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

Transcription

1 Solid Waste Management in Canada: Current Practice, Priorities and Research J. Patrick A. Hettiaratchi, PhD, PEng. Environmental Engineering Program Faculty of Engineering University of Calgary CANADA Solid 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

2 Waste Characteristics: Quantities Canada: Overall Waste Characteristics: composition City of Calgary Components Moisture Content Total wt (%) Paper Food Waste Yard Waste Wood Animal Waste Glass Plastic Metal Others Total

3 Waste Characteristics: composition Toronto Edmonton Land 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

4 Problems 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 Canada

5 Waste Diversion: Reduce.. Backyard composting Waste Diversion: Recycle.. Recyclables collection from homes Curbside collection or Blue Box programs ( expensive, but collection efficiency is high)

6 Waste Diversion: Recycle.. Recyclables collection Green Box programs (less expensive, but efficiency is low) Waste Diversion: Recycle.. Green Box operation

7 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 Compost Large scale composting is popular in Canada Single feedstock: yard waste, sludge, MSW Mixed feedstock: mix solid waste with sludge from wastewater treatment plants

8 Yard Waste Composting Windrow Composting - Equipment

9 Edmonton Co-composting Facility 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 tpa of biosolids.

10 ** 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 Co- Composting Facility

11 Edmonton Co- Composting Facility Aeration Building: size of 14 Ice-hockey rinks Co-composting in Edmonton Capital cost: approximately $100 million Overall plant size: 416,500 ft 2 (38,690 m 2 ) Compost produced: approximately 80,000 tonnes/year Compost quality: Class B (??),

12 Waste to Energy: Not popular now!! -Causes air pollution; need expensive air pollution control equipment to meet air quality standards - Produces a hazardous waste that requires a containment landfill not a sanitary landfill 100 ton/day waste-to-energy facility in Harrisonburg, VA Sanitary Landfills: accepts the majority of waste Current Conventional dry-tomb type Sanitary Landfills are designed and constructed to eliminate problems associated with Open Dumps

13 Conventional Landfill: A Designed Structure!! Current landfills are designed to control leachate.. Leachate is garbage juice or an aqueous liquid produced Dry within Tomb the landfill Leachate can contaminate Groundwater (unseen) or Surface Water (obvious) Prevention of GW contamination with bottom liner systems Area A Area B Working Face (Area D) Area C Stream X-section along the length of the landfill

14 Landfill Construction Final cover Daily cover Intermediate cover Leave it Alone!!!!! R I P

15 CH 4 Emissions from Landfills Other Problems with the Dry-tomb Sanitary Landfillling Approach 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

16 Sustainable Landfill: The Future?? The Concept: Holistic approach (not piece-meal as in conventional landfills) Increase biological activity in landfill cell; possible to extract large quantities of gas in a short period of time Stabilize the waste quickly (Anaerobic and Aerobic) Mine the cell, and extract recyclables & compost Reuse space Sustainable Landfill: Stage I Anaerobic Reactor

17 Sustainable Landfill: Stage II Aerobic Reactor

18 Calgary 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 Sustainable Landfill Operation (Calgary Biocell Concept) Anaerobic Year 1 Anaerobic Year 2 Mining/ Space Recovery Year 6 Anaerobic Year 3 Aerobic Year 5 Aerobic Year 4

19 Calgary 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 & Migration Commercial Recovery CO 2 Emissions CH 4 & CO 2 Emissions Oxidation in Landfill Cover (Methanotrophs) CH 4 & CO 2 Generation CH 4 & CO 2 Lateral Migration

20 CH 4 Oxidation in Landfill Caps 100 % Methane Oxidized Time (days) Landfill Research in Canada: Current 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

21 Landfill Research in Developing Countries What is different? waste characteristics (i.e., composition, engineering properties, 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 and design guidelines in North America and Europe are politically motivated without clear design bases only technical considerations are transferable!! Research Emphasis? Landfill Research in Developing Countries: 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

22 Conclusions Landfills are central to solid waste management in Canadian 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!! Questions??

23 Conventional Landfills in Canada: GW 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 Gravity Drainage Storage Ponds Manholes Pumping Station Protective Soil Cover Drainage Layer Compacted Clay Liner Prepared Sungrade Liner System Design Geotextile 4" Perforated Pipe Geotextile 60 Mil Textured HDPE

24 Conventional Landfills in Canada: Landfill Gas Control Landfill gas (methane) escape is the primary concern. Gas extraction systems are becoming popular New innovation: Use of Micro-turbines for power Generation (operate at low volumes; kw) Not very economical (even with micro turbines) for small and medium-scale landfills For small/medium landfills, use of methanobiocaps is being tested. The Problem with Conventional Landfills Conventional landfills are not sustainable. Landfill space decreases with time. Need to find a new landfill every few years.