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MEEF - Recycling Technologies  - previous page

 


Glass Recycling - Read Article:
Towards 90% Glass Recycling

Glass Recycling has been around in the US since glass has been used in the manufacturing of containers; for almost 100 years. Glass is one of the easiest commodities to recycle and there are many of different uses for it. In the early days and up until recently, glass bottles were returned to the company and cleaned for re-use. Today the majority of glass that is recycled is crushed and used to manufacture new containers or fiberglass insulation, but other secondary uses are developing quickly.

Conventional Glass Recycling Process

    1. Glass is collected
    2. Converted to standard furnace-ready cullet
    3. Shipped to glass plants
     

Most glass must be separated by color in order to be used in new glass production. However, some plants can use mixed color cullet to produce specialty products.

Primary Markets

Container Manufacturing

This is the oldest and most obvious market for recycled glass cullet - closing the loop. However, manufacturing activity doesn't always match with recovered supply in different parts of the world. This is because some bottle types and colors can only use certain colors and amounts of cullet, and products imported into that region may also skew the supply mix. It is often cost-prohibitive to ship glass long distances for recycling. In addition to color sensitivity, contaminate tolerances are very tight as very small impurities can cause defects. Cullet beneficiation lines needed to create furnace-ready cullet for new containers have gotten larger and more expensive as technology to remove contaminants like ceramics has become available.

Secondary Markets


Fiberglass Insulation Manufacturing

This market has emerged as a major consumer of cullet in North America, approaching to consumption of container markets. Some countries and states, like Canada and California have certification programs for manufacturers reaching 40% post-consumer content. The contamination tolerances are similar to glass container manufacturing. An advantage with Fiberglass is the ability to consume mixed colors, as long as the color mix is consistent.

Granular Products

Glass can be finely crushed using special secondary size reduction equipment (as small as 250 microns), cleaned and screened to tight gradation requirements, such that it can be in a variety of industrial applications. These granular product, have a market advantage of not being sensitive to color variations, applications include:

  • Blasting Abrasives Recycled glass can compete quite well with single use blast media such as slag, silica sand, aluminum oxide, virgin glass beads, and other material. Its angular and sub angular particle geometry mean high performance. Its higher volume-to-weight ratio over other media means more particles per pound and faster cleaning. A major industrial health advantage is that recycled glass, unlike silica sand, contains less than 1 % crystalline silica which can cause silicosis.

  • Filtration Media Another high-value use for granular recycled glass is filtration media. Glass has performed well as a substitute for sand in a broad range of filter applications, ranging from on-site waste water treatment to drinking water filtration. Its particle geometry and processed gradation, mean that it can often remove more and smaller particles from the stream. Glass also is not micro-porous like sand, meaning better resistance to the formation of bacteria and biomats in the filter media.

    For granular product availability information, visit our friends at:
    TriVitro Corporation in Kent, Washington
    www.trivitro.com
    MacGlass Recycling in Dalkeith, Scotland.
    Dryden Acqua in Edinburgh, Scotland.
    www.drydenaqua.com

Construction Aggregates

Recycled glass can be used in a surprising number of construction aggregate uses. For example, it is an excellent backfill and works as good permeability for drainage trench fill. Many other lightweight fill uses have been tested, and glass can be blended with conventional aggregates for use in structural fills or bound asphaltic pavements. The value of glass as an aggregate is lower than many other recycling uses, but processing requirements are much less intense as well. Economics improve further when aggregate applications are examined in local and rural use settings where transportation cost savings can be substantial.

Fused Glass Tiles and Decorative Products

These uses have high value-added potential, but tight processing requirements. The opportunity exists for small-scale, local processing and use. Currently there is development happening in the cost-effective production of fused glass tiles.

For examples of fused glass products, visit Bedrock Industries of Seattle, Washington at www.bedrock.com

Specialty Processing

  • Decorative / landscaping applications

  • Golf course sand

  • Colored aquarium, ash tray or potting sand

  • Specialty fillers - elastomeric coatings

  • Terrazzo Floor Sand

  • Cultured marble

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