Resource Recovery Technology for Municipal and Rural Solid Waste: Classification, Mechanical Separation, Recycling, and Transfer

By Zhao Youcai, Zhou Tao and Eugene Atta Nyankson

Resource Recovery Technology for Municipal and Rural Solid Waste: Classification, Mechanical Separation, Recycling, and Transfer describes the practical considerations in recycling solid waste—from source characterization to recycling of end product—with the aim of maximizing pollution control and resource recovery. Topics covered include source classification models, solid waste treatment and resource recovery, integrated mechanical separation and parameter optimization, and the collection and transfer of classified domestic solid waste. The book details pollution control and resource recovery in every stage of municipal and rural solid waste management for solid waste engineers, environmental scientists, and academics and students in waste management.

The book goes into significant detail on each stage of the process, including separation technologies according to the difference of particle size, material density difference, the difference in optical, electrical and magnetic effects of materials, preparation of plastic composites, and production of composite boards with organic waste from domestic solid waste. The book also includes a thorough case study of success in solid waste management using these techniques as an example of the application of these technologies.

• Compiles the latest research to deliver a comprehensive reference on pollution control and resource recovery for municipal and rural solid waste, from basic knowledge to actual process engineering
• Provides state-of-the-art source classification, mechanical separation, recycling, and transfer for municipal and rural solid waste with optimum strategies
• Includes detailed engineering designs, equipment selection, operation, and business models for source classification, mechanical separation, recycling, and transfer for domestic solid waste projects

• Language: English
• Publisher: Elsevier Science
• Release date: May 24, 2023
• ISBN: 9780323958660

Zhao Youcai

Zhao Youcai, is currently a professor of environmental engineering at School of Environmental Science and Engineering, Tongji University. He got bachelor degree from Sichuan University (1984) and Ph.D. from Institute of Chemical Metallurgy (now Institute of Process Engineering), Chinese Academy of Sciences, Beijing (1989). After finished Post-doctoral research work at Fudan University, Shanghai, he joined in Tongji University in 1991. Meanwhile, he had ever worked at Aristotle University, Greece, National University of Singapore, Tulane University, USA, and Paul Scherrer Institute, Switzerland, for 4 years as research fellow or visiting professor. He had authored or co-authored 200 publications published in peer-reviewed internationally recognized journals, 480 publications in China journals, authored 9 English books (at Elsevier and Springer) and authored or co-authored 98 Chinese books (as an author or Editor-in-chief), 4 textbooks for undergraduate, graduate and PhD students with a fourth edition of undergraduate textbook (in Chinese). Currently, his research interests include treatment and recycling of municipal and rural solid waste, construction and demolition waste, hazardous waste, industrial waste, electric and electronic waste, and sewage sludge, and polluted soil.

Book preview

Chapter 1

Source classification and yield forecast of municipal and rural solid waste

Abstract

The characteristics of municipal solid waste (MSW) and rural solid waste are introduced first in this chapter. The composition of MSW, the logistics system of MSW classification, classification and recycling modes, and the classification and traceability system are then detailed. Furthermore, the chapter emphasizes the benefits and functions of source separation and provides current source separation situations in Japan, Germany, and China. Finally, while machine learning has great potential for prediction, few studies have used deep learning approaches to forecast the quantity of MSW. As a result, the goal is to assess the feasibility and practicability of using supervised learning methods such as Attention, one-dimension Convolutional Neural Network, and Long Short-Term Memory to predict the MSW Amount.

Keywords

Municipal solid waste; rural waste; sources and characteristics; classification; deep learning; yield prediction; 1D-CNN-LSTM-attention model

1.1 Municipal solid waste

In this book, municipal and rural solid waste, also known as domestic solid waste, refers to garbage from municipal and rural areas, and in many cases, also refers to the terms refuse, municipal solid waste (MSW), domestic rural waste, trash, littering waste, and so on, and may be used interchangeably in the text.

It is generally generated in households and offices, with the exception of waste from health care. It also clearly refers to the waste in the garbage cans, which should be collected and treated by the local government and community, primarily using public funds. Larger waste, such as a bed, sofa, or kitchen tools, has a higher value and is commercially collected separately and can be recycled more easily, which will not be covered in this book.

MSW is an unavoidable byproduct of human society. The initial concern of society is the movement of waste away from the immediate human settlement. As a result of the growing human population, changes in habits and lifestyle, rising disposable income, technological and scientific advancement, and increasing production and consumption of new products, the proper treatment of solid waste has become a major problem that affects virtually all communities around the world. Furthermore, the combined action increases both the quantity and complexity of waste generated.

Because MSW generated in various localities has no ownership, it is difficult to identify the specific individuals responsible for the discarded waste. If no effective treatment methods are available, the majority of waste discarded in the environment will spread across the various environmental media and be carried to distant areas by wind or water. Furthermore, attitudes toward waste’s indiscriminate disposal in the environment have been dominated by the perception of waste as an unwanted material with no intrinsic value. Waste that is disposed of indiscriminately poses a serious threat to human health and the environment as a whole. As a result, there is a growing recognition that misplaced or unwanted waste in one location can be a valuable resource in another.

MSW generation in China exceeds 250 million tons per year, with municipal departments collecting, transporting, and disposing of it. Domestic garbage pollution control and resource utilization is an important aspect of urban public management and services. It is not only an important symbol of social civilization, but it also serves as the foundation for the general well-being or well-being of people’s livelihoods.

1.1.1 Composition of municipal solid waste

The MSW output is directly proportional to the city’s scale, population growth rate, and urban residents’ living standards. The MSW components vary across regions due to the impact of unbalanced industrial development, varying degrees of urban modernization, and different living habits. MSW can be roughly divided into organic and inorganic waste, as shown in Table 1.1. In general, the classified collection of MSW can begin with hazardous waste and bulky garbage and gradually expand to a comprehensive classified collection of useful materials such as glass and waste paper. The classified collection of MSW necessitates the close cooperation of urban residents. However, completing the difficult project will take several years.

Table 1.1

The moisture content of MSW is 50%–65%. For the compositions, the contents of food waste, plastic, paper, fiber, and construction waste are 60%–70%, 12%–18%, 8%–15%, 20%–30%, and 10%–20%, respectively. Following waste collection and transportation, the terminal disposal primarily employs a sanitary landfill and incineration for power generation. If the various components of domestic waste are fully utilized at the source, raw materials equivalent to a large amount of oil or coal can be saved each year. Similarly, the full exploitation of the sanitary landfill and dumping sites will be carried out.

1.1.2 Logistics system of classified municipal solid waste

Classified MSW comes in two varieties. One is the source classification, which means that garbage is sorted in the residents’ homes. Another type of garbage is a mixed collection that is classified at the sorting center after collection. It is worth noting that the gradual establishment and improvement of the urban garbage classification and collection logistics system will ensure long-term development. Depending on the classification and collection modes, garbage classification includes the classification of food waste and recyclable substances in MSW, as well as the collection of kitchen waste and bulky waste. The typical process of the classified MSW logistics system is shown in Fig. 1.1.

1. A large waste logistics system. Bulky waste is collected on a regular basis by special bulky waste collection vehicles and delivered to a bulky waste disposal site under this system. Due to the small total waste quantity and short collection times, the loading capacity of large-size garbage collection vehicles should not be less than 8 tons. A better-equipped bulky garbage collection truck should always include crushing or lifting capabilities.

2. A kitchen waste logistics system. Kitchen waste is defined as food cuttings and residues generated in public canteens or eateries. The average moisture content of raw kitchen waste is generally greater than 90%, with high levels of oil and salt. Organic substances such as starch, dietary fibers, and animal fats are the main solid components. Kitchen waste is perishable, and it is easy to emit odors and breed mosquitoes, flies, and mice. Because kitchen waste is high in organic matter and water, it serves as a breeding ground for microorganisms such as bacteria and viruses, posing a serious threat to human health because the growth of these microorganisms leads to the rapid spread of diseases. The use of kitchen waste as direct feed for live pigs has been banned in many places due to the risk of spreading microbial diseases. Because of its high watery and organic content, the waste logistics system cannot accommodate kitchen waste collection and transportation.

Figure 1.1 Flow chart of a logistics system for comprehensive utilization of classified municipal solid waste.

The waste generated by the kitchen unit is packed in a container or leached into a bag before being collected and transported by a special collection vehicle. This type of collection vehicle has several functions, including self-unloading, self-loading, and draining, as well as oil-water separation. After arriving at the disposal site, the kitchen waste is sorted to remove nonfermentable debris before being crushed and fed into the fermentation equipment. Following that, the kitchen waste is fermented, decomposed, and granulated into organic fertilizer. After fermentation and ripening, kitchen waste is transformed into a crude product. Trace elements and chimeric nitrogen, phosphorus, potassium, and other additives are added to create a refined product that can be used as an organic compound fertilizer. The process is shown in Fig. 1.2.

Figure 1.2 Flow chart of kitchen waste logistics system.

1.2 Rural solid waste

With the improvement of rural residents’ living and consumption standards, as well as the popularization of various daily consumer goods, the output of rural solid waste (RSW) continues to rise year after year. Its composition has gradually approached that of MSW. However, there is a significant difference between urban and rural living standards, as well as garbage management and treatment. The main characteristics of RSW are a large number of sources, complex components, a dispersed layout, and an unfavorable collection. According to the survey findings, domestic waste in villages and towns is easily influenced by fuel type, local development, seasonal changes, market fairs, and other factors, resulting in significant output and composition fluctuations. Furthermore, due to the vast territory and large differences in economic development, living habits, natural geography, and climate conditions between regions, the production status and composition of household garbage in different regions have their own distinct characteristics or attributes. These factors determine the type of treatment technology to be used for the treatment of household garbage in villages and towns, as well as the diversity and complexity of appropriate management models to be used.

Historically, the number of RSW collection and transportation facilities has been woefully inadequate. The level of containment and mechanization is low, and various facilities are not included in the collection and transportation process. Many small towns, for example, lack the necessary garbage collection bins and peel boxes, and residents dump household waste on the streets and around houses at random. Small transfer stations have been replaced in some areas by trash cans or open trash pits. Due to their limited capacity and inability to hold the amount of waste generated, these trash bins/open pits have become another source of pollution. This situation is exacerbated by a lack of specialized waste management in various regions or towns. As a result, these trash cans/open pits have created a new source of pollution. Garbage collection and transportation rely heavily on human and manual labor; labor intensity is high, and collection and transportation are inefficient. Due to poor vehicle sealing, dust and leachate from garbage are scattered along the street during transportation, exacerbating the dirty and unsanitary conditions in the various towns.

RSW is typically treated in the following ways: (1) Most villages and towns lack facilities for collecting and transporting RSW, resulting in garbage being piled up randomly or even dumped directly into rivers. (2) Although some villages and towns have open-air RSW collection points, no effective sealing or cleaning measures are in place. Domestic waste is simply landfilled near the collection point with no antiseepage measures in place, resulting in pollution of the surrounding human environment, soil, groundwater, and other environmental resources. (3) Waste is transported directly from collection points to dumping sites for treatment in some villages and towns. These landfills, on the other hand, are only simple sites built in towns or villages and cannot meet the technical and management requirements of sanitary landfills. As a result, secondary pollution is easily caused during transportation and treatment. (4) In some other villages and towns, domestic waste is treated through a simplified process of incineration and composting. Ordinary incinerators or decommissioned brick kilns are commonly used for waste incineration. The problem of domestic waste is solved during the operation process, but new pollution is produced, and the heat of incineration can no longer be used. After simple sorting, the mixed domestic waste piles up in composting (coarse composting). Fertilizer products contain a lot of ash, have a lot of impurities, are of poor quality, and are difficult to use.

Some cities prioritize the treatment of rural domestic waste and propose an integrated management model of urban and rural domestic waste, indicating that the urban domestic waste management system is expanding to villages and towns. The policy of unified management, centralized removal, and fixed-point treatment is being implemented for RSW. Some useful attempts to build a garbage collection and transportation system have been made in some rural areas, leading to the development idea of household classification, village collection, township transfer, and county treatment.

1.3 Classification and recycling modes of domestic waste

At the source, waste can be classified as dry or wet, and the corresponding terminal treatment facilities should be built based on the classification treatment mode. Dry waste can be resorted, with valuables reused and the remainder incinerated. Biochemical treatment is primarily used for wet waste, which can produce biogas and other renewable energy. Classified materials should be assigned to the appropriate logistics transportation system.

1. The Internet + garbage classification smart mode

All trash cans are outfitted with NFC electronic tags for online real-time management. To facilitate efficient online management, employees can browse relevant information such as location, collection time, collection weight, and corresponding collection vehicles.

A reward system for garbage classification can be implemented so that residents involved can exchange their daily necessities through the accumulation of points after garbage classification and recycling. The reward system can pique residents’ interest in garbage classification and provide online or on-site appointment services to make it easier for residents to participate in the management process.

To implement official garbage classification knowledge, news, events, and other notifications, the community may establish a garbage classification website and a WeChat platform. This step is to achieve a successful online search for garbage classification facilities and to provide online feedback channels for step-by-step publicity and supervision.

2. Garbage room mode

An outstanding management team has been assembled to guide residents’ garbage classification and release, manage the garbage room, and carry out secondary sorting of classified garbage.

The new type of garbage room should be convenient for garbage delivery while remaining clean and sanitary. Each garbage room follows standardized packaging procedures, such as wet garbage collection and transportation, dry garbage collection and transportation, garbage bin cleaning, and garbage room cleaning.

To actively publicize the incentive mechanism and emphasize the concept of garbage classification means benefit, a green account for domestic garbage classification can be established. Residents can earn green account points by properly sorting their dry and wet waste, which they can then redeem for prizes and resources on relevant websites and WeChat platforms.

3. Internet + intelligent four classification collection mode

In some communities, garbage will be separated into recyclables, hazardous waste, and other waste. The property management department shall assign special trash bins to each household and appoint special people to guide and assist residents in sorting garbage twice a day or on a regular basis. A portion of the community will carry out the four classifications of added food waste, forming an integrated treatment of residents’ food waste and public kitchen waste.

In terms of middle classified collection, outsourcing service companies are entrusted with the dismantling, collection, and transportation of large-scale waste. Then, establish a collection, transportation, and resource-based treatment system for low-value recyclables and hazardous waste.

4. Dichotomy mode

The villagers’ garbage classification procedures are streamlined for RSW classification. Garbage is divided into two types: perishable kitchen waste and nonperishable waste. Every home is outfitted with blue and green garbage cans, and full-time personnel come every day to recycle and sort garbage. This mode considers factors such as low awareness of rural garbage classification and a lack of knowledge about residents’ garbage classification, both of which can be carried out effectively in rural areas. Concurrently, front-end and back-end garbage classification collaboration improves classification efficiency and lowers input costs.

The most appropriate thing to do is to establish supporting facilities for the entire process of garbage placement, sorting, collection, transportation, and disposal, in conjunction with Internet+ and other technologies to achieve intelligent garbage management. It also encourages residents to sort garbage by offering incentives such as point exchange.

Waste classification is a form of human behavior education. Internationally, it is widely accepted that garbage classification is a manifestation of national quality and an essential component of modern civilization and ecological civilization. Waste classification should become a modern public lifestyle. The waste classification mode of a country is fundamentally determined by national conditions such as garbage components, land resources, ecological status, economic development, and social civilization level. The primary goal of waste classification is to ensure the safety of urban operations, to promote ecological civilization, and to reuse resources.

The waste classification model used in developed countries considers recyclable and organic waste to be priority classification items. Based on the acceptability of residents and combined with the existing classification basis in rural areas and the purpose of waste classification, the proposed garbage source-separated scheme in the rural areas are as follows:

1. No source-separation + centralized sorting (C1)

2. Recyclable waste + toxic and hazardous waste + nonrecyclable waste (C2)

3. Recyclable waste + toxic and hazardous waste + dry waste + wet waste (C3)

4. Recyclable waste + toxic and hazardous waste + perishable waste + nonperishable waste (C4)

Scheme C1 adds transfer sorting or a centralized sorting process while maintaining the current mode of waste classification. While C2, C3, and C4 classify recyclable and toxic wastes at the source, this can help reduce secondary pollution during the collection and transportation of hazardous wastes and improve the rate of waste recovery. To minimize the amount of waste removal and transportation, Scheme C3 and C4 classify perishable organic waste as wet waste and nonperishable waste as dry waste. For the subsequent resource treatment of perishable organic waste, Scheme C4 is more practical.

1.4 Classification and traceability system of domestic waste

The traceability system creates a one-person, one-code identification database, as well as a bonus point system and a commodity exchange system. The classification supervisor sends the QR code of the bagged garbage to track the information, and the users identify the user information using the QR code generated by the APP. This measure indicates that the classified garbage can be tracked, the quality of the garbage can be traced back, and the corresponding points will be awarded to residents based on the community.

According to the purchaser’s operation management or project needs, different user opening door delivery methods can be customized (Fig. 1.3).

Figure 1.3 Domestic waste classification user delivery process.

If there is no need to identify the user’s identity in order for the items to be used, a button to open the door is provided. The button is located on the right side of the delivery position (single position equipment) or in the center of two delivery positions (dual position equipment) (double position equipment). The equipment immediately opens the door for operation when the resident presses the button.

Two identification methods, IC card and QR code, are provided to purchasers who need to identify the user’s identity. APP, official account, applet, and QR code of garbage bag body are all methods for opening QR codes. Garbage bags printed with QR codes are provided for some items that require detachable bag and real-time supervision, and can be traced using this QR code. The equipment will automatically shut down after the user places the garbage bag in, and the reward will be calculated by weighing. The device’s LCD screen, APP, official account, applet, or POS machine can all be used to check the current account balance. After the delivery is completed, the current delivery reward will be displayed on the equipment's LCD screen. When you log in to the APP, the information is also sent to the APP login