Glass, Plastic or Can? continued

As a former packaging manager of a large beverage company, when it came to beverages I always wondered which was more environmentally friendly. Much like the old "Paper or Plastic" argument at the grocery store, which is better or is anything actually better for the environment? This is not an easy question to answer. Last time I wrote about sourcing, this week I want to pick up where I left off with manufacturing. Some of this info I am going to simplify a little, this is not a class!!

Glass (Bottles) 

Once the raw materials are mixed in the furnace (at 2800°) the materials are thermally mixed by carefully regulating the temperature to create convection currents. The molten glass then flows down a forehearth where it is carefully cooled before entering a feeder where it is cut into "gobs" (industry term) and these fall into an individual section (IS) machine and then the mold cavities. Most glass is formed in two stages, stage one is the formation of the parison and stage two is where the parison is transferred to the final cavity mold for container formation. Video

Once molded, the new, red-hot bottles move down a conveyer through an external & internal tin spray coating treatment (hot end coating: which increases container strength and helps with labelling) to an Annealing lehr where the glass temperature is raised up again to about 1050° and then cooled slowly to reduce internal stress caused by uneven cooling during the forming process. After all that, the containers are sent through a cold-end coating and given a water based spray to give the bottles lubricity and minimize glass checking. (chipping when traveling down a production line). Bottles are then QC'ed and palletized for shipping to the bottler. Here is a great video of the process from the Discovery Channel.

Aluminum (Cans)

Coils of aluminum are delivered to can factories by truck or rail. On average a coil is 15,000 linear feet, thickness is about .0108" Width is determined by the the die setting. It is important to note here that most beverage cans are made up of three parts: the body, the end and the tab. All three of these components are made of Aluminum, but go through different forming machines. 

On can bodies: the aluminum coils are QC'ed and placed on mandrel "uncoilers" where the aluminum is fed through lubricators and then a "Cupper" this is a die forming machine that stamps cups out of the sheet. These cups are distributed by a conveyer system to can making machines called "bodymakers" which draw and iron the cups into cans by punching them at high mechanical pressure into ironing dies. The aluminum is drawn through these dies making them thinner and longer. The bottom of the can is also formed at this point. The rough can is then ejected using air and sent to a trimmer where the end is cut off to a precision length. These trimmed cans which are oil coated are then washed and rinsed. Next stop decorating, (which I will talk about in a future post) Decorated cans are then internally coated necked and flanged in tools that give the cans their familiar reduced neck. Here is another great video again, from the discovery channel. Another from Ball Corporation.

Retained-Tab end manufacturing is much simpler. Most can ends go through a ten step forming process with the first couple of stages being similar to the body process but instead of punching "cups", the forming press makes shell blanks that are then "Curled". These curled ends then have a sealing compound applied that will help form a tight seal when the can is filled and capped. The curled are then formed further with the familiar score for the dispensing opening. At this point the can ends also might have relevant state refund information embossed. At the same time, the tab is also formed on a different machine and the two components are married until the end is fully converted. Can ends are considered a commodity, and it is really a good idea to use can ends made by the same company as the body.

PET beverage bottles: (Single layer)

The raw material is delivered to the plant in bins or boxed pallets sorted by color. This material is melted at 5-6oo° and the material is fed into molds at high pressure to create a "preform" preform molds are very expensive. Preforms are precision molded to assure plastic distribution throughout the container. It is interesting to note that the threaded neck is in its final form at this stage.

The preform is then heated again to nearly its melting point and sent into a reheat stretch-blow molder where it stretched and molded into its final shape. Often, preforms are produced and shipped to the filling plants and the bottle is molded on-site to save in shipping costs. Video, again from the discovery channel. 

So who wins manufacturing? Well, after viewing the three video's and reading my description, you should be able to see that even post sourcing, glass and aluminum can manufacturing are heavy industries. The energy costs to run glass furnaces & lehr's & aluminum die forming equipment and extruders has to be higher than the energy to heat and mold plastic bottles. The PET resin industry reports 52% less energy to produce PET over other containers. I am not biased towards plastic but I am trying to report physically and in plain terms what it takes to produce these containers/materials. I have been in glass, can and PET factories and I can tell you from experience that PET factories are far simpler and cleaner places. If anyone disagrees with me on this point please let me know. 

Scorecard: Glass = 0, Aluminum = 0, PET = 2

Up next labeling.