How is Dry Ice Made? The Complete Process

Dry ice is a remarkable substance — solid carbon dioxide (CO₂) that sublimates directly from solid to gas at -78.5°C. Its unique properties make it an essential tool across South Africa and Africa: preserving seafood in Cape Town, shipping vaccines to rural clinics in Limpopo, transporting fresh produce from Mpumalanga farms to Johannesburg, and maintaining frozen products for export. Understanding how dry ice is made, from CO₂ capture to the final solid product, not only highlights its scientific precision but also helps businesses use it safely and efficiently.

Step 1: Capturing Carbon Dioxide

The first step in making dry ice is sourcing the CO₂ gas. Carbon dioxide is a by-product of several industrial processes:

• Ethanol fermentation: Breweries and distilleries in the Western Cape generate CO₂ during fermentation.
• Ammonia and urea production: Chemical plants in Gauteng and KwaZulu-Natal capture CO₂ released during fertilizer manufacture.
• Natural CO₂ wells: Certain areas in Africa, like volcanic regions in East Africa, provide natural CO₂ sources.

Captured CO₂ is purified to food or industrial grade, removing moisture, oil, and particulates. In South African facilities, strict quality control ensures CO₂ used for food, medical, and pharmaceutical purposes meets SANS and international standards, which is critical for maintaining hygiene and safety in transport.

In Practise: A Cape Town fishery uses purified CO₂ from a nearby ethanol plant to make dry ice, ensuring their seafood remains fresh for distribution across Gauteng.

Step 2: Compressing and Liquefying CO₂

Once captured, the CO₂ gas is compressed under high pressure (approx. 60 bar) and cooled to transform it into a liquid state.

• This liquid CO₂ is stored in insulated tanks to maintain its low temperature and high pressure.
• Temperature control is critical; if the liquid warms above -56.6°C at atmospheric pressure, it will revert to gas.

In industrial-scale production in South Africa, compression systems are designed to handle tons of CO₂ per day, supporting both local businesses and export needs.

Analogy: Think of the CO₂ gas as water vapor in the air — compression and cooling condense it into a liquid, just as humid air can condense into water droplets.

Step 3: Expanding Liquid CO₂ to Make Snow

The next step is the transformation of liquid CO₂ into solid snow, which is a precursor to dry ice blocks or pellets:

1. Liquid CO₂ is released through a nozzle into a low-pressure chamber.
2. Rapid expansion causes the CO₂ to cool dramatically.
3. This rapid cooling leads to the formation of CO₂ snow — tiny, flaky particles of solid carbon dioxide.

Technical insight: This process relies on the Joule-Thomson effect, where gas expansion results in temperature drop, turning the liquid into solid without passing through a liquid-solid interface like water ice.

Step 4: Compressing CO₂ Snow into Blocks or Pellets

The CO₂ snow is compressed into the desired form, depending on usage:

• Blocks: Large slabs of 10–50 kg are common for industrial cooling and bulk transport.
• Pellets: Small cylinders (typically 16–20 mm) are ideal for shipping perishable goods, creating a uniform layer in cooler boxes.

Compression is done with hydraulic presses in modern production facilities. The process is precise: too little pressure results in fragile dry ice, while excessive pressure can create brittle blocks that crumble during handling.

Practical African example:

• South African seafood exporters in Hout Bay often use pellets in 50-litre cooler boxes to pack fresh hake or snoek for delivery to Johannesburg, ensuring even cooling and minimal waste.
• Vaccine distribution networks in Namibia and Botswana rely on dry ice blocks for larger shipments, minimizing handling and temperature fluctuations.

Step 5: Storage and Handling

Dry ice must be stored in insulated containers because it sublimates at -78.5°C. Modern plastic dry ice storage containers offered by Dry Ice Africa provide:

• Durability for transport across rough African roads.
• Extended temperature retention, keeping products frozen for hours or days.
• Safe handling, reducing CO₂ gas exposure and preventing accidental burns.

Safety tip: Dry ice should never be stored in airtight containers because sublimation generates gas pressure that can cause explosions. Always handle with gloves and proper ventilation.

Step 6: Distribution to End Users

Once formed and packed, dry ice is transported to businesses across South Africa:

• Cape Town fisheries to Johannesburg and Durban
• Gauteng e-commerce food businesses for same-day delivery
• Rural health clinics for vaccine cold chain maintenance

African logistics often require consideration of ambient temperatures, transport time, and insulation efficiency. For example, in summer, South African ambient temperatures can exceed 35°C, making cooler box selection and packing density crucial.

Practical insight: Combining dry ice with insulated plastic containers can extend cold retention by 20–30%, reducing spoilage and improving efficiency in both urban and rural contexts.

Final Thoughts

Dry ice production is a carefully controlled process, turning industrial or natural CO₂ into a versatile cooling agent. From capturing gas to compressing it into blocks or pellets, every step is critical to ensure safety, quality, and efficiency.

For South African and African businesses, understanding the process helps optimize usage in:

• Seafood transport from coastal fisheries
• Agricultural supply chains delivering fresh produce
• Medical and pharmaceutical cold chains in rural clinics
• Industrial applications, such as cleaning and refrigeration

Choosing the right plastic dry ice storage containers ensures that your dry ice performs effectively, protecting both products and end users.

By appreciating the science behind dry ice, South African and African companies can enhance product quality, streamline logistics, and support food security and healthcare delivery across the continent.

You might also like our range of polystyrene containers and cooler boxes for sale.