4 Alternative end-uses and barriers to these
4.1 Alternative end-uses
Potential end-uses for the waste tyres can be divided into categories.
- Energy recovery - tyre-derived fuel for cement kilns, smelters, paper mills and power stations or blasting material for mining.
- Civil engineering - retaining walls, building foundations, paving roads, erosion control, stemming or landfill engineering.
- Material recovery - production of steel, new tyres, road surfacing, flooring and mats, moulded products (eg, speed humps, crash barriers) or adhesives.
The following provides a brief overview of potential reuses specific to the New Zealand market. As part of an investigation into a regional waste recovery unit in Wellington, alternative end-uses have been previously evaluated and reported on in some detail. [www.mfe.govt.nz/publications/waste/devt-regional-waste-recovery-sector.]
Energy recovery
In New Zealand there are at least two operations that could use large volumes of tyres as a potentially viable alternative energy source.
- Golden Bay Cement, based in Whangarei.
- Holcim Cement, based in Westport.
The net calorific value of tyres is between 26 and 34 GJ per tonne [MWH New Zealand Ltd (June 2003). Development of a Regional Waste Recovery/Processing Sector. A Report prepared for the Wellington City Council, Ministry for the Environment and Ministry of Economic Development.] which is similar to that of common fuel sources such as coal. A tyre burns completely at 650°C, producing principally carbon dioxide and water, with the addition of some inert residues such as ash and slag. The temperature inside cement kilns, at 1800°C, is significantly higher than this and thus ensures complete combustion. Cement kilns will accept whole tyres as fuel, which saves preparation (quartering or shredding) costs.
Material recovery
One of the largest potential users of tyres for material recovery is Pacific Steel, based in Otahuhu.
The use of tyres as a material input to the steel manufacturing process was trialled at Pacific Steel for a three month period, approximately two years ago. Tyres are regarded by the company as an excellent alternative to Activated Carbon and also provide an energy input. [Personal communication. Rod Murray, Environmental Manager, Pacific Steel.] About half a million tyres per year (approximately the entire Auckland market) could be used as input.
In addition, the steel rims from the tyres can be directly fed to the steel manufacturing process. Use of tyres for steel manufacture therefore represents a "holistic" end-use. Whole tyres can be used, though halved or quartered tyres are preferred. Larger off-road haulage and tractor tyres can also be used.
The results of the three month trial showed that tyres were a technically feasible material input into the steel production process. Production yields increased and there were no significant increases in atmospheric emissions. The heat flows to the bag house were, however, more variable and, as a result, Pacific Steel would need to upgrade the baghouse.
Civil engineering and tyre transformation
There are a large number of "civil engineering related" alternative end-uses for tyres. Most of these rely on the stability and rigidity of the tyre. Examples are:
- landfill engineering;
- retaining walls and soil embankments (which require minimal processing of whole tyres);
- anti-erosion measures, artificial reefs and flood defences (using whole tyres).
Tyres can also be transformed, which is defined as gradually reducing a tyre to smaller and smaller particles and using the resultant material as a resource. This is increasingly common overseas. There are many technologies being developed to transform tyres into a Tyre Derived Product (TDP). The TDPs are created by physical grinding or by cryogenic processing (freezing and then shattering). Possible uses for TDPs include:
- stemming and drainage (using shredded tyres);
- rubber mulches (using buffings from solid rubber tyres);
- matting and flooring (using crumbed rubber);
- road surfacing (using crumbed rubber);
- spray seals (using crumbed rubber).
Road surfacing using crumbed rubber mixed with bitumen is now being widely adopted overseas. The road surface is longer lasting and also quieter than the equivalent, pure bitumen option.
There is also ongoing research into development of more durable and rubber-less tyres. There are technical difficulties associated with producing devulcanised rubber fibres for different manufacturers' standards.
In New Zealand, there are a number of new initiatives investigating civil engineering-type applications for used tyres. Through feedback received from stakeholders during this study, URS understands that companies such as the Australian-based "Ecoflex", which use tyres for a range of engineering applications, are active in the New Zealand EoL tyre market (www.ecoflex.com.au).
4.2 Barriers
There are both perceived and real barriers to alternative potential end-uses for tyres.
Environmental
Tyres are "built to last" and therefore do not degrade easily. This creates issues for regulatory authorities providing consents for using and burning tyres. There is now extensive evidence from overseas showing that tyres can be burnt at high temperatures (such as those present in an electric arc or a cement kiln) without creating unacceptable atmospheric emissions. Following a comprehensive review of alternative tyre disposal options in the United Kingdom, the Environmental Agency has recommended that burning tyres in high temperature cement kilns is preferable to landfilling, from an environmental perspective. [United Kingdom Environmental Agency. 2001. Tyres Disposal Protocol.] This supports findings from other overseas investigations that show burning tyres at high temperatures does not produce unacceptable atmospheric emissions. In Australia, for example, burning tyres as an energy source for cement kilns is common practice and is used at CemAust in Gladsone and Blue Circle at Waurn Ponds.
On the basis of information collected during this case study, Pacific Steel, for example, is confident of its ability to use tyres in the steel manufacturing process without exceeding existing resource consent conditions. The environmental issues are, therefore, more of a perceived than actual concern and it is our recommendation that further research is carried out to check this initial conclusion.
Security of supply and transport
Security of supply and transport costs have been put forward as issues for larger-scale reuse of tyres (in cement and steel manufacturing). These factors are not issues in their own right but have arisen from the cost/benefit analysis and therefore economic feasibility of any proposed reuse. Again, representatives of Pacific Steel have confirmed during this study that they are confident their proposed tyre reuse (as an alternative to activated carbon) would be economically feasible and represent a win/win economically - for both the end-user and the tyre manufacturer. This situation may be different in rural areas in New Zealand, in particular the South Island where relatively small numbers of dispersed tyres would be expensive to collect and transport to one location, for example, the Holcim Cement Plant at Westport.
Costs for landfill disposal vs alternative reuse options
We believe that lower cost landfill disposal provides a major barrier to the economic viability of alternative reuse of tyres. The topic of landfill pricing is extensive and encompasses a range of environmental and social cots, and landfill operator business issues. It is beyond the scope of this study to evaluate or comment in detail on appropriate pricing structures for waste disposal at landfill. We believe, however, that it is appropriate to conclude that if landfill disposal was more expensive (and therefore a better reflection of all environmental and social costs for linear throughput of products, as opposed to greater reuse and resource recovery) there would be greater economic incentives for alternative tyre reuse. In the South Island, for example, cheaper landfills accepting whole tyres compete for the supply with other landfills. This is a reported barrier to energy recovery at the cement kilns.
The total cost of tyre collection and transport is estimated at $1.50 to $2 per passenger tyre in the South Island. In Australia, cement manufacturers are not buying tyres but are paid for taking them. [URS. 2005. Financial and Economic Analysis of Proposed National Used Tyre Product Stewardship Scheme.] On the basis of our Australian study, it was calculated that tyres were worth (as an equivalent energy source to coal) between $74-$88 per tonne (depending on whether whole or shredded), which equates to less than $1 per passenger tyre. This is slightly more than the equivalent coal price of $60 per tonne. Tyres also contain steel, which provides a substitute to ferrous oxides, and produce lower ash percentages to coal.
The cement plants in Australia currently charge approximately or $250 per tonne (about $2.50 per tyre) for taking the tyres. Despite this current situation, the Cement Industry Federation in Australia has indicated that an estimated price of between $35-$74 per tonne (about 0.35 cents to 0.74 cents per tyre) would be the highest that kilns would pay for tyre-derived fuel.
The situation in Australia - with cement manufacturers being paid to take EoL tyres - has arisen through private sector arrangements between the cement manufacturers and the tyre retailers/collectors and is a result of negotiations from two different perspectives.
- From the cement manufacturer's perspective, use of tyres as a partial substitution for fuel may generate both supply uncertainties and quality issues. Although the tyres may represent a slight reduction in energy costs, this may be offset by the risks arising from a less reliable source and the capital costs to construct additional storage and supply facilities. There would also be operational issues as mixed fuels might lead to more process problems and capacity constraints.
- From the tyre manufacturer's perspective, the EoL tyre "energy product" has a value as either an alternative fuel or a materials source.
If landfill costs were increased, the starting position for negotiations between users (for example, the cement manufacturers) and generators (including the tyre retailers and manufacturers) would be based on the attractiveness of alternatives to landfill. Under the current arrangements it is simpler, and in many cases more cost effective, to dispose of the tyres in landfill.
Australian studies [URS Australia. 2005. Financial and Economic Analysis of Proposed National Used Tyre Product Stewardship Scheme.] have found that values for tyres as prepared units for engineering purposes, such as retaining walls, building foundation formwork and flexible roads, can be in the region of AUD $200 per tonne ($2 per tyre). Opportunities to use tyres in these market areas would appear to be available in New Zealand.
Increased values are potentially obtainable in the use of rubber crumb (1 to 2 mm) as a diesel fuel and as a substitute in blasting mixes. These uses have values in the region of AUD $500 to $600 per tonne ($5-$6 per tyre). Road surfacing using rubber crumb at the 30 mesh grade (0.5 mm) for spray seal and asphalt applications is valued at between AUD $400 to $600 per tonne ($4-$6 per tyre) in the Australian market. Rubber crumb (1 to 10 mm) for flooring and mat manufacturing is currently valued at between AUD $350 to 600 per tonne. Rubber crumb, in adhesive manufacturing, attracts prices of between AUD $550 to $900 per tonne. Although rubber crumbing appears economically attractive, feedback obtained during this case study suggests that even a coarse crumbing process (to 50 mm) costs up to $80 per tonne.
Higher end value moulded products using fine rubber powders at 100 micron and smaller have a value in the region of $500 to $1000 per tonne ($5-$10 per tyre) and can be used in the elastomer market. Steel and textile recovery, a by-product of tyre crumbing, generates recovered fibres and steel, both of which have an end-use value.
Despite the seemingly attractive economics, none of these markets for EoL tyres have been developed in New Zealand. Likely reasons for this include available tyre numbers (security of supply), transport distances and logistical issues. Also, the technologies for reuse of tyres are still very new overseas and, in many cases, are still under development.
Lack of information and tracking for tyres
Given that TyreTrack records the movement of only a third of New Zealand waste tyres, there is currently limited information on the numbers and locations of tyres potentially available for reuse. As a result, potential alternative end-users would find it difficult to develop business models that required some understanding of the distribution and nature of the input product, ie, the tyres. This situation would be resolved if participation in TyreTrack increased - either due to greater incentives or regulation to enforce mandatory membership.
Australian findings
An Australian study [Atech Group. 2001. A National Approach to Waste Tyres.] of tyre end-uses lists the following barriers to their wider uptake:
- cheap landfill pricing;
- unsupportive public procurement policies;
- private sector inertia in using different systems;
- lack of consistent and reliable EoL tyre supply;
- lack of regulation supporting the recycling of EoL tyres;
- distance from collection point to end-users;
- competition from raw materials priced at low levels;
- concern by regulators over the heavy metal leachate;
- operational difficulties in burning tyres;
- negative public perception of environmental issues associated with burning tyres;
- lack of appropriate specification for use of tyre rubber in road surfacing;
- health and safety issues.
Summary
In summary, some of the above reuses for tyres have been developed as commercially viable options overseas. So why hasn't this occurred to date in New Zealand? The answer relates to the complex economics of disposal and reuse from different perspectives, including the retailers/collectors, the alternative end-users and the landfill operators. Despite claims from some industry representatives that reuse options are already economically viable and are being hindered by perceived environmental concerns, a much higher landfill disposal fee would "drive" the market towards reuse and more accurately reflect the overall cost, including social and environmental, of tyre use and disposal.
