Anyone who has enjoyed a glass of champagne or a pint of beer or a can of Coke knows about the importance of carbonation to those beverages. The play of the bubbles in the glass and the tingle of the gas on the tongue are an intrinsic part of the enjoyment of those drinks.

Imagine the consternation in one part of the brewing industry to discover that the supply of carbon dioxide is about to be limited or even shut off! Such is the case in the British industry. Of course, the British brewers are rather apprehensive about this, especially those who operate on the small scale.

Now you might point out that brewers make lots of carbon dioxide as an inevitable part of ordinary fermentation. You would be right.

Theoretically and going by molecular weights, fermenting 180 grams of glucose should yield 92 grams of alcohol and 88 grams of carbon dioxide, and it comes close to that in practice. However, in practice, a wort (the sugary extract of malt that is fermented to make beer) may contain about 90 grams of fermentable sugar per liter; arithmetic then suggests a liter of such beer would contain about 46 grams of alcohol (4.6% alcohol) and 44 grams of carbon dioxide. Now beer requires only 5 grams of carbon dioxide per liter to be fully carbonated so ordinary fermentation yields far more carbon dioxide than a brewer actually needs in the product.

So why is there talk of a shortage?

It’s because small brewers lack the technology to capture the excess carbon dioxide, purify it and compress it to a liquid. The gas just escapes into the atmosphere. Most large brewers of course do capture the fermentation gas and find it very useful in the processing of beer primarily as a means of excluding oxygen from the process. 

Thus craft brewers around the globe find themselves in the odd position of making great volumes of carbon dioxide in primary fermentation but must buy the gas to carbonate their finished beers, usually by injecting the gas into a moving stream of very cold beer. 

Home-brewers know they can achieve carbonation by adding a small but controlled amount of sugar to each bottle before sealing it with a crown (cap). The gas produced by the trace of yeast remaining is trapped and carbonates the beer; this is called bottle-conditioning. Too much sugar of course and the bottles explode! Sierra Nevada Pale Ale is bottle-conditioned. Using a keg or a cask the same process can be used for cask-conditioning the beer; this is known in Britain as “real” ale and aficionados of it hope the shortage of carbon dioxide will make it more generally available and more popular. On a much larger scale hundreds of barrels of beer can be carbonated by the same process in large tanks; this is known in the USA by its German name: krӓusening. (ED: if you can manage an umlaut over the “u” that would be great.). AB-I and Coors for example use krӓusening to carbonate their beers.

I’m sure the carbon dioxide problem in Britain will quietly go away, as the temporarily closed production facilities come back on line. Tariffs on metals especially aluminum, on the other hand, continue make life worse for American brewers.

Some weeks ago. I wrote about the impact on brewers of tariffs imposed by the USA on imported aluminum and steel. This would primarily show up in the price of aluminum containers, mostly cans, because brewers market their products primarily in that form.  I made two main points: 1) one could not simply add the increased cost of the aluminum to the final product in consumers’ hands because there is a significant mark-up at every stage of the chain through which aluminum products, including beer cans, move from manufacturer to retailer to consumer; I promised that the cost of aluminum could not move through the American economy free of charge. 2) I mentioned an unknown prospect that tariffs might spark added price increases by e.g. producers, traders and merchants involved in aluminum supplies. According to the NYT of June 18th that prospect has become a reality, and Peter Coors in a letter to the WSJ suggests tariffs are providing a cover for artificial inflation of the cost of aluminum.

One reflection of this is the Midwest Premium. Apparently, an independent company called S&P Global Platts calculates this number according to strict and published guidelines to express the risk or uncertainty in markets; the number is currently up to over 130%. That translates to an added value of $485 per tonne of aluminum or about double the value of the 10% tariff; that has really attracted the brewers’ attention and they are pressing the government for relief. They have two arguments: 1) the calculation of the Midwest Premium is bogus (not a winning strategy) and 2) most of the aluminum in beer cans (70%) is not new aluminum (subject to tariff) but recycled from old cans (makes sense to me). 

Of course tariffs on aluminum, the trade war with China and Canada (where half of imported aluminum originates), sanctions against this country or that and gratuitous saber-rattling make for uncertain markets; and though, unlike carbon dioxide for British brewers, we are unlikely to see aluminum cut off from American brewers these are unsettled and even dangerous times.

I suggest the least of our troubles will be an increase in the price of a six-pack of our favorite beverage.       

Michael J. Lewis, Ph.D., is professor emeritus of brewing science at the University of California, Davis, and the academic director and lead instructor of UC Davis Extension’s Professional Brewing Programs. Lewis has been honored with the Master Brewers Association of the Americas’ Award of Merit and the Brewers Association’s Recognition Award. He is an elected fellow of the Institute of Brewing & Distilling. He is also a recipient of the UC Davis Distinguished Teaching Award.  He can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it.