CO2

Carbon Dioxide (CO2) gets a bad rap in the larger scheme of things. It is the bogeyman of the climate change world. Yet, without it, the way people consume food and beverages – even how food is packaged – would not be the same.

Air Liquide is an industrial gas-producing specialist, and one of the key ingredients it supplies to the food and beverage industry is carbon dioxide, in all its forms.

Frank De Pasquale is the business unit manager for CO2 and Hydrogen (H2) for the company in Australia. He has been with Air Liquide for 15 years and has been in charge of its CO2 production for the past 12 months and is well versed in its place within the sphere of the food and beverage landscape.

There is an increasing amount of CO2 in the atmosphere, but as of today this is generally not economic to recover, so industrial gas companies need to identify a suitable CO2 emission source and give it a second life by purifying it to food or industrial grade for commercial use.

“Unlike some of our competitors, we never produce additional CO2 from burning natural gas; we recycle and purify existing CO2 emissions from others. We are proud of this commitment which is part of our Corporate Climate Objectives.”

All CO2 emissions are a mixture of CO2 and various impurities, but it is what makes up those impurities that matter when it comes to commercialising the product.

“It could be 99.99 per cent CO2, but has 20 parts per billion of benzene in it, which at parts per billion level is not very much,” said De Pasquale. “However, such a little amount of this kind of impurity means that the CO2 is not suitable for the food industry.”

And how does Air Liquide source its CO2? There are several avenues it utilises. Currently it sources feedstock CO2 from seven different industrial processes, all of which emit CO2 as they make their products – three produce ammonia, one is a power station, one is a steam boiler (both are combustion flue gas sources), while there is one that produces ethylene oxide and another is from a natural gas producer. Each feedstock source has its own set of impurities that has to be dealt with, and then the gas has to be collected so it can be made commercially viable. Take ethylene oxide as example.

“We can get CO2 from a chemical process, such as ethylene oxide production,” said De Pasquale. “When ethylene is reacted with oxygen, it makes ethylene oxide and CO2. The process then requires CO2 to be removed, which we can capture, then purify for the food industry.

“However ammonia plants are definitely the best feedstock source; CO2 produced this way has the least amount of impurities in it.”

The reason for this, said De Pasquale, is that to make ammonia you need to have a reaction between hydrogen and nitrogen which results in a relatively clean stream of CO2 containing less impurities than other emission sources.

“As you go from ammonia to ethylene oxide to natural gas processing to flue gas – you get different levels of purity for CO2 and different impurities that you will need to deal with,” he said.

The cost of production varies greatly because it’s based on the processes used within the different disciplines to ensure food and beverage grade quality. In most processes, there are a few steps.

“Typically, there is some level of compression – there is also, as a general rule, a degree of filtration and drying, followed by liquefaction and distillation,  to purify the feedstock to the required quality,” said De Pasquale. “The process produces CO2 in liquid form, which is approximately -22˚C and 20 bar pressure. Not only does producing liquid aid in the purification process, it also allows us to transport it more economically than you would if it was in a gaseous form.”

Once it is trucked to a customer’s site it is loaded into a bulk tank, and the customer typically uses it in a gaseous form, which is made possible using a simple air-heat exchange system to vaporise the liquid CO2.

Dry ice is another specialty of Air Liquide’s, which is the solid form of CO2 that typically sits around -79˚C. One of the special properties of dry ice is that it sublimes from its solid form directly to its gaseous form. This is important in the food and beverage industry, when dry ice melts into a gas it does not leave a residual on the food.

“Airlines use dry ice to keep your drinks cool and to transport fresh produce from Australia to export markets. The Red Cross use it when they transport blood and other human specimens such as plasmas,” said De Pasquale. “We have a large number of meat and poultry processors that have bulk liquid storage vessels on site. The liquid CO2 is piped to their processing equipment where it converts to dry ice, which chills the meat to prevent biological or bacteriological development and facilitates product forming into beef patties or chicken nuggets.”

CO2 is a product with highly sought after properties. This explains why it is used in the food and beverage industries in its liquid, solid and gaseous forms across a range of applications.

Quality and the supply of a safe product to these industries is paramount, so how do they carry out quality control?

“We continually test the quality of our CO2 in real time,” said De Pasquale. “We have a detailed and audited food safety management system known as FSSC 22000, which is a systematic approach to controlling food safety hazards within our production and distribution activities. This ensures that we provide a safe product to the food and beverage industries. It covers everything from plant design right through to pest control and waste disposal.”

According to De Pasquale, from the process aspects, it covers everything from the feedstock CO2 stream and process conditions,  through to final product testing and distribution to the market. It is not just testing the final product, it’s about assessing, monitoring and controlling all risks, all of the time.

“We produce and test CO2 in batches; we test it online and send samples to external labs; and we also monitor process conditions,” he said. “We know if the process conditions vary, then something could be impacting on our product quality. These are real-time variables, and the last part of the system involves testing of the final product.

“If we don’t have these systems in place, by the time the final  product is made, it is typically too late. We test the final product to confirm that everything else in our system is working. It’s not a catch-all last measure – the important part is making sure the processes are in place from the beginning.”

Another major and ever-growing market for CO2 is water and waste water treatment where it is used for pH control and remineralisation. Every Australian capital city’s desalination plant uses CO2. The plant is a critical water supply source, especially as drought takes hold.

“CO2 is also one of the most humane way to process animals like chickens and pigs,” said De Pasquale. “It is used in MAP (modified atmosphere packaging) as a bacteriostatic agent, thus extending the shelf life of chilled and ambient products. Australian supermarket shelves are packed with trays or packs of MAP products ranging from meat and poultry to dairy products such as cheese and milk powder to pasta and bakery products. CO2 is used with all these products and is a key component of the system that extends shelf life.

“Another application that I should mention is glasshouse enrichment. You can grow crops in a field, but to increase the yield of your crop and also the growing season, you grow them in a glasshouse where you control the temperature and you can control the CO2. The glass house operates at a slightly elevated CO2 level, which improves crop production.”

De Pasquale is also keen to point out that he doesn’t see the production of CO2 – in the context as to why Air Liquide makes it – as an industrial process.

“The way that we run our CO2 production plants is driven by the requirements of FSSC 22000, which is strictly a food and beverage industry standard,” he said. “Our CO2 plants have this certification because the food and beverage industry is our major market and CO2 is used by this market as an ingredient or as a processing aid. So these production plants are not industrial production plants, they are food ingredient production plants.”

And when it comes to the general public, the bottom line as far as De Pasquale is concerned on the merits of CO2 in the food industry?

“Take soft drinks, sparkling water – everybody wants drinks with bubbles in it,” he said. “And what about beer and soft drinks on tap? Pubs and bars use CO2 to dispense these beverages. At the end of the day, no CO2, no beer, no soft drinks.”