Manufacture the spare part here or bring it from far away: the full cost

The argument is often told like this: manufacturing a spare part locally instead of bringing it from the other side of the world saves on transportation, and is therefore more sustainable. That's true, but it's a small part of the story.

It's worth telling the whole story, among other things because the larger part is even more favorable, and because saying it wrong gives ammunition to anyone who wants to dismantle it.

Why transportation isn't where the savings are

metal part weighing a few kilograms that travels by ship has a modest transport footprint compared to manufacturing it: melting, machining, or forging consumes far more energy than moving the finished product. If it travels by plane, the calculation changes considerably, and urgent spare parts are flown precisely because they are urgent—but they still don't represent the bulk of the production.

The bulk of it is in three places that are rarely discussed:

1. What is manufactured but never used. The classic spare parts model involves manufacturing a large batch because the tooling requires it, and then storing it. Part of that batch is never used and ends up as scrap metal twenty years later. Its entire footprint—materials, energy, transportation, storage—was for nothing. Manufacturing on demand doesn't reduce it: it eliminates it.

2. The warehouse. Storing items for years incurs ongoing environmental and economic costs: climate-controlled space, management, inventory, insurance, and obsolescence. It doesn't appear in any comparisons of footprint per item, yet it's there all the time.

3. Tooling. A mold or tooling for manufacturing fifty units has its own footprint, and this footprint is distributed among those fifty units. Without tooling, this footprint disappears—it's the same logic that makes additive manufacturing more advantageous for short production runs, explained in print or machine.

And the part that nobody includes in the environmental account

The plant is shut down. When a machine stops waiting for a spare part that takes eight weeks, not only is production lost: it's often compensated for with overtime, emergency production at another plant, or an urgent shipment by air. All of this leaves a trace that is attributed to another batch and that would not have existed if the part had arrived in three days.

It is the same economic argument of the distributed manufacturing of spare parts, viewed from the other side.

Where additive induction loses, plainly

It doesn't always win, and it's good to know when:

Additive manufacturing loses when	Because
The replacement part is a standard catalog item	A standardized bearing or screw is mass-produced with a very small unit footprint. Printing it doesn't make sense
Many identical units are needed, already	Mass production dictates
The part is simple and large	Cutting and welding sheet metal consumes less energy than melting powder layer by layer
The powder comes from far away	The material footprint has moved, not been eliminated. The powder also travels

That last point is crucial to remember before boasting about local production: manufacturing locally with powder brought from afar is only half local manufacturing. It's one of the reasons why working with powder obtained from metal waste makes sense, and why the origin of each batch matters.

How to calculate without cheating

If a number must be entered, these are the items that should appear in the two columns, and the most frequent mistake is forgetting the last four:

Material, including the energy used to manufacture the powder or raw material.
Manufacturing energy: machine, inert gas, treatment furnaces.
Post-processing and machining.
Actual transportation, including the means of transport.
Rejects: items that were not manufactured correctly.
Overproduction: the portion of the batch that will not be used.
Storage during the spare part's lifetime.
Avoided downtime, when it can be estimated.

With the eight, the comparison is honest. With the first four, the result is defensible at a fair, but not in an audit.

In summary

Manufacturing spare parts locally and on demand almost always wins, but not primarily because of transportation: it wins because it eliminates overproduction, warehousing, tooling, and downtime. This is a stronger argument than the "zero-kilometer" approach and holds up much better under scrutiny.

The rest of the sustainability approach is in is 3D printing metal sustainable?, and what happens to the leftover powder is in reuse and disposal.

If you have a candidate part in mind, the quote calculator gives you the order of magnitude without you having to send us anything.