CHE 490: Resource Recovery from Waste - Introduction and Legislative Background PDF

CHE 490: Resource Recovery from Waste Chapter 1: Introduction and Legislative Background Prof. Nariman Yousefi Winter 2025 Reference for this Chapter  Treatment, management and resource recovery from Municipal Solid Waste (MSW) George Tchobanoglous, Hil...

CHE 490: Resource Recovery from Waste Chapter 1: Introduction and Legislative Background Prof. Nariman Yousefi Winter 2025 Reference for this Chapter  Treatment, management and resource recovery from Municipal Solid Waste (MSW) George Tchobanoglous, Hilary Theisen, Samuel Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues, McGraw-Hill, 1993, New York 2 Our 89 ton legacy  An average Canadian produces ~89 tons of garbage (~5.9 lbs per day) in their lifetime!  This average person might live for 80 years, but their 89 ton legacy will remain in the environment for years, if not centuries!  What do you think your garbage legacy will be? 3  Garbology: Our Dirty Love Affair with Trash An interesting and eye-opening book written by Pulitzer prize winner Edward Humes. This book is not officially a reading material for this course but I will be making references to it throughout the course. Highly recommended for those interested in gaining extra knowledge on how we ended up drowning in our own trash! More on this book: https://www.youtube.com/watch?v=ONhxuHHdGW8 4 Some stats from Garbology  The average American has a trash legacy of 102 tons!  The biggest export of the US in 2010s? You guessed it right, trash!  New York City spends $2 billion a year on MSW management, $300 million of which is only on transportation of trash to out-of-state landfills. That’s 12,000 tons of trash per day or 62 Boeing 747s.  44% of world’s greenhouse gases are generated to manufacture products that will eventually end up in landfills as trash. 5 What is solid waste?  Solid waste describes non-hazardous refuse generated from domestic, industrial, commercial or institutional sources  Excludes waste that are hazardous, radioactive or liquid  May include dewatered solids (such as dry biosolids from wastewater treatment facilities but not liquid or sludge) 6 Solid Waste – A consequence of life  In the days of primitive society, the disposal of human and other solid waste did not pose a problem as population was small.  Waste disposal became a problem when humans started congregating in villages, cities and tribes.  Littering of food in medieval times, into streets and vacant land, led to breeding of rats and eventually the bubonic plague epidemic in 14th century, also known as the Black Death, which killed half the Europe’s population. 7 Solid Waste – A consequence of life  Only in 19th century, the society came to the realization that solid waste needs management, to control rodents and flies as vectors for diseases.  It has been shown that 22 human diseases can be traced to improper waste management.  Improper solid waste management can also result in pollution of air and water. Liquid leached from poorly designed landfills has contaminated ground and surface waters. Leachates from mining waste may contain arsenic, copper and other toxic elements that pollute water sources. 8 Waste Generation in a Technological Society  Upsurge in solid waste disposal problems started at the onset of the Industrial Revolution.  First urban sanitary act was passed in 1888 in the UK to prohibit the throwing of solid wastes into ditches, rivers and waters.  In North America, the first urban sanitary law was passed in the U.S. in 1899, to regulate the dumping of debris in waters and lands.  Along with the benefits of technology also came the problems associated with the disposal of the resultant waste. 9 Waste Generation in a Technological Society  Waste is generated in every process step that turns raw materials into a product  Best way to decrease waste is to limit the consumption of raw materials and to increase the rate of recovery and reuse of waste materials. 10 Waste Generation in a Technological Society  This concept is simple; however, implementing it in a modern society has proven to be difficult.  That’s why we constantly look for improved waste management strategies!  Unlike water-borne and air dispersed waste, solid waste does not “go away” on itself! 11 Development of Solid Waste Management  Solid waste management is the discipline associated with the control of generation, storage, collection, transfer and transport, processing and disposal of solid wastes in accord with best practices in public health, economics, engineering, and other environmental consideration.  It is an interdisciplinary process encompassing: o Political Science o City and Regional Planning o Geography o Economics o Public Health o Engineering (civil, chemical) o Materials Science 12 Development of Solid Waste Management  ”The Disposal of Municipal Refuse” was the first book published on MSW management in 1906 by B. Parsons.  The most recognized methods for MSW disposal at the beginning of 20th century were: o Dumping on land o Dumping in water o Plowing into the soil o Feeding to hogs (food waste) o Reduction o Incineration 13 Development of Solid Waste Management  Sanitary landfilling did not start until early 1940s in the US. New York City under the leadership of mayor La Guardia, and Fresno, CA were the pioneers in sanitary landfilling.  What is a sanitary landfill? An engineered ditch covered with impermeable lining to limit the leaching of liquid from waste into aquifers and other water sources. Modern landfills have pipe networks to collect the gases generated as a result of waste fermentation to avoid explosions, and use them for heating. 14 Elements of MSW Management Systems  Waste Generation: activities in which materials are identified as no longer being of value and are either thrown away or gather together for disposal.  Waste handling and separation, storage and processing at source: Separation of waste by owner into different categories (landfill, recycling, compost, etc.)  Collection: gathering of solid waste and their transport into a materials processing facility (MPF), a transfer station or a landfill. 15 Elements of MSW Management Systems  Separation, processing and transformation of solid waste: Separation and sorting of materials by size and type (e.g. paper, cardboard, metal, glass, etc.) and resource recovery from them. The organic fraction of MSW can be transformed using chemical (combustion) or biological (aerobic composting) methods.  Transfer and transport: Transfer of waste to its final destination (materials processing facility, landfill, etc.)  Disposal: Mostly landfilling. Even residue from combustion of waste or their composting will end up in landfills. 16 Integrated Solid Waste Management Integrated Solid Waste Management: The selection and application of suitable techniques, technologies, and management programs to achieve specific waste management objectives.  Source Reduction: reducing the amount or toxicity of waste generated. The most effective strategy to mitigate waste disposal problem.  Recycling: Separation of materials for reuse, reprocessing and remanufacturing 17 Integrated Solid Waste Management Integrated Solid Waste Management: The selection and application of suitable techniques, technologies, and management programs to achieve specific waste management objectives.  Waste Transformation: Physical, chemical and biological alteration of waste. Results in reduced use of landfill.  Landfilling: The most common and the least preferred method for waste management. Why is it least preferred? 18  Legislative Background of Municipal Solid Waste Management in Canada 19 MSW Legislative Background in Canada MSW Management in Canada is a shared responsibility between the federal, provincial/territorial and municipal governments The federal government provides policy framework and basic funding through the Canadian Council of the Ministers of the Environment (CCME) 20 CCME  Established in 1964  Comprised of the environment ministers from the federal, provincial and territorial governments  The 14 ministers meet annually to discuss national environmental priorities, set strategic environmental directions, and set out key performance indicators 21 CCME Organization 22 CCME Notable Policies  Strategy on Zero Plastic Waste (2018)  Phase 1 of Canada-wide Action Plan On Zero Plastic Waste (2019)  Phase 2 of Canada-wide Action Plan On Zero Plastic Waste (2020)  Canada-wide Strategy for Sustainable Packaging (2009) 23 Relevant Federal Legislations  Canadian Environmental Protection Act (1999) Environment Canada has regulation in place that mandates which substances and components can and cannot be used in products  Transportation of Dangerous Goods Act (1992) Transport Canada, also has the responsibility of monitoring and dictating how wastes are transported between provincial and national borders  Canadian Environmental Assessment Act (2012) 24 Provincial Legislations  Waste management in Canada is primarily regulated at the provincial level.  In Ontario, waste management happens at two levels: residential and the industrial, commercial and institutional (IC&I) sectors  Residential waste management and recycling services are mandated by the provincial government, but are carried out by local municipalities. Each municipality develops its own waste management program.  Members of the IC&I sector are individually responsible for complying with waste related regulations and their compliance is determined by their size. 25 Relevant Ontario Legislations  Environmental Protection Act (1990): "The purpose of this Act is to provide for the protection and conservation of the natural environment.” o Ontario Regulation 102/94: Waste Audits and Waste Reduction Work Plans o Ontario Regulation 103/94: Industrial, Commercial and Institutional Source Separation Programs o Ontario Regulation 104/94: Packaging Audits and Packaging Reduction Work Plans o Regulation 347: General Waste management  Environmental Assessment Act (1990): "The purpose of this Act is the betterment of the people of the whole or any part of Ontario by providing for the protection, conservation and wise management in Ontario of the environment." o Ontario Regulation 101/07: Waste Management Projects 26 Relevant Ontario Legislations  The Planning Act (1990): "To promote sustainable economic development in a healthy natural environment within the policy and by the means provided under this Act.”  Waste Diversion Act (2002): "The purpose of this Act is to promote the reduction, reuse and recycling of waste and to provide for the development, implementation and operation of waste diversion programs."  Waste-Free Ontario Act (2016): “An Act to enact the Resource Recovery and Circular Economy Act, 2016 and the Waste Diversion Transition Act, 2016 and to repeal the Waste Diversion Act, 2002” 27 Waste Free Ontario Act 2016  Intends to establish a full Extended Producer Responsibility (EPR) system, enabling the development of a circular economy supporting recycling and waste reduction.  Transition from municipalities collecting, processing and seeking funding for waste management to EPR system in which producers collect and process at their own expense (by 2025)  Zero waste and zero greenhouse gas emission from waste sector by 2050 28 Waste Diversion Transition As part of the transition from the the now repealed Waste Diversion Act, Ontario administered several recycling programs:  Blue Box/Blue bin recycling program (active)  Household Hazardous Waste program (active)  Paints and Coatings program (ceased 2021)  Electronic Waste (e-Waste) program (ceased 2021)  Used Battery Program (ceased 2020)  Used Tires program (ceased 2018) 29 Waste Diversion Transition  As part of Waste Diversions Act 2002, municipalities recovered parts of the collection and recycling costs of the mentioned categories from the producers.  With the introduction and phased implementation of the Waste-Free Ontario Act 2016, a transition to full EPR model will take place, where producers will be gradually responsible for all aspects of the collection and recycling of waste arising from their products. 30 Waste Diversion Transition  Ontario is transitioning the current Blue Box Program to a producer responsibility model. The new model means transitioning costs of the Blue Box Program away from municipal taxpayers and making producers of products and packaging fully responsible for the litter they create. (2023-2025)  Hazardous and Special Products requirements under a new regulatory framework, which makes producers of products such as paints, pesticides, solvents, oil filters, antifreeze and pressurized containers responsible for creating an accessible, convenient and free collection network, is now in place. (starting 2021) 31 Waste Diversion Transition  Tire Collection and Recovery requirements under a new regulatory framework, which makes tire producers responsible for creating an accessible, convenient and free tire collection and recycling or retreading network across the province, is now in place.  Waste Electrical and Electronic Equipment requirements under a new regulatory framework, which makes producers of electronic equipment like computers, televisions and stereos responsible for creating an accessible, convenient and free collection and recycling or refurbishing network across the province, is now in place. 32 Waste Diversion Transition  Battery Collection and Recovery requirements under a new regulatory framework, which makes producers of all primary and rechargeable batteries that weigh less than 5kg responsible for creating an accessible, convenient and free battery collection and recycling or refurbishing network across the province, is now in place (starting 2021)  The Ontario Deposit Return Program for beverage and alcohol containers (new program) 33 City of Toronto Solid Waste Bylaws Local municipalities control MSW through program management bylaws, such as:  Collection o Toronto Municipal Code Chapter 844 – Residential Collection o Toronto Municipal Code Chapter 841 – Commercial Collection  Fees o Toronto Municipal Code Chapter 441 – Fees and Charges  Packaging o Toronto Municipal Code Chapter 604 – Packaging 34 City of Toronto Solid Waste Bylaws Local municipalities control MSW through program management bylaws, such as:  Waste transfer and landfill o Toronto Municipal Code Chapter 864 – Waste Transfer Stations o List of prohibited Waste (schedule B)  Litter & dumping of refuse o Bylaw regarding littering and dumping of refuse 35 History of Landfilling in Toronto 36 History of Landfilling in Toronto  Toronto has been dumping its MSW in 160 landfills throughout the 20 th century. At the turn of the century though it started facing a trash crisis!  Toronto’s last landfill at Keele Valley, was near capacity in the 1990s. It was eventually closed in 2002.  The city shipped its MSW to Carleton Farms Landfill in Michigan until 2010.  The City purchased a landfill in London, Ontario (Green Lane landfill) and started shipping its waste to this site starting 2006. It has been sending its MSW to various landfills across Ontario since then. 37  CHE 490: Resource Recovery from Waste Chapter 2: Sources, Types and Composition of MSW Prof. Nariman Yousefi Winter 2025 Motivation ❑ Solid waste: all solid or semi-solid materials that the processor no longer considers of sufficient value to retain ❑ Knowledge on sources and types of MSW, along with data on composition and rates of generation, is basic to the design and operation of the functional elements of MSW treatment programs. 2 Sources of Solid Waste ❑ Residential ❑ Commercial ❑ Institutional ❑ Construction and demolition ❑ Municipal Services 3 Sources of Solid Waste ❑ Treatment Plant Sites ❑ Industrial ❑ Agricultural 4 Sources of Solid Waste 5 Types of Solid Waste Residential and Commercial Waste ❑ Includes organic (combustible) and inorganic (non-combustible) solid waste from residential areas and commercial establishments ❑ Organic fraction: food waste (garbage), all types of paper, corrugated cardboard (also known as corrugated paper and paperboard), all types of plastics, rubber, textile, leather, wood, yard wastes. ❑ Inorganic fraction: glass, crockery, tin cans, aluminum, ferrous metals, dirt 6 Types of Solid Waste ❑ There are 50 types of paper waste. They are mostly comprised of newspapers, books, magazines, commercial printing, office papers, paperboard, paper packaging, tissue paper and towels. ❑ Plastic materials are categorized in 7 groups. Polyethylene terephthalate (PETE/1) High density polyethylene (HDPE/2) Polyvinyl chloride (PVC/3) Low density polyethylene (LDPE/4) Polypropylene (PP/5) Polystyrene (PS/6) Other multilayered materials (7) 7 Types of Solid Waste ❑ Type of plastic is usually molded at the bottom of the plastic container. ❑ Mixed plastics are mixtures of two or more of the above classifications. 8 Types of Solid Waste Special and Hazardous Waste ❑ Bulky items: furniture, lamps, bookcases, filing cabinets, etc. ❑ consumer electronics: computers, monitors, printers, TV sets, etc. ❑ White goods: Home appliances such as fridge, stove, washer and dryer, dishwasher, etc. ❑ Hazardous wastes: wastes that pose substantial hazard to human health or the environment 9 Types of Solid Waste ❑ Batteries: Household facilities and vehicles. Household batteries come in variety of shapes and types (lithium, zinc, alkaline, nickel cadmium, mercury). Car batteries contain lead and sulfuric acid. The metal leachates from batteries can contaminate water (in case of landfilling) or air (in case of combustion). ❑ Used oil: From servicing of automobiles and other moving vehicles. They can contaminate ground and surface water. If mixed with other waste, will reduce the recyclability. ❑ Rubber tires: They can’t be compacted well so they waste landfill space. Highly flammable. 10 Types of Solid Waste Institutional Solid Waste: ❑ Government Centres ❑ Schools ❑ Prisons ❑ Hospitals 11 Types of Solid Waste Construction and Demolition ❑ Construction Waste: waste from construction, remodelling, and repairing of individual residences, commercial buildings, and other structures. Contains: dirt, stones, concrete, bricks, plaster, lumber, shingles, plumbing, heating and electrical parts. ❑ Demolition waste: Waste from razed buildings, Broken-out sidewalks, streets, bridges and other structures. Contains: similar materials to construction waste, as well as broken glass, plastics, and reinforcing steel. 12 Types of Solid Waste Municipal Services ❑ Street sweeping ❑ Road side litter ❑ waste from municipal containers ❑ landscape and tree trimmings ❑ catch-basin debris ❑ abandoned vehicles 13 Types of Solid Waste Treatment Plant Wastes and Residue ❑ Solid and semi-solid wastes from water, wastewater and industrial waste treatment facilities ❑ Wastewater treatment plant sludges are usually landfilled. ❑ Materials remaining from combustion of wood, coal, coke, and other combustibles are called ashes and residue and they are normally landfilled. 14 Types of Solid Waste Agricultural Waste: waste and residue resulting from agricultural activities such as row, field, tree and vine crops, production of milk, and production of animals. Industrial Waste: Solid waste generated at industrial sites 15 Composition of Solid Waste ❑ Waste composition: Individual components that make up a solid waste stream and their relative distribution, usually based on weight %. ❑ Waste composition is needed for evaluating equipment needs, systems, and management programs and plans. ❑ For example, if the stream contains lots of paper waste, shredders and balers are needed. 16 Composition of Solid Waste ❑ 50 to 75% of MSW originate from residential and commercial activities, and will have relatively uniform composition. ❑ The rest will depend on the extent of construction and demolition, extent of municipal services provided, the type of water and wastewater treatment plants in the region 17 Composition of Solid Waste 18 Distribution of Individual Waste Components Information on the physical composition of solid wastes are important in: ❑ Selection and operation of equipment and facilities ❑ Assessing the feasibility of resource and energy recovery ❑ Analysis and design of landfills 19 Distribution of Individual Waste Components 20 Distribution of Individual Waste Components 21 Physical Properties of MSW ❑ Specific Weight: Weight of a material per unit volume (lb/ft3 or lb/yd3). Specific weight can be reported for loose, as found in containers, uncompacted and compacted MSW. ❑ MSW specific weight can be affected by location, season, length of time in storage ❑ MSW specific weight can vary between 300 – 700 lb/yd3 22 Physical Properties of MSW ❑ Moisture Content: The percent of wet weight or dry weight of MSW. ❑ In MSW treatment, often the wet weight is considered as the moisture content of MSW. 23 Physical Properties of MSW 24 Physical Properties of MSW ❑ Particle size and size distribution: important for the design of screens and magnetic separators ❑ The size of a component is defined by one or more of the following measures: 25 Physical Properties of MSW ❑ Size distribution based on the largest dimension can be estimated using the following graphs: 26 Physical Properties of MSW ❑For aluminum cans, tins and glass, the size is usually calculated using eq. 4-5. Typical size distribution is given by this graph: 27 Physical Properties of MSW 28 Physical Properties of MSW ❑ Field Capacity: The total amount of moisture that can be retained in a waste sample subject to the downward pull of gravity. It is critical in determining leachates in a landfill. Water in excess of the field capacity will be released as leachate. ❑ Field capacity can be affected by the applied pressure and the state of decomposition. ❑ The field capacity of uncompacted MSW is typically 50 to 60 vol%. 29 Physical Properties of MSW ❑ Permeability of Compacted Waste: The hydraulic conductivity of compacted waste governs the movement of liquid and gases in the landfill. 30 Chemical Properties of MSW ❑ Chemical properties of MSW is important for design of the combustion and composting MSW treatment facilities. ❑ Proximate Analysis for the combustible part of MSW consists of: o Moisture (loss of moisture when heated up to 105 °C for 1 hr) o Volatile Combustible Matter (additional loss of weight in a covered crucible at 950 °C) o Fixed Carbon (combustible residue after the volatiles are lost) o Ash (weight of residue after combustion in an open crucible) 31 Chemical Properties of MSW ❑ Fusing Point of Ash: The temperature at which the ash resulting from the burning of waste will form a solid (clinker) by fusion and agglomeration. For MSW this value is typically 1100 – 1200 °C. ❑ Ultimate Analysis of Solid Waste Components: Involves determination of the percent of C, H, O, N, S and ash. It may also contain an analysis of halogens such as Cl, as well. ❑ Ultimate analysis can be used to determine the proper combination of MSW to achieve a balanced C/N ratio for composting. 32 Chemical Properties of MSW ❑ Energy Content of MSW Components: The energy content of the MSW components can be determined using a full scale or lab scale calorimeter, or by calculation, as long as the elemental composition of the MSW is known. 33 Chemical Properties of MSW ❑ If energy content of components are not available (per kJ/kg or Btu/lb), but the ultimate analysis is available, the energy content can be calculated using the modified Dulong formula: 34 Biological Properties of MSW Excluding plastic, rubber, and leather, the organic fraction of MSW can be classified as: ❑Water-soluble constituents: sugars, starches, amino acids, various organic acids ❑ Hemicellulose: a condensation product of 5 and 6 carbon sugars ❑ Cellulose: a condensation product of 6 carbon sugars ❑ Fats, oils and waxes: esters of alcohols and long chain fatty acids ❑ Lignin: a polymeric material containing aromatic rings with methoxyl groups ❑ Lignocellulose: a combination of lignin and cellulose ❑ Proteins: composed of chains of amino acids 35 Biological Properties of MSW ❑ Biodegradability of Organic Waste: Volatile solid (VS) content is used as a measure of biodegradability of MSW. VS is determined by ignition at 550 °C. ❑ VS can be misleading as some volatile components (newsprints and plant trimmings) are not highly biodegradable. ❑ The lignin component of waste can be used to determine the biodegradable fraction 36 Biological Properties of MSW 37 Biological Properties of MSW ❑ Production of Odours: Odours develop when wastes are stored for a long period of time in storage facilities, in landfills or in transfer stations. ❑ Under anaerobic condition, sulfate can be reduced to sulfide which combines with H to form H 2S: 38 Biological Properties of MSW ❑ Biological reduction of MSW can result in malodorous compounds such as methyl mercaptan and aminobutyric acid: 39  CHE 490: Resource Recovery from Waste Chapter 3: Materials Recovery from Waste Prof. Nariman Yousefi Winter 2024 Recycling of post-consumer materials ❑ Recovery of materials from waste stream ❑ Intermediate processing such as sorting and compaction ❑ Transportation ❑ Final processing 2 Main benefits of recycling ❑ Conservation of natural resources ❑ Landfill space ❑ Recycling requires materials and energy ❑ Success depends on existence of high demand for the materials 3 Key Issues ❑ Identification of Materials: o Max landfill life o Min operating costs o Legislative framework ❑ Reuse and Recycling Opportunities: o Markets for recovered materials o Collection infrastructure o Overall costs 4 Market for Plastics ❑ Low value of recovered plastics: Un-recycled materials have low value ❑ Lack of infrastructure: Not readily available in every local municipality ❑ Low specific weight ❑ Potential contamination: By foreign materials (food) and other plastics ❑ Collection infrastructure 5 Aluminum Cans ❑ Most successful recycling program with 65% recycling rate ❑ Constitute less of 1% of MSW 6 Aluminum Cans: Reason for success ❑ Recycled materials always compete with un-recycled raw materials. ❑ By comparison, raw glass, paper and plastics are relatively cheap ❑ Aluminum ore has to be exported from Jamaica, Australia, Suriname, etc. ❑ It is highly energy intensive 7 Economy of Aluminum Recycling ❑ Recycling provides a stable. Domestic source of Al ❑ Energy required to make a can from recycled Al is only 5% of the energy required to make it from unrecycled raw materials ❑ Recycled cans are uniform and easy to decontaminate ❑ Al favourably competes with glass and other metals for making containers 8 9 Paper and Cardboard ❑ By weight, paper constitutes the largest portion of MSW (25-40%) ❑ Only a small portion (25%) of paper is recycled due to economic and logistical considerations o Virgin (unrecycled) fiber is abundant and cheap in North America o Recycling centres are far from paper mills o Mill capacity to de-ink and recycle paper is limited 10 Types of Recycled Paper ❑ Newspaper: 33% of published newspapers are recycled and used in containerboard and corrugated cardboard (downgraded). ❑ Corrugated Cardboard: Largest source of paper waste that is recycled at a rate of 45%. Mostkly provided by supermarkets and big- box stores. Used as the liner (skin layer) of the cardboard boxes. ❑ High grade paper: Writing, printing, or book grade paper. Market for the untreated, uncoated long fiber paper is good. It is used as a replacement for high quality wood pulp or de-inked to be used as bond paper. 11 Major uses of recycled paper ❑ Pulp substitutes: Recycled papers that can be directly added to paper pulper without treatment ❑ De-ink grades: Recycled papers that are pulped, de-inked chemically and washed and bleached before being added to the pulp ❑ Bulk grades: Used without de-inking to make container board, liner and medium for corrugated containers, egg cartons, press boards, wall boards, etc. 12 Other uses of recycled papers ❑ Building products: Gypsum wall boards, loose fill and spray on insulations, saturated felt roofing ❑ Refuse-derived fuel (RDF): Biomass-fueled plants for energy recovery ❑ Exports: US is the largest exporter of waste paper at 23% of its annual use (6.3 million tonnes per year). Mostly exported to China, Korea, Mexico, Japan 13 Specification of Recycled Paper 14 Recycling of Plastics ❑ Use of plastics have dramatically increased since 1970 at annual growth rate of 6%. In 2021, 40 million tonnes of plastics produced in the US and 3 million tonnes in Canada. ❑ Only 9% is recycled and the rest is diverted to landfills (2023 data from Environment Canada) ❑ Plastics have largely replaced glass, metals and paper as container and packaging material ❑ Plastics constitute 7% of MSW by weight by much larger amount by volume 15 Recycling of Plastics 16 Types of recycled plastics ❑ PET and HDPE constitute the majority of the recycled plastics ❑ PET: Primarily recycled to polyester fibers used in sleeping bags, pillows, quilts and cold weather clothing. It is also used as carpet backing, fibers, molded products, etc. In addition to physical reprocessing, it can be chemically depolymerized to ethylene glycol and terephthalic acid that can re-polymerized to bottle grade PET again. Coca-cola has been using the repolymerized PET since 1991 to constitute a part of their bottle formulation. 17 Types of recycled plastics ❑ HDPE: Properties highly depends on the source of the material. Milk bottles are made from low melt index (low viscosity) resins, which allows the polymer to be stretched during blow molding. Rigid HDPE is from resins with high melt index for easy precision molding. Resins are usually not mixed and regrinds are made from single source HDPE. Recycled HDPE is used for detergent and motor oil containers. Usually made into a 3 layer container with the middle layer being recycled and inner and outer layer made from virgin polymers. 18 Types of recycled plastics 19 Types of recycled plastics ❑ PVC: Mostly used in electrical wires and drainage pipes. Very little PVC is recycled as cost of collection is high. Recycled PVS is used in shower curtains, non-food containers, truck bed liners, lab mats, floor tiles, garden hose, flower pots, etc ❑ LDPE: Mostly used in plastic bags, agriculture and construction. 16% of plastic stream of MSW is LDPE films and bags, The share is dropping due to bans on plastic shopping bags. Recycled LDPE can be used in films and bags. Printed label de-inking is a challenge leading to dark coloured recycled products. 20 Types of recycled plastics ❑ PS: 5 billion pounds is produced annually, 25% of which is used for food packaging as fast food containers, plates, meat trays, cups, utensils, and rigid packing materials. Many of these products are shifting towards other sustainable materials. PS only constitutes 1% of the MSW by volume. Recycled PS is used on making foam insulation boards, office accessories, toys, utensils and injection molded products. 21 Processing Plastics for Recycling 22 Processing Plastics for Recycling ❑ Granulation and washing: Bottles are made into small flakes by granulators. The chips are washed by hot water and detergent. ❑ Separation: Floatation in water tanks. PET sinks and HDPE and other polymers float. ❑ Drying: Spin dryer to remove excess water and then hot air drying to reduce the moisture content to below 0.5% ❑ Air classification: To separate PP (bottle caps) from HDPE (bottles and jugs) based on density. PP is lighter than HDPE. 23 Processing Plastics for Recycling ❑ Electrostatic separation: To remove aluminum contamination (usually the protective film beneath a PP cap in a bottle. ❑ Reclaim extrusion: Resin is melted for volatile compounds to evaporate. Resin might be mixed with different grades of recycled polymer or virgin polymer to modify the melt flow index. ❑ Pelletizing: The extruded melt usually looks like a strand of spaghetti. It is pelletized using a rotating knife as it exits the die. 24 Recycling of Glass ❑ Constitutes 8% of MSW by weight ❑ 90% is flint (clear), green or amber bottles. Remaining is glassware and plate glass. ❑ Recycling leads to reuse of materials, energy saving, reduced use of landfill, cleaner compost or RDF (glass is considered a contaminant in these cases) ❑ Almost all recycled glass is used to make new glass containers and bottles (30% is usually recycled). A minor amount is used to make glass wool, fiberglass, paving material (glasphalt) and construction materials. 25 Recycling of Glass ❑ Colour is usually a big problem. Producers prefer flint (clear) glass. 26 Recycling of Glass 27 Recycling of Glass ❑Manufacturers mix cullet (recycled broken glass) with raw materials (sand, soda ash and limestone) as it reduces the production furnace temperature significantly, leading to energy saving and lower cost of production. Cullet from broken of off-spec products are preferred as they are more uniform and less contaminated. Contamination affect the quality and colour of the glass. ❑ Fiberglass: Usually use cullet from in-house operations or other glass manufactures as specifications are stringent. ❑ Unsorted glass cullet is used in the manufacturing of construction materials. 28 Recycling of Ferrous Metals ❑ MSW contains 6% “tin“ cans mostly containing ferrous metals. Steel cans are called tin cans because of tin plating used to control the corrosion rate. ❑ The amount of ferrous cans are decreased significantly as they were replaced by plastic and aluminum. ❑ Ferrous metals can be also obtained from white goods (appliance), electronic equipment and cars (scarp metal). 29 Recycling of steel “tin” cans ❑ Magnetic separation to remove non-ferrous metal contaminants ❑ Shredding: Cans are shredded for the detinning process. Another magnetic separation step removes any non-ferrous contaminants such as aluminum. A vaccum system removes loose paper and plastic labels. ❑ Detinning: Done either at high temperature in a kiln to evaporate tin or by a chemical process using sodium hydroxide and other oxidizers. In chemical detinning, tin can be recovered electrochemically. ❑ Chemically detinned still is used in steel making (96% of the recycled cans). 30 Recycling of steel “tin” cans ❑ In heat detinned cans, part of the tin diffuses into steel and it is not suitable for steel making. They are used in copper making and also a source of iron oxide in paint making (as pigments). ❑ In copper extraction, copper ore is treated with sulfuric acid to produce copper sulfate, and the solution is leached through steel scrap to produce iron sulfate and to precipitate metallic copper. High surface area pellets from tin cans are ideal for this process. 1.65 ton of steel is required for producing 1 ton of copper. ❑ Major impediment to recycling is the high cost of transportation. The market price of steel also affects the demand for recycled cans. 31 Recycling of other non-ferrous metals 32  CHE 490: Resource Recovery from Waste Chapter 4: Thermal Conversion Technologies Prof. Nariman Yousefi Winter 2025 Waste Transformation by Combustion Thermal processing of MSW: conversion of MSW into gaseous, liquid, and solid products, with release of heat energy. Waste combustion has two major objectives:  Volume reduction (85-95%)  Recovery of thermal energy The main obstacle for widespread use of thermal conversion technologies is air pollution control. 2 Waste Transformation by Combustion Thermal processing of MSW can be categorized based on the amount of oxygen:  Stoichiometric combustion: combustion with the exact amount of oxygen needed to complete the combustion  Excess air combustion: combustion with oxygen higher than the stoichiometric requirement  Gasification: combustion at sub-stoichiometric oxygen level to generate a combustible gas mixture (CO, H2 and gaseous hydrocarbons) 3 Waste Transformation by Combustion Thermal processing of MSW can be categorized based on the amount of oxygen:  Pyrolysis: Thermal processing of MSW in complete absence of oxygen 4 Combustion products  Waste is mostly comprised of C, H, O, N , S  Trace amounts of metals can be found in MSW  Ideally, gases arising from (stoichiometric) combustion of MSW constitute: carbon dioxide, water, nitrogen and small amounts of sulfur dioxide  In reality, the gas composition could be different due to the nature of MSW and the combustion parameters 5 Stoichiometric combustion of MSW Under stoichiometric conditions, the following reactions will prevail: For carbon: C + O2 → CO2 For hydrogen: 2H2 + O2 → 2H2O For sulfur: S + O2 → SO2 Question: How much air is required for combustion of 1 lb of carbon? 6 Stoichiometric combustion of MSW 7 Stoichiometric combustion of MSW 8 9 Excess air combustion  MSW composition is unpredictable > stoichiometric combustion can never be achieved  Excess air is induced to promote mixing and turbulence  Excess air reduces combustion temperature  Temperatures less than 1450 ºF cause emission of odorous compounds  Temperatures above 1800 ºF reduce the emission of hazardous by- products such as dioxins, furans and volatile organic compounds 10 Combustion Systems  Combustion: thermal processing of MSW by chemical oxidation with stoichiometric or excess amounts of air.  Combustion products: hot gases (nitrogen, carbon dioxide, water), and non-combustible residue (ash).  MSW combustion systems can work either with commingled solid waste (mass-fired) or processed refuse derived fuels (RDF-fired). Mass-fired are the predominant combustion systems. 11 Combustion Systems Mass Fired Combustion Systems:  MSW is minimally processed before feeding to the combustion system  Crane operator manually rejects non-combustible items. The system must be designed to tolerate these items anyways.  The energy content of mass fired waste can vary extremely depending on the season, climate and source of waste. 12 13 Densified Refuse Derived Fuel (dRDF) Cubing and Pelleting Equipment  The technology to produce densified RDF (dRDF) from waste for combustion in incinerators, pyrolysis or gasification  Waste paper is extruded through extrusion dies with an eccentric rotating press wheel 14 Combustion Systems RDF-fired Combustion Systems:  Compared to the uncontrolled nature of unprocessed MSW, RDF can be produced with fair consistency to meet specifications for energy, moisture and ash content.  RDF can be produced in shredded, fluff, cube or pellet forms. Densified RDF (dRDF) is more costly to produce but easier to transport.  RDF systems are relatively smaller and easier to control, because of homogenous nature of RDF and its higher energy content. 15 Combustion Systems RDF-fired Combustion Systems: 16 Combustion Systems Fluidized Bed Combustion (FBC):  FBC is comprised of a refractory lined vertical steel cylinder, a sand bed, a supporting grid plate, and air injection nozzles named tuyeres.  With air injected through tuyeres, the bed fluidizes, and expands twice its resting volume.  Solid fuels such as coal or RDF are introduced below or above the fluidized bed. 17 Combustion Systems Fluidized Bed Combustion (FBC):  The “boiling” action of the fluidized bed introduces turbulence and mixing, and better heat transfer to the fuel.  FBC are versatile and can work with various types of waste.  Bed material can be plain sand or limestone (CaCO3). Limestone reacts with oxygen and SO2 to release CO2 and CaSO4 (gypsum) that is removed with the ash. Limestone beds are used for high sulfur wastes and fuels. 18 19 Combustion Systems Heat Recovery Systems:  Energy from hot flue gases are recovered by waterwall combustion chamber or waste heat boilers.  Hot temperature and steam can be used for various applications such as heating or electricity generation.  Heat recovery systems help recover part of the costs of the combustion system. They also reduce the environmental footprint of the plant. 20 Combustion Systems Heat Recovery Systems:  Waterwall combustion chamber: The walls of the combustion chamber are covered with vertically aligned boiler tubes. Water circulated in the tubes absorb combustion heat and turn into steam.  Waste Heat Boiler: The combustion chamber walls are lined with refractories to minimize heat loss. The hot flue gases pass through a separate heat boiler external to the combustion chamber. 21 Combustion Systems Steam Production Rates: 22 Combustion Systems Performance Criteria for MSW Combustion 23 Pyrolysis Systems  Pyrolysis: Thermal processing of waste in the absence of oxygen.  Pyrolysis (destructive distillation) is an endothermic reaction, and requires an external source of heat.  Most organic substances are unstable, and upon heating in an oxygen- free environment they undergo thermal cracking and condensation into gaseous, liquid and solid fractions. 24 Pyrolysis Systems Pyrolysis results in three fractions of materials:  Gas stream containing hydrogen, methane, carbon monoxide, carbon dioxide, and other organic gases.  A liquid fraction consisting of tar or oil streams, containing acetic acid, acetone, methanol, and complex oxygenated hydrocarbons. With processing the liquid fraction can be used as fuel oil.  Solid char consisting of pure carbon plus any inert material in the feed 25 Pyrolysis Systems The following pyrolysis reaction has been proposed for cellulose (C6H10O5): 3(C6H10O5) → 8H2O + C6H8O + CO + 2CO2 +CH4 +H2 +7C Liquid tar or Oil  Product fractions are highly dependant on pyrolysis temperature.  The energy content of liquid oil is about 9000 Btu/lb and the gas is about 700 Btu/ft3. 26 27 Gasification Systems  Gasification: partial combustion of carbonaceous fuel to generate a combustible fuel gas rich in carbon monoxide, hydrogen and some saturated hydrocarbons such as methane.  Gasification happens in presence of air or oxygen and is a net exothermic reaction.  Coal gasification has been in use since the 19th century! 28 Gasification Systems  The heat to sustain the process is derived from the exothermic reactions, whereas the combustible components are primarily generated by the endothermic reactions. 29 Gasification Systems  Operated at atmospheric pressure and in presence of air, the products of gasification are a low Btu (~150 Btu/ft3) gas (1-% CO2, 20% CO, 15% H2, 2% CH4 and N2 as balance), and condensable liquid such as pyrolytic oil.  When pure oxygen is used, a medium Btu gas (~300 Btu/ft3) is obtained. 30 Gasification Types Vertical Fixed Bed Gasifier  Simple and requires low capital investment  Requires uniform homogenous fuel such as dRDF  Fuel flows through the gasifier by gravity, air flows concurrently with the fuel. Gasifier operates at low temperature (1200 – 1500 ºF)  Products are low Btu gas, a small amount of liquid condensate, and char (activated carbon) 31 Gasification Types 32 Gasification Types  Gasifiers can work with pure oxygen for improved performance (Purox system)  Operating temperatures of 2600 – 3000 ºF  Product is a medium Btu gas (270 – 320 Btu/ft3) comprising 50% CO, 14% CO2, 4% CH4, 1% hydrocarbons, 1% N2. 33 Gasification Types Horizonal Fixed Bed Gasifier  The most commercially available type. It is also known as starved air combustor (incinerator), controlled air combustor, pyrolytic combustor or modular combustion unit (MCU).  MCU is comprised of a primary and secondary combustion chambers.  MSW is gasified into low Btu gases in the primary combustor under substoichiometric conditions. 34 Gasification Types  The gas is fully combusted into high temperature gases (1200- 1600 ºF) in the second combustor and can generate steam or hot water. The complete combustion gases comprise of CO2, H2O, N2) 35 Gasification Types Fluidized Bed Gasifiers  The FBC are very similar to the design explained in the excess air combustion category. FBC can be operated at stoichiometric mode as a gasifier. 36