After brewing, beer quality primarily depends on two factors: oxygen and light. Oxygen will break down all kinds of compounds in a beer and gives the beer an overall stale character commonly described as the smell (and taste?) of wet cardboard. However, the amount of oxygen getting into both package types is pretty negligible. Oxidation has more to do with how long the beer has been sitting on the shelf. Light breaks down the hops and creates a skunk-like aroma. It seems pretty obvious that the aluminum can would be better at blocking light. Yes, the use of dark brown bottles and tall sided cardboard six packs/enclosed cases does eliminate most of the potential for a bottled beer to be skunked, but still doesn't provide 100% protection like a can.
Some people claim aluminum cans impart a metallic flavor to the beer. This doesn't make a whole lot of sense though, since all aluminum cans have a plastic liner. The beer never actually touches the aluminum unless you're drinking your beer straight from the can. Then again, we probably wouldn't be talking about beer quality if you were drinking the beer straight out of the can.
Winner: Aluminum Cans
You've probably heard the recent news about Bisphenol-A (BPA). It is a chemical that leeches out of certain plastics, including the coating in aluminum cans, into your food and beverages. The opinion of most health agencies around the world right now is that low amounts of BPA aren't an issue except maybe for children. Our demographics show that we do terrible with the 0-3 year old age group on this blog, so we're not too concerned about that. More BPA will leach out over time though, and will concentrate in the beer. So if you're aging a beer for several years, it's probably a better bet to do it in a glass bottle. Glass is totally impervious and non-reactive, so there's no way it could affect the flavor of the beer or leech chemicals into it.
Winner: Glass Bottles
This one is pretty obvious. Glass bottles weight about 7 oz. each, whereas aluminum cans weight 0.5 oz. So 12 pack of bottles is going to weight about 5 lbs more to carry around than a 12 pack of cans. Also, glass bottles break and send shards of glass flying across the room when you drop them. At least if you drop a can and it splits open, you can just pop the top and start shotgunning the rest of the beer. You can also crush a can when you're done so you can go even longer without taking out the recycling. And as a little extra bonus, you don't need a special opener to open a can.
Winner: Aluminum Cans
This has to be the most hotly debated area in the cans vs bottles debate and the most difficult to analyze. To my knowledge, there isn't any comprehensive life-cycle analysis comparing glass and aluminum. Both are environmentally detrimental to process the raw materials, but recycling makes a huge difference. Aluminum and glass can be recycled indefinitely for beer containers. Using recycled aluminum can reduce the amount of energy put into the process by up to 95%. Using recycled glass on the other hand, can only reduce the energy needed to produce a bottle by about 20%. Right now, about 55% of the aluminum and 28% of the glass used in the US is being recycled, so we're still not even close to seeing that energy reduction. (I mean, seriously? Who's not recycling their empties??)
The weight and size of the containers also have a significant impact to shipping costs and environmental impact. Because of the extra weight and space required by glass bottles, you can only fit about 55% as many beers in a semi-trailer. So if you're considering buying an average case of beer from a Colorado brewery, a 12 pack of cans would produce about 6 lbs of CO2, and a 12 pack of bottles would produce
Winner: Aluminum Cans
Well, that's 3-1 for aluminum. Wait, is this the World Cup of Beer Packaging Products or the Superbowl? Anyways, after researching all this, I can say that I'm finally a can convert. Glass bottles still have a place for aging beers (or wine/liquor for that matter). Also, if you're a homebrewer and you're reusing glass bottles over and over, that obviously makes sense as well. But anything other than those exceptions, it's cans all the way! All this makes me even more excited to go buy some Oskar Blues when it finally arrives. Guess I'll just have to drink some Tallgrass at the actual Superbowl this weekend!
What do you think--cans or bottles? What's your favorite canned beer?
(By the way, if you have any questions about how I came up with my numbers, let me know and I'd be happy to chat!)
Edit: My super smart glass engineer friend with a PhD in Materials Science pointed me towards a life-cycle analysis of glass versus aluminum. One thing I noted though, is that they also show their assumed post consumer content of aluminum containers to be 40%, when estimates I've seen are closer to 70% recycled content, albeit by the aluminum industry group. This makes a big difference as increasing the recycled content of aluminum drastically reduces the energy cost. He also mentioned that his work shows that my energy consumption for glass is about 2.5 times too high. This would make the glass energy requirement closer to 0.26 kWh per bottle. This is still higher than what I calculated for aluminum though, and would still be further offset by shipping costs.