible with them. When used as ceramsite raw materials, the crushing and grinding cost can be greatly reduced, and at the same time, it can be absorbed to obtain considerable economic and social benefits.

In recent years, the development trend of China’s ceramsite raw materials is as follows. The proportion of solid waste ceramsite in ceramsite raw materials has increased significantly, among which the market share of construction waste soil ceramsite and sludge ceramsite has increased significantly. In addition, some enterprises began to try to add organic matter such as crop straw and rice husk bran to make ceramsite, which not only reduced energy consumption and cost, but also absorbed agricultural wastes. At the same time, there are only a few ceramsite enterprises using single clay as raw material. Although shale ceramsite has been developed, the addition of construction waste soil ceramsite and sludge ceramsite has reduced the proportion of shale ceramsite production in China, and the performance limitation of fly ash ceramsite has led to the reduction of its production, while coal gangue ceramsite has begun to emerge.

In the future, the raw material structure of ceramsite will be more inclined to solid waste, and sludge ceramsite, coal gangue ceramsite, tailings and waste rock ceramsite will gradually become mainstream products. Production lines and equipment with accurate design, high production efficiency, environmental friendliness, low energy consumption and diversified products will be gradually built, put into operation and used; The driving force of the policy should be to strengthen the quality inspection of ceramsite products and rationally optimize the market dispatch, and encourage and support the use of ceramsite in different industries.

4 Collaborative Disposal and Utilization in Iron and Steel Industry

China's steel industry covers major processes such as coking, sintering (pelletizing), blast furnace, converter, etc., which is characterized by long process and large amount of solid wastes and pollutants. In 2018, China's crude steel output accounted for 53.3% of the world's total, reaching 996.3 million tons, which means that about half of the steel products, by-products and solid wastes of global steel enterprises were produced in China. Following the concept of clean production and green development, China's iron and steel enterprises, by combining the solid wastes generated in the enterprises with raw materials, and burning and pyrolyzing the solid wastes in their own smelting furnaces, realized the "solid wastes do not leave the factory" and the reduction, harmlessness and resource utilization of solid wastes.

5 Conclusion and Prospect

As a typical problem, pollution and waste of resources caused by solid wastes have attracted great attention from all walks of life. At present, cement, concrete, ceramsite, steel and other industries have been widely studied and applied in the cooperative disposal and utilization of various solid wastes with their own characteristics of equipment, technology and materials. However, various industries may face some problems, such as lack of top-level design such as construction planning and incentive policies for collaborative disposal and utilization of solid wastes, lack of technical documents such as relevant standards for collaborative disposal and utilization of solid wastes in different industries, influence of the addition of solid wastes on the output and quality of equipment and products, uncertain environmental risks of products, market share of products made of solid wastes to be improved, etc. In the future, it is necessary to improve the relevant laws, regulations, policies and standards for the cooperative disposal and utilization of solid wastes by various industries to standardize, guide and encourage enterprises to carry out the cooperative disposal and utilization of solid wastes; Intensify research efforts to improve the quality of products prepared by solid waste, reduce the preparation cost of products and increase the market share of products; Carry out pilot demonstration of collaborative disposal and utilization of solid waste in various industries and gradually promote it.