June 29, 2018

expert reaction to the ongoing CO2 shortage

It has been reported that there is an ongoing CO2 shortage across Europe.

Dr Sharon George, Lecturer in Environmental Sustainability and Green Technology at Keele University, said:

“The maintenance causing the shortage is routine summer maintenance as main production is in the winter to provide fertilisers to meet demands in food production.

“The main thing with this issue is the shortage for meat and poultry production – it’s used as a tool for stunning animals for a more ‘humane’ slaughter and for keeping food fresh in transit. This is causing animal welfare issues and concerns around disruption to food manufacture. Fizzy drinks demand is not helping!

“From a sustainability standpoint this highlights the domino effects that happen when one part of a supply chain is vulnerable and how we are unaware of our food production issues until something goes wrong. At a time when we should be thinking about resilience in our systems to cope with climate change and changes in global markets this is concerning.”

Prof Laurence Harwood, Director of the Chemical Analysis Facility and Professor of Organic Chemistry at the University of Reading, said:

“Carbon dioxide is produced industrially by ‘steam reforming’ and the ‘water gas shift reaction’. In both processes, hydrocarbons are reacted with steam to produce hydrogen and carbon dioxide. The hydrogen is largely used in the Haber process to manufacture ammonia (primarily used to produce fertilizer) and the carbon dioxide has a whole series of uses, not least in the food industry, particularly for carbonated drinks. It is also used to render poultry unconscious prior to slaughter and therefore a lack of carbon dioxide could have serious consequences on food availability as well as the availability of carbonated drinks.

“Currently several (at least five) of these industrial plants in Europe have closed down for maintenance resulting in this shortage.

“On a trivial side, the Chemistry Department at Reading University is without dry ice (solid carbon dioxide) as the gas supplier BOC has declared force majeure and we are not deemed to be ‘critical’ or ‘safety critical’ users.

“Real ale and champagne drinkers shouldn’t be too worried as the carbon dioxide in their tipple is produced by the fermentation process. Other beers such as lagers are carbonated however and supplies might dry up if the situation continues.”

Dr Simon Dawson, Senior Lecturer in Food Science & Technology at Cardiff Metropolitan University, said:

“The problem with the CO2 shortage is that there really is no other alternative that can be used due to the number of benefits the gas can offer. It prevents microbial growth, is inert, can be transported/used safely, and does not affect the flavour/textural properties of a food (unless too much is used). Attempting to use another gas/gas mix would mean extensive testing which will take time/cost.

“Nitrogen or carbon monoxide can be used to kill animals, and both have been shown to be relatively humane. Nitrogen being the safer of the two gasses to handle, so there are alternatives there – providing a company’s existing equipment could be retrofitted to allow the alternative gasses to be stored/used and also monitored for effective lethality dosage.

“There are also the implications of dry ice used to transport temperature sensitive foods via postal services. Although it sublimates quite quickly, it still lasts longer than alternative inert gases (solidifies at -90°C). Nitrogen for example doesn’t becomes a solid until -210°C which would be extremely expensive to carry out and store.

“Bagged salad typically contains a high amount of CO2 (15%), high nitrogen (80%), and low O2 (5%) levels. You cannot just remove CO2 and expect the same shelf life. CO2 has excellent antimicrobial properties so preserves the bagged salad and reduces browning of salad greens. Take two bags of salad that are sealed with the same life and open one up so the modified atmosphere has been lost. The salad will quickly go limp and will degrade over a couple of days. Having high CO2 and low O2 levels in the packaging blocks the biosynthesis of ethylene, a plant ripening hormone that promotes the aging of the salad vegetables. Under modified atmosphere packaging (MAP) you could achieve about 8 days life, whereas without the MAP it would last half this long.”

Mr Tony Ennis, Director of HAZTECH Consultants Ltd, said:

“A large proportion of the CO2 we use is a by-product of ammonia production. Ammonia is produced to make fertiliser for farmers (usually in the form of ammonium nitrate). Ammonia plants tend to be large continuous production plants and typically shut down for four weeks in the summer for routine maintenance as is typical for most large chemical facilities.

“The chemistry is CH4 + H2O <=> CO + 3H2
Then: CO + H2O <=> CO2 + H2
CO2 and H2 are easily separated.

“Both of these are equilibrium reactions and require  nickel catalyst, and the process is carried out at high temperature and pressure. The catalyst is poisoned over time by Sulphur which is present in the CH4 feedstock i.e. natural gas, in small quantities, and therefore needs to be replaced periodically.

“These shutdowns are planned many months ahead in order to mobilise personnel and equipment for the shutdown (it’s a complicated process and involves many personnel and equipment). Typically a shutdown will be between 4 – 8 weeks in duration depending on the work that is being done to the plant.

“The reason that the ammonia plants shut down in summer is that demand for fertilisers is lowest in summer as farmers usually fertilise in spring.

“It is unfortunate that the closure of these plants has coincided with a particularly hot spell of weather and therefore high demand from the drinks industry in particular.

“Whilst there is CO2 in the atmosphere and produced by burning of fossil fuels, it’s expensive to separate out from these sources and therefore not generally a commercially viable operation.

“It’s also relatively difficult to transport CO2 long distances as it requires pressurised tankers, or large refrigerated tanks, thus importing CO2 is not generally practicable.

“Trivia: CO2 is also used for making the holes in crumpets.”

Declared interests

None received.