Differences Between Anaerobic Digestion and Composting. Michael Cant Principal, Solid Waste

Transcription

1 Differences Between Anaerobic Digestion and Composting Michael Cant Principal, Solid Waste

2 Introduction FirstWord second third

3 Overview Technologies Beneficial Re-Use and Products Costs GHG s Mixed Waste Processing

4 Composting

5 Open Windrow

6 Aerated Static Pile

7 Gore Composting Walker Facility

8 In-vessel Systems

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10 Anaerobic Digestion

11 Surrey Biofuel Facility - Dry AD

12 Surrey Biofuel Facility - Dry AD

13 Surrey Biofuel Facility Tunnel Design

14 Surrey Biofuel Facility - Dry AD

15 Surrey Environmental Benefits 115,000 t diverted from landfill Eventual full elimination of CO2e from CNG waste collection fleet based on RNG use 25% reduction in Surrey s corporate CO2e through RNG use

16 Harvest Power - Richmond

17 Tale of Two Digesters Dufferin 55,000 tpy SSO Complete: Q Biogas => heat + RNG? Wet/dry separation (Anaergia press) WWTP (BNR SBR) Inorganic biofilter Disco Road 75,000 tpy SSO Complete: 2013 Biogas => heat + on-site electricity + RNG? Density separation (BTA hydropulper) WWTP (BNR MBR) Inorganic biofilter

18 City of Toronto Wet AD

19 City of Toronto Wet AD

20 Disco Road

21 Pulping

22 Anaergia Press

23 Compost or Digest (or both) Composting Aerobic (air) No biogas production Contaminants in compost No further processing Large footprint Large process air volume Less expensive Anaerobic Digestion Anaerobic (no air) Biogas produced Clean final digestate Digestate processing Compact footprint No process air, less odor Depends on energy pricing

24 Beneficial Re-Use and Products Composting only makes compost how good is the quality of that material because it relies on screening? Wet digestion: makes biogas how much? Toronto makes 120 m3 biogas/incoming wet tonne at about 65% methane; makes very clean digestate because water was used to separate materials; but you need to treat your wastewater Dry digestion: makes biogas how much? Surrey (around 70 m3/tonne) but lots of leaf and yard waste in here so biogas is lower; you would not typically wet digest leaf and yard waste; what is the quality of the final product given that it requires screening? Many options for biogas: Surrey is making vehicle fuel, Toronto is looking at electricity, biofuels are an option, but it depends on economics and availability of markets

25 Costs Capital Composting: $150 to $1,000 design t AD: $250 to $850 design t (50ktpy to 120 tpy) Operating: Composting: $30 to 80 t AD: $40 to 90 t Revenues: Composting: $5 to $25 t AD: $30 to 50 t

26 GHG Emissions for 20 years (tonnes CO 2 -Eq construction) (tonnes CO 2 -Eq / yr O&M) Greenhouse Gases 1.E+05 8.E+04 Anaerobic Digestion Composting 7.9E E+04 6.E+04 Landfilling 4.E+04 2.E+04 0.E E E E E E+03-2.E E+03 Construction O&M (with off-sets) O&M (without off-sets)

27 Lessons Learned Siting facilities can be difficult Odour is the number one issue don t underestimate it Need a market for your end product Understand your feedstock what you want to collect and how Look at your entire waste system from a costing perspective Don t overestimate revenue

28 Single vs. Multi-Family Single detached homes are on the decline in Toronto and parts GTA. This trend is common to many jurisdictions across Canada and the US Gap in diversion rates between Single Family Homes and Multi- Family Homes More recyclable/organic material moving to a harder to capture housing market

29 Multi-Family Potential Case for MWP The challenge: Increased urban growth Higher levels of contamination Participation levels may be low Retrofits required Some older buildings may be exempt from future source separation programs Existing traffic congestion Composting Tunnel, Avonmouth, UK, MBT anaerobic digesters and gas holding tank, Bredbury, UK

30 Questions Michael Cant

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