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Solid Waste Management in Solid Waste Management in Canada: Current Practice, Canada: Current Practice, Priorities and ResearchPriorities and Research

J. Patrick A. Hettiaratchi, PhD, J. Patrick A. Hettiaratchi, PhD, PEngPEng..Environmental Engineering ProgramEnvironmental Engineering ProgramFaculty of EngineeringFaculty of EngineeringUniversity of CalgaryUniversity of CalgaryCANADACANADA

Solid Waste ManagementSolid Waste Management• Waste composition• Final disposal in Sanitary Landfills • Waste Minimization efforts

• Reduce and Reuse (at source)• Recycle: recyclables collection (on-site) and processing (off-site) • Recovery of Energy (waste to energy) or Resources (composting

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Waste Characteristics: QuantitiesWaste Characteristics: QuantitiesCanada: Overall

Waste Characteristics: compositionWaste Characteristics: composition

100.00Total

15.88.00Others2.63.00Metal8.62.00Plastic2.02.00Glass2.035.00Animal Waste3.020.00Wood18.060.00Yard Waste20.070.00Food Waste28.06.00Paper

Total wt (%)Moisture ContentComponents

City of Calgary

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Waste Characteristics: compositionWaste Characteristics: composition

Toronto Edmonton

Land Disposal of WasteLand Disposal of Waste• Disposal (land based) is central to any solid waste management strategy

• once produced, we cannot eliminate waste, but it is possible to reduce the amounts directed to landfills by adopting reuse, recycle, recovery

Almost always, a solid waste management plan is developed around a landfill

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Problems with LandfillsProblems with Landfills• Groundwater contamination by leachate

• can be controlled with bottom liner systems, cover systems etc. (expensive)• new ways of landfilling (bioreactors)

• Landfill gas escape into the atmosphere• gas extraction and use of passive systems for emission control• new ways of landfilling (bioreactors)

Another common approach: keep the landfill small! Divert, Divert, Divert…..

Waste Diversion in CanadaWaste Diversion in Canada

http://www.geog.utoronto.ca/info/faculty/Maclaren/Lecture%20slides1.pdf

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Waste Diversion: Reduce..Waste Diversion: Reduce..

• Backyard composting

Waste Diversion: Recycle..Waste Diversion: Recycle..

• Recyclables collection from homes • Curbside collection or Blue Box programs ( expensive, but collection efficiency is high)

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Waste Diversion: Recycle..Waste Diversion: Recycle..• Recyclables collection

• Green Box programs (less expensive, but efficiency is low)

Waste Diversion: Recycle..Waste Diversion: Recycle..Green Box operation

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Waste Diversion: Recycle..Waste Diversion: Recycle..• Recyclables processing

• Some are easily processed (metal, glass, paper – if a de-inking plant is available)

• But, others are difficult to process (plastics – since there are several varieties)

Waste Diversion: Recovery of Waste Diversion: Recovery of CompostCompost

• Large scale composting is popular in Canada

• Single feedstock: yard waste, sludge, MSW

• Mixed feedstock: mix solid waste with sludge from wastewater treatment plants

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Yard Waste CompostingYard Waste Composting

Windrow Composting Windrow Composting --EquipmentEquipment

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Edmonton CoEdmonton Co--composting composting FacilityFacility

• In operation since 1999

•The ‘largest’ in North America

The Edmonton Composting Facility composts MSW and de-watered sewage bio-solids.

Capacity: 200,000 tpa of MSW & 25,000 dry tpaof biosolids.

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** Main feature of Edmonton Co-composting Facility: 5 rotating steel drums, each drum 74 m long/4.9 m dia.

Biosolids injected into the drums together with MSW. Composting begins as the material tumble together while travelling for 1-2 days in the drum.

This stage is followed by a 14-day Aerated Windrow operation and curing

Edmonton CoEdmonton Co-- Composting Composting FacilityFacility

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Edmonton CoEdmonton Co-- Composting FacilityComposting Facility

• Aeration Building: size of 14 Ice-hockey rinks

CoCo--composting in Edmontoncomposting in Edmonton

• Capital cost: approximately $100 million

• Overall plant size: 416,500 ft2 (38,690 m2)

• Compost produced: approximately 80,000 tonnes/year

• Compost quality: Class B (??),

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Waste to Energy: Not popular now!!Waste to Energy: Not popular now!!

--Causes air pollution; need expensive air pollution Causes air pollution; need expensive air pollution control equipment to meet air quality standardscontrol equipment to meet air quality standards-- Produces a Produces a ““hazardous wastehazardous waste”” that requires a that requires a ““containment landfillcontainment landfill”” not a sanitary landfillnot a sanitary landfill

100 ton/day waste-to-energy facility in Harrisonburg, VA

Current Conventional “dry-tomb type” Sanitary Landfills are designed and constructed to eliminate problems associated with “Open Dumps”

Sanitary Landfills: accepts the majority of waste

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Conventional Landfill: A Designed Structure!!

Prevention of GW contamination with bottom liner systemsPrevention of GW contamination with bottom liner systems

Leachate is “garbage juice” or an aqueous liquid produced within the landfill

X-section along the length of the landfill

Stream

Area A

Area C

Area BWorking Face (Area D)

Leachate can contaminate Groundwater (unseen) or Surface Water (obvious)

““Dry TombDry Tomb”” landfilllandfill

Current landfills are designed to control Current landfills are designed to control leachateleachate…………....

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Landfill ConstructionLandfill Construction

Final cover

Daily cover

Intermediate cover

Leave it Alone !!!!!Leave it Alone !!!!!

R I PR I P

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CH4 Emissions from Landfills

Other Problems with the DryOther Problems with the Dry--tomb tomb Sanitary Sanitary LandfilllingLandfillling ApproachApproach

Un-sustainable??? Loss of Space…. Need to find new space every few years (Toronto, Edmonton)

Long-term liability: Need to monitor potential impact for a long- time (until waste stability is achieved)

Landfill gas

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Sustainable Landfill: The Future??

The Concept:The Concept:Holistic approach (not “piece-meal” as in conventionallandfills)

Stabilize the waste quickly (Anaerobic and Aerobic)

“Mine” the cell, and extract recyclables & compost

Reuse space

Increase biological activity in landfill cell; possible to extract large quantities of gas in a short period of time

Sustainable Landfill: Stage ISustainable Landfill: Stage I

Anaerobic ReactorAnaerobic Reactor

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Sustainable Landfill: Stage IISustainable Landfill: Stage II

Aerobic ReactorAerobic Reactor

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Calgary Sustainable BiocellCalgary Sustainable Biocell

Pilot Project (1 hectare: 50,000 tonnes of waste)

Partners/Participants: City of Calgary, University of Calgary and Stantech Consultants

Operation:

One-cell operated for six years before mining for resource and space recovery

AerobicYear 5

AerobicYear 4

AnaerobicYear 3

AnaerobicYear 2

AnaerobicYear 1

Mining/Space Recovery

Year 6

Sustainable Landfill OperationSustainable Landfill Operation(Calgary Biocell Concept)(Calgary Biocell Concept)

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Calgary Sustainable BiocellCalgary Sustainable Biocell

Pilot Project (1 hectare: 50,000 tonnes of organic waste)Conventional design for leachate collection

(composite liner etc.), leachate delivery and gas recovery

Innovative Mitigation Measures:

Biocap, or Methane Oxidation Layer (MOL), to control methane gas emissions during construction (intermediate cover) and

operation (final cover)

Gas Production & MigrationGas Production & Migration

Oxidation in Landfill Cover(Methanotrophs)

CH4 & CO2Generation

CO2Emissions CH4 & CO2

EmissionsCommercial

Recovery

CH4 & CO2 LateralMigration

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CHCH44 Oxidation in Landfill CapsOxidation in Landfill Caps

0

20

40

60

80

100

0 50 100 150 200 250 300

Time (days)

% M

etha

ne O

xidi

zed

Landfill Research in Canada: Landfill Research in Canada: Current EmphasisCurrent Emphasis

• Over the last ten years, there has been a change in emphasis;

• Consider the landfill as a single entity requiring a holistic approach for management, rather than a “collection of problems requiring solutions”. • Consider the landfill as a facility for resource recovery (i.e., energy, material and space)

• Research on Bioreactor Landfills:• leachate recirculation and high rate anaerobic degradation• aerobic bioreactors with leachate and oxygen input

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Landfill Research in Developing Landfill Research in Developing CountriesCountries

• What is different?• waste characteristics (i.e., composition, engineeringproperties, biochemical properties)• socio-political considerations (e.g. a role for scavengers in recycling?)

• Pitfalls in “copying” (from developed nations): • some of the regulations, design philosophies anddesign guidelines in North America and Europeare “politically motivated” without clear design bases• only technical considerations are transferable!!

• Research Emphasis?

Landfill Research in Developing Landfill Research in Developing Countries: EmphasisCountries: Emphasis

• waste characterization (fundamental research)• composition, • engineering and biochemical properties

• design guidelines (applied research)• technology/technique transfer (with appropriate modifications)

• socio-political considerations (applied research) • public acceptability and community involvement• (e.g. the role of scavenging in modern solid waste management

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ConclusionsConclusions

• Landfills are central to solid waste management inCanadian communities

• The Canadian landfill design, construction and operation practices are changing

• Consequently research emphasis is also changing

•Researchers and practitioners in developing countries are well advised to consider differences in philosophy, waste character before adopting Canadian landfill techniques

Thank you!!Thank you!!

Questions ??Questions ??…………

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Conventional Landfills in CanadaConventional Landfills in Canada: : GW Contamination ControlGW Contamination Control

• Techniques have been developed to• minimize leachate production

• new designs and material are used in landfill cover systems

• minimize leachate escape from the bottom of landfills• use of low permeable bottom liners• leachate collection systems• leachate treatment (in-situ by re-circulation,

ex-situ treatment methods)

Leachate Collection System

Geotextile4" Perforated Pipe

Geotextile

60 Mil Textured HDPE

Liner System Design

Drainage Layer

Protective Soil Cover

Compacted Clay Liner

Prepared Sungrade

Gravity Drainage

ManholesPumping Station

Storage Ponds

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Conventional Landfills in CanadaConventional Landfills in Canada: : Landfill Gas ControlLandfill Gas Control

• Landfill gas (methane) escape is the primary concern.

• Gas extraction systems are becoming popular•New innovation: Use of Micro-turbines for powerGeneration (operate at low volumes; 150-250 kW)

• Not very economical (even with micro turbines) for smalland medium-scale landfills

• For small/medium landfills, use of methanobiocaps is being tested.

““The ProblemThe Problem”” with Conventional with Conventional LandfillsLandfills

• Conventional landfills are not sustainable.

• Landfill space decreases with time.

•Need to find a new landfill every few years.