Natural rubber as a green commodity- Part II Kevin P. Jones, Malaysian Rubber Producers' Research Association
Introduction B anbury 4.1 GJ/tonne of pallets and bale wrapping may IN THE LAST ISSUE of Rubber Calender 6.6 need to be considered within the new Developments Dr Wan Abdul Extruder 3.8 context of environmental quality Rahaman clearly demonstrated the Curing 6.3 control. 'green credentials' for natural rubber over its synthetic rivals (the key data are repeated below). Some may be The first figure is in general Environmental processing tempted to question whether there are agreement with measurements made at hazards hidden energy costs in the transport, MRPRA at about the same time, The rubber processing industry is use and disposal of natural rubber which estimated 1.2GJ/tonne for subject to specific environmental which offset the low energy budget of mastication and 2.9GJ/tonne for control in some countries. In the the natural material which is largely mixing. Both the overall figure of United Kingdom there are specific due to its solar, rather than fossil fuel 30GJ/tonne and the individual energy health and safety/environmental origins. breakdowns are probably well in protection regulations to limit the excess of the current best industrial emission of dust and fumes from Natural rubber versus practice. One efficient Scandinavian rubber processing operations. There is synthetic rubber company claims to be able to mix for an implied assertion that such dust and an energy cost of 0.4-lGJ/tonne fumes may be carcinogenic and that Material Energy consumption, within an overall energy requirement particular precautions must be taken. GJ/tonne of 20GJ/tonne, or lower. British Access to areas where such activities Natural rubber 16 energy data for mixing reveal take place has to be limited. It is not Polychloroprene 120 considerable differences between the rubber as such which is hazardous, SBR 130 plants. but the accelerators and antioxidants Polybutadiene 108 It is often, but not invariably, which may be added to it. In this EPDM 142 necessary to thaw bales of natural respect the rubber processing industry Polyurethane 174 rubber before processing as heavily- has never recovered from the Butyl rubber 174 crystallized natural rubber can damage industrial cancers which were caused Polypropylene 110 mixing machinery. Thawing is a by the long banned alpha common, but not standard practice, in naphthylamines. The data show the amount of energy northern Europe and northern North Natural rubber processing which is required to manufacture raw America for two to seven months per sometimes involves an additional natural and synthetic rubbers. It is year. Thawing is conducted in hot environmental hazard, namely odour. obvious that natural rubber enjoys a rooms which are maintained at Although such odours may be very considerable competitive edge in 40-45°C. The dwell time ranges from characterized as being typical energy terms as compared with two days to over a week. It has been agricultural, most such odours are synthetics. The energy required to calculated that the energy required to emitted in urban environments, where harvest, process and transport natural thaw natural rubber is 42 + 15? MJ per there is likely to be little sympathy. rubber is approximately one quarter of tonne, where t is the number of days The odours originate from the ageing that required for the feedstocks for the taken to thaw. If a period of four days of proteinaceous material, and is a synthetics. is involved, then the energy involved particular attribute of low grade would be 100MJ. There has been a rubbers. In some cases the unpleasant trend for the US rubber industry to odours may be carried over into rubber Natural rubber's hidden move south: this will have lessened products. When this happens it is energy costs the need for hot rooms in that country. probable that the processor will There are some modest energy In any event the energy cost of complain. Nevertheless, malodorous penalties involved in the processing of thawing is relatively trivial. At the products may still reach the market natural rubber, as compared with its worst it is likely that mixing natural place. If such products are identified competitors. These are the need to rubber may involve an energy penalty as being natural rubber this may lead thaw bales under certain circum- of between 10% and 15% as compared to a consumer backlash. A recent stances and a possible increase in the with SBR: this is trivial in overall issue of Rubber Developments number of mixing cycles. The typical energy terms. (Volume 46, page 35) showed how power requirements for rubber such odours could be greatly processing (natural or synthetic), diminished by using SMR CV. including overheads like office Packaging lighting, are probably in the region of Many countries, and notably Germany, 20-30GJ/tonne. The US Big Five take a keen interest in packaging and Recyclability (Goodyear, Firestone, etc) consumed argue that it is part of the supplier's The automotive industry is being 31GJ/tonne in 1976: some of the task to arrange for its disposal, politically dri ven to introduce individual process requirements for preferably by re-use or through a programmes for recycling the material energy at that time are: recycling operation. The construction from their products once they have
Rubber Developments vol 47 no 3/4 1994 37 NR as a green commodity
Major operators such as BMW are advertising their efforts to exploit an environmentally-friendly image. The increase in the use of thermoplastics is assisting this process. The picture shows a computer image of the new BMW 3 series; the recyclable components are coloured green, and the recycled components blue. become life expired. Considerable difficult. This even applies to dioxide produced is liable to damage progress is being made in Europe and thermoplastic elastomers, where in the incinerators. Radiation curing of the major operators, such as BMW. service degradation and pollution the gloves can eliminate this problem. are advertising their efforts to exploit damages the potential for recycling. Radiation curing also reduces the zinc an environmentally-friendly image. Nevertheless, a producer of TPEs effluent problem which is associated The increase in the use of thermo- claims that it is possible to recycle with traditional curing methods for plastics is assisting this process and automotive boots provided that they latex products. many of the manufacturers are coding are subjected to a washing process. thermoplastic components to assist Furthermore, TPEs do save raw with the recycling process. An materials as the waste from scrap is Tyre recycling important side effect of this policy is greatly reduced: in the case of TPNR, Between 60% and 70% of natural that vehicle manufacturers are seeking however, the raw material does rubber is consumed in tyres. In some to reduce the variety of thermoplastic involve the use of a material countries, notably the USA, Japan, materials to ease the recycling (polypropylene) with a high energy France, Germany, the UK and Brazil, operations. content (HOGJ/tonne). over 75% of the natural rubber With the exception of tyres, the consumed is in the form of tyres. In British automotive industry does not many countries, especially those with appear to be interested in recycling the Natural degradation high population densities, there is a elastomeric components even if Very thin rubber products, such as growing awareness of a tyre disposal thermoplastic elastomers (which are balloons and condoms, will degrade problem and this is accentuated when inherently recyclable) are substituted. naturally especially if they are serious fires occur at tyre dumps. The industry considers that all the subjected to natural sunlight. As is These fires can cause serious air engine compartment components will evident from the problems which are pollution as well as damage to water have been polluted by oils and exhaust associated with sealing rings natural courses. Consequently, some gases, and that the external rubber rubber is capable of being countries ban tyre dumping. components, like weatherstripping, biodegraded. It should be possible to If the life of the product is extended will have been polluted by cleaning compost thin rubber articles: then the disposal problem is reduced. agents or by environmental pollution. unfortunately the most important There is considerable evidence that If pressed to introduce recycling it is outlet for thin rubber articles is the tyre life has increased. This has crea- probable that the automotive industry medical industry, and the hazards of ted problems both for the tyre manu- will attempt to restrict the range of medical applications are liable to facturers and for suppliers to the elastomers employed to reduce the preclude the adoption of composting. industry, but it has coincidentally problems of classification at disposal. The presence of sulphur in medical reduced the scale of the disposal It is generally agreed that any form gloves may create problems for their problem. Automotive manufacturers of elastomeric product recycling is disposal by burning as the sulphur are seeking products which last for the
38 Rubber DevelopmentCOPYRIGHTs vol 47 no 3/4 1994 © MALAYSIAN RUBBER BOARD NR as a green commodity
whole vehicle life: any progress in this suggest that the addition of tyre crumb Nevertheless, a new reclaiming plant direction will be regarded as steps in any way detracts from the life of is being built in the Netherlands - towards easing the environmental road surface dressings. mainly to accommodate waste tyres. burden. Although the use of recyclable Pyrolysis is frequently proposed as Retreading truck and aircraft tyres crumb from tyres is using only a very a means of extracting a useful range of is normal practice. Aircraft tyres are small proportion of the millions of raw materials from discarded rubber designed for multiple retreading and scrap tyres discarded every year, it is products. Such raw materials include airliner tyres may be retreaded up to an idea worth pursuing. Progress is oils and carbon blacks. There is little eight times. Truck tyres may also be being made: two schemes which evidence that commercial success has retreaded more than once. In some make use of crumbed tyres are been achieved with such processes, countries truck tyre life is also featured on page 43 of this issue. although new processes continue to be prolonged by regrooving. Relatively Although tyre recycling involves advocated. few passenger tyres are retreaded and natural and synthetic rubbers, any An exciting novel method of this is mainly due to the lightweight attempts seen being made to reduce recycling is currently undergoing tests carcasses which are employed. It is the worldwide scrap tyre problem, can at present. 'De-Link' is a material that arguable that this may be better in only improve natural rubber's image breaks the crosslinks in vulcanized environmental terms than retreading as a green material. rubber, the recycled product can be as the lighter weight will assist to revulcanized without the addition of reduce vehicle fuel consumption. extra materials and is likely to be a There are a limited number of non- Reclaim suitable material for a wide range of destructive markets for old tyres. Chemical reclamation is capable of products (see the announcement on These include their use as reefs for producing a material that can extend page 46). fish farming, as fenders for boats and the overall life of the elastomer Combustion remains the most jetties, as footwear in poor countries, involved. The practice has virtually promising technique for the bulk and as swing seats for children. The ceased in the west, but has continued disposal of discarded tyres. It is a outlets extremely are restricted in in Eastern Europe and in India. technique which is employed in some relation to the scale of the problem. Energy is involved in the process, and tyre plants to get rid of waste and some methods also employ solvents. faulty products: the heat generated is It could be argued whether it is used to mitigate the loss. Some Rubber crumb from tyres justifiable to recycle products made cement works add tyres to lessen the If the old tyres are crumbed then the from natural rubber in energy considerable call for fossil fuels in potential markets are increased to accounting terms. Some speciality cement manufacture. The process include play areas for children (which elastomers are still reclaimed in the appears to be limited by the amount of can greatly enhance safety) and west: this may also be indicative of non-elastomer present in the tyre and rubberized bitumen for roads. The their high original energy inputs. by anti-pollution legislation. use of rubber in roads has had a long, long history and there is little doubt that the use of a wide variety of elastomers, including natural rubber in several forms, enhances the life and skid resistance of roads. Unfortunately, this is achieved by increasing the cost of a very cheap material and by marginally increasing overheads in a highly competitive industry. Thus a major market has never emerged despite pressure from both natural and synthetic rubber producers. With few exceptions road funding is provided via central or local governments which attempt to minimize the cost of road repair. Most such bodies appear to be keenly interested in short term cost savings. This has inhibited the development of a market for rubber in roads. The same bodies, or more correctly The West Midlands Whole-Tyres-to-Electricity Facility at Wolverhampton, owned different arms of the same bodies, are and operated by Elm Energy and Recycling (UK) Ltd, was the first power station of also aware of the problem of tyre its kind in the UK. It generates over 175 OOOMW of electricity per year for the Grid disposal. It is possible that this second by burning used whole tyres, and also produces useful by-products for the steel and group might persuade those zinc industries. Elm Energy's initial proposal for a tyre combustion facility was responsible for road repairs to incorporate tyre crumb as a made in 1989, in response to the Department of Trade and Industry's requirement component. There is no evidence to for a long-term solution to the nationwide problem of scrap tyre disposal.
! Rubber Developments vol 47 no 3/4 1994 39 NR as a green commodity
Gates' Wellington boots (LEFT) andDunlopillo mattresses (ABOVE), were both advertised as 'green' products to try and promote sales.
A number of tyre disposal plants are proposed or are under construction. These are intended to produce heat to generate electricity. Problems include the elimination of sulphur dioxide from flue gases, gaining environmental approval to build such plants, obtaining contracts for electricity sales, and gathering sufficient fuel and storing it prior to use. Rubber has a high calorific value, but the geometry of tyres precludes efficient storage. Unfortunately, crumbing which eases storage adds to the energy and economic overheads. It must be emphasized that the natural rubber element within the tyre will not add to the global CO, budget when the tyre is burned. As the natural rubber is produced from trees - the same trees are highly capable of re-absorbing the CO2 to produce further rubber. Moreover, as fuel has to be burned in high latitude locations to provide heat and energy, old tyres form a useful fuel source, and a far less environmentally damaging one than the displaced coal or oil.
Exploitation of green image Gates exploited the greenness of natural rubber to promote sales of its Wellington boots. Consumer market research had shown that the general public was unaware of the difference between rubber and plastic boots. This research also showed that the public appreciated the excellent environmental image of natural rubber. On the other hand the company is also cautious about a potential backlash
40 Rubber Developments vol 47 no 3/4 1994 NR as a green commodity
from the inclusion of environmentally Other consumer products which reduce the fuel consumption of cars unfriendly materials, like carbon might exploit the natural rubber green and other vehicles, or it can be shown black, in its black boots. image include hot water bottles, swim that tyres last longer because of it. Dunlopillo foam also ran an fins, bathing caps, bladders for sports Furthermore, there are considerable advertising campaign which exploited balls and sports and leisure footwear. energy accounting problems within the the connection between environ- There is a draft European Union concept of a green tyre, but such mentally-friendly rubber trees and its directive which may require footwear products are being marketed. Lighter product. The campaign was consid- manufacturers to place a symbol on tyres reduce vehicle fuel consumption, ered to be a success, but the company products which contain natural rubber. but the lighter construction lessens the is cautious in case of backlashes from Tyres form a far more complex potential for retreading. such issues as energy consumption in market to exploit. Clearly all natural For every 100 parts of rubber in a production, effluent disposal and the rubber used in place of synthetic is an typical tyre, there are 55-60 parts of inclusion of SBR latex in its products. environmental gain. Furthermore, an carbon black and 20-30 parts of oils. Most of the major tyre companies increase in the use of natural rubber The former is produced by combustion are introducing green tyres, which would reduce rolling resistance, hence of fossil fuels: therefore the energy claim to be green through reducing lower fuel consumption. Neverthe- content is high (104GJ/tonne). The rolling resistance (without loss of wear less, if this displacement leads to latter is much lower: 7GJ/tonne. properties), hence reduced fuel higher tyre wear, or poorer wet grip, Although the quantity of sulphur in consumption and reduced CO2 or greater noise then there may be no rubber products may not appear to be emissions. Michelin, Goodyear and environmental gain as environment- high it does create considerable Continental have announced such alism is a holistic concept. problems for waste disposal by products. Winter tyres based on combustion as this leads to the OENR could also claim to be more production of sulphur dioxide which is environmentally friendly than their a major cause of environmental studded counterparts. General environmental debits damage to forests, buildings and If an extreme stance is taken, then no health. industrial material can be The German environmental environmentally friendly, as the ministry has published a report which Suitable products for processes and in many cases the end- claims that vehicles, especially their promotion as green products uses exploit the use of fossil fuels. tyres, may be polluting the Latex products are especially suitable. This is especially the case for tyres environment with heavy metals as Household gloves have been marketed which are intimately associated with they wear. The quantities involved per in this way. They are consumer the automotive industry: to use tyres annum are 44 tonnes of lead, 32 products and they are a visible one has to burn fuel - even tonnes of zinc, and 8 tonnes each of product. Balloons have been the electrically powered vehicles are chrome and nickel (not all of which subject of backlash in the form of likely to use power generated from can be attributed to tyres). There are danger to wildlife: in this case a more fossil fuels. Thus natural rubber, fears that such metals may find their degradable product might have a sales which has been shown to be a 'green way into water courses and thus lead edge, although this implies better material' is exploited within an to the pollution of drinking water packaging and the risk of consumer energy consuming context. Globally, supplies. disappointment if the product is 14% of the carbon dioxide derived stored. from fossil fuels can be attributed to Latex thread and garment tapes road vehicles. In the USA this could be marketed as being contribution reaches 24% of carbon Conclusion environmentally preferable to the dioxide production. Natural rubber is an inherently energy-based polyurethane materials. Private motoring is an extremely environmentally-friendly material as This may be difficult to achieve, popular activity, and it would be an its demands for energy during its however, as the actual quantities of extremely difficult political production are trivial. In comparison material employed greatly favours manoeuvre to limit it. Nevertheless, synthetic rubbers are a contributor to polyurethane: the threads are far finer. the public has mixed perceptions the increase in global CO2 levels. Latex foam is less environmentally depending upon use versus Furthermore, although natural rubber damaging than its cheaper polyurethane environmental damage. In the United may require some extra energy to competitors. Polyurethane not only Kingdom the presence of a small plot process this is still insignificant in requires very high energy inputs, but of environmentally sensitive relation to the total energy inputs for is also associated with the use of CFCs woodland has been sufficient to synthetics. and with dangerous household fires. interfere with a major stretch of The only limitations to exploiting Unfortunately many, but not all, of the traffic-relieving road near London. this 'green' image are the dangers of the latex foam manufacturers also The Swiss have recently decided to backlashes in various forms from a have more important interests in ban trucks from using their Alpine lobby which is not noted for its urethane foams. Low cost is very roads for transit traffic as it endangers balanced opinions. It is hoped that this important in the furniture and car their mountain forests and increases paper has indicated the care necessary seating markets. Rubberized fibres the risk of avalanches. to ensure that such sources of (hair or coir) are environmentally Within this context natural rubber environmental dispute are known friendly materials and are competitive in tyres is only liable to be perceived within the rubber industry and, if with foams for upholstery. as green if it can diminish tyre noise, possible, minimized.
% Rubber Developments vol 47 no 3/4 1994 41 SCRAP RUBBER - REFUSE OR RESOURCE?
You will be very aware of the problem of waste rubber, especially used tyres, in the national waste stream. The problem is topical and many of your potential clients are trying to devise strategies to deal with it. .It is highly likely that you will be asked to advise them with information and recommendations for solutions.
Scrap rubber: the / / This report is designed to help you; it You are now able to buy a computer disc' with all has been produced by Rubber this information on,^^B-t^^^^mun Scat ions have '?$(*&---, " ."^s Consultants, who are world experts in taken the informati^ff ' " itlwell respected all aspects of rubber, and it contains a publication 'Clolh:' '" • -'plus information wealth of information in its 125 pages. contained in both . -;n Kubbcr Journal and Rubber £ PlasticS-i-.., - \ -o provide the most importan! sel of figures so far produced on the It reviews the various types of rubber, global tyre in; the additives with which they are compounded, their principal properties, The sstem in: the products in which they are used and , and kboth simple to use the volumes produced. on any lEM-compatible P " The alternatives to dumping are set out with special attention being given to tyres and other automotive wastes. also possum- iu The options include the use of crumb rubber in road construction, retreading, granulation, pyrolysis and incineration with and without heat or material --ft version of the World TV re Report recovery. on disc is now available, VAT) which will int. iude a free update, The Study is available for £180, in hard copy format, from Rubber Consultants. For further information contact Grain Communications Ltd, 2nd Floor, Cowcross Court, 75/77 Cowcross Street, London EC1M 6BP. For further information please use Tel: +44 (0)171 608 1173. the RD fax back sheet Fax: +44 (0)171 608 1116. 42 Rubber Developments vol 47 no 3/4 1994 ---^