Carbon dioxide (CO2) does not always enjoy the best of reputations. But we should not forget that liquid carbon dioxide (LCO2) plays an important role in the food and beverage industry – for example freezing pizzas, making soft drinks sparkle and keeping packaged foods fresh. CO2 is recovered from the unwanted off-gas streams emitted by processes such as fertiliser, plastics and food production. Captured, purified and then usually liquefied, it is ultrapure and ideal for use in foodstuffs.
Until recently, BOC did not have its own LCO2 production plant, using third-party suppliers instead. Leading food company Cargill made CO2 which it had no use for as a by-product of its manufacturing processes. Spotting a mutually beneficial opportunity, the two companies formed a partnership which resulted in the recent opening of BOC’s first UK CO2 purification plant at Cargill’s Manchester site.
The waste CO2 is a by-product of Cargill’s wheat fermentation process, which produces potable alcohol for products such as perfumes, mouthwash and beverages. Capturing and purifying the majority of this waste CO2 and converting it into food and beverage grade liquid CO2 will help Cargill’s Trafford Park facility towards its goal of achieving zero waste.
gasworld spoke exclusively with Matthew Onions (left), Product Manager for Carbon Dioxide at BOC, to discover more about the partnership between BOC and Cargill and how BOC captures and purifies CO2.
“BOC had been looking for an opportunity to produce its own source for a number of years,” explains Onions. “There are plenty of operations around the country producing CO2 but it needed to be in the right location, producing the right quality of raw CO2, to be viable.”
“The location of the Cargill plant was ideal and it produces good quality raw CO2. We’ve been working with Cargill for many years – they are a customer of ours - so it was naturally a great fit.”
“What’s unique about this particular plant is that it was designed and built by Linde Engineering, a division of our parent company the Linde Group. This means that time from design to construction and installation was very short. We went from contract signing in September 2015 to shipping pure LCO2 out to customers by August 2017,” Onions said.
The process of capturing and purifying CO2
“One of Cargill’s products is ethanol. Raw CO2 is produced as a by-product of the ethanol fermentation process. Before the BOC plant was built the gas was vented to atmosphere – so we’ve effectively redirected the raw gas stream for onward processing,” Onions explained.
“It’s a careful process - first you must take out all the moisture from the raw CO2. If the very cold, liquid end product has moisture in it then it could freeze and cause all sorts of problems. The pure CO2 produced by the plant then goes into storage tanks. We have four of these on site, each holding about 300 tonnes of CO2.”
When asked if he thinks this project underlines how important environmental sustainability is, Onions replied, “Definitely. We are taking a waste product and putting it to good use. We’re purifying it, cleaning it, liquefying it and transporting it for others to use in a variety of ways such as putting the fizz in soft drinks. We’re not having to manufacture CO2 for this purpose, we’re simply taking a waste material and reusing it so we’re getting extra life out of it.”