Development of a Regional Waste Recovery / Processing Sector

Acknowledgements

Executive summary

1. Introduction

2. Total waste stream and quantities of plastic, glass and tyres

3. Projected waste quantities

4. Reprocessing technologies for tyres

5. Reprocessing technologies for plastic

6. Reprocessing technology for glass

7. Conclusion

References

Appendix A: Template for Assessing the Regional Suitability of Waste Reprocessing Technologies for Tyres, Plastic and Glass

Appendix B: Major European PET and HDPE Reprocessors

6. Reprocessing technology for glass

6.1 Introduction

Glass is an important industrial material, with its main uses in glazing and packaging of foodstuffs. Glass waste arisings occur in both the domestic waste streams (principally containers) and industrial wastes (principally flat glass from construction and demolition). Not all types of glass can be economically reprocessed at present and the available markets for each glass type vary considerably.

The graph below illustrates that glass consumption in New Zealand has increased significantly between 1994 and 2001 from 84,040 to 138,245 while the quantity of glass collected has also increased from 30,340 tonnes to 61,630 tonnes, respectively. This equates to 45% of glass is currently collected.

In the Wellington region approximately 16,069 tonnes of glass exists in the waste stream and of that 9,441 tonnes was landfilled in 2002, while 6,628 tonnes was diverted through kerbside collection and drop off sites. This is comparable with Christchurch, where an average of 6,000 tonnes of glass is diverted per annum.

6.2 The Various Glass Types

Glass covers a range of materials each with different properties and applications. The principal types are:

• Container glass for bottles and jars;
• Flat glass for glazing (buildings and motor vehicles);
• Fibre glass for insulation and reinforcement;
• Other types include tableware, lighting (e.g. fluorescent tubing) and scientific/technical glassware.

Although the primary manufacturing routes of these glass types is fundamentally similar, the chemical compositions and physical properties are different. The most common type of glass is 'soda-lime', which is composed of silica sand (SiO2), soda ash (Na2CO3), limestone (CaCO3) and other minor additions melted together. Melting is carried out at high temperatures, generally around 1500°C, in large continuously operated furnaces. Once melted the liquid glass is formed to shape using a variety of production processes and allowed to cool. Soda lime glass is used for the production of containers (bottles and jars), flat glass (windows), domestic tableware and lighting (fluorescent tubes). Each of these applications employs slightly different compositions of the basic soda lime glass. Other types of glass that enter the waste stream are:

• Cathode Ray Tubes (CRT) for TV screens and PC monitors are manufactured from a wide range of glass compositions but usually include large amounts of lead oxide (PbO) and boric oxide (B2O3).
• Lead Crystal tableware, which is typically composed of 55% silica (SiO2), 33% lead oxide (PbO) and 11% potassium oxide (K2O).
• Heat resistant glass ('Pyrex') is a borosilicate glass containing up to 12% boric oxide (B2O3).
• Glass fibre is another borosilicate glass similar in composition to heat resistant tableware

  (Waste Resource Action Programme, (WRAP), 2002).

6.3 Glass Reprocessing and End Markets

6.3.1 Introduction

The main use for recycled glass is in the container manufacturing industry as glass can be recycled indefinitely by remelting and forming it into new products. Recycling in the container (and possibly the flat glass) sector is often termed primary recycling and could be carried on continually as a 'closed loop' system. Secondary markets, such as aggregates only involve a single use of the recycled product and are sometimes known as 'open loop' recycling.

Before it can be used as a raw material in any application recycled glass requires some initial sorting to remove contaminants. Depending upon the final application, reprocessing may involve a number of steps that include:

• Size reduction by crushing
• Screening to remove gross contamination
• Magnetic and 'eddy current' separation to remove ferrous and non-ferrous metals
• Air classification to remove light materials such as paper and wood
• Optical sorting to remove ceramics and unwanted colours
• Size classification
• Washing and drying

Every application has different specifications relating to the maximum levels of impurities and the particle size distribution. For example when flat glass is recycled into new window glass the maximum level of impurity will be less than 1g per tonne. For some aggregate applications the specification is much more generous and the glass only requires crushing and screening.

Until recently, virtually all recycled glass in the UK was used as a feedstock for container glass manufacture. As a result, the UK glass reprocessing capacity was geared to meet the requirements of this application. Consequently, typical reprocessing plants are large and capable of processing up to 50 tonnes per hour. A similar situation exists in New Zealand where the majority of the glass collected from kerbside collection and bring systems is transported to ACI, a glass manufacturer in Auckland.

Glass manufacturers generally recycle their own internally generated scrap within the glass melting process and theoretically it would be possible for all glass makers to augment their own internal recycling with post-consumer recycled glass to provide a reduction in raw material and energy costs. There are some possible negative effects of recycling glass, all of which relate to impurities that may be introduced into the glass furnace. Small pieces of ceramic material derived from pottery or other contaminants can pass through the furnace unmelted and give rise to 'stone' defects in finished products that will lead to rejection. Metals can react in the furnace, giving rise to gas bubbles in the glass melt, again ending up in the finished product and causing rejects. Even more problematic are 'glass ceramic' materials and heat resistant borosilicate glasses (e.g. 'Pyrex') which are difficult to detect in the raw cullet and which will cause defects in finished products and cause blockages in the glass moulding machines.

In theory furnaces can operate using 100% cullet, and this level is claimed by some foreign operators of green glass furnaces such as Vetropak in Switzerland. However, 90% is probably a more reasonable figure if quality is to be maintained. In theory the same applies to flint and amber furnaces; however flint furnaces are more sensitive to colour contamination and 70-80% is probably the practical maximum.

Currently UK container glass furnaces use on average 30% external cullet, though there are large variations in this figure depending on the colour of the glass. There is a great deal of scope for increased clear (and amber) cullet consumption. The precise colour specification for the container has a major influence on the percentage of cullet that can be used. These specifications are frequently tighter than many used in continental Europe and would have to be relaxed if cullet contents in amber and clear glass are to rise above 70% (WRAP, 2002).

6.3.2 Alternative Markets for Recycled Glass

Much of the work in developing new markets for recycled glass has been carried out in the USA during the last decade by the Clean Washington Center (www.cwc.org) being pre-eminent in this field. The following physical and chemical properties of glass make it suitable for these alternative uses:

• It is a hard (albeit brittle) material with good compressive strength;
• Chemically it is inert and most common types of glass contain no substances harmful to health;
• It is a rich source of soda (Na2O) and can act as a fluxing agent; and
• Its aesthetic qualities make it suitable for a number of decorative applications.

A range of alternative uses for recycled glass has been included below:

Table 6.1: Alternative uses for recycled glass

Use	Application	Products to be Replaced	Potential Advantages of Recycled Glass Product	Potential Disadvantages of Glass Product
Aggregate	Loose fill Asphalt Concrete Pipe bedding Backfill Decorative Golf bunkers	Crushed rock Gravel Sand	Resistant to load under compression / impact Good drainage properties Colourful for decorative applications	Engineering specifications can be material specific Availability of other waste materials, e.g. colliery spoil
Abrasive	Shot blast Bonded Frictionators	Silica sand Copper slag Anthracite	Glass contains no crystalline silica Low heavy metal content Angular particles for effective performance	None identified
Cationic exchange	Zeolites	Naturally occurring zeolites		Still in development phase
Decorative Art	Tiles Drinking glasses	Virgin glass materials	Colourful Low cost 'Recycled' marketing value	Difficulties in securing reliable / consistent source
Filler	Paint Plastic	Titanium dioxide Calcium carbonate	Low cost	No commercial applications to date Small particle sizes required may be difficult to achieve
Filtration media	Drinking water Wastewater Swimming Pools Fisheries	Sand Anthracite Garnet	Resists bacterial growth	Drinking water industry approval required for use as drinking water filtration media
Flooring	Terrazzo Synthetic marble Resin composite	Crushed rock	Colourful Glass / resin composite can be highly resistant
Flux / Binder	Bricks Ceramics Pottery	Mineral fluxes Clay	Reduced firing temperature & time Reduced HF emissions May enable use of existing clay reserves
Hydroponics	Rooting medium	Expanded clay aggregate	Free flowing Easily sterilised	Can cause cuts in handling
Packing	Water well	Sand	Good drainage	High levels of cleanliness required
Insulation	Construction	Virgin glass materials	Low cost

(WRAP, 2002)

1. Aggregate

The USA experience has shown that crushed recycled glass can successfully be used in aggregate applications. Typically the applications have been using minus ½ inch cullet because the screening of this sized glass will remove the majority of impurities and the risks of cuts to the skin during handling are much reduced. However, much of the test data is based upon glass and natural aggregate blends and in all the case studies the glass was used in combination with sand and gravel. These observations are reflected by the policies of the regulatory authorities across the USA where glass is generally restricted to non-structural fill applications; is blended with natural aggregates and generally must be minus than ¾-inch (19 mm):

6.3.2.1 Washington State

Allows up to 15% recycled glass to be used in a number of unbound aggregate applications. Particle sizing: no more than 10% should be retained in a ¼-inch (6 mm) sieve.

100% cullet permissible for wall backfill, pipe bedding, drainage backfill and drainage blankets. Particle sizing: 100% less than ¾-inch (19 mm).

6.3.2.2 Oregon

Up to 100% cullet can be used in non-structural fill, drainage blanket, pipe bedding and surface drains. Particle sizing: 100% less than ½-inch (12 mm).

6.3.2.3 California

Up to 100% cullet can be used for sub-base of flexible and rigid pavement.

Surfacing material must be placed over all aggregate bases containing cullet.

6.3.2.4 Connecticut

Up to 25% cullet can be used for embankments. Particle sizing: 25% must be less than 1-inch (25 mm).

Aggregate containing cullet cannot be placed within 5 feet from the face of any slope.

6.3.2.5 New York

Embankments may contain up to 30% by volume of cullet and road sub-base courses may contain up to 30% by weight of cullet. Particle sizing: must be less than ?-inch (9.5 mm).

Glass cannot be used in any applications where it comes into contact with synthetic liners or geo-textile materials.

6.3.2.6 New Hampshire

Up to 5% cullet can be use in road base courses material. Particle sizing: must be less than ½-inch (12.5 mm).

Base courses containing cullet must be capped with non-cullet aggregate.

Concrete Aggregate

Glass can be used to substitute some of the aggregates used in concrete production due to the following useful properties:

• With almost zero water absorption it can contribute to the durability of the concrete.
• Its hardness is superior to most natural aggregates.
• Concrete flow properties can be improved by using glass and, therefore higher-strength lower water mixes can be employed.
• The unique aesthetic properties may appeal in decorative applications.
• Very finely ground glass has pozzolanic properties contributing to the concrete strength.

However the major drawback of glass is that the alkali in the cement can react with the silica in the glass. This 'alkali - silica reaction' (ASR) produces a gel on the aggregate surface which swells and can cause the concrete to crack. For this reason the concrete industry has avoided using glass as an aggregate, particularly as the ASR reaction may take several years to manifest itself. However, recent work has demonstrated that the ASR reaction can be avoided either by using a fine sized glass aggregate, less than about 1 mm, or by suppressing the reaction with admixtures or using a low alkali cement. Other work has shown that with additions of very fine glass powder (<600 microns) the glass undergoes pozzolanic reactions, which have the potential to increase the concrete strength .

The annual UK consumption of cement is around 12 million tonnes/year, all of which is used in concrete production and requires an estimated 40 million tonnes of aggregates. About 70% of UK concrete is produced as 'ready mix' for onsite placement and only aggregates specified in BS 882:1992 are used. BS882 defines the physical and chemical properties of natural aggregates for concrete manufacture. The word 'natural' is important here, as it excludes glass (WRAP, 2002 & ENDS, 2002).

Decorative Aggregates

Glass used as decorative mulch and as a landscaping aggregate has received significant publicity. This is a crushed and graded product (usually minus 20 mm) and is often 'tumbled' to remove sharp edges. There are no universally accepted standards or specifications for this product, the (subjective) aesthetic properties being most important. A number of companies produce this material in the UK and it commands an excellent retail price.

2. Filtration

Granular media filtration currently has a number of applications in the treatment of potable water, municipal wastewater and industrial wastewater. Types of media used include anthracite and garnet, but the most common is sand. Crushed glass of a suitable particle size distribution and quality may be a potential granular media for such filtration applications.

Depending on the application, filter beds may consist of one or more type of media, of single or varying particle sizes. The particle size of the filtration media is one of the critical factors in the removal efficiency of particulate material from an aqueous stream. If the media particles are too small, there may be too much resistance to the flow of the stream and very little void space for the collection of solid waste. If the media particles are too large, many of the small solids particles in the influent will pass through.

In the UK, Dryden Aqua are conducting research with East of Scotland Water into the use of glass as a filtration media for drinking water. Dryden Aqua market their crushed glass Advanced Filtration Media in three particle size ranges, and claim that its smooth micro surface prevents build-up of bacteria. Due to the surface properties of the crushed glass, it may remove smaller particles from the influent water stream, which may result in reduced flocculent requirements.

Dryden Aqua have also conducted trials in Israel on drinking water filtration. Due to Israel's naturally dry climate, water is very scarce, so municipal wastewater is treated to enable it to be re-used as drinking water. Wastewater is initially settled in lagoons before being passed through sand/anthracite filters and subsequently to a disinfection process. Dryden Aqua have used a pressure filter with AFM in parallel with the existing filter media, and shown that the resulting turbidity is twenty times less than that with the traditional filter. This provides scope for reducing the dosage levels of coagulant and reduces the load on the downstream disinfection treatment.

3. Abrasives

Blast Abrasives

The principal application for glass is as a 'blast abrasive' where the granular or powdered abrasive is fired at the substrate by high-pressure air or water. The aim of blast cleaning is to prepare the surface (usually metal) for subsequent painting or coating by removing unwanted oxide, paint, etc., without causing excessive damage to the underlying substrate.

A variety of abrasives are used and they are classified either as recyclable (where the abrasive is collected an re-used) or expendable (where the abrasive is generally used once and then disposed of). Recyclable abrasives are generally used in factory situations in closed booths, and common materials are alumina, silicon carbide and steel shot. Expendable abrasives are generally used for on-site cleaning, such as structural steel work on structures such as bridges. Expendable abrasives include metal slags and natural minerals such as garnet or sand; copper slag is commonly used and is often known as 'J-Blast'.

Extensive test work was carried out by the Clean Washington Center in 1997, comparing the performance of crushed glass against copper slag. This study compared the consumption rates, cleaning rates and breakdown characteristics of the abrasives when cleaning a variety of coatings off steel and aluminium. The general conclusion was that glass performed equally well, or slightly better in some applications, when compared to copper slag. Some of these tests have subsequently been confirmed by work carried by ReMaDe Scotland. Other trials carried out in the UK have demonstrated that glass performs equally to copper slag and sand in wet blast applications. One of the major problems with copper slag is the significant heavy metal content (copper, nickel and lead) which rules it out from environmentally sensitive areas where overspray may contaminate water courses (e.g. work over or adjacent to rivers). In some cases the spent abrasive is classified as special waste which increases the disposal costs. There are significant health risks attached to using sand in dry blast situations since air borne crystalline silica can cause silicosis. Despite these risks sand is reported to be widely used by many of the small blasting contractors due to its very low cost. Glass contains less than 1% crystalline silica and poses no such similar risks.

4. Bricks & Ceramics

Glass as a Fluxing Agent

Plate and container glasses contain around 15% Na2O and when finely ground and heated will soften and fuse at around 1000°C. When mixed with clay materials finely ground glass will act as a 'flux' and bond to the clay. Similarly, finely ground glass can also be used in pottery glazes.

Bricks

When incorporated into brick-making clay, glass has the effect of lowering the firing temperature during the brick-making process, saving energy. It will also produce a stronger, more frost-resistant brick. These benefits were highlighted in the early 1990s by CERAM but glass was never adopted by the brick-makers. However, interest has been revitalised and there is a research project currently ongoing involving CERAM, the major UK Brick companies and Glass Recycling Systems Ltd.

The clay facing brick industry manufactures some 3 billion bricks per year, using about 7 million tonnes of clay (dry weight). In total there are approximately 80 brick-making factories in the UK and the major players are Hansen and Ibstock, each with about 35% of the UK market.

By adding about 5% glass to the clay mix, firing temperatures can be reduced by about 50°C. Most bricks are fired around 1050°C and this reduction will give estimated energy savings of 5%. The brick industry in the UK is subject to Climate Change Levy Agreement with the Government and has to achieve energy saving targets in order to receive a rebate on the Climate Change Levy. A 5% saving would be an important contribution to meeting their targets.

However, energy savings may not be the only benefits:

• It has been speculated that the addition of glass may reduce hydrogen fluoride (HF) emissions.
• The improvement in brick strength may enable some manufacturers to produce frost-resistant bricks using their existing clay resources.

Work to date has shown that finely ground glass with a particle size of <75 mm is required and that this application should also be reasonably tolerant to the chemical composition of the glass used, with both plate and container glass (of any colour) being suitable. Organic content needs to be less than 1% and metals less than 0.5%. These levels of impurities present no challenge to standard cullet processing; however, to achieve the level of fineness ball milling will be required.

6.3.3 Other Potential Uses

There are a number other potential uses for glass that still require development before commercialisation.

5. Paint Filler

The Clean Washington Center refers to the use of finely ground glass to a size of 8 mesh (2.36 mm) as a filler for paint . This is specialist exterior paint with a sand textured finish. As a general filler for paint, glass may be cost competitive with calcium carbonate, which is the most common filler. The other common filler is titanium dioxide. However, glass is less opaque than these fillers, and in order to achieve the required optical properties very small particle sizes are required, typically between 0.2 and 0.4 mm to obtain maximum optical properties from titanium dioxide .

6. Zeolites

Work has been carried out in the United States on the application of glass as a zeolite for a number of applications. A zeolite has a crystal structure that allows ions of a specific size to react with it. The reactive surface sites dictate its ion exchange properties. There are in excess of 40 naturally occurring zeolite materials. The applications for zeolites are wide-ranging, from use as a water softening agent in washing powder detergent to cat litter.

The Cambourne School of Mines at Exeter University has conducted initial laboratory studies using crushed glass as a zeolite. The finer the glass particles, the more reactive it is, due to the greater total surface area. It is generally required that the glass is crushed to less than 100 mm. To form the zeolite, the crushed glass is dissolved in sodium hydroxide. Two products are formed - the liquid extract is a reactive sodium silicate solution, and the solid residue has cationic exchange properties. Both phases may have applications as zeolites. Other solutions may be used to dissolve the glass depending on the desired zeolite properties.

The research on zeolites is currently in the development phase, certainly in the UK. The applications for glass zeolites is most likely to be in the higher value end of the market, due to the current low cost of natural zeolites from China. Quality requirements, such as the cleanliness of the glass, have not yet been determined. However, it is anticipated that for higher quality applications higher quality glass will be required.

7. Foam Glass

Pittsburgh Corning Europe operate three European factories producing a rigid foamed glass insulation product for the construction industry. It is known that their Belgian factory uses recycled flat glass as a feedstock for the process, however there is no data available concerning the quantities or specifications. Orvco, a waste and recycling technology company based in Christchurch, have plans for the development a foam glass plant in New Zealand. The capital investment required is $2 M and this could process the entire mixed glass waste stream generated across the Wellington region.

8. Glass Tiles

Innolasi Oy in Finland have recently established an operation to produce glass tiles mainly for construction cladding applications. Crushed glass (of particle size between 0.1 and 10 mm), binders and pigments are pressed and fired at temperatures around 1100ºC for 20 hours. This product is marketed as a premium material and is expensive compared to other cladding materials. The new factory is expected to produce around 3,000 tonnes of tiles per year.

9. Sports Turf Applications

The Sports Turf Research Institute (STRI) are investigating the use of ground glass for sports turf applications. In particular, STRI are considering three general applications:

• Construction use - Golf courses are typically constructed using 90% sandy material. Ground glass may be a suitable substitute for sand on green areas. This may be pure glass sand or a mixture of glass with natural sand and soil. Issues such as plant root abrasion will need to be considered.
• Bunkers - Angular material is preferred in bunkers as it aids stability. Clear glass may be preferred for visual impact.
• Earthworm control - The use of sand on the land surface creates an abrasive, drier layer which quickly becomes acidic. These conditions deter earthworms. In addition, a firmer surface is created and fewer pesticides may be required. Glass sand may be a suitable material for worm control.

The glass will be crushed by a reprocessor to the colour and size grading specified by the STRI. The most common particle size gradings are 0.125-0.5 mm and 0.25-0.75 mm. The application of glass sand will be of use in reducing transport costs where natural sand reserves are geographically remote from the golf course. In addition, natural supplies of medium grade sand for golf courses are relatively scarce (WRAP, 2002).

6.3.4 Glass Reprocessing in the UK

The use of recycled glass as an aggregate has been driven mainly by Valpak over the last two years. In an attempt to increase the quantity of glass recycled Valpak have targeted the collection of mixed coloured glass from the commercial sector. These collection schemes have involved contracts with a number of large aggregate companies such as Day Aggregates and RMC. It is understood that there are also agreements with Tarmac, Foster Yeoman and Lafarge. It is estimated that Valpak sourced some 50,000 tonnes of glass through these arrangements in 2001, 80,000 tonnes in 2002 and they are planning to increase this to 100,000 tonnes by 2003. Day Aggregates in London have been reprocessing bottle bank glass for the past 12 months or so producing a glass 'sharp paving sand' to BS 7533 (ENDS, 2003).

- Day Aggregates

The glass is first crushed in a hammer mill to produce a minus 15mm material. This is then screened to remove corks and other contaminants and then passed through a Vertical Shaft Impactor (VSI) mill to produce the fine sized material. A final washing stage produces a very clean high quality material that is sold as a sand substitute for a variety of general uses. The main market is bedding sand for clay pavers and pipes.

• RMC

Valpack supplies unprocessed glass to a number of RMC's hot mix asphalt depots. The glass is processed in a standard aggregate crusher (Ammann RC12 Asphalt Granulator) and is sized to minus 19 mm and the size gradings meet those specified in BS 4987. After crushing, the glass is screened to remove corks, caps, etc., before being incorporated into a hot macadam base course product known as 'Glasphalt'. 30% of the natural aggregate content is substituted by glass and the product has almost identical properties to material made from quarried aggregates . Glasphalt is a 'hot mix' product and has to be manufactured close to its point of use. As of February 2002 it was available from six of RMC's regional depots. This application has the potential to consume very large quantities of glass, with a typical single carriageway road requiring approximately 240 tonnes of glass for every kilometre. Development work started on this product in 1999 and extensive trials have been carried out. Full approval is anticipated in 2002/3.

• Conway Concrete Products

Working with The Welsh Environment Trust (WET), Conway Concrete Products (CCP) in South Wales have substituted around 20% of their sand with crushed glass in the manufacture of a number of concrete products (paving flags, bin wall blocks and garden products). Using fine glass (<2 mm) and at these levels of substitution extensive testing has shown no evidence of ASR. The glass is supplied under a complex arrangement involving contracts with local authorities, WET, CCP and Onyxpak (the packaging compliance scheme). In 2001, CCP used approximately 3,500 tonnes of glass but this is projected to rise to about 30,000 tonnes/year.

• Spartan Tiles

Spartan Tiles in Essex produce a concrete decking tile from a dry pressed sand/cement mixture. The tiles are not manufactured to any recognised quality standards. Initial trials substituting all the sand with glass 'sharp sand' (<5 mm) supplied by Day Aggregates have been very promising. Given the considerable marketing advantages of a product with a high recycled content, Spartan would like to convert to 100% glass providing the physical properties of the tiles match those made with sand and the glass can be obtained at price equal or less to that of sand. Further development work is required but there is a potential for 8,000 tonnes/year of crushed glass.

• Tarmac

Discussions were held with Tarmac Topblock Ltd who are one of the largest producers of concrete blocks for the construction market. Their main driver for adopting glass would be cost savings however they are concerned about the effects of ASR and obtaining a reliable supply of consistent quality glass.

• Foster Yeoman

Foster Yeoman have plans to process up to 60,000 tonnes/year of glass into a 'sand' product at their Torr Quarry, Shepton Mallet, Somerset. This will mainly be used in bound sub-base materials for road construction. They also see an opportunity in the field of decorative aggregates and are considering colour sorting technology.

• Windmill Aggregates

Windmill Aggregates produce and distribute recycled glass gravel known as "Crystaleis" for decorative purposes in the garden and floral industries, whilst some is used in the construction industry. Some large lumps of glass are also supplied for decorative uses. Around 1,500 tonnes per year of all types of recycled glass are used, including TV screens, industrial waste glass and bottle bank cullet. The requirements for glass are that it is colour segregated. Windmill Aggregates purchase the glass ready-crushed, and they carry out some cleaning and grading before packaging and distributing. The screening/grading equipment has a capacity of 10 tonnes/hour. Windmill Aggregates are considering investment into a new bagging line which will double their existing capacity. They envisage a rapid expansion of their business in the next 12 months as they have broken the barrier of supplying a large garden centre chain with glass gravel for pots, and it is expected that other shops will follow. It is anticipated that demand will be around 50-100 tonnes per week.

• The Recycled Glass Company

The Recycled Glass Company crushes and melts recycled glass bottles to make decorative chippings. The company processes around 1000 tonnes of glass per year sourced from the Local Authority in Somerset.

6.3.5 Glass Reprocessing in New Zealand

ACI in Auckland are the major player in glass reprocessing in New Zealand. The company has been involved in recycling since 1973 and has made an immense contribution to the glass recycling industry. ACI remain the main player with regards to cullet consumption and glass container manufacturer and this is set to continue over the forthcoming years. In 1973 the company established the National Glass Reclamation Programme that saw the introduction of a network of glass recycling bottle banks across the country and launched a school recycling education programme.

In 1997 the quantity of cullet used in the manufacturing process was 37,000 tonnes, however the forecast for 2003 is that 84,000 tonnes of glass cullet will be used in the manufacturing process with a total throughput capacity of 130,000 tonnes.

The percentage cullet used in the manufacturing process varies according to the colour glass as amber glass is more tolerant of contaminants than flint (clear) with amber production using approximately 70% cullet where as flint is reduced to 15%. The current target is to use 20% flint in clear glass manufacturing and to increase the overall proportion of cullet in the manufacturing process from 50%. ACI believe that increased public education is the key to improving source segregation in the bottle banks to prevent cross contamination of the various colour glasses and to remove other contaminants such as bottle tops.

ACI are confident that its current use of cullet will increase as greater diversion of glass is achieved. Many kerbside collection systems across New Zealand are relatively new with the largest local authority (Manakau City Council) only introducing its kerbside collection systems in the last year. As such systems mature and other disincentives to landfilling are introduced (such as full cost pricing of landfills and producer responsibility initiatives) increased diversion rates, such as those observed in Christchurch, Waitakere and North Shore City Council's, are expected.

The biggest barrier to expanding the quantity of cullet used at the plant is contamination issues, which require increased education, and capacity of the plant. In order to redress the latter, plans are currently underway to expand the plants throughput capacity from 2 furnaces to three. The capital investment is expected to be in the range of $50 to $100 million and the commissioning stage is not anticipated for 3 to 4 years. In the meantime stockpiling of cullet will occur until the new furnace is online.

Glass reuse in Christchurch began in the 1930's when Southern Cross Bottle Recyclers Ltd. began their collecting and washing operation for local distilleries and wineries in Christchurch. The company was very successful until the mid-1990's when the increased availability of cheaper imported new bottles adversely effected the company. Similarly, ACI glass bottle manufacturer in Auckland was also affected resulting in a decrease in the price paid to suppliers for sorted cullet. This further impacted on Southern Cross Bottle Recyclers' operations as cullet sales from broken or un-reusable bottles was another major revenue stream for the company. Conversely, the company has recently completed an export order of cleaned bottles to Fiji. They were more than 25% cheaper than any alternative source and all arrived intact and undamaged.

As market fluctuations have occurred the company has reassessed its own operations and markets in order to survive in this competitive market. In order to maintain a competitive edge the plant has been relocated to the Recovered Materials Foundation (RMF) site in Christchurch where materials recovered through the Christchurch City Council kerbside recycling collection are dropped off for processing. This reduces any transport and double handling costs. Having their operations sited next to the glass collection point also minimises breakages and enables a wider range of glass bottles and jars to be recovered for smaller cottage industries and other niche markets. The RMF strongly supports the bottle reuse industry and has invested in the design and development of a new bottle washing and a de-labeling machine.

With regards to the crushed glass market, the RMF has undertaken considerable investment and research into glass crushing and screening and market development. An initial crushing plant was build in 1998. This plant was replaced in 2001 as it could not supply increasing demand for the crushed glass product. The glass crushing plant and screening plant cost $410,000, including $70,000 purpose designed building to house the plant to minimises dust and noise concerns.

The dry process uses two basic quarrying methods (hammermill and barmac) to crush the glass together with custom designed processes to transfer and screen the final product into a range of grades to customer specifications. This produces evenly shaped cubic fracture particles that can be readily handled without causing a hazard though shards and glass fragments.

The RMF is concentrating its efforts on higher value markets as natural sand and shingle are readily available and cheap and therefore it is not economically viable to compete with raw material costs. Their current markets for the crushed glass include a sandblasting media, filtration media, glass flooring and an array of art glass applications. The RMF have also designed glass tiles using mixed cullet not reliant on high quality sorting and are in the process of commercializing the tile production. When complete the tiles will use up 3,000 tonnes of glass each year (approximately half of the 6,000 tonnes of glass collected for recycling in Christchurch in 2002).

Another development in Christchurch is the introduction of glassphalt as a replacement for asphaltic concrete. Whereas asphaltic concrete comprises a mixture of crushed rock aggregates, sand and bitumen as a binder, glassphalt substitutes a proportion of the sand or aggregates with crushed glass. The glass fractions generally less than 20% by weight of the total mix and unlike many glass uses glassphalt is not sensitive to the use of window and / or high temperature glasses, differing glass colours and it can tolerate a small amount of contamination.

Theoretical usage of glassphalt could be relatively high. For example, 10% glass content of a 100 m section of road resurfacing could utilise the equivalent of approximately 50,000 bottles. In addition, if glassphalt was used for footpath resurfacing alone it could potentially consume between 1,000 to 1,500 tonnes of recycled glass per annum in Christchurch (RMF, 2003).

Several successful trials have been carried out in Christchurch by City Care Ltd. on behalf of the RMF using crushed glass generated from their own plant. These trials demonstrated that when using 10% crushed glass the glassphalt met both Transit New Zealand and Christchurch City Council specifications. Subsequently, a section of road in Christchurch has been resurfaced by City Care Ltd. on behalf of Christchurch City Council. This is thought to be the first application of glassphalt on a highway in New Zealand (RMF, 2003).

It is anticipated that given the volumes of cullet currently being generated in New Zealand and the capital investment required for a new plant, it is unlikely that a new glass manufacturing plant would be established anywhere else in the country. In terms of glass reprocessing the focus for the Wellington region might therefore best evolve around developing and introducing alternative operations and markets for crushed or powdered glass. In order to attract and develop end use markets for crushed glass a centralised glass crushing plant may be introduced or alternatively a mobile crushing facility may be used to service the various population centres. Orvco have estimated that the capital investment required for the centralised crushing plant is $800,000, while the mobile plant will cost between $200,000 to $350,000, depending on the requirements and intended end use. For example, $200,000 would provide equipment capable of providing glass aggregate that may be used in asphalt, for example, while an additional $75,000 would be required to provide a feedstock for granules, while an additional $75,000 would be required to provide the necessary equipment to produce filtration media.

It is noted that this may be considered a 'Catch 22' scenario whereby capital investment in crushing plant may not in itself secure end use markets to the region. However without crushing facilities there is no consistent source of raw materials feedstock to encourage the development of alternative end use markets. Examples of alternative end markets, their value, current and potential UK consumption and potential market barriers are included below: