Your figures
Association figure: 60 to 180 cycles over 10 to 30 years, arithmetically two to six per year. In our experience that is more of a lower limit – what matters is how far the keg travels.
How long the keg stays in your fleet before it is retired. In our refurbishment shop, vintages from thirty years ago are routine – kegs are rarely retired because of age.
The share of kegs that comes back from a cycle – the most sensitive value in this calculation. Permanent marking raises it: a keg you can see the owner of usually finds its way back.
One way. The keg travels it twice – out full, back empty.
Break-even point 38 uses, distance threshold 245 km.
Why there are no kilograms of CO₂ here
It would be easy to turn these inputs into a figure in kilograms of carbon dioxide. It would also be wrong. A sound figure would need manufacturing data for the specific keg, the electricity mix at the place of manufacture, the actual cleaning media and a comparison container with the same system boundaries. We have none of that.
What we do have are two published life cycle assessments with clear threshold values. You can hold your own figures against those – and that is exactly what this calculator does. It tells you which side of the threshold you are on, not how many kilograms you save.
The three thresholds in detail
- 15 to 20 cycles – break-even point against single-use plastic according to a simplified assessment from 2013, prepared on behalf of a keg manufacturer and expressly not ISO-compliant.
- 38 cycles – the same point according to a reviewed study from 2022 for the Swedish market.
- Around 60 cycles – break-even point of the same study against plastic containers in a closed recycling loop.
The return rate is not a side issue
The formula behind it is not an estimate but probability theory: if a keg comes back from each cycle with probability r, it reaches on average 1 divided by (1 minus r) cycles. No more is possible, however durable the steel is.
| Return rate | average cycles | enough? |
|---|---|---|
| 90 % | 10 | below all three thresholds |
| 95 % | 20 | above the mildest only |
| 97 % | 33 | below the reviewed figure |
| 98 % | 50 | above two of three |
| 99 % | 100 | above all three |
From 95 to 99 per cent is four percentage points – and a factor of five in service life. That is why returns are not a service in this industry but the business itself.
The method comes from a study on reusable take-away packaging. The formula itself is format-independent; applying it to kegs is our analogy and not a statement of that study.
Six fillings a year is not much
The association range of two to six cycles a year is an average across everything – and averages hide exactly what matters here: distance decides the cycle speed, not the keg.
Anyone selling within sight of the church tower turns their fleet far more often. The keg goes out in the morning, is empty within the week, and does not sit around somewhere for weeks. Conversely, in export business one to two cycles a year is the rule – that is how the technical literature on keg inspection describes it, and it matches what we see.
The difference is a factor of five to ten. A keg that takes three times as long for one cycle still ages by the calendar but collects only a third of the fillings. That is why the default here is set to eight and not to the association average: for regional sales six is too low, for export even two is still optimistic. Set the slider to your own situation.
Thirty years is not an outlier
The default setting of this calculator is twenty years, and that is already cautious. In our refurbishment shop, kegs with vintages from the eighties and nineties are routine. They do not come in because they are finished, but because they are due – and afterwards they go back into circulation.
After a complete overhaul such a keg looks almost like new. Our view is that it can do the rounds for another thirty years. That is an observation from day-to-day operations, not a study – but it is an observation on thousands of kegs.
It is backed up by the manufacturer side: a German manufacturer gives a thirty-year warranty on the tightness of all weld seams and on corrosion protection, on condition that the kegs are maintained every seven years. What matters here is what that commitment does not cover: it applies to weld seams and corrosion protection, not to the whole keg with all its wear parts. Spear, seals and springs are not included.
What actually kills a keg: frost
The most common reason why an otherwise healthy keg has to be retired is not wear but a winter. If liquid residues remain in an empty keg and it stands outside in the yard in heavy frost, the bubble freezes up.
The ice expands, the container expands with it – and does not go back. The capacity of the keg has changed as a result. Such a keg normally has to be retired, and you cannot always see the damage from the outside.
Prevention costs nothing: store empties fully drained and protected from frost. That is the single most effective measure for the service life of a fleet – more effective than any material decision.
Do not throw away retired kegs
If you have kegs sorted out: get in touch before they go to the scrap dealer. We look them over and save what can be saved – often more than a first glance suggests. Whatever really is beyond repair we recycle as stainless steel scrap at a fair rate. Both are better than giving the difference between material value and residual value away to the smelting furnace.
The distance that few people mention
The second finding of the reviewed study speaks against the steel keg, and that is why it is here: from a distribution distance of around 245 kilometres the single-use container can become the better choice in terms of greenhouse gases. Against plastic in a closed loop the threshold drops to around 150 kilometres.
The reason is mundane: six kilograms of empty weight travel along, and twice at that. The single-use container weighs a sixth and travels once. Every extra kilometre penalises the reusable system twice.
That is not an argument against the keg but one for short distances. Reuse is a regional system. Anyone exporting draught beer over long distances should not justify it with the life cycle assessment – the data does not support that.
What this calculator cannot do
- It gives no kilograms of CO₂, because the basis for that is missing.
- It does not calculate a German life cycle assessment – there is none. Both underlying studies concern other markets.
- It does not know your return rate. If you do not measure it, the slider is an assumption and not a result.
- It does not account for refurbishment. What a complete overhaul saves compared with a new keg is not modelled in either study – presumably in favour of the reconditioned keg.
If you do not share the assumptions: all four sliders are yours. Change them and see what happens – that is the actual purpose.