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Waste Management Decision Tool

This tool is intended to support decision makers in understanding options at every stage of integrated sustainable solid waste management. It provides key information on the different options, including processes, infrastructure, opportunities, and challenges.
Developed in cooperation with International Solid Waste Association (ISWA), Nimmi Damodaran and ICP

Municipal Solid Waste

Collection Recycling Organic Waste Treatment Thermal Waste To Energi Disposal Site

COLLECTION

MORE INFORMATION

BASICS OF COLLECTION

WHAT IT IS

Solid waste is collected from generators using trained staff and specially built vehicles. Collection frequency is based on multiple factors, including cost, resident expectations, waste quantity, waste type, and climate.

Importance/Value

Comprehensive collection of waste is important, as poor collection leads to:
  • Local flooding from waste dumped on streets and clogging drains
  • Spread of disease from vermin
  • Loss of real estate value from unslightly littering and odour
  • Water polution due to leachate from dumped waste
  • Air pollution from residents burning uncollected waste
  • Black carbon and carbon dioxide emissions from burning waste and methane emissions from decomposition of organic waste contributing to climate change
  • Marine litter from plastic waste being carried by streams and rivers to the ocean

Stakeholders

  • Waste generators: Outreach is essential to communicate the importance of not littering and delivering waste for collection, and segregating waste if source segregation is being implemented
  • Waste collectors: Training is essential to ensure that staff collect waste on an established schedule; maintain professional demeanor; and collect sorted recyclables, or sort recycleables, if source segregation is being implemented. Incorporation of informal sector workers in collection activities provides them steady income and improves their working conditions

REQUIRED INFRASTRUCTURE

  • Clearly labeled (pictograms and/or words) bins to contain separate streams of waste if source segregation is being implemented
  • Collection vehicles outfitted with compartments if source segregation is being implemented, with optimal route planning

FINANCIAL VIABILITY

Collection costs can be covered by a combination of:
  • Collecting user fees from households
  • Incorporating cost of waste management in local taxes
  • Charging fees based on amount of waste collected (pay-as-you-throw programs)
  • Charging fees based on amount of income (e.g., pegged to electricity bills as a proxy for income)
  • Selling waste outputs, including recyclables, compost, biogas, refuse-derived fuel (RDF)
  • Fees from extended producer responsibility (EPR) schemes
  • Landfill taxes
Types Of Collection Will it be segregated?(L) Will it be segregated?(R) Who will segregated ? (L) Who will segregated ? (R) Material Recovery Facility

COLLECTION

BASICS OF COLLECTION

COLLECTION VEHICLES

Vehicle type
  • Handcarts
  • Pedal bikes/tricycles
  • Animal carts
Considerations
  • Non-motorized
  • Least cost
  • Navigable on small roads
  • Ideal for numerous stops
  • Ideal for frequent (e.g., daily) collection with low quantities
  • Low capacity
Vehicle type
  • Motorized tricycles
  • Tractors-trailer systems
  • Trucks
Considerations
  • Motorized
  • Ideal for fewer stops
  • Ideal for less frequent (e.g., weekly) collections with large volumes of waste
  • Mid to large capacity
Vehicle type
  • Fore and aft tippers
Considerations
  • Most Expensive
  • Most Capacity
  • Fewer Stops
  • Ideal for less frequent (e.g., weekly) collections with large volumes of waste
  • Large capacity

COLLECTION

TYPES OF COLLECTION

WHAT IT IS

DOOR-TO-DOOR

  • Also referred to as curbside or kerbside collection
  • Involves collecting household waste and recyclables using trained staff and specialty built vehicles
  • Depending on the model, residents bring waste to the collector when alerted or leave containers with waste at the curb

COMMUNAL COLLECTION

  • Also referred to as drop-off collection
  • Residents bring waste to large, centrally located bins
  • Collection vehicles empty bins regularly

REQUIREMENTS

DOOR-TO-DOOR

  • Bins for every household, with lids if left at curbside
  • Waste generators trained on segregation
  • Trained collectors
  • Predictable collection
  • Efficient collection route planning
  • Enhancements include mobile applications and GPS/QR codes to track collection activities

COMMUNAL COLLECTION

  • Large community-scale bins
  • Designed to prevent animal intrusion
  • Conveniently located for easy access to residents
  • Enhancements include smart bins that alert municipality when full to avoid overflowing bins or unnecessary trips by collection vehicles If bins are empty
  • Waste generators trained on segregation

ADVANTAGES

DOOR-TO-DOOR

  • Convenient for residents
  • Consistency in waste collection
  • Reduction of litter and dumping with regular collection
  • Higher rate of segregation and lower contamination rate

COMMUNAL COLLECTION

  • Fewer stops by collection vehicles
  • Less waste accumulates in residents homes
  • Potential avoidance of narrow roads that are difficult to navigate
  • Ideal for less frequent (e.g., weekly) collections with large volumes of waste
  • Large capacity

DISADVANTAGES

DOOR-TO-DOOR

  • Costlier than communal collection
  • Potentially difficult with narrow roads
  • Illegal dumping if schedule is not maintained
  • Missed collection if residents not at home

COMMUNAL COLLECTION

  • Illegal dumping if not conveniently located
  • Illegal dumping of bulk and hazardous waste
  • Littering around bins if not maintained properly
  • Overflowing bins if waste is not collected regularly

COLLECTION

SEGREGATION VERSUS NO SEGREGATION

DESCRIPTION

SEGREGATION

  • Waste is typically segregated as recyclables, organics, and other. Recyclables may be further segregated by category (e.g., glass, paper, metal). Non-recyclable combustibles in other may be segregated for refuse-derived fuel (RDF)
  • Waste that cannot be recycled or treated is disposed of in landfills

NO SEGREGATION

  • All waste is disposed of in landfills

INFRASTRUCTURE REQUIREMENTS

SEGREGATION

  • Bins
  • Materials recovery facilities (MREF)
  • Organic waste treatment facilities (composting or anaerobic digestion)
  • Landfills

NO SEGREGATION

  • Large-capacity landfills

ADVANTAGES

SEGREGATION

  • Mining waste for resources, which helps move to a circular economy
  • Revenues from sale of recyclables, compost, and biogas
  • Generation of green jobs
  • Preservation of resources by reducing use of virgin feedstock through recycling
  • Reduction of methane emissions by diverting organic waste from landfills
  • Extension of landfill life

NO SEGREGATION

  • Low costs of disposal in most developing countries where there are no tipping fees

DISADVANTAGES

SEGREGATION

  • Higher collection costs
  • Volatility of recyclables market

NO SEGREGATION

  • Increased methane emissions and leachate from organic waste in landfills
  • Increased black carbon emissions from landfill fires
  • Increased emissions from waste transportation vehicles as they travel to landfills distant from cities
  • Waste of resources
  • Challenges faced in developing new landfills if current disposal sites reach capacity

COLLECTION

WHO WILL SEGREGATE WITH DOOR TO DOOR COLLECTION?

DESCRIPTION

WASTE GENERATORS

  • Waste generators provide segregated waste to collectors
  • Waste collectors collect and transport waste in a segregated manner

WASTE COLLECTORS

  • Waste collectors collect mixed waste and segregate at point of collection
  • In some cities, waste collectors earn extra income by selling the segregated recyclables to third parties

MATERIALS RECOVERY FACILITY

  • Mixed waste is transported to a materials recovery facility where it is manually or mechanically sorted

REQUIREMENTS

WASTE GENERATORS

  • Clearly marked bins for every household (e.g., colour coded as blue for recyclables, green for organic, brown for all other, pictograms)
  • Collection vehicles
  • Waste collectors trained to segregate waste as they collect

WASTE COLLECTORS

  • Collection vehicles

MATERIALS RECOVERY FACILITY

ADVANTAGES

WASTE GENERATORS

  • Low-cost source segregation
  • Better segregation, depending on number of classifications
  • Cleaner recyclables
  • Higher quality organic waste

WASTE COLLECTORS

  • Better recycling rates
  • Higher quality organic waste
  • Economical If labor cost is low

MATERIALS RECOVERY FACILITY

  • Lower impact on waste generators
  • Faster collection of waste

DISADVANTAGES

WASTE GENERATORS

  • Lack of training may result in improperly sorted recyclables
  • Bins may be used for other purposes, especially in low-income areas

WASTE COLLECTORS

  • Time consuming resulting in more expensive labour costs

WASTE COLLECTORS

  • Most expensive, segregation costs are high
  • Poor quality recyclables
  • Contaminated organic waste

MATERIAL RECOVERY FACILITY

COLLECTION

SORTED RECYCLABLES “CLEAN MRF”

  • Waste generators provide recyclables sorted by type (e.g., glass, paper, plastic)
  • Waste collectors collect and transport sorted recyclables in a segregated manner

MIXED RECYCLABLES “DIRTY MRF”

  • Waste generators provide mixed recyclables
  • Waste collectors collect and transport mixed recyclables separately from non-recyclables

PROCESSING FOR SALE

SORTED RECYCLABLES “CLEAN MRF”

  • Recyclables that may be further sorted (e.g., separation of paper by type, glass by colour, plastics by type and colour) manually or mechanically
  • Recyclables baled by type for sale

MIXED RECYCLABLES “DIRTY MRF”

  • Recyclables sorted manually or mechanically
  • Manual sorting: Sorting by workers as recyclables move on conveyor belts
  • Mechanical sorting: Sorting by equipment, including conveyor belts, trommels, screens, air separator, optical sorter, magnetic separator
  • Recyclables baled by type for sale

ADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Lowest cost.
  • Cleaner recyclables allow higher material recovery rate
  • Increased segregated categories (e.g., glass segregated by colour) result in higher sale value

MIXED RECYCLABLES “DIRTY MRF”

  • Better segregation by material type using trained workers

DISADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Improper segregation if waste generator is not trained

MIXED RECYCLABLES “DIRTY MRF”

  • More expensive than processing sorted recyclables
  • Potential contamination of recyclables

COLLECTION

MATERIAL RECOVERY FACILITY

COLLECTION

SORTED RECYCLABLES "CLEAN MRF"

  • Waste generators provide recyclables sorted by type (e.g., glass, paper, plastic)
  • Waste collectors collect and transport sorted recyclables In a segregated manner

MIXED RECYCLABLES "DIRTY MRF"

  • Waste generators provide mixed nacyclables
  • Waste collectors collect and transport mixed recyclables separately from non-recyclables

PROCESSING FOR SALE

SORTED RECYCLABLES "CLEAN MRF"

  • Recyclables that may be further sorted (e.g.. separation of paper by type, glass by colour, plastics by type and colour) manually or mechanically
  • Recyclables baled by type for sale

MIXED RECYCLABLES "DIRTY MRF"

  • Recyclables sorted manually or mechanically
  • Manual sorting: Sorting by workers as recyclables move on conveyor belts
  • Mechanical sorting: Sorting by equipment, including conveyor belts, trommels, and different modes of separation (screens, air separator, optical sorter, magnetic separator)
  • Recyclables baled by type for sale

ADVANTAGES

SORTED RECYCLABLES "CLEAN MRF"

  • Lowest cost
  • Cleaner recyclables allow higher material recovery rate
  • Increased segregated categories (e.g., glass segregated by colour) result in higher sale value

MIXED RECYCLABLES "DIRTY MRF"

  • Better segregation by material type using trained workers

DISADVANTAGES

SORTED RECYCLABLES "CLEAN MRF"

  • Improper segregation if waste generator Is not trained

MIXED RECYCLABLES "DIRTY MRF"

  • More expensive than processing sorted recyclables
  • Potential contamination of recyclables

COLLECTION

WHO WILL SEGREGATE WITH COMMUNITY COLLECTION?

DESCRIPTION

WASTE GENERATORS

  • Waste generators drop off segregated waste into communal bins
  • Waste collectors collect segregated waste

MATERIALS RECOVERY FACILITY

  • Waste generators drop off mixed waste into single mixed-waste bin
  • Waste collectors collect and transport mixed waste to a materials recovery facility where it is manually or mechanically sorted

REQUIREMENTS

WASTE GENERATORS

  • Large, clearly marked (e.g., colours, pictograms) communal bins with clear instructions (e.g., different bins for plain glass, coloured glass, paper, cardboard, plastic organic waste) located at convenient locations and well maintained
  • Collection vehicles for segregated waste
  • Waste generators trained to segregate waste
  • Waste collectors trained to collect segregated waste

MATERIALS RECOVERY FACILITY

  • Facility, equipment, and labor to manually or mechanically sort recyclables from mixed waste

ADVANTAGES

WASTE GENERATORS

  • Lower cost due to savings in labor and transportation costs
  • Better segregation, depending on number of community bin categories
  • High-quality organic waste

MATERIALS RECOVERY FACILITY

  • Lower impact on waste generators because they don't have to to segregate

DISADVANTAGES

WASTE GENERATORS

  • Lack of training can result in improperly sorted recyclables

MATERIALS RECOVERY FACILITY

  • Most expensive segregation
  • Poor quality recyclables
  • Contaminated organic waste

ORGANIC WASTE TREATMENT

MORE INFORMATION

BASICS OF ORGANICS WASTE MANAGEMENT

WHAT IT IS

  • Organic waste is biodegradable waste from living matter (plant or animal) that can be decomposed by microorganisms
  • Organic material in municipal solid waste is primarily food waste from households and commercial enterprises and green waste from plant and tree maintenance in private and public spaces
  • Organic waste can be treated through composting, anaerobic digestion, or insect-based technology

IMPORTANCE/VALUE

  • The vast majority of municipal solid waste, particularly in developing countries, is organic in nature
  • Organic waste is dense and costs more to dispose of at landfills due to higher transportation costs and disposal fees
  • If disposed of in landfills, organic waste generates methane, which:
    • is a potent greenhouse gas
    • is a precursor to ground-level ozone, and
    • causes fires resulting in air pollution and emissions of black carbon, a short-lived climate pollutant
  • Leachate from organic waste in landfills can contaminate groundwater if it is not managed properly
  • Landfill life can be extended if organic waste is diverted and treated
  • Organic waste is a resource that can generate renewable energy, enrich the soil, and provide animal feed

Stakeholders

  • Waste generators who need to segregate organic waste and provide clean feedstock for processing
  • Waste collectors who need to work with waste generators to collect segregated organic waste and ensure clean feedstock
  • Project developers who municipalities may rely on to build organic waste treatment facilities
  • Consumers of organic waste treatment products (compost, digestate, biogas, animal feed)

REQUIRED INFRASTRUCTURE

  • Space and equipment for selected organic waste treatment facilities

FINANCIAL VIABILITY

Costs can be covered by:
  • Sale of compost as a soil amendment
  • Sale of biogas and digestate from anaerobic digestion
  • Reduced costs of disposal
  • Sale of animal feed from insect-based technology
anaerobic-digestion Thermal Waste To Energi disposal-site

ORGANIC WASTE TREATMENT

WHAT TYPE OF TREATMENT

PROCESS

COMPOSTING

  • Preparing the feedstock, including sorting to remove inorganics, dewatering, and adding bulking agents and nutrients
  • Decomposing aerobically (in the presence of oxygen), where microbes break down organic material resulting in compost and carbon dioxide
  • Curing, where material continues to degrade slowly resulting in a more stable product
  • Finishing, including screening out bulking agents, and blending with other additives

ANAEROBIC DIGESTION

  • Preparing the feedstock to remove impurities and macerating (adding water to create a slurry) to achieve the right consistency
  • Decomposing anaerobically (in the absence of oxygen), where microbes break down organic material resulting in biogas and digestate
  • Collecting the biogas and upgrading, if necessary, depending on intended use
  • Processing of digestate, if necessary, depending on intended use

INSECT-BASED TECHNOLOGY

  • Preparing the feedstock, including removing hazardous and inorganic material; dewatering, if necessary, to maintain the right moisture (70-80%); and processing into a paste or slurry
  • Having black soldier flies (BSF) mate where females lay about 500 eggs each, and the resulting larvae are scattered on the organic waste slurry which they consume and reduce the volume of waste
  • Harvesting the larvae that grow up to five times the size at their introduction into the waste
  • Processing harvested larvae into protein and oil for animal feed and supplements
  • Composting the reduced waste residue or using it in biodigesters to produce soil amendments and biogas

OUTPUT

COMPOSTING

  • Compost used as soil amendment
  • Combustible rejects, from initial sorting, and final screening processes used as an energy source
  • Rejects disposed at landfills

ANAEROBIC DIGESTION

  • Biogas used as an energy source in multiple ways, including heating, electricity generation, and transportation fuel
  • Digestate used as a soil amendment. Digestate is often dewatered, and the liquid is applied on land and the solid is either applied directly on land or composted
  • Rejects disposed at landfills

INSECT-BASED TECHNOLOGY

  • Insect-based protein for animal feed and potentially for human consumption
  • Insect-based oil for animal supplements
  • Residue that can be composted or processed in an anaerobic digester to produce biogas and digestate

ADVANTAGES

COMPOSTING

  • Easily done even at the household level
  • Less challenging than anaerobic digestion
  • More suited for green waste

ANAEROBIC DIGESTION

  • Renewable energy, important in the face of climate change
  • Shorter processing time than composting
  • Produces more energy than consumed
  • Causes less odour
  • More suited for food waste

INSECT-BASED TECHNOLOGY

  • Substantial reduction of the volume of waste (50-75%)
  • Animal feed produced in a sustainable and profitable manner

DISADVANTAGES

COMPOSTING

  • Poor feedstock which often leads to contaminated compost
  • Limited demand for contaminated compost
  • Neighborhood opposition to siting facilities
  • Typically, longer processing time
  • Does not reduce emissions of carbon dioxide, a greenhouse gas

ANAEROBIC DIGESTION

  • Poor feedstock leads to low-quality biogas
  • More complex process with multiple stages that require separate equipment
  • Costly to build and operate
  • Often plagued by operational issues due to poor training

INSECT-BASED TECHNOLOGY

  • Waste must be of appropriate quality as several factors could cause contamination (hazardous waste, high lignin content) that will affect the size of the larvae and could even kill them
  • Neighborhood opposition to siting facilities

ORGANIC WASTE TREATMENT

COMPOSTING

INPUT

HOUSEHOLD COMPOSTING

  • Food and green waste from individual households

DECENTRALIZED COMPOSTING

  • Food and green waste from communities or neighborhoods within a city

CENTRALIZED COMPOSTING

  • Food and green waste from across a city potentially including sewage sludge or manure

OUTPUT

HOUSEHOLD COMPOSTING

  • Compost as soil amendment

DECENTRALIZED COMPOSTING

  • Compost as soil amendment
  • Combustible rejects for thermal waste to energy
  • Rejects disposed at landfills

CENTRALIZED COMPOSTING

  • Compost as soil amendment
  • Combustible rejects for thermal waste to energy
  • Rejects disposed at landfills

REQUIREMENTS

HOUSEHOLD COMPOSTING

DECENTRALIZED COMPOSTING

  • Space for small Windrow Composting or space and equipment for In-vessel Composting with appropriate mixing, aeration, and moisture control
  • Labor to manage and operate the facility
  • Quality testing of compost

CENTRALIZED COMPOSTING

  • Space for Windrow Composting with screening equipment and small loaders or tractors to move and turn the material; or space and equipment for In-vessel Composting with appropriate mixing, aeration, and moisture control
  • Labor to manage and operate the facility
  • Quality testing of compost

ADVANTAGES

HOUSEHOLD COMPOSTING

  • Reduces waste to be collected
  • Soil amendment readily available to home composters
  • Suitable for households with space to compost

DECENTRALIZE COMPOSTING

  • Simpler technology than centralized systems
  • Lower capital costs than centralized systems
  • Higher quality of compost due to easier quality control with smaller volume of feedstock
  • Suitable for multiple households and large organic waste generators

CENTRALIZED COMPOSTING

  • Centralized control
  • Economies of scale for operating plant and marketing compost
  • Suitable for city-wide operations

DISADVANTAGES

HOUSEHOLD COMPOSTING

  • Potential odour and vermin problems

DECENTRALIZED COMPOSTING

  • Potential failure if community interest or participation declines
  • Potential odour and vermin problems

CENTRALIZED COMPOSTING

  • Requires substantial land, skilled labor, and mechanized equipment
  • Higher operation and maintenance costs
  • Maintaining quality of feedstock is difficult

ORGANIC WASTE TREATMENT

INSECT-BASED TECHNOLOGY

PROCESS

  • Food and green waste from communities or neighborhoods within a city

OUTPUT

  • Insect-based protein and oil to be used in animal feed
  • Compost when residue is composted
  • Biogas and digestate when the residue is processed in an anaerobic digestor

REQUIREMENT

  • Space and equipment for preprocessing (sorting, shredding, ensuring right moisture content) waste; breeding black soldier flies; waste treatment; and harvesting larvae
  • Trained labor to ensure proper feedstock (organic waste free of toxins and hazardous material), breeding and harvesting

ADVANTAGES

  • Substantial reduction of the volume of waste (50-75%)
  • Animal feed produced in a sustainable and profitable manner

DISADVANTAGES

  • Waste must be of appropriate quality as several factors could cause contamination (hazardous waste, high lignin content) that will affect the size of the larvae and could even kill them.
  • Neighborhood opposition to siting facilities

ORGANIC WASTE TREATMENT

ANAEROBIC DIGESTION

INPUT

DECENTRALIZED

  • Food and green waste from communities or neighborhoods within a city

CENTRALIZED

  • Food and green waste from across a city

OUTPUT

DECENTRALIZED

  • Biogas used as an energy source.
  • Digestate used as a soil amendment
  • Rejects disposed of at landfills

CENTRALIZED

  • Biogas used as an energy source
  • Digestate used as a soil amendment
  • Rejects disposed of at landfills

REQUIREMENTS

DECENTRALIZED

  • Typically uses systems that process up to 5 tonnes and requires equipment to process the feedstock for digestion, digest the waste, purify and store the gas, and process the digestate for use as soil amendment

CENTRALIZED

  • Typically uses systems with modules processing up to 50 tonnes each and requires equipment to process the feedstock for digestion, digest the waste, purify and store the gas, and process the digestate for use as soil amendment

ADVANTAGES

DECENTRALIZED

  • Waste can be diverted to other decentralized systems if one fails temporarily
  • Costs (capital and transportation) are lower
  • Output can be used locally (e.g., electricity generation for local street lighting and compost for local urban forestry)

CENTRALIZED

  • Achieves economies of scale due to larger operations
  • Larger volumes of gas haves potential to be injected in pipelines as renewable natural gas

DISADVANTAGES

DECENTRALIZED

  • Potential failure if community interest or participation declines
  • Resistance from local neighborhood

CENTRALIZED

  • Poor feedstock, which leads to low-quality biogas
  • More complex process with multiple stages that require separate equipment
  • Costly to build and operate
  • Often plagued by operational issues due to poor training
  • Waste piles up if system fails

ORGANIC WASTE TREATMENT

HOUSEHOLD COMPOSTING

INPUT

  • Food and green waste from individual households

OUTPUT

  • Compost as soil amendment

REQUIREMENTS

ADVANTAGES

  • Reduces waste to be collected
  • Soil amendment readily available to home composters
  • Suitable for households with space to compost

DISADVANTAGES

  • Potential odour and vermin problems

ORGANIC WASTE TREATMENT

DECENTRALIZED COMPOSTING

INPUT

  • Food and green waste from communities or neighborhoods within a city

OUTPUT

  • Compost as soil amendment
  • Combustible rejects for thermal waste to energy
  • Rejects disposed at landfills

REQUIREMENTS

  • Space for small Windrow Composting or space and equipment for In-vessel Composting with appropriate mixing, aeration, and moisture control
  • Labor to manage and operate the facility
  • Quality testing of compost

ADVANTAGES

  • Simpler technology than centralized systems
  • Lower capital costs than centralized system
  • Higher quality of compost due to easier quality control with smaller volume of feedstock
  • Suitable for multiple households and large organic waste generators

DISADVANTAGES

  • Potential failure if community interest or participation declines
  • Potential odour and vermin problems

ORGANIC WASTE TREATMENT

CENTRALIZED COMPOSTING

INPUT

  • Food and green waste from across a city potentially including sewage sludge or manure

OUTPUT

  • Compost as soil amendment
  • Combustible rejects for thermal waste to energy
  • Rejects disposed at landfills

REQUIREMENTS

  • Space for Windrow Composting with screening equipment and small loaders or tractors to move and turn the material; or space and equipment for In-vessel Composting with appropriate mixing, aeration, and moisture control
  • Labor to manage and operate the facility
  • Quality testing of compost

ADVANTAGES

  • Centralized control
  • Economies of scale for operating plant and marketing compost
  • Suitable for city-wide operations

DISADVANTAGES

  • Requires substantial land, skilled labor, and mechanized equipment
  • Higher operation and maintenance costs
  • Maintaining quality of feedstock is difficult

ORGANIC WASTE TREATMENT

DECENTRALIZED ANAEROBIC DIGESTION

INPUT

  • Food and green waste from communities or neighborhoods within a city

OUTPUT

  • Biogas used as an energy source
  • Digestate used as a soil amendment
  • Rejects disposed of at landfills

REQUIREMENTS

  • Typically uses systems that process up to 5 tonnes and requires equipment to process the feedstock for digestion, digest the waste, purify and store the gas, and process the digestate for use as soil amendment

ADVANTAGES

  • Potential failure if community interest or participation declines
  • Resistance from local neighborhood

DISADVANTAGES

  • Waste can be diverted to other decentralized systems if one fails temporarily
  • Costs (capital and transportation) are lower
  • Output can be used locally (e.g., electricity generation for local street lighting and compost for local urban forestry)

ORGANIC WASTE TREATMENT

CENTRALIZED ANAEROBIC DIGESTION

INPUT

  • Food and green waste from across a city

OUTPUT

  • Biogas used as an energy source
  • Digestate used as a soil amendment
  • Rejects disposed of at landfills

REQUIREMENTS

  • Typically uses systems with modules processing up to 50 tonnes each and requires equipment to process the feedstock for digestion, digest the waste, purify and store the gas, and process the digestate for use as soil amendment

ADVANTAGES

  • Poor feedstock, which leads to low-quality biogas
  • More complex process with multiple stages that require separate equipment
  • Costly to build and operate
  • Often plagued by operational issues due to poor training
  • Waste piles up if system fails

DISADVANTAGES

  • Achieves economies of scale due to larger operations
  • Larger volumes of gas haves potential to be injected in pipelines as renewable natural gas

ORGANIC WASTE TREATMENT

COMPOSTING

ONSITE COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Organizations that are going to compost small amounts of wasted food can compost onsite. Composting can significantly reduce the amount of wasted food that is thrown away. Yard trimmings and small quantities of food scraps can be composted onsite. Animal products and large quantities of food scraps are not appropriate for onsite composting

THINGS TO THINK ABOUT

  • The climate and seasons changes will not have a big effect on onsite composting. Small adjustments can be made when changes happen such as when the rainy season approaches
  • Food scraps need to be handled properly so they don't cause odors or attract unwanted insects or animals
  • Onsite composting takes very little time or equipment. Education is the key. Local communities might hold composting demonstrations and seminars to encourage homeowners or businesses to compost on their own properties
  • Creating compost can take up to two years, but manual turning can speed up the process to between three to six months
  • Compost, however, should not be used as potting soil for houseplants because of the presence of weed and grass seeds
  • You can leave grass clippings on the lawn-known as "grasscycling." These cuttings will decompose naturally and return some nutrients back to the soil, similar to composting
  • You can put leaves aside and use them as mulch around trees and scrubs to retain moisture

ORGANIC WASTE TREATMENT

COMPOSTING

VERMICOMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Red worms in bins feed on food scraps, yard trimmings, and other organic matter to create compost. The worms break down this material into high-quality compost called castings
  • Worm bins are easy to construct and are also available for purchase. One pound of mature worms (approximately 800-1,000 worms) can eat up to half a pound of organic material per day. The bins can be sized to match the volume of food scraps that will be turned into castings
  • It typically takes three to four months to produce usable castings. The castings can be used as potting soil. The other byproduct of vermicomposting known as "worm tea" is used as a high-quality liquid fertilizer for houseplants or gardens

THINGS TO THINK ABOUT

  • Ideal for apartment dwellers or small offices
  • Schools can use vemiiculture to teach children conservation and recycling
  • It is important to keep the worms alive and healthy by providing the proper conditions and sufficient food
  • Prepare bedding, bury garbage, and separate worms from their castings
  • Worms are sensitive to changes in climate
    • Extreme temperatures and direct sunlight are not healthy for the worms
    • The best temperatures for vermicomposting range from 55° F to 77° F (12.8° C to 25° C) o In hot, arid areas, the bin should be placed under the shade
    • Vermicomposting indoors can avoid many of these problems

ORGANIC WASTE TREATMENT

COMPOSTING

ONSITE COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Organizations that are going to compost small amounts of wasted food can compost onsite. Composting can significantly reduce the amount of wasted food that is thrown away. Yard trimmings and small quantities of food scraps can be composted onsite. Animal products and large quantities of food scraps are not appropriate for onsite composting

THINGS TO THINK ABOUT

  • The climate and seasons changes will not have a big effect on onsite composting. Small adjustments can be made when changes happen such as when the rainy season approaches
  • Food scraps need to be handled properly so they don't cause odors or attract unwanted insects or animals
  • Onsite composting takes very little time or equipment. Education is the key. Local communities might hold composting demonstrations and seminars to encourage homeowners or businesses to compost on their own properties
  • Creating compost can take up to two years, but manual turning can speed up the process to between three to six months
  • Compost, however, should not be used as potting soil for houseplants because of the presence of weed and grass seeds
  • You can leave grass clippings on the lawn-known as "grasscycling." These cuttings will decompose naturally and return some nutrients back to the soil, similar to composting
  • You can put leaves aside and use them as mulch around trees and scrubs to retain moisture

ORGANIC WASTE TREATMENT

COMPOSTING

VERMICOMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Red worms in bins feed on food scraps, yard trimmings, and other organic matter to create compost. The worms break down this material into high-quality compost called castings
  • Worm bins are easy to construct and are also available for purchase. One pound of mature worms (approximately 800-1,000 worms) can eat up to half a pound of organic material per day. The bins can be sized to match the volume of food scraps that will be turned into castings
  • It typically takes three to four months to produce usable castings. The castings can be used as potting soil. The other byproduct of vermicomposting known as "worm tea" is used as a high-quality liquid fertilizer for houseplants or gardens

THINGS TO THINK ABOUT

  • Ideal for apartment dwellers or small offices
  • Schools can use vemiiculture to teach children conservation and recycling
  • It is important to keep the worms alive and healthy by providing the proper conditions and sufficient food
  • Prepare bedding, bury garbage, and separate worms from their castings
  • Worms are sensitive to changes in climate.
    • Extreme temperatures and direct sunlight are not healthy for the worms
    • The best temperatures for vermicomposting range from 55° F to 77° F (12.8° C to 25° C) o In hot, arid areas, the bin should be placed under the shade
    • Vermicomposting indoors can avoid many of these problems

ORGANIC WASTE TREATMENT

COMPOSTING

AERATED (TURNED) WINDROW COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Aerated or turned windrow composting is suited for large volumes such as that generated by entire communities and collected by local governments, and high- volume food-processing businesses (e.g., restaurants, cafeterias, packing plants). It will yield significant amounts of compost, which might require assistance to market the end-product. Local governments may want to make the compost available to residents for a low or no cost
  • This type of composting involves forming organic waste into rows of long piles called "windrows" and aerating them periodically by either manually or mechanically turning the piles. The ideal pile height is between four anc eight feet (1.22 to 2.44 meters) with a width of 14 to 16 feet (4.27 to 4.88 meters). This size pile is large enough to generate enough heat and maintain temperatures. It is small enough to allow oxygen flow to the windrow's core
  • Large volumes of diverse wastes such as yard trimmings, grease, liquids, and animal byproducts (such as fish and poultry wastes) can be composted through this method

THINGS TO THINK ABOUT

  • Windrow composting often requires large tracts of land, sturdy equipment, a continual supply of labor to maintain and operate the facility, and patience to experiment with various materials mixtures and turning frequencies
  • In a warm, arid climate, windrows are sometimes covered or placed under a shelter to prevent water from evaporating
  • In rainy seasons, the shapes of the pile can be adjusted so that water runs off the top of the pile rather than being absorbed into the pile
  • Windrow composting can work in cold climates. Often the outside of the pile might freeze, but in its core, a windrow can reach 140° F (60° C)
  • Leachate is liquid released during the composting process. This can contaminate local ground water and surface-water supplies. It should be collected and treated
  • Windrow composting is a large-scale operation and might be subject to regulatory enforcement, zoning, and siting requirements. Compost should be tested in a laboratory for bacterial and heavy metal content
  • Odors also need to be controlled. The public should be informed of the operation and have a method to address any complaints about animals or bad odors

ORGANIC WASTE TREATMENT

COMPOSTING

IN-VESSEL COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • In-vessel composting can process large amounts of waste without taking up as much space as the windrow method and it can accommodate virtually any type of organic waste (e.g., meat, animal manure, biosolids, food scraps). This method involves feeding organic materials into a drum, silo, concrete-lined trench, or similar equipment. This allows good control of the environmental conditions such as temperature, moisture, and airflow. The material is mechanically turned or mixed to make sure the material is aerated. The size of the vessel can vary in size and capacity
  • This method produces compost in just a few weeks. It takes a few more weeks or months until it is ready to use because the microbial activity needs to balance and the pile needs to cool

THINGS TO THINK ABOUT

  • Some are small enough to fit in a school or restaurant kitchen
  • Some are very large, similar to the size of school bus. Large food process and plants often use these
  • Careful control, often electronically, of the climate allows year-round use of this method
  • Use in extremely cold weather is possible with insulation or indoor use
  • Very little odor or leachate is produced
  • This method is expensive and may require technical expertise to operate it properly
  • Uses much less land and manual labor than windrow composting

ORGANIC WASTE TREATMENT

COMPOSTING

AERATED (TURNED) WINDROW COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Aerated or turned windrow composting is suited for large volumes such as that generated by entire communities and collected by local governments, and high- volume food-processing businesses (e.g., restaurants, cafeterias, packing plants). It will yield significant amounts of compost, which might require assistance to market the end-product. Local governments may want to make the compost available to residents for a low or no cost
  • This type of composting involves forming organic waste into rows of long piles called "windrows" and aerating them periodically by either manually or mechanically turning the piles. The ideal pile height is between four anc eight feet (1.22 to 2.44 meters) with a width of 14 to 16 feet (4.27 to 4.88 meters). This size pile is large enough to generate enough heat and maintain temperatures. It is small enough to allow oxygen flow to the windrow's core
  • Large volumes of diverse wastes such as yard trimmings, grease, liquids, and animal byproducts (such as fish and poultry wastes) can be composted through this method

THINGS TO THINK ABOUT

  • Windrow composting often requires large tracts of land, sturdy equipment, a continual supply of labor to maintain and operate the facility, and patience to experiment with various materials mixtures and turning frequencies
  • In a warm, arid climate, windrows are sometimes covered or placed under a shelter to prevent water from evaporating
  • In rainy seasons, the shapes of the pile can be adjusted so that water runs off the top of the pile rather than being absorbed into the pile
  • Windrow composting can work in cold climates. Often the outside of the pile might freeze, but in its core, a windrow can reach 140° F (60° C)
  • Leachate is liquid released during the composting process. This can contaminate local ground water and surface-water supplies. It should be collected and treated
  • Windrow composting is a large-scale operation and might be subject to regulatory enforcement, zoning, and siting requirements. Compost should be tested in a laboratory for bacterial and heavy metal content
  • Odors also need to be controlled. The public should be informed of the operation and have a method to address any complaints about animals or bad odors

ORGANIC WASTE TREATMENT

COMPOSTING

IN-VESSEL COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • In-vessel composting can process large amounts of waste without taking up as much space as the windrow method and it can accommodate virtually any type of organic waste (e.g., meat, animal manure, biosolids, food scraps). This method involves feeding organic materials into a drum, silo, concrete-lined trench, or similar equipment. This allows good control of the environmental conditions such as temperature, moisture, and airflow. The material is mechanically turned or mixed to make sure the material is aerated. The size of the vessel can vary in size and capacity
  • This method produces compost in just a few weeks. It takes a few more weeks or months until it is ready to use because the microbial activity needs to balance and the pile needs to cool

THINGS TO THINK ABOUT

  • Some are small enough to fit in a school or restaurant kitchen.
  • Some are very large, similar to the size of school bus. Large food process ng plants often use these.
  • Careful control, often electronically, of the climate allows year-round use of this method.
  • Use in extremely cold weather is possible with insulation or indoor use.
  • Very little odor or leachate is produced.
  • This method is expensive and may require technical expertise to operate it properly.
  • Uses much less land and manual labor than windrow composting.

ORGANIC WASTE TREATMENT

COMPOSTING

AERATED (TURNED) WINDROW COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • Aerated or turned windrow composting is suited for large volumes such as that generated by entire communities and collected by local governments, and high- volume food-processing businesses (e.g., restaurants, cafeterias, packing plants). It will yield significant amounts of compost, which might require assistance to market the end-product. Local governments may want to make the compost available to residents for a low or no cost
  • This type of composting involves forming organic waste into rows of long piles called "windrows" and aerating them periodically by either manually or mechanically turning the piles. The ideal pile height is between four anc eight feet (1.22 to 2.44 meters) with a width of 14 to 16 feet (4.27 to 4.88 meters). This size pile is large enough to generate enough heat and maintain temperatures. It is small enough to allow oxygen flow to the windrow's core
  • Large volumes of diverse wastes such as yard trimmings, grease, liquids, and animal byproducts (such as fish and poultry wastes) can be composted through this method

THINGS TO THINK ABOUT

  • Windrow composting often requires large tracts of land, sturdy equipment, a continual supply of labor to maintain and operate the facility, and patience to experiment with various materials mixtures and turning frequencies
  • In a warm, arid climate, windrows are sometimes covered or placed under a shelter to prevent water from evaporating
  • In rainy seasons, the shapes of the pile can be adjusted so that water runs off the top of the pile rather than being absorbed into the pile
  • Windrow composting can work in cold climates. Often the outside of the pile might freeze, but in its core, a windrow can reach 140° F (60° C)
  • Leachate is liquid released during the composting process. This can contaminate local ground water and surface-water supplies. It should be collected and treated
  • Windrow composting is a large-scale operation and might be subject to regulatory enforcement, zoning, and siting requirements. Compost should be tested in a laboratory for bacterial and heavy metal content
  • Odors also need to be controlled. The public should be informed of the operation and have a method to address any complaints about animals or bad odors

ORGANIC WASTE TREATMENT

COMPOSTING

IN-VESSEL COMPOSTING

Note: Verbatim from United States Environmental Protection Agency - Types of Composting and Understanding the Process

https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process

DESCRIPTION

  • In-vessel composting can process large amounts of waste without taking up as much space as the windrow method and it can accommodate virtually any type of organic waste (e.g., meat, animal manure, biosolids, food scraps). This method involves feeding organic materials into a drum, silo, concrete-lined trench, or similar equipment. This allows good control of the environmental conditions such as temperature, moisture, and airflow. The material is mechanically turned or mixed to make sure the material is aerated. The size of the vessel can vary in size and capacity
  • This method produces compost in just a few weeks. It takes a few more weeks or months until it is ready to use because the microbial activity needs to balance and the pile needs to cool

THINGS TO THINK ABOUT

  • Some are small enough to fit in a school or restaurant kitchen
  • Some are very large, similar to the size of school bus. Large food process ng plants often use these
  • Careful control, often electronically, of the climate allows year-round use of this method
  • Use in extremely cold weather is possible with insulation or indoor use
  • Very little odor or leachate is produced
  • This method is expensive and may require technical expertise to operate it properly
  • Uses much less land and manual labor than windrow composting

RECYCLING

MORE INFORMATION

BASICS OF RECYCLING

WHAT IT IS

Recycling refers to processing materials from the waste stream, ideally by source segregation, and turning them into useful new products. Commonly recycled material includes glass, paper, cardboard, metal, plastic, and textiles. Less frequently recycled material includes motor oil, electronic waste, batteries, and tires.
Recycling requires:

IMPORTANCE/VALUE

Recycling has numerous advantages including:
  • Reducing waste disposal costs by reducing the amount to be landfilled
  • Conserving natural resources by reducing the use of virgin material
  • Saving energy and reducing pollution and greenhouse gas emissions associated with obtaining virgin material (mining minerals, harvesting lumber) and processing it
  • Providing employment opportunities

Stakeholders

  • Waste generators: Outreach is essential to communicate the importance of recycling and increase awareness of how to identify and segregate recyclables
  • Waste collectors: Training is essential to ensure that staff collect sorted recyclables separately from other waste
  • Informal sector: Integration of the informal sector into the formal waste management system is essential to preventing loss of their income
  • Operators of MRFs and MBTs: Training is required to ensure proper sorting, which increases the value of recyclables
  • Recycling companies: It is important to work in close cooperation with recycling companies to ensure a market for recyclables

REQUIRED INFRASTRUCTURE

  • Bins for separate collection of recyclables
  • Collection vehicles outfitted with compartments for recyclables
  • MRFs for sorting of recyclables, if recyclables are not segregated at collection
  • Mechanical Biological Treatment Facilities (MBTs) if recyclables are to be recovered from mixed waste

CHALLENGES

  • Recyclables must be clean enough to be reprocessed. Contamination (e.g., food residues) lowers the quality of recyclables and may cause whole batches of material to be discarded
  • Low market value and high operating costs may make it uneconomical to recycle
  • Lack of MRFs and appropriate technology affect the ability to recycle
  • Displacement of the informal sector can affect a marginalized community

FINANCIAL VIABILITY

Recycling costs can be covered by:
  • Imposing user fees on waste generators (e.g., residential and commercial)
  • Sale of recyclable material
  • Extended producer responsibility schemes
mechanical-biological materials-recovery thermal-waste-to-energy disposal-site

RECYCLING

MATERIALS RECOVERY FACILITY

COLLECTION

SORTED RECYCLABLES “CLEAN MRF”

  • Waste generators provide recyclables sorted by type (e.g., glass, paper, plastic)
  • Waste collectors collect and transport sorted recyclables in a segregated manner

MIXED RECYCLABLES “DIRTY MRF”

  • Waste generators provide mixed recyclables
  • Waste collectors collect and transport mixed recyclables separately from non-recyclables

PROCESSING FOR SALE

SORTED RECYCLABLES “CLEAN MRF”

  • Recyclables that may be further sorted (e.g., separation of paper by type, glass by colour, plastics by type and colour) manually or mechanically
  • Recyclables baled by type for sale

MIXED RECYCLABLES “DIRTY MRF”

  • Recyclables sorted manually or mechanically
  • Manual sorting: Sorting by workers as recyclables move on conveyor belts
  • Mechanical sorting: Sorting by equipment, including conveyor belts, trommels, and different modes of separation (screens, air separator, optical sorter, magnetic separator)
  • Recyclables baled by type for sale

ADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Lowest cost
  • Cleaner recyclables allow higher material recovery rate
  • Increased segregated categories (e.g., glass segregated by colour) result in higher sale value

MIXED RECYCLABLES “DIRTY MRF”

  • Better segregation by material type using trained workers

DISADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Improper segregation if waste generator is not trained

MIXED RECYCLABLES “DIRTY MRF”

  • More expensive than processing sorted recyclables
  • Potential contamination of recyclables

MECHANICAL BIOLOGICAL TREATMENT FACILITY

WHAT IT IS

MBT combines technologies to manage mixed waste with the goal of recovering recyclables and energy from waste and biologically treating the remainder to reduce the volume to be disposed in landfills. The key stages include:

  • Waste preparation: Manual screening of unsuitable material (e.g., bulky items) and mechanical processing (e.g., shredding, crushing, screening) to obtain the right sized particles for separation and treatment
  • Waste separation: Using properties of materials (e.g., size, density, volume, magnetism) to separate materials for recycling, RDF, and biological treatment
  • Biological treatment: Using aerobic decomposition or anaerobic digestion technologies to treat the organic material

IMPORTANCE/VALUE

MBT has numerous advantages including:

  • Recovering recyclables from mixed waste
  • Reducing waste disposal costs by reducing the amount to be landfilled
  • Producing refuse derived fuel (RDF) from non-recyclable combustibles in the waste stream
  • Producing biogas if anaerobic digestion is used for organic waste treatment

STAKEHOLDERS

  • Waste generators: Impact on waste generators is low as they are not required to segregate waste
  • Waste collectors: Impact on waste collectors is low as they are not required to implement segregated waste collection
  • Operators of MBTs: Training is required to ensure proper operation to increase the value of outputs and maintain equipment
  • Recycling companies: It is important to work with recycling companies to ensure a market for recyclables
  • Industrial users of RDF: Input from RDF users (e.g., cement kilns) is essential to ensure that the output from MBTs meets the requirements of the industrial users

REQUIREMENTS

CHALLENGES

  • The quality of recyclables is usually poor due to contamination with mixed waste and therefore usually has low market value
  • Waste, particularly in developing countries, is high in organic content. Segregating and biological treating organic waste results in high value compost and digestate, whereas mixed waste results in low quality compost-like material to be disposed in landfills
  • Poor maintenance and presence of rocks and stones in waste frequently leads to equipment failure

FINANCIAL VIABILITY

MBT costs can be covered by:

  • Sale of recyclables depending on quality of material
  • Sale of RDF depending on meeting market requirements
  • Reduced landfilling costs

RECYCLING

MECHANICAL BIOLOGICAL TREATMENT FACILITY

SEPARATION TECHNOLOGIES

MANUAL SEPARATION

DESCRIPTION

  • Waste moves on conveyor belts and is screened by manual labor

CONCERNS

  • Training of labor is required to ensure proper operation
  • Health and safety concerns of waste workers

BAG SPLITTER

DESCRIPTION

  • Gentle shredder intended to split plastic bags to spill waste contents

CONCERNS

  • Rigid objects can damage the splitter

SHREDDERS

DESCRIPTION

  • Waste is passed through equipment with knives and hooks to break the material into smaller sizes

CONCERNS

  • Rigid objects (e.g., rocks and stones) can damage equipment
  • Glass can be crushed and not available for recycling

PEBBLE MILL

DESCRIPTION

  • Heavy balls in a rotating cylinder separate and pulverize waste

CONCERNS

  • Glass can be crushed and not available for recycling

SCREW MILL

DESCRIPTION

  • Screws pull in waste into a shaft and use crushing tools to separate

CONCERNS

  • Glass can be crushed and not available for recycling
  • Plastics can be shredded only to a limited extent

HAMMERMILL

DESCRIPTION

  • Screws pull in waste into a shaft and use crushing tools to separate

CONCERNS

  • Hammers wear out.
  • Glass can be crushed and not available for recycling
  • Not suitable for high organic content moist waste

RECYCLING

MECHANICAL BIOLOGICAL TREATMENT FACILITY

SORTING TECHNOLOGIES

SIEVE SEPARATION

DESCRIPTION

  • Material is separated by size with the use of different sized sieves

OUTPUT

  • Coarse and fine fractions

MAGNETIC SEPARATION

DESCRIPTION

  • Magnets separate ferrous metals from the waste stream

OUTPUT

  • Iron and steel.

AIR SEPARATION

DESCRIPTION

  • Lighter waste is separated using air flow

OUTPUT

  • Plastics.

EDDY CURRENT SEPARATION

DESCRIPTION

  • Electric conductivity of different materials is used to separate them

OUTPUT

  • Non-ferrous metals

WET FLOAT-SINK SEPARATION

DESCRIPTION

  • Density of materials is used to separate them, and the process cleans them
  • Gravel

OUTPUT

  • Metals
  • Plastics
  • Purified organic matter
  • Sand
  • Silt
  • Stones

MANUAL SORTING

DESCRIPTION

  • Hand sorting of material

CONCERNS

  • Glass
  • Metals
  • Plastic

RECYCLING

MECHANICAL BIOLOGICAL TREATMENT FACILITY

BIOLOGICAL TREATMENT TECHNOLOGIES

AEROBIC DECOMPOSITION

DESCRIPTION

  • Similar to Composting technologies for treating segregated organic waste

OUTPUT

  • Output cannot be used as compost due to contamination by other waste material
  • Output can be used for RDF but depends on the calorific value of the material

ANAEROBIC DIGESTION

DESCRIPTION

  • Similar to Anaerobic Digestion technologies for treating segregated organic waste

OUTPUT

  • Weak gas production due to mixed waste.
  • Digestate cannot be used as soil amendment due to contamination

RECYCLING

MECHANICAL BIOLOGICAL TREATMENT FACILITY

WHAT IT IS

MBT combines technologies to manage mixed waste with the goal of recovering recyclables and energy from waste and biologically treating the remainder to reduce the volume to be disposed in landfills. The key stages include:

  • Waste preparation: Manual screening of unsuitable material (e.g., bulky items) and mechanical processing (e.g., shredding, crushing, screening) to obtain the right sized particles for separation and treatment
  • Waste separation: Using properties of materials (e.g., size, density, volume, magnetism) to separate materials for recycling, RDF, and biological treatment.
  • Biological treatment: Using aerobic decomposition or anaerobic digestion technologies to treat the organic material

IMPORTANCE/VALUE

MBT has numerous advantages including:

  • Recovering recyclables from mixed waste
  • Reducing waste disposal costs by reducing the amount to be landfilled
  • Producing refuse derived fuel (RDF) from non-recyclable combustibles in the waste stream
  • Producing biogas if anaerobic digestion is used for organic waste treatment

STAKEHOLDERS

  • Waste generators: Impact on waste generators is low as they are not required to segregate waste
  • Waste collectors: Impact on waste collectors is low as they are not required to implement segregated waste collection
  • Operators of MBTs: Training is required to ensure proper operation to increase the value of outputs and maintain equipment
  • Recycling companies: It is important to work with recycling companies to ensure a market for recyclables
  • Industrial users of RDF: Input from RDF users (e.g., cement kilns) is essential to ensure that the output from MBTs meets the requirements of the industrial users

REQUIREMENTS

  • Separation equipment
  • Sorting equipment
  • Biological treatment equipment

CHALLENGES

  • The quality of recyclables is usually poor due to contamination with mixed waste and therefore usually has low market value
  • Waste, particularly in developing countries, is high in organic content. Segregating and biological treating organic waste results in high value compost and digestate, whereas mixed waste results in low quality compost-like material to be disposed in landfills
  • Poor maintenance and presence of rocks and stones in waste frequently leads to equipment failure

FINANCIAL VIABILITY

MBT costs can be covered by:

  • Sale of recyclables depending on quality of material
  • Sale of RDF depending on meeting market requirements
  • Reduced landfilling costs

RECYCLING

MATERIALS RECOVERY FACILITY

COLLECTION

SORTED RECYCLABLES “CLEAN MRF”

  • Waste generators provide recyclables sorted by type (e.g., glass, paper, plastic)
  • Waste collectors collect and transport sorted recyclables in a segregated manner

MIXED RECYCLABLES “DIRTY MRF”

  • Waste generators provide mixed recyclables
  • Waste collectors collect and transport mixed recyclables separately from non-recyclables

PROCESSING FOR SALE

SORTED RECYCLABLES “CLEAN MRF”

  • Recyclables that may be further sorted (e.g., separation of paper by type, glass by colour, plastics by type and colour) manually or mechanically
  • Recyclables baled by type for sale

MIXED RECYCLABLES “DIRTY MRF”

  • Recyclables sorted manually or mechanically
  • Manual sorting: Sorting by workers as recyclables move on conveyor belts
  • Mechanical sorting: Sorting by equipment, including conveyor belts, trommels, and different modes of separation (screens, air separator, optical sorter, magnetic separator)
  • Recyclables baled by type for sale

ADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Lowest cost
  • Cleaner recyclables allow higher material recovery rate
  • Increased segregated categories (e.g., glass segregated by colour) result in higher sale value

MIXED RECYCLABLES “DIRTY MRF”

  • Better segregation by material type using trained workers

DISADVANTAGES

SORTED RECYCLABLES “CLEAN MRF”

  • Improper segregation if waste generator is not trained

MIXED RECYCLABLES “DIRTY MRF”

  • More expensive than processing sorted recyclables
  • Potential contamination of recyclables

THERMAL WASTE TO ENERGY

MORE INFORMATION

BASICS OF THERMAL WASTE TO ENERGY

WHAT IT IS

  • Thermal waste to energy (WtE) is the process of using waste to produce heat, fuel, and/or electricity by incineration or flameless oxidation processes
  • Typical Fuels for WtE processes are:
    • Mixed waste or residual waste from segregated collection
    • Pre-processed (e.g., shredded, screened) high calorific refuse derived fuel (RDF)
  • Typical WtE processes include:
    • Mass burn or incineration of mixed waste to produce energy
    • Coprocessing where waste or RDF is used as fuel at coal-fired power plants or industrial plants (e.g., cement kilns)
    • Pyrolysis where waste is heated in the absence of oxygen to produce char, synthesis oil, and synthesis gas for energy
    • Gasification where waste is heated at high temperatures with oxygen to produce synthesis gas for energy
    • WtE is less appropriate for waste with high moisture (e.g., organic waste), making it less suitable for developing countries where organic fraction is high. When waste contains high moisture/humid organic content, pre-treatment is required to increase the calorific value of the waste input
    • Flue ash collected by pollution control systems should be treated as toxic and disposed in hazardous waste disposal sites

IMPORTANCE/VALUE

  • Recovery of energy from waste materials
  • An alternative to waste disposal, which consumes substantial landfill volume and generates highly contaminated leachate and landfill gas that includes methane, a potent greenhouse gas
  • Reduction of the volume of waste by about 75%
  • Conversion of most of the reactive material in waste to inert substances
  • Safe sink for contaminants if bottom ash is disposed of at a sanitary landfill

STAKEHOLDERS

  • Waste collectors
  • Facilities producing RDF from mixed waste
  • Industrial facilities using RDF as substitute fuel or using electrical power and heat (combined heat and power)
  • Landfill operators who are interested in increasing landfill lifetime by identifying alternative waste management processes
  • Municipal or private waste management companies
  • Electricity suppliers

REQUIRED INFRASTRUCTURE

  • Space and equipment for WtE plant depending on type and scale
  • Facility for producing RDF
  • Infrastructure for sale of energy products such as electricity, heat, synthesis gas, or char
  • Demand for product (e.g., heat, electricity, RDF, synthesis gas, char) in proximity to producing facility
  • Safe disposal for residual ash (sanitary landfill) and toxic flue gas cleaning residues (hazardous waste landfill)

FINANCIAL VIABILITY

This waste treatment technology has the highest capital expenses costs can be covered by:
  • Gate fees
  • Taxes
  • Subsidies
  • Sale of energy (e.g., electricity, steam, synthesis gas, char)
disposal-site

THERMAL WASTE TO ENERGY

MASS BURN

PROCESS

GRATE-FIRED

  • Waste is incinerated as it is transported by moving metal grates through the combustion chamber
  • Processing temperature is ~850-1100°C
  • Organic matter is almost completely oxidated at perfect process conditions
  • It includes heat recovery, electricity production, flue gas cleaning, ash treatment

FLUIDIZED BED

  • Preprocessed waste (e.g., shredded, screened) is held in abeyance in the combustion chamber by air flow and a flying sand bed that optimizes the oxidation rate and energy yield
  • Processing temperature is ~550-900°C
  • Organic matter is almost completely oxidated at perfect process conditions
  • It includes heat recovery, electricity production, flue gas cleaning, ash treatment

OUTPUT

  • Heat/steam
  • Electricity
  • Low-quality ferrous metals
  • Bottom ash (25%) disposed of in landfill or occasionally used for road construction (depending on chemical properties and legal regulations)
  • Exhaust gas cleaning residues (e.g., flue ash) disposed of in hazardous waste landfill

ADVANTAGES

GRATE-FIRED

  • Best proven and widespread thermal waste treatment technology
  • Applicable to a wide range of waste types and particle sizes
  • Appropriate for material with a wide range of calorific values

FLUIDIZED BED

  • Higher energy yield and oxidation rate compared to grate-fired incineration
  • Proven technology
  • Economically superior to grate-fired incineration
  • Low total organic carbon in ash
  • Low nitrogen oxide emissions
  • Easier desulfurization of flue gas

DISADVANTAGES

GRATE-FIRED

  • Electricity generation is typically not energy efficient. Direct use of heat for industrial or heating purposes is energy efficient but requires demand from nearby facilities
  • Organic fertilizers and soil enhancers are lost
  • Mineral fertilizers are lost
  • Non-ferrous metals are typically lost
  • Ferrous metals are low quality
  • Minerals/construction materials are lost
  • Toxic organic components (e.g., dioxins, furans) are generated, requiring emissions control systems

FLUIDIZED BED

  • Depending on technology, maximum particle size should not be more than 60-350 mm
  • Capital expenditure is higher
  • More fly ash is produced
  • Organic fertilizers and soil enhancers are lost
  • Mineral fertilizers are lost
  • Non-ferrous metals are typically lost
  • Minerals/construction materials are lost
  • Generation of toxic organic components (e.g., dioxins, furans) requires emissions control systems, but is lower than for grate-fired systems

THERMAL WASTE TO ENERGY

COPROCESSING

PROCESS

  • Separation of high calorific waste (e.g., paper and plastic that is not recyclable)
  • Shredding of separated waste
  • Pelletization of shredded waste in some instances (e.g., for use in power plants)
  • Transportation to facilities to be used as a supplemental fuel in industrial processes using coal (e.g., cement kilns)

OUTPUT

  • Heat/steam
  • Electricity
  • Ash

ADVANTAGES

  • Reduces use of fossil fuels
  • It is more efficient due to lower moisture content and removal of non-combustible material
  • Requires lower capital expenses than incineration
  • Ash can be mixed in cement production if the quality of the ash does not compromise the quality of the cement

DISADVANTAGES

  • Burners and boilers may become corroded with chlorides in combustible waste, forming hydrogen chloride
  • Fine particles of glass and metals can adversely affect burners and boilers
  • Requires pretreatment and waste of higher calorific value than incineration

THERMAL WASTE TO ENERGY

PYROLYSIS

PROCESS

  • Thermal decomposition of organic material in an inert atmosphere (absence of reactive agents such as oxygen)
  • Slow, flameless oxidation in a heated rotating tube
  • Processing temperature 250–700°C

OUTPUT

  • Synthesis gas
  • Pyrolysis oil (in rare cases processing to chemicals)
  • Bio-char
  • Heat/steam
  • Electricity
  • Metals
  • Ash

ADVANTAGES

  • Multiple products are produced - synthesis gas, pyrolysis oil, and char
  • Bio-char can replace fossil fuels such as coal (e.g., steel production)
  • Effective carbon dioxide sink, as char can store it for hundreds of years if not used and landfilled in a safe manner
  • Bio-char is a good soil enhancer when produced with clean feedstock and well operated processes avoiding the generation of carcinogenic polycyclic aromatic hydrocarbons

DISADVANTAGES

More applicable for single type of material (e.g., plastic waste) than mixed waste due to:

  • Different substances requiring different pyrolysis temperatures
  • Poor quality of gas, oil, and char often preventing their use
  • Loss of organic fertilizers and soil enhancers as a result of input variations
  • Loss of mineral fertilizers
  • Generation of highly toxic organic substances (e.g., dioxins, furans)

THERMAL WASTE TO ENERGY

GASIFICATION

PROCESS

COMBUSTION OF SYNTHESIS GAS

  • Partial conversion of solid organic substances at high temperatures to gaseous substances (synthesis gas) with addition of a gaseous gasification agent (steam, oxygen, air)
  • Typically, a two-step process including incineration and a subsequent processing chamber for the synthesis gas
  • Processing temperature 400–1600°C

USE OF SYNTHESIS GAS TO PRODUCE CHEMICALS

  • Partial conversion of solid organic substances at high temperatures to gaseous substances (synthesis gas) with addition of a gaseous gasification agent (steam, oxygen, air)
  • Input should be free of metals and minerals (e.g., by pre-treatment using wet separation)
  • Two-step process:(1) Pressurized internally circulating fluidized bed (PICFB) incineration (500-900°C) and 2) Pressurized entrained flow (PEF) gasifier for the hydrocarbon-rich .gas and coke < 0.5mm (1200-1400°C)

OUTPUT

COMBUSTION OF SYNTHESIS GAS

  • Heat/steam
  • Electricity
  • Low-quality ferrous metals
  • Bottom ash disposed of in landfills
  • Slag

USE OF SYNTHESIS GAS TO PRODUCE CHEMICALS

  • Chemicals (methanol and hydrogen that serve as feedstock for production of chemicals)
  • Heat/steam
  • Electricity
  • Low-quality ferrous metals
  • Bottom ash (low amount) disposed of in landfills
  • Slag (low amount)
  • Exhaust gas cleaning residues disposed of in hazardous waste landfill

ADVANTAGES

COMBUSTION OF SYNTHESIS GAS

  • Most widespread type of gasification Higher energy yield, some of which can be used to glaze the ash/slag and convert it to an inert material

USE OF SYNTHESIS GAS TO PRODUCE CHEMICALS

  • Conversion of plastic waste components to raw materials (chemicals)
  • Higher position in waste hierarchy than mass burn as resources are recovered

DISADVANTAGES

COMBUSTION OF SYNTHESIS GAS

  • Higher capex than incineration
  • No recovery of energy spent for production of the burned materials
  • Loss of organic fertilizers and soil enhancers
  • Loss of mineral fertilizers
  • Loss of non-ferrous metals
  • Ferrous metal recovery only in low quality
  • Loss of minerals/construction materials
  • Generation of toxic organic components (e.g., dioxins, furans) requiring emissions control systems

USE OF SYNTHESIS GAS TO PRODUCE CHEMICALS

  • Higher capex than incineration
  • Feasible only at large scale
  • Limited current use (e.g., primarily in Japan)
  • Need for pre-treatment to ensure appropriate feedstock
  • Generation of toxic organic components (e.g., dioxins, furans)

DISPOSAL SITE

MORE INFORMATION

BASICS OF DISPOSAL

WHAT IT IS

  • Waste that cannot be recycled or treated needs to be disposed of and is typically disposed of on land
  • The disposal is done at (1) sanitary landfills with environmental and safety controls in place, (2) dumpsites with no controls, or (3) controlled dumpsites, which may have some environmental and safety controls but are not as comprehensive as sanitary landfills

IMPORTANCE/VALUE

  • Disposal sites are necessary for unprocessed waste due to inadequate recycling and treatment processes or rejects when processes are in place
  • Lack of disposal sites and use of dumpsites instead of sanitary landfills result in:
    • Odour issues and diseases from vermin
    • Loss of real estate value
    • Air pollution from burning waste
    • Marine plastic pollution from plastic waste blown by wind and carried by streams and rivers to the ocean
    • Climate change from black carbon (burning waste) and methane emissions (decomposition of organic waste)

STAKEHOLDERS

  • Local government authorities responsible for waste management
  • Project developers, on who municipalities may rely on to build, operate, and monitor disposal sites

REQUIRED INFRASTRUCTURE

Dumpsites:

  • Disposal site with access and internal roads

Controlled dumpsites:

  • Suitable disposal site with access and internal roads and fencing
  • Scales for weighing waste at entry
  • Equipment for compaction
  • Material and equipment for temporary cover, if the surface is left open without placing fresh compacted waste daily

Sanitary landfills:

  • Suitable disposal site with access and internal roads and fencing
  • Scales for weighing waste at entry
  • Equipment for compaction
  • Material and equipment for temporary cover, if the surface is left open without placing fresh compacted waste daily
  • Basal liner system to prevent subsurface contamination
  • Leachate collection and treatment system
  • Landfill gas collection, treatment, and flaring/utilization systems
  • Landfill cover

FINANCIAL VIABILITY

Costs can be covered by:
  • Tipping fees paid by waste collectors
  • Gate fees for commercial or industrial waste generators
  • Sale of landfill gas (direct use) or electricity generated from the landfill gas

DISPOSAL SITE

SANITARY LANDFILL

FEATURES

  • Location selected considering physical and environmental conditions, population, and regulations
  • Designed by engineering experts
  • Controlled access with fencing or walls
  • Waste disposed of in a small area (the "working face”) at a time rather than spreading across the landfill
  • Temporary cover applied when there is no daily disposal at working face
  • Compaction with heavy equipment to ensure efficient use of space and stable surfaces
  • Slope stability assured by proper planning
  • Accounting of daily waste intake with weighing scales
  • Use of multiple liners at the base to prevent soil and water contamination (e.g., natural geological or compacted clay, high-density polyethylene membrane)
  • Leachate collection and treatment systems
  • Landfill gas collection systems with flaring of gas or collection for direct use or electricity generation
  • Equipment for air, water, and soil monitoring
  • Equipment for air, water, and soil testing
  • Capping with multiple layers (e.g., gravel, compacted clay, high-density polyethylene membrane, topsoil) during site closure

OUTPUT

  • Methane that is captured and flared or used for energy (electricity or direct use of gas)
  • Leachate that is treated and disposed either in sewage system or water bodies depending on the level of treatment

ADVANTAGES

  • Safe storage of waste
  • Isolation of waste from human settlements and ecologically sensitive areas
  • Prevention of groundwater contamination
  • Prevention of flammable, toxic, and greenhouse gas emissions
  • Prevention of high remediation costs from environmental pollution compared to dumpsites
  • Energy, and possibly revenue, generation from captured methane

DISADVANTAGES

  • Capital and operating costs higher than for controlled or uncontrolled dumpsites

DISPOSAL SITE

CONTROLLED DUMPSITE

FEATURES

  • A previous dumpsite where some environmental and safety measures are instituted, or a new site chosen by local authorities but operated with inadequate environmental and safety measures
  • Accounting of quantity of waste intake with weigh scales at entry
  • Fencing or walls to control access, but may still allow access to informal sector recycling
  • Poor understanding of types of waste being disposed of
  • Large, open areas of waste attracting animals and vermin
  • Inadequate compaction of waste
  • No liners at the base
  • Inadequate measures for air and water pollution control
  • No monitoring systems

OUTPUT

  • Methane released into the air
  • Other gaseous emissions recognized as odour and smoke
  • Toxic leachate released into the ground and and water bodies
  • Paper and plastic litter from being windblown

ADVANTAGES

  • Centralized disposal as opposed to littering across the urban area
  • More controls than at dumpsites
  • Capital and operating costs lower than sanitary landfills

DISADVANTAGES

  • Unsafe conditions if informal sector recyclers operate on the dumpsite
  • Disease from insects and vermin that can infect workers and nearby populations
  • Emissions of methane, a potent greenhouse gas and a precursor to ground-level ozone, which causes respiratory problems
  • Fires that release particulate matter, dioxins, and other pollutants into the air
  • Regional and global climate change effects due to methane emissions from decomposing organic matter and black carbon from fires
  • Rainwater intrusion and biological degradation of organic waste causing leachate infiltration into soil and groundwater
  • Often close to human settlements or ecologically sensitive areas
  • Slope failures from unstable surfaces and steep slopes that sometimes result in deaths
  • High remediation costs due to catastrophic environmental pollution or safety problems
  • Loss of real estate value from unsightly littering and odour
  • Marine litter from windblown plastic waste carried by streams and rivers to the ocean

DISPOSAL SITE

DUMPSITE

FEATURES

  • Poor site selection without consideration of location characteristics or regulations
  • Waste is dumped in an unplanned manner
  • Poor or no accounting of quantity and type of waste being disposed
  • No compaction of waste
  • Large open areas of waste attracting animals and vermin
  • No liners at the base
  • No access control (e.g., no fencing)
  • No control measures for air and water pollution
  • No monitoring systems

OUTPUT

  • Methane released into the air
  • Other gaseous emissions recognized as odour and smoke
  • Toxic leachate contaminating the ground and water bodies
  • Paper and plastic littering from being windblown

ADVANTAGES

  • Centralized disposal as opposed to littering across the urban area
  • Low capital and operating costs

DISADVANTAGES

  • Unsafe conditions with informal sector recyclers operating on the dumpsite
  • Disease from insects and vermin that can infect workers and nearby populations
  • Emissions of methane, a potent greenhouse gas and a precursor to ground-level ozone that causes respiratory problems
  • Few or no limitations on types of waste accepted
  • Fires that release particulate matter, dioxins, and other toxic pollutants into the air
  • Regional and global climate change effects due to methane emissions from decomposing organic matter and black carbon from fires
  • Rainwater intrusion and biological degradation of organic waste causing leachate infiltration into soil and groundwater
  • Often close to human settlements or ecologically sensitive areas
  • Slope failures from unstable surfaces and steep slopes that sometimes result in deaths
  • High remediation costs due to catastrophic environmental pollution or safety problems
  • Loss of real estate value from unsightly littering, odour, and contaminated land and water bodies
  • Marine litter from windblown plastic waste carried by streams and rivers to the ocean