There is a lot of arithmetic in sustainability marketing and very little of it is shown. So rather than asserting a figure, this article builds it from component masses, states its assumptions, and then argues against itself.
Step one: the baseline
You cannot have a saving without a baseline, and the baseline has to be the honest one: manufacturing an equivalent new container from virgin material, cradle to gate. For a 275-gallon composite IBC that means four things.
| Component | Mass | Intensity (lb CO₂e/lb) | lb CO₂e | Share |
|---|---|---|---|---|
| HDPE bottle | 38 lb | 3.32 | 126 | 40.0% |
| Galvanised steel cage | 70 lb | 1.89 | 132 | 41.9% |
| Pallet base (weighted average) | 32 lb | 1.09 | 35 | 11.1% |
| Assembly and inbound freight | — | — | 22 | 7.0% |
| Total | 140 lb | — | 315 | 100% |
Resin intensity from supplier environmental product declarations; steel and galvanising from published mill figures; pallet weighted across plastic, steel and timber by our own intake mix.
The important structural fact here is that the steel cage carries slightly more embodied carbon than the plastic bottle. Almost everyone assumes the opposite, because plastic is the component people have opinions about. Drawing, cutting, welding and hot-dip galvanising a steel frame is an energy-intensive sequence.
Step two: what our own process costs
A saving is a net figure, so our own operation has to be inside the boundary. For a reused unit that means collection freight, handling, wash water heating, test energy, replacement fittings where fitted, and outbound freight.
| Activity | lb CO₂e | Basis |
|---|---|---|
| Inbound collection freight | 14 | Allocated across 48 units per trailer |
| Weigh, grading and handling | 3 | Utility billing, FY2024 |
| Wash water heating and pumping | 19 | Wash-line metering, net of 92% recirculation |
| Pressure test and compressed air | 2 | Test-rig run logs |
| Replacement valve, gasket, cap | 4 | Fitted on 61% of units; averaged |
| Outbound freight | 11 | Allocated across 48 units per trailer |
| Total | 53 | Per reused unit |
So: 315 lb avoided, 53 lb spent, giving a net saving of 262 lb CO₂e per reused tote. That is the number, and it is a subtraction rather than an assertion.
- 315lb
- Baseline, new unit
- 53lb
- Our process
- 262lb
- Net saving
Step three: the other two paths
Not every tote can be reused, so the model needs figures for the alternatives. Both are allocated against the same component table, which is the whole reason for building it that way.
Rebottling
A new bottle in a reclaimed cage and pallet. The bottle's 126 lb is spent again; the cage's 132 lb and the pallet's 35 lb are saved. Add our process at 139 lb — higher than reuse because a new bottle has its own inbound freight and moulding — and the net saving is 176 lb CO₂e.
Reprocessing
Granulation, hot wash and pelletizing. Here the container is gone, so the credit is the resin value only: 126 lb of displaced virgin HDPE, less our process cost of 73 lb, giving 53 lb. Note what has happened — reprocessing saves roughly one fifth of what reuse saves.
Recycling recovers the material. Reuse recovers the material and the manufacturing. Roughly 60% of a tote's carbon is in forming, welding and galvanising — processes recycling throws away and reuse keeps entirely.
Step four: amortisation across lives
The figures above price a single cycle, which understates the case considerably. Embodied carbon is a one-time cost spread across however many service lives the container delivers.
| Service lives | Embodied per trip | Plus process per trip | Total per trip |
|---|---|---|---|
| 1 (one-way, landfilled) | 315 lb | 0 lb | 315 lb |
| 2 | 158 lb | 53 lb | 211 lb |
| 4 | 79 lb | 53 lb | 132 lb |
| 6 | 53 lb | 53 lb | 106 lb |
| 12 | 26 lb | 53 lb | 79 lb |
| 19 (best observed) | 17 lb | 53 lb | 70 lb |
The curve flattens because our own process cost becomes the dominant term past about six lives. Beyond that point, the way to improve is to make the wash and the freight more efficient, not to extend the life further.
That flattening is one of the more useful things we have learned from running this model. Past roughly six reuses, extending service life further delivers diminishing returns, and the leverage moves to water heating efficiency and freight consolidation.
Where the model understates — three exclusions
All three of these work against us. They are excluded because we cannot measure them precisely enough to publish, not because they are not real.
- 01Avoided disposal freight. If your empties were previously going to a landfill or a broker, those truck miles disappear. We do not know your previous arrangement, so it is scored as zero.
- 02Avoided landfill methane and leachate management. Well documented in the literature and highly site-specific. Scored as zero.
- 03The subsequent lives. The headline figure prices one cycle. A tote that goes around six more times after this one delivers six more times the saving, and that is not in the number.
Where the model could be accused of overstating — three soft joints
The substitution ratio
We credit recovered HDPE as displacing virgin resin pound for pound. In reality recycled HDPE often substitutes at a discount because of quality constraints. Our flake is single-stream and hot-washed, which justifies a high ratio, but 1.0 is the top of the defensible range. A conservative reader should discount our reprocess figure by up to 20%.
The full-trailer freight assumption
Per-unit freight is allocated across 48 units. A six-unit pickup in a distant band carries far worse per-unit freight than our published figures imply. We do not currently publish a band-adjusted factor, and we should.
Service-life observation bias
Our observed service lives come from units that came back to us. Units that went out and never returned are invisible to the model. They may have been reused elsewhere; they may have been landfilled by a third party. We cannot distinguish the two, and we do not pretend to.
What to do with this
If you want a defensible number for your own reporting, take the 262 lb figure, multiply by the units you actually diverted, and cite the boundary and sources rather than the headline. If you want a conservative number, discount by 20% and drop the reprocess credit entirely. Either way, the arithmetic is reproducible, which was the point of writing it down.