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Jul 09, 2023

The CO2 Shortage: Replacing CO2 with nitrogen in the brewhouse

December 16, 2022Keith Gribbins There are a scary number of applications where

December 16, 2022Keith Gribbins

There are a scary number of applications where a craft brewery uses CO2 in the brewing, packaging and serving process: maintaining proper head pressure on tanks for process applications; moving beer or product from one tank to another; carbonation of that product; scrubbing oxygen prior to packaging; packaging of beer in a can filler or keg racker operation; pre-purging brite tanks after cleaning and sanitization; and pouring draft beer at a restaurant or pub. That's just for starters.

"We use CO2 everywhere throughout the brewery and taproom," said Max McKenna, senior marketing manager at Boston-based Dorchester Brewing Co. "It's used to purge tanks, on the packaging line, in the cellar to carb beer, in the taproom to serve beer — at every stage along the way."

Like many craft breweries, Dorchester Brewing has been dealing with shortages of commercial-grade CO2 for its operations (read about all the causes of those shortages here).

"Due to our contract, we haven't seen a price hike from our current CO2 supplier, despite the rising prices in other parts of the market," said McKenna. "The impact so far has been mostly around limited allocation."

To supplement these CO2 shortages, Dorchester Brewing has been using nitrogen instead of CO2 for certain applications.

"There are a number of operational functions that we’ve been able to transfer to nitrogen," continued McKenna. "Some of the most impactful are for purging tanks and for blanketing gas during the canning and seamer processes. So far, these have been the biggest delta for us, since those processes require such a high volume of CO2. We also for a long time have had dedicated nitro beer lines in the taproom. We use a dedicated nitrogen generator to generate all of our nitrogen for the taproom — for both the dedicated nitro lines and also for our beer gas mix."

N2 is the most economical inert gas to produce, and it can find some productive applications in the cellar, packaging hall and taproom of a craft brewery. N2 is cheaper to buy than beverage-grade CO2, and it's usually more readily available, depending on your regional supply.

N2 can be purchased as a gas in high pressure cylinders and in liquid form in dewars or large storage tanks. Nitrogen can also be produced onsite, using a nitrogen generator. Nitrogen generators work by removing the oxygen molecules in the air.

Nitrogen is the most abundant element in earth's atmosphere (78 percent), and the rest is oxygen and trace gases. This also makes it more environmentally friendly because you’re emitting less CO2.

In brewing and packaging, N2 can be used to prevent oxygen from getting into the beer. If used properly (most folks mix CO2 with N2 when handling carbonated beer), N2 could be used for tank cleaning, pushing beer from tank to tank, pressurizing kegs before storage, purging cans during under-lid gassing and infusion of nitro instead of CO2 as an ingredient for flavor and mouthfeel. In the bar, nitro can be used in tap lines for nitro beers and in high-pressure/long distance applications where nitrogen is blended with a specific percentage of CO2 to prevent a foamy beer at the tap. N2 can even be used as a stripping gas for water deaerating, if that's a part of your operations.

Now, as we’ve mentioned in previous CO2 Shortage articles, nitrogen is not an exact swap for CO2 in all applications in a brewhouse. These gases behave differently. They have different molecular weights and different densities.

For instance, CO2 is much more soluble in liquids than N2. This is why nitrogen creates smaller bubbles and has a different mouthfeel in beer. It's also why brewers use a liquid N2 drip to nitrogenate beers and not N2 gas. Folks say that CO2 also adds a hint of bitterness or tartness that nitrogen does not produce, which can maybe alter flavor profiles. Moving to nitrogen won't fix everyone's CO2 problems.

"There's potential there," said Chuck Skypeck, technical brewing projects director at the Brewers Association, "but nitrogen is not a panacea and it's not a quick fix. CO2 and nitrogen behave very differently. For instance, you’re purging a tank, you’re going to get a lot more mixture with nitrogen and the air that's in the tank than you would get when purging with CO2. So, it's going to take a whole lot more nitrogen. That's one finding that I keep hearing over and over again.

"One brewer, who I know is really smart, started substituting nitrogen for CO2, and their oxygens went way up in their beer, so they’re working with blends of nitrogen and CO2 now and having a little bit better luck. So, it's not just, ‘Hey, we’re going to start using nitrogen and solve all our problems.’ It’d be great to see more in the literature about it, and we’re starting to see more folks that are actually doing some research and, you know, coming up with best practices for making that substitution."

Delivery of these gases will be different as both have different densities, which can cause some engineering or storage changes. Listen to Jason Perkins, brewmaster at Allagash Brewing Co., discuss reengineering his canning line and gas manifold to utilize CO2 for filler bowl pressure and N2 for the seamer and bubble breaker. Storage may vary.

"There are definitely some differences, partially due to how we’re sourcing nitrogen," said McKenna. "We’re sourcing pure liquid nitrogen in dewars, so the storage of that does look pretty different from our bulk CO2 tank — smaller, on casters, stored in the walk-in cooler storage. A lot of the processes that we’ve transitioned are a pretty clean one-for-one swap from CO2 to nitrogen, but again, one of the things that we’ve been really careful about is how to effectively and responsibly make the transitions to ensure that the beer is maintained at the highest quality at every step along the way. Talking with the manufacturers of our equipment for the processes that we’ve transitioned has been key, and in some cases, it is pretty simple plug-and-play replacements, while in other cases it does require some extra investment in materials, infrastructure, fabrication, etc."

According to this excellent article from The Titus Co. (a provider of air compressors, air dryers and air compressor services out of Pennsylvania), nitrogen generators work in one of two methods:

Pressure swing adsorption: Pressure swing adsorption (PSA) works by separating molecules using a carbon molecular sieve. This sieve has pores the same size as oxygen molecules, catching these molecules as they pass while letting larger nitrogen molecules by. The generator then releases oxygen through another chamber. The result of this process is nitrogen can be up to a 99.999% purity level.

Membrane nitrogen generation: Membrane nitrogen generation works by separating molecules using polymer fibers. The fibers are hollow with surface holes small enough for oxygen to pass through, but too small for nitrogen molecules, removing oxygen from the gas stream. Generators using this method can produce nitrogen with up to a 99.5% purity level.

Well, PSA-type N2 generators can make high volume, high-flow ultra-pure nitrogen, and the purest grade nitrogen is what a lot of breweries demand. Ultra-pure means like 99.9995 percent vs. 99 percent. Membrane N2 generators are great for smaller breweries that need low volume, low-flow alternatives where purity of 99 to 99.9 percent is acceptable.

Utilizing the latter technology, Atlas Copco's nitrogen generators are basically a compact industrial air compressor with a special membrane to separate nitrogen from the compressed air stream. Craft breweries are a big target audience for Atlas Copo. Using onsite nitrogen generation, brewers are typically paying about $0.10 to $0.15 per cubic foot, according to this Atlas Copco white paper. How does that compare to your CO2 costs?

Nitrogen generators come in all types of sizes.

"We offer six standard packages which cover 80 percent of all breweries — from a few thousand barrels a year to several hundred thousand barrels a year," said Peter Asquini, industrial gases business development manager at Atlas Copco. "A brewery can oversize its nitrogen generator to accommodate for growth while maintaining efficiency. Plus, the modular design can add a second generator if the brewery's business expands substantially."

Asquini understands these generators won't fulfill every brewer's needs.

"Using nitrogen is not about fully replacing CO2," explained Asquini, "but we think brewers can reduce their consumption by around 70 percent. The main driver is sustainability. Any brewer can create their own nitrogen very simply. You will no longer be using a greenhouse gas, which is better for the environment. It will give you a payback from month one which will go straight to the bottom line, and if this cannot be shown before you purchase, then don't purchase. That's our simple rule. The demand for CO2 to make products such as dry ice, which uses a significant amount of CO2 and is necessary to transport vaccines, is proliferating. Breweries across the United States share concerns over supply levels and question if they can cope with breweries’ demand while keeping pricing levels consistent."

Atlas Copco summarizes the P.R.I.C.E. benefits of going with nitrogen in this video:

As mentioned, N2 purity will be a big concern for craft brewers. Just like CO2, nitrogen will interact with the beer or wort and impurities can be passed along. That's why a lot of these nitrogen generators for food and beverage applications will be touted as oil-free units (learn about the purity benefits of oil-free compressors below in the Last Word sidebar).

"When the CO2 gets to us, it's been vetted for quality and contamination — another really important piece of working with a great supplier," said McKenna. "For nitrogen, it is a little bit different, which is why we’ve been sourcing pure liquid nitrogen so far. One other thing that we’re looking into is sourcing and pricing an in-house nitrogen generator — again, with a focus on the purity of the nitrogen that it generates to limit oxygen pickup. We’re looking at this as a potential investment moving forward so that the only wholly CO2-dependent processes in the brewery would be carbonating beer and taproom service operations.

"But one thing that's really important to consider — again, the sort of seemingly nitpicky thing that can get overlooked, but is crucial to maintaining beer quality — is that any nitrogen generator needs to be generating nitrogen that's pure out to the second or third decimal [i.e. 99.99 percent pure] to limit oxygen pickup and risk oxidation. This sort of precision and purity costs more on the nitrogen generator, but ensures the quality of the nitrogen, and therefore the beer."

Brewers will need plenty of data and QC when employing nitrogen. As an example, if a brewer is using N2 to move beer between tanks, CO2 stability should be tracked throughout the process, in the tank and in the can or bottle. There are certain applications where pure N2 probably won't work — like in the filler bowl — when pure N2 would cause the CO2 to purge out of the solution. So, some beer makers will use a 50/50 mix for CO2 and N2 for filler bowl apps, and others will just stay away from it completely.

N2 Pro Tip: Let's talk maintenance. Nitrogen generators really are as close to fit-and-forget as possible, but some consumables, such as filters, require semi-regular changes. Real service is often required about every 4,000 hours. The same team who takes care of your air compressor would also take care of your generator. Most generators come with a simple controller — similar to your iPhone — and come with full remote monitoring capability via an app.

Tank purging will be different with nitrogen for multiple reasons. N2 mixes well with air, so it doesn't interfere as well with O2 as CO2. N2 is also lighter than air, so it will fill tanks from the top down vs. CO2 which fills from the bottom up. It takes a lot more N2 to purge a tank than CO2, and bulk blasting is often required. Are you still saving money?

There will also be new safety concerns when dealing with a new industrial gas. A brewery will definitely need to install O2 meters so employees can visually see air quality in an enclosed environment — like if you’re now storing dewars of N2 in your cooler.

But the costs benefits can easily outweigh, say, a CO2 recapture unit. In this webinar, Dion Quinn, from Foth Production Solutions (an engineering company), cites the cost to generate N2 is $8 to $20 per ton vs. collecting CO2 via a recapture unit, which can cost $50 to $200+ per ton.

The benefits of a nitrogen generator would include eliminating or at least downgrading reliance on CO2 and nitrogen contracts and deliveries. It may save on storage because a brewery could produce and store only as much as they needed, eliminating the need for both storing and hauling around nitrogen bottles. As with CO2, customers pay for nitrogen transport and delivery. This becomes less of a concern with a nitro generator.

Nitrogen generators are normally easy enough to incorporate into a brewhouse setting. Smaller nitrogen generators can be wall mounted, so they don't take up any floor space, and they are low noise. These packages can cope well with changing ambient temperatures and have a great temperature change tolerance. Outdoor installs are possible but not recommended in climates with extreme highs and lows.

When sizing a nitrogen generator, Asquini suggests answering these four questions:

There are a number of nitrogen generator manufacturers, including Atlas Copco, Parker Hannifin, South-Tek Systems, Milcarb and Holtec Gas Systems. Asquini noted that a small nitrogen generator costs around ~$800 per month, based on a five-year lease-to-own program.

"Lastly, if nitrogen is right for you, then you have many choices of supplier and technology to make," said Asquini. "Find the one that's right for you and make sure you fully explore the TCO [Total Cost of Ownership] and compare electricity costs between units and service costs. You will often find the one with the lowest purchase price is not the right one for your operations."

Click here to see other CO2 Shortage articles.

A nitrogen generator system uses an air compressor, and most craft breweries already have a compressor, which is convenient.

What is an air compressor used for in a craft brewery? Pushing fluids through piping and tanks. Energy for pneumatic transportation and control. Aeration of wort, yeast or water. Modulating valves. Purging gas to displace solutions in tanks during the cleaning process and to help during the keg washing process.

Exclusively using 100 percent oil-free air compressors is required for many applications throughout breweries. If oil comes into contact with beer, it damages the beverage by killing the yeast and flattening out the frothy head, making for bad brewskis.

It's also a safety hazard. Because food and beverage production is so sensitive, strict quality and purity standards are in place and rightfully so. An example: The Sullair SRL Series of oil-free air compressors in the 10- to 15-hp (7.5- to 11-kW) range is an ideal fit for craft breweries. Breweries enjoy the quietness of these types of machines. The SRL Series offers noise levels as low as 48 dBA, making the compressors suitable for indoor applications without a separate sound attenuated room.

When air purity is critical, such as at brew pubs and craft breweries, oil-free air is essential. Oil particulates in compressed air can contaminate downstream processes and production. With many breweries producing thousands of barrels or cases a year, no one can afford taking on that kind of risk. An oil-less compressor is especially beneficial for applications in which the air comes in direct contact with the ingredients. Even for applications where there is not direct contact between the ingredients and the air, like a packaging line, an oil-less compressor can be beneficial in keeping the final product clean enough to put your mouth on.

Learn more about these compressors in this story with Ghostfish Brewing Co.: