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vironmental Technology ProfileOCETA Environmental Technology Profile
Wright Environmental has developed a system of composting for the waste management and recycling industry which controls odours and will compost the entire organic waste stream in a safe, efficient and cost-effective manner. This versatile technology is a continuously loading, fully enclosed, flow-through process that transforms food and other organic material into compost in a 14-28 day retention span. The process outputs a soil conditioner suitable for agricultural and horticultural purposes. The composting vessel can be custom designed to handle a range of capacities. A modular stainless steel construction allows outdoor operation and continuously composts from hundreds of pounds to hundreds of tons per day. Figure 1 shows the in-vessel composter site at the Ontario Science Centre in Toronto, Canada.
Figure 1: The Wright Environmental In-Vessel Composter located at the Ontario Science Center in Toronto, Ontario.
Wright Environmental Technology will accept all organic feedstock which might include: biosolids, food waste including red meats and fats, fish waste, pulp sludge, packing and cannery waste, leaf and yard waste, and contaminated soils from bioremediation projects. Depending on the quantity and type of waste to be treated, composting units can be custom designed for capacities from 300 lb. (136 kg)/day up to 100's of tons/day, requiring between 80 to 1,500 square feet (7 - 140 mē) of area for operation.
In 1994, an independent odour testing panel found no detectable odours from the vessel. The unit can be located indoors or outdoors in any environment, with only a small shed needed to contain the loading zone, and can be used as an on-site or central composting facility. Capital, engineering and energy costs associated with building construction are thus avoided.
Wright composting units are installed throughout North America and in Europe. Table 1 lists some operating facilities and their daily capacities. Many of the system users produce compost for their own grounds, eliminating the purchase costs for top soil and artificial fertilizer. The produced compost is of a high quality, suitable for marketing in agricultural, horticultural and other markets. By the end of 1996, the Ontario Government projects that composting at its facilities will divert 2,000 tonnes of food waste from landfill sites annually, and save approximately $200,000 in waste disposal costs.
| TABLE 1 | |
| SELECTED OPERATING FACILITIES | |
| Location | Capacity |
| Ontario Science Center North York, Ontario | 1.5 tons/day |
| Department of National Defence HQ Ottawa, Ontario | 750 lb./day |
| Ste. Anne des Plaine Institution Laval, Quebec | 10 tons/day |
| Mountain Institute Agassiz, B.C. | 1500 lb./day |
| Atlantic Institute Renous, N.B. | 1500 lb./day |
| Jasper National Park Jasper, Alberta | 2000 lb./day |
| San Francisco State University California | 1000 lb./day |
| Belfast Northern Ireland, UK | 1000 lb./day |
Figure 2: The composting vessel is a double-walled tunnel (stainless steel interior, burnished steel exterior) insulated to control the heat produced when organic materials decompose. Temperature and moisture levels inside the vessel's seven air zones are monitored constantly, and air flow is independently controlled in the three composting zones (shown) to assure optimum composting conditions. The mixing zones (between each composting zone) assure proper mixing and aeration for bacterial growth.
The In-Vessel Composter located at the Ontario Science Centre presently handles food
waste from seven Provincial Government facilities. A schematic of the machine is shown in
Figure 2. Food waste is mixed with an equal volume of amendment material, including wood
chips, paper sludge, cardboard, etc., which increases its bulk and porosity. The waste is
mixed with waste amendment by a drag chain mixer which has two opposed two-speed augers.
The mixture is then fed into the composter via a conveyer and enters the unit through a
hydraulic door. Bacterial activity begins almost immediately and air is continuously
circulated around and through the composting material. As the waste travels inside the
vessel, it passes through three composting zones and two mixing zones. The temperature and
humidity levels are monitored within each zone and airflow rates are controlled to
optimize composting conditions. Oxygen in the vessel is maintained at 17%, and the process
is very water efficient. In the mixing zones, specially designed spinners throw the waste
forward to ensure it is well mixed and aerated. Air is continuously drawn out of the
composter in order to maintain a negative pressure. This prevents air from escaping from
the vessel and ensures that all exhausted air is passed through a biofilter to remove
contaminants and odours. After spending approximately 28 days in the vessel, the finished
compost is removed from the vessel and filtered on a shaker screen. Large pieces are
separated to be recirculated through the composter as amendment. The finished compost is
now ready to be used.
Wright Environmental Management Inc. was formed in 1992. Along with equipment sales and tailored leasing packages, Wright Environmental provides service contracts to their customers for the supervision of the compost process, maintenance of the composting unit, removal of the finished compost product, or the full design, building and operation of the composting unit. Wright Environmental won the 1993 Financial Post Environmental Award for Business and received a letter of commendation from Canada's Minister of the Environment. Wright Environmental currently has offices in Ontario, British Columbia, New York, Virginia, and in Northern Ireland, UK.
Profile Print Date: 10/96
Catalogue # 09-009
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