City of Vancouver
Figure 2: Composting Facility Grinding Plant
J. Paul Henderson, M.A.Sc., P.Eng.
email@example.com (Paul Henderson)
City of Vancouver Engineering Department
Solid Waste Management Branch
Composting Council of Canada Annual Conference
November 1-4, 1995.
Vancouver's Composting Strategy
In 1989, Vancouver City Council set a 50% waste reduction goal. At the same time, a waste reduction strategy was laid out to achieve the goal. The strategy included multi-material recycling and composting. Since 1989, Vancouver has been implementing components of the waste reduction strategy.
The composting component of the waste reduction strategy has been implemented with three principles in mind. The principles are source separation, incremental implementation and the use of a multi-component strategy.
Source separation has been a fundamental component of all of Vancouver's waste reduction and recycling programs. Source separation ensures high quality and consequently high value products, and also includes residents in the waste reduction system.
Vancouver has implemented its composting strategy incrementally by continually building on programs. Centralized composting for example began with the composting of leaves collected from City streets using a minimal technology approach. The following year drop-off and residential collection systems were added to the program. In 1995, Vancouver has just completed a 2.4 million dollar yard and garden waste composting facility, which is designed to process approximately 22,000 tonnes per year of yard waste.
Other components of Vancouver's composting program include backyard compost bin distribution, composting education and worm bin distribution.
Subsequent to Vancouver setting its 50% waste reduction goal, the Province of British Columbia has set a 50% per capita waste reduction goal and mandated that all Regional Districts develop a Solid Waste Management Plan predicated on achieving the waste reduction goal. The Greater Vancouver Regional District (G.V.R.D) has just completed stage three of the Solid Waste Management Plan, and submitted the Plan to the Minister of Environment Lands and Parks for approval. Stage three includes strategies and specific program requirements to achieve the Provincial Goal. The G.V.R.D Solid Waste Management Plan includes further expansion of backyard compost bin distribution programs, additional composting education, and the provision of convenient yard waste composting facilities to all Regional residents. Vancouver's strategy is consistent with the Solid Waste Management Plan.
Since 1990, Vancouver has been promoting backyard composting by offering composters for sale to the public and by offering composting education.
The backyard compost bin distribution program has provided backyard composters to approximately 16,000 Vancouver households (18% of Vancouver households) for $25 per composter. The composters are estimated to divert approximately 250 kg per unit per year from the waste stream, for a total of 4,000 tonnes per year. Vancouver City Council has approved the distribution of an additional 8,000 composters through a truckload sale to be held in the spring of 1996.
An innovative feature of Vancouver's program is that composters purchased for distribution are required to be rodent resistant. Accordingly, they have a secure top and bottom, have no holes exceeding 1.3 cm, and are made of durable, rodent resistant material. This requirement has been important in ensuring continued support for the program from both the public and environmental health professionals.
The City of Vancouver also provides an extensive backyard composting education program. The education program provides ongoing support to residents who have purchased backyard composters plus provides promotion for the City's composting programs. The City funds City Farmer, a non-profit urban agriculture advocacy society, to deliver composting education to Vancouver residents. Funding to City Farmer is also provided by the Greater Vancouver Regional District.
City Farmer staffs and maintains a Compost Demonstration Garden and Compost Hotline telephone service year-round. The Garden and Hotline not only provide information on composting to residents, but also act as a resource centre for industry and government. City Farmer conducts composting workshops for groups ranging from school children to seniors through-out Vancouver. In a year, approximately 6,500 people either visit the Garden, call the Hotline, or attend a workshop. Many more people are reached through City Farmer's media interviews and contacts which in 1994 exceeded 70 and included Sesame Street, W5, Canadian Gardening and many local media.
In 1993, Vancouver provided 200 residents with worm composters for use in homes without yards. Each participant was provided with a 50 litre worm bin, worms, bedding, Mary Applehof's book on worm composting, "Worms Eat My Garbage", and a one-hour instructional workshop. The workshop was conducted by City Farmer and is considered critical in ensuring continued use of the worm bins. The workshop focused on all aspects of worm composting from worm anatomy and life-cycle to castings harvesting.
Approximately six months following distribution of the worm bins a follow-up survey was sent to all of participants in the program. The survey showed that approximately 70% of the participants were using their bins.
Vancouver's worm bin distribution program is being expanded by 500 bins in 1995.
Since 1990, Vancouver has been collecting leaves each fall for composting. Leaves are collected in paper leaf collection bags, by front-end loaders from City streets, or dropped off at depots. In 1994, a total of 5,000 tonnes of leaves were collected for composting.
Leaves are processed at the City's composting facility. Processing involves windrowing, periodic mixing with a front end loader or excavator, mixing with a windrow turner, and screening with a trommel screen. The total process takes just under one year and produces a 2 cm minus compost that is essentially free of foreign matter. The compost meets the criteria for unrestricted distribution as described in B.C. Ministry of Environment, Lands and Parks' "British Columbia Production and Use of Compost Regulation".
Up to 1995, leaves have been processed on a hog fuel (shredded wood waste) base. Hog fuel is used because it is inexpensive and provides a relatively good working surface. Some problems that have resulted from working on a hog fuel surface are the loss of compost into the working surface, and restricted equipment use during wet weather.
Another potential problem is contamination of the compost by hog fuel getting mixed into the compost. If mixed compost and partially decomposed wood waste are applied to plants, soil bacteria use all of the available nitrogen, essentially robbing the plants of nitrogen. This process is called nitrogen immobilization, and can result in reduced plant growth or potentially death. Contamination of the compost is avoided by minimizing windrow turning, careful equipment operation, and by putting a layer of sand on top of the hog fuel prior to constructing windrows.
Following processing, the compost is sold to the City's Park Board and landscapers primarily as a landscape mulch.
Yard and Garden Waste Composting Facility
In December 1992, Vancouver City Council approved the construction and operation of a yard and garden waste composting facility at the City's Landfill in Delta. The facility represents a 2.4 million dollar capital investment, and is designed to process approximately 22,000 tonnes per year of yard and garden waste.
The composting facility includes a 1.8 hectare roller compacted concrete paved surface, a 400 hp electric grinding plant, a front-end loader, a windrow turner and a trommel screen.
A paved surface was selected for several reasons:
- increased windrow management to ensure rapid decomposition and the maintenance of aerobic conditions results in a requirement for all weather site access. Under Vancouver's climatic conditions all-weather access for wheeled vehicles can only be assured by having a paved surface.
- a paved surface ensures that the product is not lost into the surface and also that the product is not contaminated by the base material.
- the maintenance costs of a paved surface are low since frequent regrading and addition or removal of material are not required.
- surface water can be controlled , thus avoiding ponding
- site clean-up is much easier.
Both the maintenance of aerobic conditions and surface water control are requirements of the "British Columbia Production and Use of Compost Regulation".
The design and construction of the composting facility paved surface has been a relatively complex task due to the geotechnical characteristics of the site and the requirement for a heavy duty pavement structure on which to conduct composting operations.
To provide a paved surface, designs were developed for two alternative systems; either a roller compacted concrete (RCC) surface or a combination of conventional concrete and asphalt. RCC is an industrial pavement used extensively in extreme duty applications such as log sort and log storage areas. RCC has been used at four other composting sites in Canada. Tenders were sought for both options. Following receipt of tenders, an evaluation of the two options was conducted. The City, in cooperation with the pavement design consultant, determined that over the design life of the surface, the RCC option was least expensive due to reduced long-term maintenance costs. This was in spite of an initial 10% capital cost premium for RCC.
The final design for the surface included 200 mm of 20 mm minus gravel overlaid by 250 mm of RCC in the initial processing area and 200 mm of RCC in the windrow composting area. A site plan showing the facility layout is provided in Figure 1. The total cost of the paved surface excluding site preparation was approximately $35 per square metre.
The other key capital component of the composting facility is an electric yard waste grinding plant. The plant is similar in design to that used in the wood processing industry. The system was constructed by a local company, and was selected through a City issued request for proposals.
The grinding plant includes an infeed hopper, an infeed conveyor, a vibrating finger screen, a metal detector, a 400 hp fixed hammer hog, and outfeed conveyors. The system is designed to remove fine materials prior to grinding to reduce energy consumption and striker plate (hammer) wear. The metal detector protects the striker plates from ferrous contaminants. The design also allows metering of material into the grinder to reduce surge loading. The system is designed to produce 7.5 cm minus material (7.5 cm maximum in any direction) at a minimum rate of 25 tonnes per hour. The total cost of the grinding plant was $750,000. A photograph of the grinding plant is provided in Figure 2.
A breakdown of the facility capital costs is provided in Table 1. The total capital cost of the facility was approximately 2.4 million dollars.
Figure 1: Vancouver Composting Facility Site PlanThe material flow for the facility is shown in Figure 3. Source separated yard and garden compostables will be dropped off at the Vancouver South Transfer Station and Vancouver Landfill. Landscapers and residents dropping off yard waste will be charged a disposal fee. The fee is lower than the fee for refuse disposal to encourage source separation. On-site staff will check material quality.
Table 1: Vancouver Composting Facility:
ITEM COST Site Development Costs . Site Preparation (including preloading) $315,000 Pavement Construction $615,000 Site Trailer $10,000 Power Supply $125,000 Subtotal $1,065,000 . . Equipment Costs . Grinding Plant $750,000 Compost Turner (Wildcat LS177a) $125,000 Front-End Loader (Case 821B) $220,000 Trommel Screen (Retech Eliminator) $190,000 Pick-Up Truck $20,000 Subtotal $1,305,000 Total $2,370,000A list of acceptable and unacceptable material is provided in Table 2. The material will be delivered to the composting facility and dropped off in front of the grinding plant. Material will be loaded into the grinding plant with a front end loader. Following grinding, the material will be ferried into windrows with a front end loader. If required, water will be added to the ground material with spray nozzles located on the grinding plant. Windrows will be mixed on an approximately weekly basis for approximately eight weeks. Windrows will be combined as required to account for shrinkage and to maximize space utilization.
Figure 3: Composting Facility Material Flow
Following windrowing, the material will be stockpiled for up to six months to cure. The material will then be screened with a trommel screen to 2 cm minus prior to distribution.
Both curing and screening will be conducted on rock surfaces rather than the RCC pad because these operations will be less likely to result in contamination or loss of the compost, and screening can be conducted during dry weather thus reducing trafficability concerns.
The compost will be used within City operations and sold to landscapers or to the public.
Annual operating costs are not currently available as the facility is just commencing operation. The facility will be operated by 2-3 City staff depending on material quantity and time of year.
Table 2: Vancouver Composting Facility:
YES grass YES leaves YES trimmings (max. 25 centimetre diameter, 2 metre length) YES plant debris NO plastic bags NO soil or rubble NO manufactured wood products NO food waste NO sod
The City of Vancouver will continue to include composting in its waste reduction strategy. This is consistent with the requirements of the Regional Solid Waste Management Plan, which has composting as a fundamental component.
Vancouver's composting strategy will continue to be based on source separation, incremental implementation and a multi-component approach.
To date Vancouver has only included food waste composting in its composting strategy through the promotion of backyard and worm composting. It is expected that Vancouver will not expand its centralized composting program to provide food waste composting due to the additional collection and facility requirements. Food waste composting will be left to the commercial sector, which currently processes food waste from restaurants, food processors and grocery stores throughout the lower mainland. Centralized composting of residential food waste is not a component of the Regional Solid Waste Management Plan.
The next expansion of Vancouver's program will likely involve an extension of yard waste collection systems. The current system requires that participants drop-off their compostables at either the City's Transfer Station or at the composting facility. Two potential expansion options are the addition of residential collection or additional drop-off depots. These options will only be considered once City staff gain operating experience with the composting facility.Urban Home Composting.
Composting With Red Wiggler Worms
Composting Activities For Children
The Greater Vancouver Regional District, which includes the City of Vancouver, has put up a variety of material on Composting.