Solid waste is not useless waste, but useful resources and valuable wealth. The ultimate way out for solid waste treatment lies in "waste recycling", which has become a fundamental policy in waste management systems in countries around the world. Solid waste resource utilization can not only create social benefits, make the best use of resources, and achieve certain economic benefits, but also effectively protect the environment.

Solid waste, if properly treated, has the following uses:

1. The use of crushed materials as building foundation cushion or road base is the simplest and most commonly used method of recycling;

2. Produce brick products such as concrete block bricks, paving bricks, and recycled permeable bricks after crushing;

3. Replacing some natural sand and gravel aggregates to produce recycled aggregate concrete - this is the most valuable treatment method for waste concrete, and recycled concrete made from recycled aggregates belongs to green concrete.

01. Overview of Solid Waste in China

Construction waste

Construction waste refers to the solid waste generated in the process of demolition, construction and decoration of buildings, including muck, concrete blocks, crushed stones, brick fragments, waste mortar, slurry, asphalt blocks, waste plastics, scrap metal, waste bamboo and wood, etc.

Handling the current situation

At present, the vast majority of construction waste is transported by construction units to the suburbs or rural areas without any treatment, and is stored or buried in the open air, consuming a large amount of construction funds such as land acquisition fees and garbage removal fees. At the same time, the scattering and flying dust and sand during the cleaning and stacking process have caused serious environmental pollution. The fine powder and soluble phenolic alkali components of waste concrete diffuse underground through wind and rain, which can deteriorate the soil and groundwater quality.

Existing utilization rate

Tunnel slag

Tunnel slag refers to the stone waste excavated during the tunnel excavation process. With the development of highways in China and the emphasis on environmental protection, the proportion of tunnels in mountainous highways is increasing, with some mountainous highway tunnels accounting for over 40% of the total length of the route. During the excavation process of these tunnels, a large amount of tunnel slag is inevitably generated. Due to factors such as construction technology and organization, a large amount of tunnel slag cannot be reasonably utilized and often requires the construction of specialized spoil areas for disposal. Abandoned cave debris not only occupies land resources but also affects the environment, and sometimes forms safety hazards due to improper disposal.

Recycling

In 2016, the Ministry of Transport issued guidance on the implementation of green road construction, requiring road construction to be "zero waste and less borrowing", to preserve and utilize the waste soil from traditional practices, and to turn solid waste into resources.

Recycling: It can generate machine-made sand for road construction, sand and gravel aggregates, concrete mixing plants, earthwork engineering, housing construction, environmentally friendly bricks, etc.

Tailings

The part of the useful target components in the products of beneficiation operations that are low in content and cannot be used for production is called tailings. Tailings are treasures that need to be excavated. Experts believe that the current task of China's mining circular economy is to develop and utilize a large amount of tailings that have been put on hold for a long time.

Recycling

Recycling: tailings with certain useful components can be purified and recycled. Tailings with other components can be used as building raw materials after treatment. Through reprocessing, they can be made into cement, sand brick, tile, refractory glass, foam and other materials; Tailings can be used as raw materials for road construction or anti slip materials for road surfaces; You can also cover the tailings dump with soil to create fields, plant crops, or plant trees for afforestation.

Gangue

Coal gangue is a solid waste discharged during the coal mining and washing processes. It is a black gray rock with lower carbon content and harder hardness than coal that accompanies the coal seam during the coal formation process. This includes the excavation gangue during the tunnel excavation process, the gangue extracted from the roof, floor, and interlayer during the mining process, and the washed gangue extracted during the coal washing process.

Recycling

Recycling purposes: coal, chemical raw materials (pyrite), power generation, manufacturing of building materials, production of low calorific value gas, manufacturing of ceramics, production of soil conditioner, or road paving, underground filling, and ground filling. Grass planting and afforestation can also be carried out on the gangue hills after spontaneous combustion to beautify the environment.

02. Urgent Utilization of Solid Waste Resources

At present and in the future, China cannot continue to rely on traditional extensive growth methods to promote modernization. It is necessary to accelerate the development of circular economy, reduce energy consumption and waste emissions from the source, achieve efficient utilization and recycling of resources, and promote sustained and healthy economic and social development. Therefore, the utilization of solid waste resources is urgent.

03. Main processes of solid waste resource utilization

Sorting: Remove large pieces of debris from raw materials through heavy-duty sieves or manual labor;

• Iron removal: Remove small and medium-sized steel bars, iron wires, and other debris;

• Crushing: Crushing large aggregates into particle shapes that meet the regeneration requirements;

• Screening: Screening and classification according to regeneration requirements;

• Wind selection: remove lightweight impurities from the aggregate again;

• The entire process involves dust removal techniques such as spraying, fog cannon, and nanofilm dust suppression.

04. Main equipment for solid waste resource utilization

Crushing and screening is an important process for solid waste regeneration. Currently, the equipment commonly used for solid waste treatment is crawler mobile crushing and screening equipment.

It has the following advantages:

• Without the need for foundation and supporting construction, it can be processed on-site at the demolition site, which is very convenient;

• Able to quickly move workstations, eliminate material pouring processes, and reduce regeneration costs;

• Flexible combination and matching under different working conditions to reduce investment costs;

• Simple equipment operation and maintenance, reducing personnel investment costs;

• The equipment is equipped with supporting sound insulation equipment and dust removal equipment for dust and noise reduction treatment, which has met the national workshop environmental protection testing standards.

The ban on mining of river sand and the consolidation of the sand and gravel industry have resulted in a shortage of sand and gravel, and prices have skyrocketed. The resource utilization of solid waste is particularly urgent, and its recycled materials can replace some artificial and natural sand and gravel aggregates to achieve recycling, which is a new opportunity for the development of the sand and gravel industry.