How to choose the volume of a CO₂ storage tank

An oversized tank ties up money and vents product through the safety valve. An undersized one stops the line when the tanker is late. Here is how to find the middle.

Tank volume is not a case of «the bigger the better». An oversized vessel costs more, takes longer to pay back and, at low turnover, vents product through the safety valve. An undersized one turns into constant calls to the supplier and a stopped line whenever a delivery is late.

Three figures to start from

• Average daily consumption in kilograms or tonnes.
• Peak daily consumption — season, extra shift, bottling campaign.
• The delivery interval your gas supplier can realistically hold.

The working rule: the tank should hold one and a half to two full deliveries. A road tanker in Ukraine brings roughly 20–24 tonnes, so a 30 m³ tank takes a full tanker and still leaves a working reserve.

From cubic metres to tonnes

Liquid CO₂ is stored at about −20 °C with a density near 1.03 t/m³, and tanks are filled to 90–95% of geometric volume. In round numbers: 10 m³ is about 9.5 tonnes, 30 m³ about 29 tonnes, 50 m³ about 48 tonnes. Manufacturer data sheets show more: the ZVT 30 at 29.55 m³ is rated at 30,965 kg. The maker counts colder, denser liquid (about 1.1 t/m³) at 95% fill; at a storage pressure of 18–22 bar the liquid is warmer, so plan for 5–8% less than the rated figure.

Typical configurations

• 3–6 m³ — a small brewery or bottling line moving from cylinders to liquid CO₂.
• 10–20 m³ — brewery, small bottling line, greenhouse of one to two hectares.
• 30 m³ — beverage plant, food producer, greenhouse complex. The most common choice.
• 40–60 m³ — large production, dry ice workshop, greenhouse complex, several consumers at once.
• Several 50–60 m³ tanks — CO₂ distributors and large greenhouse complexes; for one greenhouse business we installed four 60 m³ tanks.

What else changes the answer

• Boil-off. A vacuum-insulated tank loses roughly 0.15–0.3% per day. At low turnover an oversized tank simply vents gas you paid for.
• Peak demand is covered by the vaporizer, not by the tank. A 50 m³ tank with a 130 kg/h vaporizer will not save a line that needs 400 kg/h.
• Site constraints: space for the foundation, safety distances and access for a tanker.

A worked example

A beverage plant uses 12 tonnes of CO₂ a month, evenly across the month, and the supplier delivers once a week. Weekly demand is about 3 tonnes, so in theory a 5 m³ tank would do. In practice we would put in 20–30 m³: the supplier will not drive a tanker for three tonnes at a reasonable price, and a full delivery has to fit somewhere. The tank is chosen by the economics of delivery, not only by consumption.

Mistakes we see most often

• Sizing by average consumption while the plant works in campaigns. Two weeks of bottling at triple rate empty a tank that looked comfortable on paper.
• Forgetting the vaporizer. The tank is generous, the vaporizer is minimal, and the line starves at peak.
• Choosing volume before agreeing delivery logistics with the gas supplier. Their minimum shipment often decides the answer.
• No reserve for growth in the piping and foundation, so the next step means rebuilding the whole site rather than swapping the vessel.

Send us your monthly consumption and delivery schedule — we will size the tank and vaporizer and show the calculation, free of charge.