The mission statement for the Region of Ottawa Valley includes the evocative wish to “walk lightly on the environment.” With a diversion goal of 65 per cent of all residential and Industrial, Commercial and Institutional (IC&I) wastes as well as the development of the Ottawa Valley Waste Recovery Facility (OVWRC) last year, the nation’s capital region can now do just that.
Joe Hall, site manager of the OVWRC points out, Ottawa Valley is a “proactive community that sees the merit of managing its resources at home.” He says that had it not been for the attitude of civic leaders, the composting program and indeed the whole concept of the OVWRC would not have come to fruition.
The overall facility and the composting facility in particular are models that other communities of similar size should explore.
The facility serves the 40,000 residents of communities including the Township of Laurentian Valley, The Town of Petawawa, the City of Pembroke, the Township of North Algoma-Wiberforce and the Sebastopol Ward of Bonnechere Valley.
Situated on a 150-hectare site 15 km south of Pembroke, the facility boasts a full array of waste management infrastructure including: a landfill, materials recovery facility, construction & demolition waste facility, household hazardous waste facility and a composting facility. This one-stop-shop to achieve the region’s mission statements and diversion goals currently receives about 30,000 tonnes of residential and IC&I wastes annually. Of that about 3,300 tonnes are compostable wastes.
Three of the communities have curbside cart-based collection programs for organic waste and the other two have depots. This integrated system gives them the option of co-collection in the future, which could have a positive impact on collection costs.
Ottawa Valley undertook a significant search for technologies and ultimately selected an in-vessel system for composting developed by Engineered Composting Systems and distributed in Canada by Ottawa’s WCI Waste Conversion Inc. Eleven containers were purchased, providing an annual design capacity of 4,500 tonnes. The facility was designed for ready expansion to 16 containers. The containers are used year-round, even through blustery and bone-chilling winters with temperatures as low as -30C.
In addition to the containers, the OVWRC composting facility consists of an 8,000 square foot enclosed receiving/preparation/loading hall, biofilter, outdoor container pad, outdoor curing pad, scale-house and office, as well as an open windrow leaf and yard composting pad.
Materials received at the facility include residential organic wastes, including yard wastes and from some communities kitchen wastes. IC&I wastes are also accepted at the site and include grocery store and restaurant wastes.
Organic waste is received on the composting facility floor. Material is loaded onto a belt and conveyed past a picking station where large contaminants are removed (less than three per cent by weight) before feeding into a shredder. The shredded material is then conveyed up to a second picking platform for hand sorting, and finally under a magnet for ferrous removal. Typically two sorters are utilized.
A compost feedstock mix (typically consisting of 3:1 volume ratio of raw feedstock to wood chips) is loaded into a mixing unit using a pay loader. The prepared compost feedstock is then loaded into the containers via a conveyor system. Loaded containers are moved with a roll-off vehicle to the outdoor composting pad.
The design retention time of organic waste in these containers is 14 days, though five to eight days is common practice. The composting system, with fully automated aeration and control capability, delivers high-rate composting and pathogen reduction (temperatures >55C) during this period.
Proprietary software automatically controls the in-vessel composting process through temperature feedback to ascertain the aeration requirements for each container. Probes at two levels measure the temperature of the material and help determine how much aeration to supply and in which direction (bottom up or top down). This control design minimizes temperature and moisture gradients across the biomass in each container to accelerate stabilization. Temperature profile data for each container is available for the operator and also preserved in archives for future access.
The aeration control system manages containers through three distinct control regimes:
1. Heat-up regime to accelerate temperatures up to 55C;
2. Pathogen reduction (PFRP) regime consisting of three days >55C; and,
3. Lower temperature regime (typically 45C) for optimal stabilization.
Supply air for the containers consists of a blend of air collected from the receiving hall and recycled exhaust air from the containers. This ensures warm supply air for winter operations, minimizes moisture loss in containers, and reduces exhaust air volumes. Building air not used to aerate containers is sent to a biofilter for scrubbing and released to the atmosphere.
When the container composting process is complete, the roll-off vehicle discharges the contents of the containers on the curing pad. This compost is cured for approximately six months.
Compost is screened and is sold for $10/yard. In 2003 the OVWRC sold its entire inaugural production run of 2,000 yards within one month. The product was sold to residents and topsoil producers.
The overall facility costs were $11-million. Capital costs of the composting portion of the facility were $2.42-million.
Annual operating costs are $51.21/tonne, with debt retirement adding another estimated $75.75/tonne. These calculations are based on the approximately 3,300 tonnes of organic waste processed in 2002. As the facility approaches its rated capacity of 4,500 tonnes it’s expected that these per tonne operating costs will decrease by approximately 20 to 25 per cent.
Paul van der Werf owns and operates composting and waste management consultancy 2cg, based in London, Ontario. To contact Paul, visit www.2cg.ca