A random call from a reporter piqued my interest: Does recycling glass really save energy? That is, after you take into consideration all the energy spent to collect glass from people's homes, truck the collected glass to a distribution center, route it to a glass manufacturer, and then melt it down for reuse, does glass recycling really save anything, compared with using virgin materials?
I was actually fearing the worst here. Obviously, given all the energy costs of recycling glass, it's conceivable that it isn't a very good deal for the environment. Plus the reporter was asking specifically because he'd heard some mention that the benefits of glass recycling were overblown.
As it turns out, though, I shouldn't have worried. From just about every serious analysis I dug up, it seems that glass recycling really does save energy, compared with using virgin material. Some handy citations: here, here, here, and this extensive lit. review (PDF).
But as with most things, there is a bit of a twist.
As several of the studies point out, glass recycling saves energy -- but much less energy per ton of glass than, say, recycling newspaper, steel, and aluminum. (See, e.g., page 31 of the lit. review.) And because the theoretical energy savings of glass recycling appear to be relatively slim, it could mean that actual savings depend on lots of devilish details -- how far the glass is shipped, how dispersed are the neighborhoods from which glass is collected, whether people make special car trips to recycling centers, etc.
One of those devilish details -- covered here, about 3/4 of the way down the page -- is the type of furnace used to melt the recycled glass. From the article:
[C]leaner-operating electric furnaces ... use less energy and thus create less emissions than natural gas-powered furnaces, [but] cannot use as much recycled glass, so they are not as efficient.
That is, by using an efficient, low-emissions furnace, you can actually decrease the overall energy efficiency of your glass recycling operation. Darn.
And then there's this: Even though using recycled glass does appear to have a lower environmental cost than using virgin materials, the environmental cost is not zero. Obviously -- from an energy standpoint at least -- it's better to drink water from the tap than water shipped in glass bottles, even if the bottles are made from recycled glass.
But more to the point, it may be that buying a drink in a lightweight plastic bottle uses less energy than buying a beverage in container made from recycled glass -- even if the glass bottle is re-recycled, and the plastic bottle just gets thrown away after a single use. This study from Israel (PDF) suggests as much -- though it points out that this is only true for certain types of plastics, and may only be true for the specific circumstances in Israel's recycling system. And in the same vein, this analysis from the Institute for Lifecycle Environmental Analysis suggests that paperboard cartons have a lower environmental cost than bottles made from recycled glass.
Of course, I'm no expert here. All the information I have on the subject comes from a bit of googling -- and much of it seems to be at least a decade old. But it looks like glass recycling really is worthwhile ... and, simultaneously, that the gradual trend among beverage bottlers to replace glass with plastic may not, on balance, be such a terrible development.
Comments
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Chris Schults Posted 4:57 am
20 Jan 2006
Support Grist: http://www.grist.org/support
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jdhlax Posted 6:32 am
21 Jan 2006
Jeff Hoffman
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kirbgood Posted 12:55 pm
21 Jan 2006
Just using common sense, the Ball Glass plant in Seattle gets its silica sand from Lane Mountain, 250 miles away, it's sodium carbonate from Wyoming, 500+ miles away, and its calcium carbonate from Vancouver Island, 200 miles away. The raw materials are shipped that distance, then they lose 15 percent of their weight during melting (mostly carbon dioxide and NOx). i'll bet CO2 wasn't counted as a pollutant in those older articles.
In addition, old glass melts and fines at a lower temp than virgin glass batch. In fact in the days before recycling was formalized, glass plants would add old glass to flux the virgin batch materials.
The Container Recycling Alliance used to make a cogent case that the most efficient thing to do with glass bottles was wash them. Liability concerns killed the practice in the U.S., despite that fact that many of us managed to live through drinking from chipped Coke bottles in the 60's. And people seem to survive in Mexico, where the Coke bottles are still washed.
The subject of glass vs plastic is too complex to have an easy answer, and includes the topics of raw materials for both, manufacturing practices for both, weight of both, and environmental stability of both.
The one comment in the article I might take issue with is the "efficient electric furnaces." The electricity is created by the transformation of gas to mechanical power to electricity to electrical resistance heat in the glass batch. That wouldn't seem to be very efficient vs burning the gas in the chamber with the glass. Even here in the Pacific Northwest, with hydro, each incremental additional kilowatt hour still comes from gas or coal.
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amazingdrx Posted 9:24 pm
21 Jan 2006
What would make glass recycling the clear energy conservation winner over oil based plastic containers thrown in a landfill?
Storing peak energy from wind and solar power in recycled glass. When peak power production occurs that exceeds demand, energy intensive processes like glass recycling can take advantage of that excess.
And then recapturing heat energy from the cooling glass with cogeneration would reintroduce some of the waste heat back into the power grid.
Of course with modern robotics and sensing equipment, that could indicate when a glass container is fatally chipped, simply washing glass containers a few use cycles before they need to be actually melted down would be the clear winner.
Organic milk is sold around here in old fashioned glass milk bottles. Combining the energy savings of washable reuse with glass recycling.
Transportation of materials for recycling could also be done with peak renewable power by battery electric powered trucks that would recharge when excess power is generated by wind and solar and transport the materials later on.
High energy manufacturing processes are already being used to buffer inconsistency between supply and demand on the power grid by running factories during offpeak time periods and shutting them down during peak demand.
With robotics this is easier to acomplish given the time flexibility of machines versus the human labor force.
http://amazngdrx.blogharbor.com/blog
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jdhlax Posted 12:26 pm
22 Jan 2006
Jeff Hoffman
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tnhomestead Posted 7:16 am
29 Jan 2006
seems a shame there is a village needing an idiot somewhere in texas
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