The Circular Economy - Final Exam - GJU

THE CIRCULAR ECONOMY LEARNING OBJECTIVES explain the idea, concepts and principles of a circular economy describe the main types and purposes of material loops explain the major strategies for achieving a circular economy explain how a transition to circularity may take place reflect on...

THE CIRCULAR ECONOMY LEARNING OBJECTIVES explain the idea, concepts and principles of a circular economy describe the main types and purposes of material loops explain the major strategies for achieving a circular economy explain how a transition to circularity may take place reflect on challenges and limitations regarding circularity The present chapter addresses wider context of waste management and the efforts to reshape it for environmental, economic and social purposes. This effort has been gaining ground for at least half a century, culminating in the present effort to achieve a circular economy. A circular economy is an economic system that aims to achieve sustainability goals through more efficient and circular use of materials. Defined as a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials & products for as long as possible. A circular economy replaces the linear model of take-make-dispose with a model in which materials and products are used more intensively, for longer, and repeatedly. Circular economy is usually presented as an effort to achieve sustainability. Sustainable development emphasises our long- term obligations to respect the needs of future generations, as well as the economic, social and environmental conditions required to meet them. The environment Sustainable yield; the rate at which we extract materials should not exceed the rate at which materials regrow. Stocks of nonrenewables should, in the long run, be substituted with stocks of renewable materials. Respect limits to the environmental pressures that ecosystems can endure. CE is tailored to addressing environmental pressures directly related to material use; it is not a comprehensive strategy for all manners of environmental protection.  Economy In the long term, the economy should gain from the protection of the natural environment, because it critically depends on it for the provision of natural resources. In the short term, benefits may also be expected in the following forms: Cost- savings. The extended, repeated and intensified use of materials can reduce virgin material demand and thus the input costs for businesses’ activities. Price volatility. Raw materials prices can be volatile, which exposes businesses to the risk of rapidly increasing input costs, which are unlikely to be shouldered by the consumer. Criticality. Recycling responds to concerns over criticality, and so do other circular activities like reuse and remanufacturing, because they all reduce the dependence of manufacturers on raw materials. Marketing. Businesses expect to gain from an increasing demand for circular products and services.  Society A circular economy has the potential to address some of the profound social impacts of production and consumption, although the concept is more often promoted for its potential environmental and economic benefits. The circular economy is therefore also relevant to the Sustainable Development Goals (SDGs) MATERIAL CIRCULARITY Material loops CE often distinguishes between two types of materials or ‘nutrients’ in the economy: biotic and abiotic. MATERIAL CIRCULARITY Material loops The narrower loops are generally considered preferable to the wider loops because they tend to be more environmentally friendly. In addition, slow loops may be considered more attractive than fast loops; the longer a material stays in the economy before being circled back, the less effort this requires per unit of time. MATERIAL CIRCULARITY Material loops The narrower loops are generally considered preferable to the wider loops because they tend to be more environmentally friendly. In addition, slow loops may be considered more attractive than fast loops; the longer a material stays in the economy before being circled back, the less effort this requires per unit of time. The older versions of the waste hierarchy often listed only the three Rs of reduce, reuse and recycle. A much longer list of 10 Rs describes the priorities in a circular economy Value creation The circular economy is motivated by the observation that many common activities destroy material value. For example, by design, disposable plastic cutlery renders the material unusable after a very short life of limited functionality. Even if the plastic is recycled, it yields secondary material of lower quality and value. The maintenance of value in a circular economy can be interpreted as maximising the added value. The following strategies may be applied to increase value: Producing more products from the same inputs through, for example, more efficient production or lightweight product design. Producing products again from the same inputs through, for example, recycling of the product at the end- of- life. Providing more product functionality based on the same input by, for example, renting the product to several users instead of selling it to one person. This works only if consumers are willing to pay enough for renting the product instead of owning it. While the above strategies can maintain value, none is beneficial to the material supplier, who stands to lose when material purchases are reduced. Value for whom, when and where?  CIRCULAR STRATEGIES Micro- level. This lowest level relates to individual products or businesses. Relevant strategies include product design and business model innovation. Meso- level. This middle level relates to activities across businesses. Relevant strategies focus on improving supply chains and industrial symbiosis. Macro- level. This top level refers to decision- making at the city, region, national or global level to monitor and support micro- and meso- level activity. Limits to circularity The following constraints prevent the creation of a perfect circle without waste: All circular- economy activity, even the higher priorities of reuse and repair, require energy to implement, including for transport, cleaning and disassembly. Many materials are not available to be circled back into the economy. Leaving aside that materials and products are dispersed or locked in use, their circulation is rarely 100- per- cent efficient. In the long term, it is therefore necessary to shift towards biotic materials. Limits to circularity The following constraints prevent the creation of a perfect circle without waste: Global growth in consumption, driven by a growing number of people and greater prosperity is still poses a challenge. The mentioned limitations are exacerbated by changing fashion and technology, which means that yesterday’s products, even if still technically functional, may not be desirable today. Limits to circularity There is the problem of the rebound effect. When waste prevention reduces the cost of a product, it can be sold at a cheaper price, which often means we buy more of it. This is called the direct rebound. Alternatively, we may spend the money we saved on other goods that have environmental impacts too. This is called the indirect rebound. ACHIEVING CIRCULARITY There is the problem of the rebound effect. When waste prevention reduces the cost of a product, it can be sold at a cheaper price, which often means we buy more of it. This is called the direct rebound. Alternatively, we may spend the money we saved on other goods that have environmental impacts too. This is called the indirect rebound.  LIVE Introduction to Life Cycle Assessment (LCA) Introduction to Life Life Cycle Inventory Cycle Assessment (LCA) Analysis and Data Collection Methods Intro to LCA Framework and Defining Goal and Scope Importance, Applications, and Benefits of LCA What is Life Cycle Assessment (LCA)? LCA is a powerful tool used to assess the environmental impact of products, processes, and services, typically throughout their entire life cycle. In this course we will focus on LCA of PRODUCTS and PROCESSES related : - Buildings - Infrastructure - The built environment in general  What do we mean when we say environmental impact? Environmental impact inlcudes a wide range of negative effects (or stressors) a product or activity has on the environment. OUTPUTS: IMPACT: INPUTS: - Water pollutants Global warming Raw material - Air pollutants Ozone depletion Energy - Land pollutants Resource depletion Water - Solid waste Acidification of water bodies - Other environmental And many more stressors These environmental stressors can have serious implications on our quality of life and that of other living things. What is Life Cyle Thinking (LCT)? Life cycle thinking is a crucial approach for LCA. Life cycle thinking is based on three key principles: 1.Systems perspective: products and processes are parts of interconnected systems 2.Long-term view: considering impacts of activities of the entire life cycle, rather than short-term benefits or costs 3.Interdisciplinary approach: integrating the knowledge and expertise from various disciplines (environmental science, engineering, economics, and social sciences). How do we map out the life cycle of a product? https://www.youtube.com/watch?v=BiSYoeqb_VY How do we map out the life cycle of a building? Take a moment to map out the life cycle of a building. What does a building life cycle look like? 1.Raw Material Extraction and Processing: extracting and processing materials such as wood, cement, aggregates, and sand 2.Manufacturing and Transport: transporting the raw material to the manufacturing facility (by land, sea, and/or air) using them to produce construction products like concrete, glass, insulation, tiles, paint, pipes, bricks transporting the products to the construction site (by land, sea, and/or air) 3.Construction: assembling and constructing the building on-site 4.Use and Operation: using electricity and water, generating waste, etc. 5.Maintenance and Renovation: using products and activities to maintain and repair the building 6.End of Life: demolishing deconstructing, or fully renovating the building. Fun fact about LCA It was developed in the 1960s, as a response to growing concerns about environmental pollution and resource depletion. Coca Cola was the first company to implement LCA in 1969. Coca Cola was comparing different beverage containers to determine the lowest releases to the environment and use of natural resources. Watch this informative video for more information on Coca-Cola and their LCA. https://www.youtube.com/watch?v=KDqdjq11-7o  LIVE Importance, Applications, and Benefits of LCA  ⓒ All rights reserved. American University of Beirut. Introduction to Life Importance, Cycle Assessment (LCA) Applications, and Benefits of LCA Intro to LCA Framework Life Cycle Inventory and Defining Goal and Analysis and Data Scope Collection Methods LCA in the Context of the Built Environment LCA Role: Shapes community and cities sustainability. LCA helps us: Reduce resource consumption Minimize environmental footprint What is Environmental Footprint? Environmental footprint measures the impact of buildings and infrastructure on the environment. Some types of environmental footprint: Water Footprint: Fresh water volume used over a product's life cycle. Carbon Footprint (or Climate Change Footprint): Total greenhouse gases (GHG) emitted, affecting the ozone layer. Expressed in CO2e. Resource footprint: Consumption of primarily non-renewable natural resources. Atmospheric Footprint: Damage to the atmosphere from pollutants and forest degradation. Waste Footprint: Environmental contamination from products or services. Biodiversity Footprint (or Ecological Footprint): Adverse effects on terrestrial and marine ecosystems LCA for Sustainable Construction LCA Applications in Building and Infrastructure Development: Key Decisions: Building Design Material Selection Construction Methods Supports: Sustainable infrastructure planning Urban development impact assessment Environmental Impact Reduction: Mitigating climate change Reducing water pollution Reducing resource depletion PROBE TRUE OR FALSE Carbon Footprint measures the total amount of carbon dioxide emissions, expressed in CO2e. Correct answer: False Feedback for True: Carbon Footprint measures the total amount of Green House Gas (GHG) emissions, expressed in CO2e. Benefits of LCA LCA enables the construction sector to contribute to the UN Sustainable Development Goals (SDGs) Responsible consumption and production (SDG 12) Sustainable cities (SDG 11) Climate action (SDG 13) LCA helps construction projects achieve green certifications, like LEED and BREEAM.  LCA enables life cycle design This short video introduces the concept of life cycle design, and how life cycle assessment can enable it. https://www.youtube.com/watch?v=mbVHvTqBG24 Environmental Product Declarations (EPDs) – a Practical Application of LCA What are Environmental Product Declarations (EPDs)? EPDs are standardized verified documents that provide transparent and comparable information about the environmental performance of products over their life cycle: - Resource depletion - Global warming potential - Energy consumption - Water consumption - Emissions to air, water, and soil EPDs are verified by a third party. LEED awards points for using building materials with verified EPDs. LCA in practice In 2011, the National Trust for Historic Preservation conducted a used LCA to compare Building Renovation vs. New Construction over a 75-year life span. It examined four impact categories: - Climate change - Human health - Ecosystem quality - Resource depletion It tested: 6 different building types, including single-family home, multifamily building, and commercial office 4 different climates in the US: Chicago, Atlanta, Phoenix, and Portland The main question was: Does demolishing old buildings and reconstructing new environmentally friendly (green) buildings have less impact on the environment compared to renovating and reusing old traditional buildings?  LCA in practice It can take between 10 and 80 years for a new energy-efficient building to overcome, through more efficient operations, the negative climate change impacts that are created during the construction process. PROBE MULTIPLE RESPONSE LCA enables the construction sector to contribute to which of the following UN Sustainable Development Goals (SDGs)? A.No poverty (SDG 1) B.Reduced inequalities (SDG 10) C.Sustainable cities (SDG 11) D.Responsible consumption and production (SDG 12) E.Climate action (SDG 13) Correct Answer: C, D, E MULTIPLE CHOICE According to the case study, why is building renovation almost always more sustainable than new construction? A. Old buildings are more energy-efficient than new buildings. B. It can take many years for a new energy-efficient building to overcome the negative environmental impacts that are created during the construction process. C. New buildings that claim to be energy-efficient are actually not. Correct Answer: B Feedback for A: Old buildings are not necessarily more energy-efficient than new buildings. And in either case, it can take many years for a new energy-efficient building to overcome the negative environmental impacts that are created during the construction process. This is why renovating old buildings is more sustainable in most cases. Feedback for C: Even if new buildings are truly energy-efficient, it can take many years for a new energy-efficient building to overcome the negative environmental impacts that are created during the construction process. This is why renovating old buildings is more sustainable in most cases.  Hazardous Waste and Risk Management – PCE5333 Dr Ahmad B. Albadarin PCE Program Fall Semester 2024 1 Waste Collection and Treatment LEARNING OBJECTIVES The purpose and concept of waste treatment Physical, physicochemical, biological and thermal treatments Technological basis of widely applied treatments Discuss the main environmental impacts of treatment technologies. 2  The Global Waste Problem: Statistics on global waste generation, focusing on different waste streams (household, industrial, etc.). The environmental and societal impacts of improper waste management. The Waste Hierarchy: Reduce, reuse, recycle, recover, dispose as the guiding principle for sustainable waste management. 3 https://www.youtube.com/watch?v=tZNaCVMsx10 https://www.youtube.com/watch?v=MHnDqelUh-4 4 Industrial Waste Collection Incredibly diverse, varying greatly depending on the industry's processes and the materials used. Examples range from construction debris and manufacturing scrap to hazardous chemicals and biological materials. Unlike household waste, which often has standardized collection and treatment processes, industrial waste requires customized solutions tailored to the specific waste stream's characteristics (hazardous vs. non-hazardous, volume, composition, etc.). This diversity presents significant challenges for efficient and environmentally sound collection and disposal. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/industrial-waste-management 5 Collection Methods & Infrastructure Different collection methods are used based on waste type and volume. These include: Bulk containers: Used for larger volumes of non-hazardous waste. Specialized vehicles: Tankers for liquids, enclosed trucks for hazardous materials. On-site treatment and pre-processing: Many industries process waste on-site to reduce volume or hazard before transport. Infrastructure requirements are varied. Some industries may have dedicated on-site facilities, while others utilize external contractors for collection and disposal. Regulations surrounding transportation of hazardous waste are strict and require specialized licensing and handling procedures (e.g., manifests). 6  Challenges and Complexities Hazardous Waste Management: This presents the greatest challenge; it requires careful handling, specialized containers and transport, and licensed disposal facilities. Specific regulations (e.g., EPA in the US) must be strictly adhered to. Liability and Risk Management: Industrial waste generators are liable for the proper handling and disposal of their waste, potentially facing severe penalties for non-compliance. Comprehensive risk assessments are vital. Cost of Management: Proper industrial waste management can be expensive, often exceeding the cost of managing equivalent amounts of household waste. This is especially true for hazardous waste. 7 8  Common Challenges in Waste Management Systems Proper Waste Segregation: Separating waste effectively is crucial. However, segregation remains a significant challenge. The manual separation process is time-consuming and labor-intensive. On-Time Waste Collection: This approach has limitations. Collection schedules often need to account for waste quantity variations. Collection teams might waste resources checking empty bins or encounter overflowing bins on other days. Proper Waste Disposal: Currently, most disposal methods are energy-intensive and require significant resource investment for maintenance. Equipment breakdown can lead to waste management crises or toxic chemical leaks. Raising Waste Pollution Awareness: Effective waste management goes beyond collection and disposal. Even cities with robust systems struggle with this aspect. 9 Overview of Waste Treatment Processes 10 Overview of Waste Treatment Processes Encapsulation produces a solid mass of material that is resistant to leaching. https://www.youtube.com/watch?v=rovhyqsnjdU 11 Waste stabilization is designed and built for wastewater treatment to reduce the organic content and remove pathogens from wastewater. https://www.youtube.com/watch?v=zPxdC7fFecw Coagulant BMG-P2: reduction of fat content in wastewater from an agricultural company by more than 18 times - from 320 to 17 mg/dm3 12  Biological Treatment Aerobic Treatment Processes Activated Sludge Process (ASP) Description: This process involves returning a portion of the sludge biomass from the secondary clarifier back to the aeration tank, where it is mixed with incoming wastewater. Aerobic microbes degrade the organic matter in the presence of oxygen. Efficiency & Benefits: High efficiency in reducing biochemical oxygen demand (BOD) and suspended solids. It’s flexible and can handle varying loads but requires significant energy for aeration. Applications: Municipal and industrial wastewater treatment. 13 Rotating Biological Contactors (RBC): A fixed-film biological treatment technology where wastewater flows over rotating disks coated with biofilm. The rotation enhances oxygen transfer to the biofilm. Efficiency & Benefits: Reliable treatment with low energy requirements compared to activated sludge. It has good resistance to shock loads. Applications: Suitable for small to medium-sized wastewater treatment plants. https://www.youtube.com/watch?v=_8aLWA6A58A 14 Composting Organic waste is biologically decomposed by aerobes into compost, under controlled aerobic conditions. Efficiency & Benefits: Reduces the volume of organic waste, producing valuable compost. It requires proper management of moisture and aeration. Applications: Treatment of solid organic waste, including yard and food waste. 15 Anaerobic Treatment Process Anaerobic Digestion: A process where microbes break down organic matter in the absence of oxygen, producing biogas (mainly methane and carbon dioxide). Efficiency & Benefits: Produces renewable energy (biogas), reduces sludge volume, and is efficient for high-strength wastewaters. It is generally slower than aerobic processes and sensitive to temperature fluctuations. Applications: Treatment of sludge from wastewater plants, agricultural waste, and industrial effluents. https://www.renergon-biogas.com/en/anaerobic-digestion-explained/ 16 Comparison and Applications Efficiency: Aerobic processes generally convert organic matter faster than anaerobic, but anaerobic digestion is more energy-efficient due to biogas production. Benefits: Aerobic treatment typically results in higher quality effluent suitable for discharge. Anaerobic treatment has the advantage of energy recovery through biogas. Applications: Selection depends on the type and concentration of waste, energy conservation needs, and specific operational priorities. 17 18 19  Sustainable & Emerging Technologies in Waste Management https://www.youtube.com/watch?v=uUmtJIBibMM Advanced Oxidation Processes (AOPs) AOPs utilize strong oxidizing agents to degrade recalcitrant organic pollutants in wastewater. These processes are designed to generate highly reactive species, particularly hydroxyl radicals ( OH), which can effectively decompose complex organic molecules Key Components of AOPs: Oxidants: Ozone (O₃): A powerful oxidant that can directly oxidize organic pollutants. Hydrogen Peroxide (H₂O₂): When activated (for instance, with UV light or transition metals), it can generate hydroxyl radicals. Ultraviolet (UV) Light: Used to activate hydrogen peroxide and enhance its oxidative potential. 20 AOPs have several advantages: Higher Treatment Efficiency: They can achieve removal efficiencies greater than 90% for a wide range of pollutants, including pharmaceuticals, pesticides, and industrial chemicals. Degradation of Recalcitrant Compounds: AOPs effectively break down compounds that are resistant to biological treatment, leading to complete mineralization (conversion to CO₂ and water). Reduced Sludge Production: Since AOPs tend to break down pollutants into simpler, non-toxic byproducts, there is often less sludge produced compared to conventional treatment methods. https://www.youtube.com/watch?v=hlERVxDJCqo 21 Integration of AI and ML in Robotic Sorting Systems Object Recognition: AI Algorithms: Advanced image recognition techniques powered by AI are used to analyze images of waste materials on conveyor belts. Machine Learning models are trained on large datasets of images to identify different types of recyclable materials (plastic, glass, metal, paper). Sensors and Cameras: High-resolution cameras and sensors capture real-time images of the materials as they move through the sorting line. Data Processing: Real-time Analysis: The data from the cameras is processed by AI algorithms, which assess the material type based on predefined criteria, including shape, color, and material composition. 22 Benefits of AI and ML in Waste Sorting Improved Accuracy: Enhanced detection of different materials and minimizing contamination levels reduces errors in sorting, leading to higher quality recycled materials. Higher Efficiency: AI-enabled robotic systems can work 24/7, significantly boosting the overall productivity of MRFs. This operational efficiency allows for faster processing of larger volumes of waste. Reduced Contamination: By accurately identifying and sorting recyclables from contaminants, AI and ML systems help maintain cleaner recycling streams, which are essential for effective recycling processes. Cost Savings & Revenue: The reduction in contamination rates leads to less waste sent to landfills and lower operational costs associated with managing contaminated recyclables. Drive higher revenues from selling clean, high-quality recyclables. Data-Driven Decision Making: Insights gathered from AI systems can inform waste management strategies, helping facilities optimize their operations and improve overall recycling performance. 23  Hazardous Waste and Risk Management – PCE5333 Dr Ahmad B. Albadarin PCE Program Fall Semester 2024 1 ASSESSMENT METHODS Learning Objectives explain the main purposes of conducting an impact assessment conduct a basic material flow analysis and reflect on the results conduct a basic lifecycle assessment and reflect on the results describe other types of assessment methods relevant to waste. 2  This chapter describes the purposes, steps and limitations of two dominant techniques that focus on understanding resource flows and their impacts: material flow analysis (MFA) and lifecycle assessment (LCA). Other methods include environmental impact assessment (EIA), social impact assessment (SIA), cost- benefit analysis (CBA) and environmentally extended input- output analysis (EEIO). 3 MATERIAL FLOW ANALYSIS (MFA) In order to improve a waste management system, improvement, as discussed, probably means ensuring universal collection, moving up the waste hierarchy and lowering environmental impacts. To achieve this, we would need to know how it currently performs, how this is likely to develop into the future and which actions can make a substantial difference, conduct a material flow analysis. An MFA develops a model of the processes in a system, such as a product lifecycle or waste management system, and how they are connected; it also records the amounts of materials that flow between different parts of the system and accumulate within it. 4 MFA is ‘a systematic assessment of the flows and stocks of materials within a system defined in space and time’. In other words, any material that enters the system (an input) must either leave the system (an output) or stay there (a stock); material cannot simply disappear, though it may change its form. Input − Output = Stock change In practice, all three may be measured or estimated separately and then compared for validation; if the values do not add up, the analyst has to do further work to harmonise the material balance. 5 The third study is called a dynamic MFA because it investigates how flows change over a timeframe of several years; material systems that change substantially within a given time-period 6 In the cited study, the total stock of mercury in products in India was estimated to increase by around 60 per cent over two decades. This was calculated from estimates of inputs of mercury into the economy, the lifetimes of products that contain mercury and the outputs of mercury from the economy. 7 Key concepts System boundary. The system boundary defines the system in space and time and dictates which materials, processes, flows and stocks are included in the analysis. Materials. Materials is an umbrella term for all physical substances, ranging from natural rocks such as metal ores to products such as smartphones. Water and air are often excluded, but they should be considered when the water content of materials changes or when conversions take place. 8 Processes. Processes carry out the transformation, transport or storage of materials. Transformation refers to changes in the characteristics of material flowing into a process, such as waste separation activities, leading to material outflows of a different composition. Flows. Flows occur between the processes in a system. They are usually described in terms of the mass units of a material per unit of time. An example of a flow is ‘7.8 Mt of cement in the UK per year’, which described the amount of cement that was produced in the UK in the year 2015. Stocks. Stocks describe the mass units of materials that accumulate in storage in the defined time period. An example of a stock would be the total amount of cement in concrete buildings in the UK. 9 Transfer coefficients. They describe the partitioning of materials in a process. For example, when a mixed waste flow enters an MRF, it may be separated into a paper, metal, plastic and residual waste fraction. The transfer coefficient describes which fraction of the input is converted into one of these separate waste flows. Product lifetimes. The relation between stocks and flows is often mediated by how long products are used before they are discarded. 10 Generic process diagram for MFA. 11 The process diagram provides the start for your data collection process. This is an iterative process, because data collection efforts often reveal the need to adjust the process diagram. 12 How to close the gaps in a material balance Stock dynamics Stoichiometry Proxies The number of cars that are scrapped can be inferred from car sales and the typical car lifetime. Stoichiometric equation for chemical oxidation of cyanide shows that one molecule of hydrogen peroxide is required to destroy a molecule of dissolved cyanide. Data for a larger or smaller geography, for earlier or more recent years or for a technology resembling the one you are studying. The proxy data may need scaling or averaging 13 MFA of coprocessing of contaminated waste: Waste incineration plants use filters to clean combustion gases before they enter the atmosphere. This leads to a new waste product, air pollution control residue (APCR), which is a dust rich in toxic metals that is not accepted at a regular landfill. An alternative is to encapsulate the APCR in concrete structures, for example, in buildings, by using it in the production of cement (‘coprocessing’) used for concrete. 14 MFA analysis indicated that the contaminants in APCR affect the cement production process and the quality of the resulting cement. In conclusion, only a limited amount of APCR should be coprocessed, while important questions remain regarding the fate of the contaminants upon future demolition of the concrete structure. 15  Keep in mind, differences in data sources are not the only sources of uncertainty. The sources of uncertainty in MFA can be categorised into two main types. First: A model of uncertainty is introduced when deciding on the system scope and boundary when drawing your process diagram. Second: data uncertainty. In the case of data that is missing entirely, assumptions may be used to fill the gap, but the validity of these assumptions must be well justified. 16 An assessment of data quality. 17 The foremost limitation of MFA is that the assessment does not provide a direct description of the impact of the system or its individual components; it simply shows material stocks and flows. For example, an MFA cannot tell whether the recycling of material A has more benefits than the recycling of material B; it can only tell which material is recycled more. 18  A COMMON STOCK- AND- FLOW PROBLEM Few people call themselves material flow analysts, but even fewer people have never engaged in some form of MFA. Think of a fridge, which people like to be well stocked. To keep the stock at a stable level, stock losses (the food you eat) must be compensated for with stock additions (new purchases). Consider the following situation, in which Martha, Stuart and John share a fridge. Can you conduct an MFA to calculate how much edible food is left after four weeks? 1) Every week, Martha buys 3 kg of groceries, Stuart buys 1 kg and John buys 2 kg. 2) Every week, Stuart eats 2 kg of food, Martha eats 1 kg and John eats 2 kg. 3) Every week, 10 per cent of the leftover food in the fridge goes bad. What is your system boundary and what are the key processes, flows and stocks in your system? Compare your answer with someone else. If there is a discrepancy, you may have to redo the calculation using a spreadsheet to avoid mistakes. How representative is this problem of a real- world situation? How could you use product lifetimes to estimate the stock dynamics more reliably? What could Martha, Stuart and John do to lower the fraction of food going bad? 19 20 ENERGY RECOVERY AND DISPOSAL LEARNING OBJECTIVES understand the purpose of energy recovery and controlled disposal explain the operation and pollution control for MSW incineration describe the process and main aspects of anaerobic digestion explain landfill design, operation, closure and landfill mining describe the main characteristics of other final disposal methods Energy recovery has the additional benefit of replacing some of the energy otherwise provided through fossil fuels (though energy recovered from waste plastics is still of fossil origin). https://www.youtube.com/watch?v=alljc5elqqw WASTE AS A FUEL Key properties relevant to material use as fuels for energy recovery.  The higher heating value (HHV) is equivalent to the heat of combustion at 25°C (e.g., 17 MJ/ kg in the case of cellulose). The lower heating value (LHV; fourth column of Table 8.1) does not include the heat of vaporisation. The lower heating value is of interest for energy recovery processes because after energy recovery takes place, the water is often emitted as a gas, rather than being condensed. The gross heating value (GHV) of a fuel is the LHV of the combustible organic matter in the fuel, minus the energy lost to evaporation of the moisture content. Example: The table compares the lower heating value of a variety of waste fuels with those of fossil coal and natural gas. Based on its definition, and given that the heat of vaporisation of water is about 2.3 MJ/ kg, can you estimate the GHV for these wastes using the other information in Table 8.1? How does MSW compare to plastics from end- of- life vehicles? Finally, what additional information would you need for the calculation of the HHV? Combustion directly yields heat, whereas anaerobic digestion and gasification yield fuels that are combusted to release heat. Electrical energy recoverable from waste for different waste management options, adjusted for efficiency of electrical generation. MUNICIPAL SOLID WASTE INCINERATION One of the attractions of incineration for MSW management is that the destruction of the organic content can reduce the large waste volumes that we generate by 90 per cent. Energy recovery The hot flue gas containing the energy from MSW combustion is channelled into a boiler. In the boiler, the heat energy in the flue gas is transferred to water in a wall of tubes. The heat energy is transferred to the water in the boiler. The cooled flue gas is drawn through the air pollution control systems by an induced- draft fan and emitted from the stack. The boiler contains tubes that are part of a separate pressurised closed loop that includes a steam turbine. Heating the water in the tubes causes it first to evaporate, and then to heat up beyond boiling temperature, turning into high- pressure steam. The steam is used to drive the steam turbine, which rotates an electrical generator. Flue gas cleaning Flue gas from municipal waste incineration mainly contains unreacted nitrogen andexcess oxygen, together with the main reaction products from thermal oxidation of MSW: CO2 and water. There are many technologies for emissions control and new ones are continuously being invented. The European Best Available Techniques (BAT) Reference Document for Waste Incineration refers to no fewer than 408 technology combinations. Flue gas cleaning In modern incinerators, the combustion temperatures and residence times are designed to avoid the formation of dioxins and furans in the boiler and air pollution control systems. Since no practical process can be 100- per- cent efficient, very small quantities of dioxins and furans are still formed and emitted. Polychlorinated dibenzo- p- dioxins (PCDDs or ‘dioxins’) and polychlorinated dibenzofurans (PCDFs or ‘furans’) are toxic and carcinogenic, even in small quantities. Flue gas cleaning Acid gases: Commonly used semi- dry scrubbers spray hydrated lime (Ca(OH)2) slurry into the flue gas stream to cool it and react with the acid gases to form solid salts, including Ca(SO4).H2O and CaCl2. NOx can be reduced to N2 by injecting ammonia as a reducing agent, either with a catalyst (selective catalytic reduction (SCR)) or without (selective non- catalytic reduction (SNCR)). Some metals, especially mercury, remain in the gas phase. Activated carbon may be injected into the flue gas (after a wet scrubber) for the removal of mercury and trace organic pollutants, such as dioxins, by adsorption. Flue gas cleaning Fly ash is removed together with the waste products from the other treatments: the solid salts and excess reagent from the scrubbing of the acid gases, and activated carbon. Modern incinerators frequently use fabric filters in a baghouse for particulate removal. Despite more stringent regulation of emissions from incinerators and resultant technological improvements in modern incineration practice, incinerators remain unpopular neighbours. WASTE RECYCLING LEARNING OBJECTIVES After studying this chapter, you should be able to: explain the purpose, concept and types of recycling explain the recycling process for metals, plastics and paper evaluate the challenges and limitations of recycling critically reflect on the benefits of recycling practices Introduction Widely recycled materials include metals, paper, plastics and glass. Waste that is collected and treated for recycling becomes a secondary feedstock and is often cheaper than primary (virgin) feedstock. This makes recycling attractive from an economic standpoint. Besides, recovering a material instead of disposing of it in landfill reduces the land requirements and other impacts of landfills. With closed- loop recycling, waste is used for its original purpose. With open- loop recycling, the waste is used for a different purpose. Recycling does not include the use of waste for generating energy, which is called energy recovery. The concept of recycling: Recycling is the reprocessing of waste into a feedstock for making new materials and products. Source-separation as a potential first step in the recycling process. Recycling is much more than source- separation. Recycling consists of: collection of recyclables from production, manufacturing or after use, as separate (e.g., cardboard, glass, metals) or mixed waste streams; separation of recyclables from nonrecyclable waste and into desired fractions (e.g., separate bales of PET bottles and multilayer cartons); cleaning and processing of separated recyclables into a workable form, such as liquid plastic; processing into a secondary feedstock, such as plastic pellets, which can be directly used to make new products. https://www.youtube.com/watch?v=zyF9MxlcItw What drives recycling: Many recycling efforts are driven by cost-saving. The economic benefits of recycling are potential savings in landfill costs for waste managers (when landfill fees exceed the net cost of waste separation) and potential savings in the material costs of producers (when secondary materials are cheaper than virgin materials). The positive environmental image of recycling can also have a positive impact on prices and sales when consumers are environmentally minded. The benefits of recycling: The main environmental benefit of recycling is a reduction in the extraction of primary resources and their processing, which conserves resources and often reduces the environmental impacts associated with processing. Process energy may be reduced. Transport emissions may be reduced. Process nonenergy emissions. Forest carbon storage may reduce emission. Measuring recycling  CASE STUDY: Jordan and Lebanon Between 2010 and 2020, Jordan received $29.7 billion in aid; only $1 out of each $200 of it was targeting waste management. During that same period Lebanon received about $13 billion in aid, $1 out of each $270 it was for waste management. In 2013, however, Lebanon managed to recycle less than fifth (17%) of all generated waste, burying or openly dumping recyclable materials worth approximately one billion and 50 million dollars over the last decade. Jordan generated about 28 million tons of municipal waste over the last decade and in 2021 generated three million tons. This amount is expected to climb to 5.2 million tones. About 48% of Jordan’s waste is landfilled, 45% is openly dumped, and only less than tenth (7%) is recycled. Based on the Jordanian recyclables trading market prices, we estimated that at least $1 billion worth of recyclables has been buried or dumped over the last decade. A process diagram of the PET bottle recycling system. The environmental benefits of recycling critically depend on the extent to which it displaces primary material production, so the following must be kept in mind: Secondary feedstocks can rarely fully substitute primary feedstocks. Often, at least some primary (raw) material needs to be mixed in to ensure sufficient product quality. For example, when recycling aluminium cans. For food- grade plastic packaging, regulations stipulate a maximum amount of secondary material to prevent migration of contaminants into the food. Closed- loop recycling tends to be more beneficial than open- loop recycling because it substitutes the original primary feedstock, potentially multiple times, rather than a different type of material.  Some materials can be made from various secondary feedstocks, meaning substitution could take place between wastes. For example, for the production of insulation material, a manufacturer could choose between cullet (waste glass) and wastepaper. A recycled material from one country may substitute primary feedstocks from another country, which can strongly affect the comparative environmental benefits due to differences in production technology. Finally, recycling may reduce one environmental impact but increase another. Sometimes, recycling saves energy but requires more water or chemicals than primary processing, or more transport. The imperfect circle Recycling of secondary resources often has clear environmental benefits compared to primary feedstock production; it may require less energy, create fewer harmful pollutants, conserve natural resources and reduce waste- to- landfill. However, recycling cannot create a perfectly circular system: Recycling at a high quality requires energy, and the higher the quality that is demanded, the more energy is needed. Circulation of materials is possible only when materials are not locked into in- use stocks such as infrastructure and buildings. The imperfect circle Even if materials were not added to stock, inevitable losses during cycling imply a need for additional virgin material. Even if there were no in- use stocks and no processing losses, the growth in demand for products still prevents the loop from being closed. Fashion and technology change over time, meaning different materials may be needed now than can be recycled from past discards. To make new cars, phones and computers, producers often use newly invented materials that are not yet available through recycling.