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== Recycling Glass in the US ==

[[Image:Glass.jpg]]

In 2006 glass constituted 5.3% of the total municipal solid waste (MSW) generated in the United States (EPA 2008a).  This amounts to 13.2 million tons of glass.  Of the 13.2 million tons, 2.88 million tons, or 21.8%, was recycled (EPA 2006).  This is compared to only 750,000 tons of glass that was recovered in 1980.  There has been a significant increase in the amount glass that is recycled, although it should be considered that total waste generation has grown as well.  The majority of glass in the waste stream is from soft drink, beer, food, wine, and liquor containers (2008b).  

The majority of recycled glass is used to make new containers, although some other uses include kitchen  tiles, counter tops, and wall insulation.  Recycled crushed glass is known as cullet.  When making new glass from raw materials, manufacturers mix sand, soda ash, limestone, and cullet.  The mixture is then heated and molded.  Some of the benefits of using cullet as opposed to raw materials include:

- reduced cost

- longer life for the furnace: glass can be made at a lower temperature with cullet

- cullet demands less energy

- reduced nitrogen oxide and carbon dioxide emissions due to less energy use

(EPA 2008b)

<h2> Curbside Recycling and Unit Pricing </h2>

Jenkins, et al. (2003) conducted a study comparing the effectiveness of curbside recycling programs versus unit pricing programs on 
the recycling rates of glass bottles, plastic bottles, aluminum, newspaper, and yard waste.  In theory, a curbside program reduces a household’s cost of recycling because it is more convenient and requires less time than going to a drop-off center.  With a unit pricing program, households pay per unit of trash they put out.  As a result, the program increases the cost of discarding waste relative to the cost of recycling.  A household would therefore divert recyclable waste rather than pay for it to be picked up as trash.  The study analyzed data from middle and upper income households in 20 metropolitan areas in the US and compared the impact of curbside recycling programs and unit pricing programs.

The study found that both introducing a local drop-off program and introducing a curbside recycling program increases the recycling rate of the materials studied.  A curbside recycling program has more significant impacts than a local drop-off program.  For glass bottles in particular, the drop-off program increased the probability that 95% of all glass bottles would be recycled by 42%. This may be because glass bottles are difficult to store and transport relative to other materials; a closer drop-off location is a positive incentive to recycle them.  A curbside recycling program increases that probability for 95% of glass to be recycled by over 50%.  This study found that for unit pricing programs, increasing the price of disposal did not increase the intensity of the recycling effort.  This could be due to the fact that the price per unit of disposal was too low to induce an effect.  Additionally, the unit price is only an indirect price signal for recycling and so may be less effective than other methods.  Another interesting fact that the study found was that each additional person in a household makes that household more likely to recycle over 95% of their glass bottles (Jenkins 2003).  Based on the results of this study, the preferable means of increasing the rate of glass bottle recycling is the introduction of additional drop-off centers and curbside recycling programs.  
  


<h2> Energy Savings From Recycling Glass </h2>

The effectiveness of recycling glass is a highly debated subject.  According to Cooper in the CQ Researcher, it requires only a little less heat to process recycled glass than to make glass from silica.  When transportation costs to the remanufacturing facility are considered, the minimal gains may be reduced or eliminated (Cooper 1998).

A study by Krivtsov et al. assessed the energy savings of recycling glass using two modeling case studies from the UK and Switzerland.  The study used a model that includes all energy consumed from the point the glass becomes waste until it is reprocessed.  This includes energy consumption from refuse collection, landfill transfer, curbside collection, household transport to drop-off centers, transport from drop-off centers to processing plants, activities at the processing plant, cutlet transfer, and glass manufacture.  This study found that with a recycling rate of 25.16%, the overall energy expenditure per year was 68,600 gigajoules (GJ).  The primary source of energy consumption was in the manufacturing process.  It is believed that if the volume of recycled glass increases, it will outweigh increased energy consumption from glass collection, transport, and processing at the processing plant.  The results of the study predict that if the recycling rate increased to 100%, there were be a resulting 5.4% in energy savings.  The authors also note that curbside collection would considerably decrease the total energy consumption.  Thus, an increase in curbside collection and increase in recycling rate would decrease the total energy consumption per ton of glass recycled.  In general, this study supports that recycling glass does produce some energy savings (Krivtsov et al. 2004).  However, based on the models used for this study, the energy savings are only expected to be 5.4% if the recycling rate is 100%.  It is unlikely that such a recycling rate will be achieved, and so the benefits are relatively minimal.  While the models in this study were based on other countries, the results are still applicable as a general model.  


<h2> Marketing Recycled Glass </h2>

One of the problems with recycling glass is finding markets willing to buy the end product.  In the early 1990s, Washington State faced a lot of difficulty selling recycled green glass cutlet, partially due to large volumes of imported wine and beer.  Bottler’s were then unable to use the large quantities of glass cutlet.  As a result, Clean Washington Center began researching alternative uses for glass cutlet.  The list is very large and some of the categories include: construction/aggregate materials like roadbed; fiberglass, foamglass and rockwool insulation; pressed glass applications in dinnerware and art glass; industrial mineral uses (Steuteville 1993).

Although in some circumstances it is difficult to market recycled glass, in general it is not.  According to the EPA, the demand for glass cullet is greater than the supply.  High quality cullet, which has no contamination, is used for making new containers, "abrasives, aggregate substitute, bead manufacturing, decorative appliances, fiberglass," and match tips.  Lower quality cullet that may have some contamination can be used in "the manufacture of fiberglass insulation, roadbed aggregate, driving safety reflective beads, and decorative tile" (EPA 2008b).

[[Image:Glass cullet2.JPG]] 


<h2> Conclusion </h2>

The effectiveness of recycling glass is still being debated.  Unlike some other recyclable materials, it is not clear that the resource savings from recycling glass are significant, if present at all.  While further research is necessary to determine the true benefits [or costs] of recycling glass, some policies to increase the rate of recycling include additional drop-off centers, curbside recycling collection, a potentially unit pricing trash collection.






<h2> Sources </h2>

Cooper, M.  1998.  The Economics of Recycling.  The CQ Researcher, Congressional Quarterly Inc.  March 1998 8(12): 265-288.

EPA.  2006.  Municipal solid waste generation, recycling, and disposal in the United States: Facts and figures for 2006.  United States Environmental Protection Agency, Washington, District of Columbia, USA.

EPA. 2008a.  Municipal solid waste: Basic Information.  United States Environmental Protection Agency.  Updated January 3, 2008.  URL: http://www.epa.gov/msw/facts.htm

EPA. 2008b.  Municipal solid waste: Glass.  United States Environmental Protection Agency.  Updated January 1, 2008.  URL: http://www.epa.gov/msw/glass.htm.

Jenkins, R, S Martinez, K Palmer, and M Podolsky.  2003.  The determinants of household recycling: a material-specific analysis of recycling program features and unit pricing.  

Journal of Environmental Economics and Management March 2003 45(2): 294-318.
Krivtsov, V et al.  2004.  Analysis of energy footprints associated with recycling of glass and plastic – case studies for industrial ecology.  Ecological Modelling May 2004 174(1-2): 175-189.

Steuteville, R.  1993.  Exploring new uses for glass cutlet.  Biocycle January 1993 31(1): 42-43.