Glass has been recycled longer than almost any other material except iron, and now it’s processed on a large scale in most industrialized countries. Even though the raw materials to produce new glass are cheap the process needs a lot of energy and much of this can be saved by recycling. Depending on its quality waste glass can be handled in various ways. In many countries breweries and other businesses that use glass run their own operations, cleaning and sterilizing returned bottles for reuse. Damaged bottles are sent off for further reprocessing along with glass obtained from bottle banks and household waste collections; separated by color, it can be melted down and formed into new objects with much lower energy consumption than producing new glass.
Despite the relative ease of recycling glass, however, the percentage reprocessed is still far below what it could be. In many areas it’s actually fallen over the past decades. As glass is replaced by plastics in many applications some recycling facilities have closed down through lack of demand, and the result is that glass that would have been processed goes to landfill. This is most common in smaller towns or sparsely populated areas.
One example of the decline in glass recycling is Anchorage, Alaska. The plant there closed in 2009, despite the fact the city produces 15,000 tons of glass waste every year, and transport issues make it difficult and expensive to ship this to alternative facilities. For the last five years the only collection program in the city has been a small-scale one run by Target stores, and this hasn’t been able to handle more than a fraction of the volume. Now Central Recycling Services, which acquired the plant in 2011, plans to reopen it. Part of the deal is that they dispose of around 800 tons of glass left behind by the previous operator, and to do this they plan to develop a new use for lower grade glass waste.
While the most familiar method of reusing glass is to make new containers from it there are also other potential applications. Glass is an abrasive material, and when it’s powdered the result is an abrasive that can be used for sandblasting. This was tried in Anchorage in 2007 but proved to be uneconomical. CRS have a new idea though; they plan to convert the scrap glass into a gravel-like substance that can be used as a concrete aggregate. Glass is ideal for this as it’s very strong in compression. CRS’s priority is to clear up the facility so they can restart conventional processing but huge amounts of low-quality glass waste, mostly broken and unsorted mixed-color scrap, is discarded every year; if they can develop an economical process for converting glass into gravel it could be quickly rolled out on a larger scale.
Anchorage city council is fully behind CRS’s efforts to make this a viable proposition and has pledged up to $85,000 to help them find a processing technique. The potential gains, both financial and environmental, make that a very shrewd investment.