Hi all ~
I have seen various computer models that tally up the environmental impacts of recycling glass. The latest -- and very clearly stated -- is in the 2001 edition of "Integrated Solid Waste Management: A Life Cycle Inventory", by Forbes McDougall, et. al.
On pages 441-442, Table 22.3 compares about 50 parameters, and I would be glad to copy and either mail or fax the tables to people.
Here are some of the data, expressed on a metric ton basis of finished product:
Parameter Virgin Recycled
Engery (GJoules) 14.5 11.04
Carbon dioxide 145,600 57,000
NOx 1500 2880
Suspended solids - water 7760 796
Chlorides -water 99,900 8,410
Total organics - water 68.5 80.7
On the energy issue, a gigajoule is a billion joules and there are 1054 joules in a BTU. Thus, making a metric ton of glass from recycled material saves about 3.3 million BTUs, or 3 million BTUs per US ton, according to this source. In comparison, according to data in the March/April 1981 issue of BioCycle, an article by Jerry Powell puts the savings at 2.95 million BTUs a ton, although the article has alternative estimates of 1.3 to 2.5 million BTUs. In the same article, it is noted that a gallon of gasoline has 128,000 BTUs.
The data do not include the impacts of collection, processing or transportation, which is included in other sections of the book.
Other LCA models also exist, including one by Argonne National Labs, which looked at the distance to which cullet can be transported before the energy of transportation exceeds the energy savings. If I can find the data of these other studies, I will let people know.
It should be noted that on a per ton basis, the energy savings from glass are less than the savings from all other products listed in the above book. The book listed above does not evaluate the relative importance of the various environmental impacts nor does it look at a possible economic value for the individual impacts, as is done in environmental valuation studies.
John Reindl, Recycling Manager Dane County, WI