North American Recycled Rubber Association
1621 McEwen Drive, Unit 24
Tel: (905) 433-7669
Scrap Rubber Reclamation in Canada
Philip E. Coulter
Secretary & Director of Research for N.A.R.R.A.
Scrap Rubber reclamation in Canada is divided into three main processing categories; namely, mechanical grinding at ambient conditions, cryogenics, and microwave/pyrolysis.
Mechanical grinding is the most common process currently occurring in British Columbia, Alberta, Manitoba, Ontario, and Quebec. This method consists of mechanically breaking down the rubber shred into small particles using a variety of grinding techniques, such as "cracker mills", "granulators", etc. The steel bead and wire mesh in the tires is magnetically separated from the crumb during the various stages of granulation and the fibre in the tire is separated by sieve shakers.
The advantages of mechanical grinding are several. The system is well developed with a variety of components available to reduce the crumb at relatively low cost. Comparatively, the system is easy to maintain and requires few people to operate and service and replacement parts are generally easy to obtain and install. A variety of companies sell component parts and total systems in a highly competitive market.
The disadvantages are only two, namely, the considerable added cost and energy required to produce the extremely fine mesh sizes, such as 60 mesh and higher. Secondly, although some system sellers might disagree, the operation can become very dirty internally which so far has not become a health issue but in some regions government health and fire officials could be concerned. It is therefore most imperative that the factory space be kept thoroughly cleaned on a regular basis to prevent the build up of fine black powder.
Cryogenics consists of freezing the shredded rubber (using liquid nitrogen for example) to extremely low temperatures, generally in a "freezing tube". The frozen rubber is then very easily mechanically crushed into small particles with the fibre and steel being removed in the same way as in mechanical grinding.
The advantage of this method is a cleaner, slightly faster operation resulting in the production of fine mesh sizes economically. The disadvantage is represented by the slightly higher production cost due to the added cost of liquid nitrogen. There is on going controversy as to the particle shape which turns out to be relatively smooth and oval compared to the mechanically ground particle which is irregular in shape and surface texture. This has posed a problem in certain after-market products. Cryogenically ground scrap rubber is highly disirable in asphalt applications particularly in the U.S. Southern states.
The microwave/pyrolysis category includes two separate approaches to generating the original elements from which the rubber was made. Carbon black, fuel oil, sulphur ash, steel, and fibre represent the results of these two separate methods of cured rubber reduction. The microwave technology is still relatively new, although a working system has been demonstrated in Ontario now for the last two years, with a plant currently underway in California as a franchised operation from the Ajax location. The pyrolysis method is also relatively undeveloped although considerable time and cost have been invested in research and development over the last few years. Currently a plant is operating, to the best of our knowledge, in British Columbia with a plant due to start in 1996 in Deep River, Ontario. Both systems' technology has been kept relatively hidden from general knowledge except for those who are serious interested in investing.
The first two methods do require the services of some form of initial tire breakup such as shredding or slicing into 1" - 6" chips complete with steel and fibre. The third method (microwave/pyrolysis) generally uses whole tires and is currently favouring passenger tires. It is to be noted that a passenger tire of some 20 lbs. contains 6 lbs of fibre, 4 lbs. of steel and the balance of usable rubber.
Generally speaking, the current market demand for scrap tires is related to the demand of crumb for after-market products. Currently in Alberta, there is a reduced amount of tire supply to meet the growing number of companies now involved in shredding/crumbing. Whereas, in Ontario there is relatively little shredding and crumbing resulting in 70% of the annual generated tires being exported for incineration in the U.S. All provinces, with the exception of Ontario and the four Eastern provinces, currently have tire levies and/or subsidies in place. Manitoba has a $3.00 levy , Quebec has an excellent subsidy arrangement for their processors, New Brunswick and Nova Scotia are expected to be on line this year with similar programs involving a $3.00 up front levy to the hauler/shredder/processor, with Prince Edward Island and Newfoundland sending their tires to either province for processing. Hopefully Ontario will have something in place by the end of the government's fiscal year.
A further method of disposing scrap rubber is through incineration, either by way of shredded or whole tires in cement kilns as an ingredient in cement production, or in steam power plants for electricity production as a blend with coal. Although a plant is currently being constructed in Ohio which will burn whole tires directly for electricity production.
A wide variety of after-market products are currently being manufactured from various sizes of crumb rubber, including the surfacing of outdoor running tracks, production of speed bumps and wheel chocks, sound installation, as well as the wide variety of rubber/plastic compounding for consumer products such as garbage pails, compost boxes, shoe soles and heels, etc.
At this stage in the overall development of the rubber reclamation industry we are somewhat in the same position as the motor car was in 1910, but moving ahead at about 25 times the speed so that in three years we will be currently abreast of where the motor car is today in terms of modern technology applications for improved economics and end product quality. Look forward to a enormous growth in this industry over the next four or five years as the"window of opportunity" peaks!
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