Dry Ice Scotland: Decarbonising an industry

Dry ice is essentially carbon dioxide (CO2) that has undergone cooling and condensing. Used primarily to maintain a stable temperature – around -78.5C – during food and beverage transportation, demand for dry ice has increased during the ongoing Covid-19 pandemic, not only due to home food deliveries, but also to keep vaccines cooler for longer. 

Scottish brothers Richard and Ed Nimmons of Dry Ice Scotland (DI Scotland) spoke to gasworld about all things dry ice, as well as the company’s push towards sustainability. Following a £4m investment to expand its production efforts, the Perthshire-based DI Scotland is looking to further reduce its carbon footprint. 

Starting out ten years ago, Richard (later joined by Ed) began by founding a dry ice blasting business before developing mobile dry ice production technology. This company was sold, and the capital was used to start a large-scale dry ice production facility with a sustainable twist. Rather than outsourcing their CO2, the brothers wanted to have their own source. With sustainable solutions company Pentair installing and commissioning a new CO2 recovery site on behalf of the company, renewably sourced bio-CO2 is set to play a crucial role in contributing to decarbonisation of DI Scotland’s production process.

“CO2 from a carbon-neutral source is not only ecological, but also economically self-sustainable. We wanted to do something which would be there in many years to come,” said Richard. 

Not wanting to encourage the processing of hydrocarbon by-products to capture CO2 for liquefication, the brothers’ dry ice manufacturing process begins at a nearby anaerobic digestion (AD) plant. The biomethane produced at the plant is captured before going through a gas upgrader before membrane technology separates the CO2 from the methane. 

Following the recent commissioning of the new production site, patented Pentair technology recovers the captured CO2 before it’s purified and liquefied into bio-CO2. 

Richard explains, “After this process, the gas is then stored in our hundred tonne storage tanks next to the site.” 

Having the CO2 source in such proximity allows for a continuous production process, with the company running liquefaction 24 hours a day and dry ice production 12-16 hours a day. 

The dry ice production process involves the liquid CO2 being transported from a controlled and cool environment through insulated, pressurised pipework before finally being released quickly into a pelletiser. The pelletiser fires the liquid CO2 into an almost ambient pressure chamber, essentially filling the chamber with snow. 

At the end of the chamber is a diplate, which contains holes that can range from 1.7mm to 19mm. Snow from the chamber is excreted down the cylinder and pushed through a diplate – typically containing 3mm holes – at around 2.5k psi. The resultant extremely dense dry ice then goes onto a conveyor belt which deposits it onto a reformer. 

“The reformer squeezes 3mm pellets into a slice, like a large kind of rectangle shape, where it then gets wrapped into a plastic wrapper,” explained Richard. “The wrapped slice goes into food logistics like online groceries or even airline catering.” 

Though the food and beverage industry is the company’s bread and butter, the past 18 months has seen DI Scotland provide dry ice for the medical industry, specifically for the transport of Covid-19 vaccines. 

Richard explained that the difference between the dry ice produced for the food and beverage industry and for vaccines is that the reforming can be skipped, and the pellets are deposited straight into the box.  

How is DI Scotland’s manufacture process any more sustainable? 

Following production, the dry ice immediately wants to return to its prior gaseous state, in the same way that regular ‘wet’ ice begins to melt and return to a liquid state when removed from freezing temperatures. The sublimination of dry ice means that, eventually, the dry ice will be released into the atmosphere as gaseous CO2. 

Although not a carbon negative process, the CO2 feedstock is essentially carbon neutral due to the sustainable source of biogas; and the company’s ability to capture CO2 without having to rely on emission-producing transport trucks means that CO2 that would have been emitted has been avoided. 

Emphasising that the process is carbon capture and utilisation (CCU) rather than carbon capture and storage (CCS), Richard added, “We are carbon capturing, we’re capturing the carbon dioxide that comes off the AD plant and we’re utilising it, and we’re using a sustainable energy mix to cool it and condense it.” 

“That’s the liquid CO2, and then we use renewable energy to also compress it into a pellet or slice, so as far as that’s concerned, we’re not emitting any new CO2.” 

When it comes to sustainability, DI Scotland focuses on reducing the amount of harmful emissions produced in the entire supply chain that would have occurred, such as those emitted from diesel driven refrigerants. 

Richard elaborated, “If we make our dry ice cheaper than gel packs or diesel driven refrigeration, and I think we’re pretty much there, again that will reduce the amount of landfill and emissions. There’s been lots of different things we can work on.” 

“This will have a positive effect on the environment by reducing the emissions that would have occurred,” he added. 

The company also supports a form of circular carbon economy by focusing on recovery. For every 2.1 tonnes of liquid, one tonne of dry ice is made. Any waste gas is recovered, liquefied, and processed directly into pellets. 

Another aspect of DI Scotland’s long-term strategy for the new site and all future sites is, as a ‘number one rule’, to focus on net zero produced CO2. 

“We’re looking at the most sustainable methods because, behind that, there’s obviously various grades of how sustainable the process is,” explained Ed. “So that’s a really important factor in our selection.” 

Given the recent CO2 shortages seen throughout Europe, certain companies have been able to fill a supply gap in the market. DI Scotland is no exception, with Richard revealing that the company is getting requests daily from companies for supply. 

He added that, although not ideal, the company has seen this extra shortage-induced demand help support recovery costs incurred through commissioning the new plant.  

CO2 shortages 

CO2 shortages have dominated the industrial gas headlines throughout 2021, with reports going so far as to suggest that Christmas could be cancelled. Although sensationalist, there are concerns of a prolonged supply crisis heading into 2022. 

When asked whether technology such as that used by DI Scotland’s new plant could alleviate shortages, Richard praised the benefits of acquiring CO2 from a renewable source, stating that if companies continue along a non-sustainable path, shortages could be here for the ‘long-term’. 

“Until companies like us start liquefying more CO2 in this manner, it will always be like that,” he said. “It has to be an ecological source because of the external strains that are never going to go away, as well as the potential carbon taxes that you pay.” 

“We feel that what we’re doing is we’re just cutting out all that and going to the existing emitters. We’ve got reassurance that the investment will be a long-term goal,” he added. 

With the recent international climate summit COP26 bringing a global eye to decarbonisation of industrial sectors, the brothers considered the event an opportunity to showcase Scotland’s first carbon capture project. 

“For us, our project is a perfect example of local carbon capture combined with commercial, net zero utilisation,” added Ed. 

As awareness increases of the need to contribute towards an energy transition, bolstered by talks at COP26, DI Scotland’s dry ice operation shows no sign of slowing down. 

“We’re already talking to the next sites, which are producing large and meaningful volumes,” said Richard. “It’s safe to say we’ve got two or three projects in the pipeline.”