How much CO₂ is really in a cylinder, and when to move to a tank
A 40-litre cylinder does not hold 40 kg. Here is how much CO₂ each size really carries, how many cylinders your consumption burns through, and the point where a tank starts to cost less.
«How many kilograms are in a 40-litre cylinder?» is one of the most common questions we get. The answer confuses people because a cylinder is measured in litres of water capacity, while the gas inside is sold by the kilogram — and the two numbers are not the same.
Litres of the shell, kilograms of the product
The number stamped on the neck — 10, 20, 40, 50 — is the water capacity of the steel shell, not the mass of CO₂. Carbon dioxide is liquefied under pressure, and the filling ratio is limited by the cylinder's test pressure: roughly 0.6 to 0.75 kg per litre. Overfilling is dangerous, so a filling station will never give you «40 kg in 40 litres».
| Cylinder (water capacity) | CO₂ mass | Gas released | Gross weight |
|---|---|---|---|
| 10 l | 6–7 kg | 3.2–3.8 m³ | ~22 kg |
| 20 l | 12–14 kg | 6.5–7.6 m³ | ~40 kg |
| 40 l | 24–28 kg | 13–15 m³ | ~85 kg |
| 50 l | 30–35 kg | 16–19 m³ | ~105 kg |
Two practical consequences. First, when you compare supplier quotes, compare the price per kilogram of CO₂, not per cylinder. Second, one or two kilograms always stay in the cylinder as an unusable heel and go back to the filler — you paid for gas you never used.
How many cylinders your production actually burns
Take a 40-litre cylinder at 24 kg as the working unit and divide your monthly consumption by it. The result is usually higher than people expect.
| Consumption | Cylinders per month | Swaps per week | What it means in practice |
|---|---|---|---|
| 100 kg | 4 | 1 | Cylinders are comfortable |
| 500 kg | 21 | 5 | Still workable, storage starts to hurt |
| 1 t | 42 | 10 | Two swaps every working day |
| 3 t | 125 | 29 | A dedicated person on cylinders alone |
| 10 t | 417 | 96 | Only a stationary tank makes sense |
At around one tonne a month the logistics stop being background noise. Someone rolls cylinders, someone signs delivery notes, the line stops while a cylinder is being changed, and the yard permanently holds two sets — full and empty.
The costs that never appear on the invoice
- The heel: 1–2 kg per cylinder, which is 4–8% of the contents.
- Manual handling. A full 40 l cylinder weighs about 85 kg and must be moved, secured and connected.
- Downtime at every swap, multiplied by the number of swaps.
- Deposit or rent on the cylinder fleet, plus the space to store two sets of them.
- Pressure drop at the end of a cylinder, which shows up as unstable process parameters before anyone notices the cylinder is empty.
What the next step looks like
For nitrogen, oxygen and argon the intermediate format is a cryogenic cylinder: a vacuum-insulated vessel of 180–500 litres that holds liquefied gas and replaces a whole pack of pressure cylinders — see cryogenic cylinders. For CO₂ the usual next step is a stationary tank from 10 m³, which holds about 9.5 tonnes and is refilled by road tanker.
| Format | Typical consumption | Inside | Servicing |
|---|---|---|---|
| 40 l cylinders | up to 300 kg/month | gas under 50–60 bar | manual swap |
| Cryogenic cylinder 180–500 l | 0.3–1.5 t/month | liquefied gas | swap every 1–3 weeks |
| Stationary tank 10–30 m³ | from 2 t/month | 9.5–29 t of liquid | tanker refill on schedule |
How to find your own break-even point
- Pull the delivery notes for the last three months and add up the kilograms, not the cylinders.
- Divide the total invoice by those kilograms — that is your real price per kilogram, heel included.
- Add the hours your staff spend on swaps and the cost of the downtime around them.
- Compare the result with a tank: bulk CO₂ delivered by tanker is normally two to four times cheaper per kilogram.
In most cases the arithmetic turns at somewhere between one and two tonnes a month. Below that, cylinders win on simplicity; above it, a 10–20 m³ tank pays for itself in a year or two on the price of gas alone.
Frequently asked questions
Why does a 40-litre cylinder hold only 24 kg?
Because litres describe the volume of the shell and kilograms describe the liquefied CO₂ inside it. The filling ratio is limited to roughly 0.6–0.75 kg per litre so that the liquid has room to expand when the cylinder warms up. A cylinder filled to the brim would build dangerous pressure on a hot day.
Can we fill our own cylinders from a stationary tank?
Technically yes — it needs a filling ramp, a pump and cylinder weighing. Legally it is a separate activity with its own permits, personnel training and cylinder inspection records. For most producers it is simpler to keep bulk supply for the process and buy the few cylinders they still need.
You may also need
Cryogenic tanks for liquid CO₂ (carbon dioxide) 10–100 m³
Cryogenic tank for liquid CO₂ 10 m³
Model: CT-CO2-10
Stationary vacuum-insulated cryogenic tank for storing liquid CO₂ (carbon dioxide), geometric volume 10 m³. Supplied with valves, pressure control, vaporizers and a pressure-reducing unit; turnkey installation available.
Price on request
Made to order
Cryogenic tanks for liquid CO₂ (carbon dioxide) 10–100 m³
Cryogenic tank for liquid CO₂ 20 m³
Model: CT-CO2-20
Stationary vacuum-insulated cryogenic tank for storing liquid CO₂ (carbon dioxide), geometric volume 20 m³. Supplied with valves, pressure control, vaporizers and a pressure-reducing unit; turnkey installation available.
Price on request
Made to order
Cryogenic cylinders for liquid nitrogen (LIN, N₂)
Cryogenic cylinder for liquid nitrogen
Model: CC-N2
Portable vacuum-insulated cylinder for storing liquid nitrogen (LIN, N₂) with gas or liquid withdrawal. Volume, working pressure and configuration are selected for your process.
Price on request
On request
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