We Re-Ran Our Carbon Numbers and They Went Down
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We had assumed one reconditioned tote displaces exactly one new tote. A procurement analyst pointed out that some buyers would have bought nothing, or drums, or a cheaper unit elsewhere. Accepting a more conservative substitution rate cut the headline per-unit figure, so that is the figure we publish.
In February a procurement analyst at a food processor we supply sent us a two-page note about our carbon claim. It was polite, specific and correct, and it is the most useful thing anybody has sent us about our own sustainability reporting.
The argument was about one word: substitution.
What we had been claiming
Our published figure was an avoided-emissions number. Reconditioning a 275 gallon IBC rather than manufacturing a new one avoids a quantity of carbon dioxide equivalent, and we multiplied that per-unit figure across every container we had processed.
The per-unit arithmetic is straightforward enough to audit. A new unit is roughly 164 lb CO₂e cradle-to-gate: about 68 lb for the HDPE resin, 9 lb for blow-moulding, 100 lb for the galvanised cage, 14 lb for forming and galvanising, 38 lb for a steel pallet, 5 lb for assembly and testing, less end-of-life recovery credits for the steel and the polymer.
A reconditioned unit is roughly 93 lb: the wash energy, the caustic production, yard handling, replacement hardware, facility overhead, plus a pro-rata share of the original manufacture amortised across the service lives the cage will deliver.
So 164 minus 93 is 71 lb avoided per container. That was the number on our website.
The challenge
The note made a simple point. The 71 lb figure assumes that every reconditioned tote we sell prevents the manufacture of exactly one new tote. A substitution rate of 1.0.
That is the standard convention in this kind of accounting, and it is also optimistic. Some share of our buyers, in the absence of a cheap reconditioned unit, would have:
- Bought nothing, and made do with drums they already owned.
- Bought drums instead, which has its own and different footprint.
- Bought a reconditioned unit from somebody else, in which case we displaced a competitor's sale rather than a factory's output.
- Delayed the purchase indefinitely, because the project was marginal at a new-unit price.
Every one of those cases means the avoided emission is less than 71 lb, and the fourth case means it is close to zero.
What we did about it
We could have argued. The convention is on our side, every life-cycle study in this space uses it, and nobody audits a used-container dealer's carbon page. Instead we did two things.
First, we ran the figure at a range of substitution rates so we could see how sensitive the answer was. It is very sensitive — substitution is by far the biggest lever in the whole calculation, larger than the emission factors, larger than the number of assumed service lives, larger than anything to do with the wash line.
| Substitution rate | Avoided CO₂e per unit |
|---|---|
| 1.00 (every sale displaces a new unit) | 71 lb |
| 0.95 | 66 lb |
| 0.90 | 63 lb |
| 0.85 | 60 lb |
| 0.80 | 56 lb |
| 0.70 | 49 lb |
Second, we changed what we publish. The headline figure is still quoted at the convention, because that is what makes it comparable with other people's numbers, but it now carries a stated range of 58 to 84 lb and a link to the method — including an explicit paragraph naming substitution as the weakest assumption and showing the table above.
Why publish the method rather than the number
Because a number without a method is a claim, and claims in this area are routinely inflated by a factor of two or three. Once the arithmetic is on the page, a customer can argue with a specific line rather than with our marketing. We have had the workbook challenged twice now — once on substitution and once on the end-of-life credit method — and on both occasions the figure went down.
That is slightly uncomfortable and entirely the point. A sustainability figure that only ever moves upward is not a measurement.
What did not change
The ordering. At any substitution rate between 0.7 and 1.0, reconditioning avoids roughly three times what recycling and remoulding does, because recycling spends granulation, flake washing, drying, pelletising and moulding energy and then displaces virgin resin at less than one to one. The ratio is robust even when the absolute figure is not.
Which is the only conclusion we actually need our customers to believe: save the form first, and destroy the material only when there is nothing else left to do with it.
740 words · published 30 May 2023 by Marguerite Okonkwo, Operations lead at IBC Tote Market LLC. We correct posts rather than quietly deleting them; if something here is wrong, tell us and we will say what changed.