Database of Waste Management Technologies Life

Case Study 9 - Anaerobic Digestion (AD)

 

General Information Photo Gallery
Name: Dufferin Organic Processing Facility, Toronto, Ontario

Anaerobic digester on the Dufferin AD plant

Owner: BiogenGreenfinch
Operator: BiogenGreenfinch
Technology: AD
Designed Capacity: 25,000 tpa
Cost: $ 10 million in 2000 (Built cost)
Location: Toronto, Ontario, Canada
Served Area: n/a
Commercial Start Up: 2009
Contact Details
Address: Dufferin Transfer Station,
35 Vanley Crescent
Toronto, Ontario M3J 2B7,
Canada
Phone Number: +1 416 392 9670
Fax: -
Email: lbutt@toronto.ca
Website: www.canadacomposting.com 

 

Short Description

The Dufferin Organic Processing Facility (DOPF) started operations in 2002 and was designed as a demonstration plant with nominal capacity of 25,000 tons/year to treat SSO (Source Seperated Organic) waste. The facility utilizes patented BTA process that includes wet pretreatment and single-stage low-solids, mesophilic anaerobic digester. A trommel screen and material recovery system were installed prior to the BTA anaerobic digestion to open plastic bags and sort out the contaminants.

The hydro-mechanical (wet) pretreatment system is comprised of a hydropulper followed by a hydrocyclone. This is a batch process with a dual objective, to separate contaminants from the organic waste and to transform the SSO into organic pulp

Contaminants are separated in two stages: first the floating materials (textile, plastic, foils etc) and the heavy fraction (bones, glass, stones, coins, etc) are removed in the hydro pulper; second, the grit fraction (small pieces of heavy material such as glass are removed in the hydro-cyclone.

Typically, contaminants comprise 23%, by weight, of the proceed SSO, (<20% light fraction, 1.5% heavy fraction, 1.5% grit fraction). Pulped organics with a solids content of 8-9% are fed into a digester with a liquid capacity of 3,600 m3 and designed retention time of 17-24 days. The sludge coming out of the digester is filtered to separate fraction. About 0.33 tons of digested solids are produced per ton of SSO feedstock to the plant and further processed to final compost. One the average, 30-60 tons per day of this material are transported to off circulated into the hydro-pulper.

Since May 2008, after some changes in the equipment and operating procedures, the plant is now operating at about 190% of the nominal capacity, i.e. 42,500 tons/year. On average, 185-200 tons/day are processed in summer and 135 tons/day in winter.

Current biogas production is 100-120 m3/metric ton of SSO (residence time of 20-23 days). Since this plant was primary designed as a demonstration plant, it does not have an energy conversion system and all biogas is combusted in an open flare. It has been estimated that if the DOPF were to use the biogas to run a gas engine, out of 35,000 metric tons of SSO processed in 2007, it would have generated 4,500 MWh of electricity, i.e. about 130 kWh per ton of SSO processed. This amount corresponds to about one fourth of the electricity generated per ton of MSW combusted in U.S. WTE facilities (550 kWh/ ton MSW).

Contaminants are separated in three forms: A light fraction of materials floated in the hydropulper - textiles, plastics, foils etc, a heavy fraction - bones, glass, stones, coins, etc that settle at the bottom of the hydropulper, and a grit fraction - small pieces of heavy materials are removed in the hydro-cyclone.

Typically, the total residue of Dufferin represents 23% of the inlet stream to the plant (<20% light fraction, 1.5% heavy fraction, and 1.5% grit fraction) and is sent to landfill.

The Dufferin facility that was built for $10 million in 2000. This number corresponds to only $400 per annual ton of capacity and is relatively low because Dufferin was a demonstration prototype and did not include equipment for generating electricity from its biogas product. Also the AD filter cake is sent to an off-site composting facility for curing.

 

Key Facts

Treatment Capacity: 42,500 tpa
Input Material: Source separated organic waste (SSO) 42,500 tpa
Output Products: Digested Solids 14025 tpa (0,33 tons per ton of SSO)
Biogas 100-120 m3/metric ton of SSO
Residues 9,775 tpa (23% per ton of SSO)

 

Extra Information

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