Carbon Dioxide (CO2) is used throughout the brewery as a processing aid in the cellar and at the packaging line. While most brewers do not think of this gaseous compound as a traditional ingredient like hops, malt or water, a sure supply of high-quality CO2 is essential to maintaining and ensuring beer flavor quality. Carbon Dioxide is also an important resource to the medical, oil, food, and chemical industries. Depending on your region, the reliability and quality of purchased CO2 supply may at times be inconsistent. For example, your supplier may source CO2 from petroleum refining, ethanol production, or other processes.
A reliable supply of carbon dioxide is dependent upon a number of global and political factors, and brewers would do well to economize their resources in the event of a supply shortage. As an added benefit, economizing brewery CO2 can help to achieve financial and sustainability goals.
Tips for Reducing Carbon Dioxide Use
CO2 system leaks can be both costly and hazardous; seek out and repair leaks. Receivers or cylinders that build condensation or frost on the outside even when no systems are actively drawing CO2 can indicate your system may have a leak. Install a flow meter near your receiver or cylinder bank and isolate different brewery work zones to help narrow down leaks.
- Check Connections: Ensure that connections at gas sources are tight and shut off when not in use
- Routine System Maintenance: Inspect hose connections and clamps, and replace damaged rubber washers
- Identify and Repair Leaks: When necessary, apply soapy water or mild foaming sanitizer over connections to help visualize leaks
- Test Running and Idle Equipment: Seek out leaks both with equipment running as well as idle, as some equipment only receives CO2 under pressure when running
- Compressed Gas Audits: Audit companies can inspect your CO2 system in parallel with other compressed gas systems, and can provide tips for optimizing performance. Some utilities may offset some of the costs associated with such audits.
Further reduction of carbon dioxide can be achieved through careful monitoring and by metering precise usage for different processing steps (i.e. tank purging and carbonation). Carbon dioxide is used in the cellar to pressurize fermentation vessels, purge tanks, and to move and carbonate beer. There may be opportunities to use CO2 more efficiently in cellar operations:
- Tank Purging: Tank purging often consumes more CO2 than any other cellar operation. Use low pressure gas supply and control gas flow with valves on inlet and outlet. When counter-pressuring a tank for filling, be sure the CO2 regulator is set to a pressure at or below the pressure safety relief on the tank to minimize vented CO2. A dissolved oxygen (DO) meter can be especially helpful in developing brewery standard operating procedures (SOPs) that ensure adequate purging without overconsumption. Smaller breweries may be able to water pack (hot or deaerated water) and drain tanks under oxygen-free N2 or CO2.
- Carbonating: Before carbonating beer it is important to know the temperature and target level of CO2; a carbonation chart is an indispensable tool to help manage carbonation levels and CO2 consumption. To maximize solubility of CO2, allow beer temperature to reach the appropriate setpoint and increase contact time by employing a carbonation stone. Carbonate beer to target by measuring CO2 in bright beer tank and in package.
- Cleaning: Caustic cleaning of bright beer tanks can create inefficiencies when CO2 must be removed from the tank prior to cleaning to prevent neutralization and tank implosion under vacuum. Installing a system and procedures for periodically performing acid clean in place (CIP) under CO2 counter-pressure on bright beer tanks may conserve CO2. This method is brewery specific and additional safety precautions must be employed: Under Pressure CIPs. We strongly recommend contacting your chemical supplier for specific guidance on usage since protocols vary.
In packaging, carbon dioxide is typically used for bottle pre-evacuation and counter pressurization, can lid underletting, and keg purging and counter pressurization. Canning, bottling, and kegging are CO2 intensive processes; canning operations consume especially high amounts of CO2 compared to bottling and kegging. Packaging operations may be optimized to better conserve brewery CO2:
- Canning: Under-lid gassing just prior to seaming can consume nearly as much CO2 as the filler. As a long-term solution, consider ways to optimize the amount of CO2 used for can under-lid purging such as warming the feed stream; this process can deliver the same volume of CO2, while consuming decreased total mass. (Presentation: A novel method for reduction of carbon dioxide consumption during can seaming process)
- Nitrogen Package Purging: Nitrogen may be used to purge oxygen from empty containers when filling, and in package headspace post filling. Consider installing equipment that uses liquid nitrogen to purge packages; small breweries may look to rent portable dewars while larger operations may store refillable liquid nitrogen in bulk tanks. Survey peers and vendors to assess whether this step will decrease CO2 consumption during packaging and resulting total package air levels.
- Package Conditioning: Many brewers package their beer at lower levels of carbonation with the intent of finishing the beer in the package. Advantages of this strategy include lower CO2 usage in the cellar and lower total package air. Disadvantages can include technical knowledge and equipment needed to reliably result in desired carbonation level, a ready supply of wort or other fermentable sugar at the time of packaging, and the potential for introduction of microbial beer spoilers.
Carbon Capture and Reuse
Some breweries may have processes or equipment whereby CO2 is separated from production related sources and stored for future use in carbonating and packaging beer. While carbon capture options for craft brewers are becoming more diverse, this investment may not make financial sense for everyone. Here are a few ways brewers of any size can move and reuse CO2 in production:
- Use fermentation CO2 for carbonating beer (use a Spunding valve to capture natural carbonation from fermentation).
- Purge conditioning and bright beer tanks by transferring CO2 produced during active fermentation via pipe or hose. Avoid contaminating a clean tank with foam, different yeast strains or microbes from the fermenter, and maintain atmospheric pressure in the tank being purged.
Safety Considerations when Working with Compressed Gases
Install CO2 safety alarms in your brewery, fermentation area, cellar and packaging areas, and work in well-ventilated areas. Hazardous levels of CO2 can collect in enclosed work areas, cellars, and cooler rooms. Always wear appropriate personal protective equipment (PPE) and refer to Safety Data Sheets when working with compressed gases.
- Never exceed the intended operating pressure limit of any brewery vessel such as fermentation vessels or bright tanks, kegs, compressed gas cylinders, and cryogenic (liquid) gas reservoirs. Consult and adhere to maximum operating pressure ratings which should be listed on the vessel exterior and/or in manufacturing literature.
- Install, set, and use pressure gauges and gas regulators to monitor equipment and prevent both overpressurization and negative pressure conditions. Never rely on a pressure relief valve alone to maintain safe operating pressures.
- At all times, ensure that pressure and vacuum relief devices are employed to prevent serious vessel failure and fatal injuries. Periodically inspect and test pressure and vacuum relief devices for blockage and proper function.
Refer to the following resources on CO2 safe handling, recapture, and workplace considerations:
- OSHA: Limits for Air Contaminants
- CDC: Immediately Dangerous To Life or Health (IDLH) Values – Carbon Dioxide
- Brewers Association Resource: CO2 Hazards
- Brewers Association Resource: Compressed Gas Cylinders Management
- Brewers Association Resource: Small-Scale CO2 Capture Technology
- MBAA Safety Toolbox Talk: Pressurized Vessels & Equipment in the Brewery
- Brewers Association Resource: Preventing Package Over-Pressurization