The Dongara Pellet Factory Inc. is a new facility located in the southeast corner of Vaughan, Ontario at the intersection of Highway 27 and Highway 407. The plant is the end result of an RFP issued in 2003 to handle 70,000 tonnes of municipal solid waste for York Region (just north of Toronto). After winning the RFP the project grew in scope and ultimately secured a 20-year contract to receive 100,000 tonnes per year of waste from York Region, with the intent to ramp up to 200,000 tonnes, some of which will likely come from York and the remainder from the surrounding regions.
The facility receives municipal waste from a combination of street and compactor trucks from surrounding transfer stations. Waste is processed to remove recyclables and unwanted residue and hazardous materials, with positively selected waste shredded and sent to fiberizing and pelletization equipment. Fuel pellets are then produced with chemistry within customer and environmental agency limits, based on end use, paying particular attention to thermal and elemental breakdown. (See overview article, page 14.) The tonnage of fuel pellets produced is approximately 95 per cent of incoming waste tonnages, through the replacement of residue, recyclables and moisture with high BTU additive, which ranges anywhere from 15 to 30 per cent by weight, dependent on season.
The fuel pellets are formulated to have an energy content of approximately 10,000 to 12,000 BTU/lb, with a density of approximately 40 to 45 lbs/cu ft, and moisture content no greater than eight per cent. This makes the fuel pellet competitive with coal in energy content, but with much cleaner chemistry, thus allowing possible end-use customers currently using dirtier fuels to improve their emission profiles.
The facility started receiving municipal waste under contract in July, 2008. The patented technology, exclusively licensed to Dongara, is owned by Sentinel Waste International Ltd, a private company in Canada, with a planned transfer of the technology to Dongara over a limited time period. The dense fuel pellets are currently used to heat large com-
mercial greenhouses in Ontario, as well as transported for use in cement kilns. In both cases they displace coal, coke or bunker C oil.
The primary objective of this process, trademarked as Enerpax+, is to reduce the transportation of significant volumes of municipal waste presently disposed of in landfill into an environmentally acceptable fuel product, used beneficially by energy consumers currently dependent on coal, oil or natural gas. A side benefit is that the volume of methane gas released from landfill is reduced. The process captures and recycles up to 98 per cent of all recyclable materials still within the waste such as Type 1 and 2 plastics, aluminum, tin, and glass.
Residential waste is dropped on the tip floor. The building is kept under negative pressure to mitigate odour release. Obvious hazardous or large materials are removed to the side for later use or disposal. The remainder is moved to subfloor pits, then opened and transferred onto a series of transverse conveyors, where it passes through size-separation trommels, coarse screens and Ti-Tech plastic removal systems, as well as magnets and eddy currents to select and separate ferrous and non-ferrous materials. Much of the front-end system at the plant was supplied by Bollegraaf and is arranged in an efficient footprint. Material suitable for pelletization is positively selected, with a small amount of residue set aside for disposal.
The materials suited for fuel pellet production are shredded, fiberized and stored in storage silos. This material is later combined with high-BTU admixture materials such as carpet waste, poly film or other acceptable plastic derivatives. The materials are transferred through pellet mills to produce the final fuel pellet, stored, then transported to end users.
The pellets have been tested by four accredited independent labs. Tests indicate that constituent elements will allow emissions that are superior in environmental terms than those presently seen from the burning of coal, bunker C oil, coke, tire derived fuel, or other non-engineered residential waste products. The facility incorporates an in-house certifiable-level testing laboratory to ensure the pellets and other materials are systematically tested on an ongoing basis for consistency and to ensure no harmful chemicals make their way into the pellet prior to shipping.
The environmental impacts of the pellet production plant are minimal, as no burning takes place throughout the process. Air emissions are restricted to ensure that the Ontario odour limit is maintained within the property; this is achieved by use of a bio-filter located under the plant floor that allows exhaust of air to a maximum of 200,000 cfm.
Odour, dust and debris are contained within the facility through an air supply system that ensures a negative air balance, using approximately 3 to 3.5 air changes per hour, with as high as 5 to 6 air changes in high odour centres within the plant. Air filtration screening inhibits dust from leaving the plant via the exhaust location. Debris is contained since all waste is off-loaded inside the tip floor area.
Water pollution control is dealt with by the use of a biological treatment system including pre-treatment and tertiary treatment systems; this ensures water quality reaches regional requirements to discharge to the local sanitary sewage system. Approximately 25 per cent of wastewater emerging from processing and wash-down of the plant is recycled after treatment to minimize discharge to the local system, as well as to minimize incoming water requirements.
Noise from machinery and motors is contained within the plant using appropriately designed exterior wall skin. Every kW used at the plant to produce pellets, on an hourly basis, generates at least eight to nine times that in electrical energy via the end process of burning./gasifying the pellets.
Stone, large gravel and large pieces of glass are separated and issued to companies in the brick and concrete industries. PVC, as an unwanted material in the pellet, is also separated and sent to markets such as lawn furniture manufacturers. The residue is a mix of small fractions of glass, sand and gravel, as well as items such as “kitty litter” and other non-use-able organic wastes. Typically, residue represents about seven to eight cents of incoming waste.
Guy Crittenden is editor of this magazine. Contact Guy firstname.lastname@example.org