Solid Waste & Recycling

Feature

New Organics Program

The County of Northumberland's waste management program offers valuable lessons for municipalities across Canada. The Ontario County recently discovered the impact of organics diversion through anaero...


The County of Northumberland’s waste management program offers valuable lessons for municipalities across Canada. The Ontario County recently discovered the impact of organics diversion through anaerobic digestion, while learning how to better address waste management costs and logistics issues. (See “Anaerobic Digestion” in the August/September 2001 edition.)

The County, which operates a dry MRF that had a recovery rate of 66 per cent last year, expects to divert up to 80 per cent of all waste this year. “Northumberland County will surpass any provincial targets and become a leader in overall waste diversion in Canada,” says Karl Allen, marketing development co-ordinator of waste services.

On August 8, 2001, the county signed a 21-year contract with Newmarket-based Canada Composting Inc. (CCI) to process its residential wet waste. This contract was finalized following a recent pilot project that achieved a significant wet waste diversion rate.

Pilot project overview

The county delivered 36 tonnes of wet waste in November 2000 and 120 tonnes in January 2001 to CCI. The wet waste accepted by CCI has maximum contamination of 25 per cent non-processable materials.

The structure of the collection system did not change for the most part. The 1999 population was 79,120. Of the 33,141 households, 31,796 are served by curbside collection (primarily single family and small multi-family dwellings in buildings containing five or fewer units). Residents put dry waste in blue bags/boxes and wet waste (kitchen scrap and yard waste) in standard garbage bags.

The county received funding and support from the Waste Diversion Organization of Ontario (WDO), Corporations Supporting Recycling (CSR), and CCI. In addition, Toronto-based Enviros-RIS was contracted to complete an in-depth project evaluation to outline overall system implementation costs and environmental impacts.

Technical details

The waste was hauled using walking floor trailers from the county’s landfill. Upon arrival, the waste was weighed and unloaded onto the tipping floor. A detailed visual audit was performed prior to processing.

Large items were handpicked and deposited into a “rejects” bin, and other smaller items such as electrical cords, rope and wood pieces were removed where possible. Materials containing petroleum-based residual (including automotive oil filters) were also removed. The weight of the hand-sorted reject items was recorded as part of the “overs.”

Upon completion of an initial sort, the waste was deposited via loader into the feed hopper. The material entered a trommel (a large rotating cylinder designed to rip open bags and help break up any large masses) where six-inch holes in the trommel screen allowed smaller pieces to pass through to the conveyor below.

Larger items continued down the trommel to a separate conveyor where they were carried across to the overs bin. The overs were weighed onsite and recorded. Small pieces that passed through the screen made their way to the magnetic separator where ferrous material was removed and deposited into a side bin. The weight of the ferrous material was obtained and recorded.

Following the magnetic separation, the material was fed into one of three pulpers where it underwent CCI’s patented BTA process. Non-pulpable, heavy materials such as metals and bones sank to the bottom and were removed and deposited into a bin. (See Cover Story in the August/September 2001 edition.)

The heavy fraction was visually assessed and weighed and the details recorded. The light fraction (primarily plastics) was removed from the pulpers with a rake and compacted into trailers located on the north side of the building. Auditors estimated the weight based on the predetermined weight of a full compactor load. It is important to note that 30 per cent of the gross weight of the light fraction is attributed to process water from the pulper.

Once the pulping process was complete, the material moved to the hydrocyclone, where a third fraction was removed. The grit, mainly consisting of bits of glass, metal and dirt, was deposited into a bin and weighed.

The weight of the rejects, overs, and three fractions from the trial load was combined to determine the total amount of material removed for disposal. The waste remaining, the pulper feed, and the separated ferrous stream was considered the diverted portion of the original material. The pulper feed became compost, reusable process water, and energy.

Results & costs

The results of the pilot project reveal that Northumberland can divert 77 per cent of curbside wet waste by utilizing CCI’s anaerobic digestion processing facility. (See Summary of Results chart.)

On August 10, the county began hauling wet waste to CCI. Costs to the county will be as follows:

Collection — Collection activities have not changed. Dry waste is offloaded at the existing MRF and wet waste is offloaded at an adjacent transfer facility.

Organic processing costs — The CCI tipping fee is $55 per tonne. It is speculated that this rate will drop in further negotiations with CCI, since Northumberland’s wet waste stream has a lower percentage of non-compostables than any other Ontario municipality (other than Guelph, which has a similar two-stream collection system).

One of the primary economic benefits of this system is the avoided disposal cost at the county landfill. Residue disposal has decreased to approximately 3,014 tonnes/year at $70 per tonne. This system will also extend the remaining life of the county’s two landfill sites.

Transfer — For the pilot, the county arranged a private contract to haul the wet waste to Newmarket on a back-haul at a cost of approximately $300 per trip. The hauling fee is now $545 per trip with a maximum of 40 tonnes. It is likely that the county will soon implement a permanent transfer station.

Station cost — In 1999, the county investigated the cost of establishing a transfer station adjacent to the MRF to transfer approximately 35,000 tonnes per year of residential and Industrial, Commercial and Institutional waste (IC&I). The estimated cost of this facility ranged between $392,000-728,000. Based on that evaluation, Enviros-RIS has projected the cost of a smaller facility to transfer between 10,000-15,000 tonnes per year (7,327 tpy of “wet” and 3,014 tpy of residue, plus additional capacity for future growth).

Assuming a 15-year replacement life for the facility at an interest rate of 6 per cent, the annual amortized cost of the facility would be $20,593. It is anticipated that the station would transfer wet waste to CCI using open-top transfer trailers (not the compaction trailers used in the original station design). Residue from the MRF would be isolated on the transfer tipping-floor and loaded into transfer trailers for trips to the county’s landfill site. A front-end loader and operator would direct incoming vehicles, store incoming material on the tipping floor, and to load the trailer.

Operation and maintenance costs for the station are estimated at $50,000 per year ($30,000 for the loader and operator and $20,000 for fuel, insurance, utilities, etc.).

Conclusion

The overall cost of the new organics waste management system — which represents a dramatic increased in Northumberland’s residential waste stream — is approximately $3-million, which is essentially offset by landfill disposal savings.

While there is great promise in the new system, some cost components still require confirmation. The county needs to finish negotiations with private sector haulers to determine transfer haul costs from the proposed transfer station to CCI.

Connie Vitello is editor of this magazine.

Chart 1

Material % Unacceptable (paint cans, carpets, wood, etc.) 5%
Yard waste 15%
Food waste 43%
Contaminants (clothing, footwear, etc.) 2%
Other (pl
astics)
25%
Cardboard, paper 10%
Total 100%

Chart 2

Material Weight (kg) % of total Weight
Rejects, heavies, grit 5,315 18.8%
Light fraction (plastics) 1,260 4.4%
Ferrous 190 0.7%
Pulp (paper, organics) 21,560 76.1%
Diversion 21,750 76.8%
Disposal 6,575 23.2%
Total 28,325 100.0%

Summary of Results

Material Weight (kgs) % of Total Summary
Pulp 21,560 76.1
Ferrous 190 0.7 76.8% Diverted
Sub-Total 21,750 76.8
Disposal 6,575 23.2 23% For disposal
Total Load Weight 28,325 100.0

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