Solid Waste & Recycling

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Guelph Wet-Dry Efficiency Examined

On November 30, 1998, the Planning, Works and Environment Committee (PWEC) of the City of Guelph requested that the city establish a team of local manufacturing experts to assess the operational effic...


On November 30, 1998, the Planning, Works and Environment Committee (PWEC) of the City of Guelph requested that the city establish a team of local manufacturing experts to assess the operational efficiencies of Guelph’s Wet-Dry Recycling Centre from a manufacturer’s perspective. In early 1999 the committee was formed by local business leaders who spent several hundred hours working with city staff as well as a representative of multistakeholder group CSR: Corporations Supporting Recycling (Geoff Rathbone) to evaluate processing and diversion efficiencies.

The group’s findings were presented in a report by Janet Laird, Ph.D., the manager of solid waste services for the City of Guelph. It recommends that Guelph staff continue to evaluate their analysis of the costs and benefits of different waste collection options to improve the diversion rate on the residential dry stream. Support for this evaluation was the only recommendation presented to improve the operation by the committee.

Findings

Many processing modifications have been implemented since the start-up of the facility in November 1996 to reduce costs. The modifications included: the installation of a third conveyor line to allow containers to be added downstream for fibre separation (to fully utilize mechanical sorting equipment); the installation of a “reversing” conveyor to allow product diversion to the baler without using outside bulk shipment bins; and, the redesign and upgrade of the ballistic separator to achieve increased separation of container fibre. No major new efficiencies can be realized through further process modifications.

The group reported that overall diversion from residential and industrial, commercial and institutional (IC&I) waste processed is high — at 55 to 58 per cent. The processing of wet and dry IC&I waste and residential wet waste is efficient, and no improvements were identified.

However, the amount of residual waste in the dry stream makes processing of this stream less efficient (according to labour per tonne recovered and tonnes recovered per hour). (See box.) Staff have been urged to continue their evaluation of two-stream collection (required by the Certificate of Approval) compared to other collection options.

Collection options to be considered should include those that remove non-recoverable or non-marketable materials from the residential dry bag:

Modified two-stream — Residents would place dry residue, which is currently placed in the dry bag, in the wet bag. This option would be viable if the Super Blue Box Recycling Corporation (SUBBOR) demonstration is successful. The $20-million mixed waste processing demonstration facility in Guelph aims to provide up to 100 per cent diversion of municipal solid waste from landfill and produce sustainable energy by preventing conventional landfill-associated greenhouse gas emissions. (See “Composting Matters” in the December/January 2000 edition.)

Three-stream — Residents would place dry and wet “residue” in a third “garbage” bag. (This option would be considered if the SUBBOR demonstration is unsuccessful.)

According to Ms. Laird, there is support for these recommendations and the staff is already working on an updated cost/benefit analysis of the current two-stream system versus three-stream for residential collection and processing. Data from the SUBBOR demonstration should be ready by mid-2000.

Wayne Arndt, P.G.M.M., P.C.M.H. is with the solid waste management department of the City of Guelph, Ontario.

Guelph Wet-Dry Data

According to Cathy Smith, Wet-Dry Industrial Coordinator, the external review found no major plant process efficiencies that could be gained since the operation has already been fine-tuned over the years.

Past modeling suggested a less-than-satisfactory 25 per cent recovery rate for the dry residential waste stream. Facility staff and consultants from Enviros-RIS are evaluating methods to boost this rate, including a switch to 3-stream collection or adding the dry residual waste to the wet stream (and sending it to the SUBBOR digester).

In 1999 Guelph collected at curbside a total of 24,800 tonnes of residential waste. About 9,160 tonnes of this was wet waste, 6,412 tonnes of which (70 per cent) was diverted from landfill. Roughly 15,640 tonnes of the total was dry waste, 2,200 tonnes of which (14 per cent) was diverted.

Ms. Smith explains that the facility reports 25 per cent diversion for dry residential waste (not 14 per cent) because the 25 per cent number refers to the percentage of dry waste that actually gets processed. Some dry waste is not processed because the plant can only realistically process seven or eight tonnes per hour, not the 12 tonnes assumed in the plant design. (The rest currently goes to landfill.) The challenge to plant throughput has been exacerbated by a 36 per cent increase in waste volume due to population growth since the plant was built. (She says it’s not economical to add a second shift.)

Despite the 36 per cent growth in waste, garbage is collected with 11 trucks — just two more than in 1996. Collection of wet, dry and yard waste costs $78 per household per year. Net costs for processing and disposing waste were only $8 per household in 1999. Ms. Smith points out that this is very cheap considering that it includes HHW depots, landfill tip fees, public drop-offs for wood waste and white goods, and the Wet-Dry operation itself. The facility has to cope with costly slow-downs (typically 15 minutes each day) to deal with medical sharps incidents that have grown along with increased home care services in the area.


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