Solid Waste & Recycling



Recycled curbside glass has been perceived as a commodity with a high processing cost and low revenues. As collection systems have evolved from source separation to two-stream collection and single-st...

Recycled curbside glass has been perceived as a commodity with a high processing cost and low revenues. As collection systems have evolved from source separation to two-stream collection and single-stream collection using compactor vehicles, the recovery rate of color-sorted glass at material recovery facilities (MRFs) for new bottle manufacturing has rapidly decreased. The end result is that much of the broken glass is ending up in landfill or in low-end aggregate applications at significant cost to municipalities.

With the vision of turning glass into a profitable commodity, Niagara Recycling developed a unique glass recycling system that turns glass into a sand-like product.

Niagara Recycling is a not-for-profit company whose mandate is to divert waste from landfill and provide employment opportunities for developmentally challenged adults in the region. The company operates a state-of-the-art 100,000 square foot recycling facility in Niagara Falls, Ontario that is owned by the Regional Municipality of Niagara (Niagara Region).

The vision began with a pilot project in 2000 which allowed Niagara Recycling to send processed glass samples into the marketplace for testing on various potential end markets and to develop design criteria for the type of system required to meet volume targets and market specifications. The pilot project was a success and resulted in the company partnering with Niagara Region in February 2004. The glass recycling system was redesigned and expanded to allow for full-scale production at a throughput rate of up to 10 tonnes per hour, depending on the quality of the feedstock.

Finished product

“We’ve been thrilled with how successful this venture has been,” says General Manager Norman Kraft, general manager. “The Niagara MRF is the only municipal MRF in Ontario to incorporate a glass recycling system that produces a finished product for the retail sector.”

The end result is an impressive abrasive glass product called “Niagara Ecoglass” that has been developed to meet the size and quality specifications of the sandblasting industry in Ontario, Quebec and the United States.

The glass recycling system will process over 10,000 tonnes annually based on current demand. This is expected to rise as interest in recycled glass as a blasting abrasive grows.

In Niagara, approximately 3,500 tonnes of curbside-collected glass are received annually at the MRF, resulting in a need to source glass from other recycling programs. Programs looking for alternate glass markets can contact Niagara Recycling, for quality specifications and pricing.

“One of the keys to the project’s success is the marketing of the finished product,” says Kraft who noted that a long-term supply agreement has recently been obtained with Opta Mineral’s Inc. of Waterdown, Ontario. Opta Minerals processes, sells and distributes abrasives and other industrial minerals. The company has production and warehouse facilities throughout North America, including Waterdown and Brantford, Ontario. Niagara Ecoglass is currently being distributed in Ontario, Quebec, New York and Michigan.

The benefits of Niagara Ecoglass as a sandblasting abrasive over conventional abrasives are numerous:

1. Glass is safe to use as it contains no crystalline silica and no heavy metals.

2. Glass is economical as over 25 per cent less material is required and over 20 per cent less time required than other abrasives on the market.

3. According to end users it takes up to five times as long to flash back to rust.

4. Glass produces less dust during the sandblasting process.

5. Glass is environmentally friendly.

How the system works

The mixed broken glass passes through a pre-cleaning process where metal, large plastics, fibre and other contaminants are removed. The glass is then fed into a primary grinder for initial sizing. The ground glass is discharged onto a scalping screen that removes large contaminants such as corks, plastics and large labels.

The screened glass is directed into a natural-gas dryer to reduce moisture levels to allow for efficient screening. The dry glass is then conveyed to a multi-deck screening system that generates four sizes of crushed glass products. The larger glass particles are transferred to a secondary glass grinder that further crushes the glass into fine sizes. The finished products are either packaged in plastic 50 lb bags or into 3,000 lb supersacs. Dust collection hoods are located at all points where dust is generated. The residues, which include paper, are sent to a local landfill. This represents approximately 15 per cent of the total throughput.

One of the greatest challenges in processing curbside glass is to ensure the finished product is free of any paper contamination that may clog the nozzles of sandblasting machines. A custom designed paper removal system has been designed at various stages after the drying process to ensure efficient removal of paper particles.

Market value as an abrasive

The typical value of processed curbside container glass in MRFs range from approximately $25 per tonne to negative $30 per tonne, plus freight. The price received depends on the type of collection system. A municipality that separates glass at curbside will receive approximately $25 per tonne for clear glass and $0 per tonne for colored glass, not including freight.

A municipality that separates glass in the MRF will receive the same values for color-sorted glass but will have a significant mixed glass component, resulting in negative values. Single-stream collection programs or two-stream (fibres and containers) compaction-based collection programs will typically generate 75 per cent to 100 per cent of the glass as fines less than two inches in size. This glass is heavily contaminated, resulting in a disposal cost of up to $30 per tonne plus freight. The cost assessed for this type of glass reflects the degree of secondary processing required at the glass processing centers, hence, pre-cleaning systems consisting of vacuum or trommel screens should be installed in MRFs to make the glass more marketable and reduce disposal costs.

“In Niagara, the development of the glass recycling system has eliminated the need for any colour sorting,” said Barry Friesen, director, Waste Management Services and acting commissioner of Public Works for Niagara Region. “The mixed broken glass that’s directed to the glass recycling system is sold as an abrasive at a much higher price per tonne. When all operating costs are factored in, the glass recycling system has turned glass into a profitable commodity in the Niagara Region.” A simple comparison of the new glass recycling system to the traditional system of manual sorting shows a net gain of approximately $40 per tonne.

By meeting the stringent quality specifications of the abrasives industry, other high-end marketing opportunities for the crushed glass can be pursued in the future. These include glass-epoxy flooring, use in tiles and countertops, and filter sand for pool, hot tub and other industrial water applications.

The Niagara glass-recycling system demonstrates that by moving beyond the traditional MRF role of simply processing recyclables for resale to secondary processors, MRFs can explore other enhanced processing opportunities to increase their bottom line.

Guy Crittenden is editor of this magazine

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