The testing of CO2 has fortunately evolved over the years—both through more capable onsite production and storage testing equipment, and relatively simple offsite process. This involves taking a small, low pressure gasified CO2 sample that can be internationally shipped when needed as a “non-hazardous” gas sample to a qualified CO2 testing laboratory for a comprehensive quality analysis.
This offsite sampling requires the use of sample containers comprised of inert, specially coated (passivated) materials that will not adsorb the critical impurities of interest such as sulfur agents.
Use of state-of-the-art instruments, both onsite and offsite, allows for the testing of all critical CO2 impurities to the very low (parts per million to parts per billion) levels needed to ensure CO2 sensory desirability and consumer safety.
Significance of CO2 Quality
Unlike many commodity gases such as nitrogen, oxygen, and argon that basically come from non-complex “air” as a primary source, Dr. Pachuta explains commercially produced CO2 for beverages typically originates as a byproduct or a “waste” product from more chemically complex sources.
These include natural wells, fermentation of grains and grasses (corn, molasses, sorghum), combustion of many fuels including coal, fuel oils, natural gas, plus natural gas based-synthesis of soil fertilizers (ammonia-sources), chemical processes (neutralization of mineral acids), synthesis of various chemicals (glycols), and quite recently “anaerobic” digestion of various vegetable, animal, and waste stream biomass materials (biogas).
“In all cases, the trick is to accurately determine the identity, levels and risks of all common types and amounts of potentially harmful sensory or health-impact impurities that may be present from a given CO2 source,” Dr. Pachuta says. “This information is used to design effective industrial cleanup processes, which can consistently remove these undesired impurities down to very low, safe, acceptable levels for use in beverages and other food applications.”
Due to the physical properties of CO2 and the strict controls over the supply chain, the chance of contamination problems with the CO2 is pretty low. Containers of CO2 are under pressure. Pressurized product flows out of the container, prohibiting the introduction of contaminants into the container as long as there is product in the container.
“The safety issues are not so much contamination in the supply chain, but more about safe handling and storage given the properties of CO2 itself,” Willenbrock says. “CO2 is produced, stored, and transferred under pressure, which virtually eliminates the chance for contamination. In a closed container, such as a high-pressure cylinder, CO2’s a liquefied gas under pressure. If you overfill the cylinder and the temperature change increases, the pressure can rapidly increase to an extent that the cylinder can rupture, causing extensive injuries to individuals and equipment.”
Storage of CO2 in tanks and cylinders in enclosed areas without adequate ventilation and atmospheric monitoring are concerns. Even small leaks from equipment could lead to an oxygen deficient atmosphere in the area, exposing anyone entering to possible asphyxiation. Even with what may be considered “sufficient oxygen” to sustain life, an environment containing high levels of CO2 can cause personal harm very quickly.
Recent CO2 Trends
With an increasing interest in the use of more economic and non-traditional sustainable sources of commercial CO2, the specific challenges are to design appropriate sampling, analytical methods, test programs, and reasonable purity specification limits that will identify and track the most likely impurity “suspects” present in a feed gas source or produced during the manufacturing process.
Dr. Pachuta says the next step is developing appropriate and routine onsite monitoring and periodic testing programs to assure a CO2 producer can effectively remove these source-based impurities from all CO2 loads destined for beverage and other food uses (dry ice for food preservation).