Structural elements
Motherboards, casing, assembly, auxiliary boards and other residual parts are often poorly documented, but omitting them can understate equipment impacts. This chapter defines how to complete a partial inventory without duplicating known components.
Characteristics
| Characteristic | Unit | Treatment | Purpose |
|---|---|---|---|
| Host equipment | Category | Documented archetype | Phone, laptop, desktop, server, switch |
| Inventory detail | Coverage | Explicitly assessed | Basis for the completion approach |
| Casing mass / class | g or kg | Unknown if unavailable | Support a compatible material estimate |
| Auxiliary assemblies | Count / configuration | Documented archetype if necessary | Complex equipment coverage |
| Uncovered residual | Defined inventory or share | Explicit assumption | Contributions omitted by the component model |
Modelling principle
The aim is transparent coverage rather than artificial precision. More detailed real data take precedence over a default residual when compatible.1
| Available evidence | Model representation |
|---|---|
| Mostly known inventory | Residual factor covering missing parts only. |
| Less complete configuration | Structural archetype matching the equipment family. |
Embodied impacts
Calculation
The residual derives from a documented equipment/category factor, or from a compatible complete inventory minus known components.
Subtraction is valid only when configuration, lifecycle stages, units and characterisation methods match. A negative residual should trigger a consistency review; arbitrarily clipping it to zero or interpreting it as an environmental credit would lack justification.
When data are missing
An inventory limited to major components may omit the casing, motherboard or assembly. A grouped estimate of these missing parts can complete the calculation only when its coverage is precisely known.
| Situation | Fictional example |
|---|---|
| Starting information | A laptop’s CPU, RAM and SSD are already counted. Its casing and motherboard are not. |
| Selected reference | A documented estimate covers the casing and motherboard, excluding CPU, RAM and SSD. |
| Calculation inputs | This estimate is added to the known components. A factor for a complete laptop would not be suitable: it would count the CPU, RAM and SSD again. |
If the additional estimate’s contents are unknown, adding it is not justified. Remaining gaps and the selected reference appear in the assumptions register.
End of life
End-of-life impacts are not necessarily isolated for structural parts. Their coverage in the selected equipment or component inventory determines any remaining gap.
Operational impacts
- Passive parts
- Casing and other passive parts have no autonomous electricity consumption.
- Active assemblies
- Boards, auxiliary electronics and conversion losses contribute to equipment consumption.
These contributions are often included in a complete equipment power measurement. Whether a separate term is required depends on equipment type, the existing measurement boundary and components already counted. A complete wall measurement already includes residual power.
Allocation and annualisation
Structural parts follow the host equipment's retained lifetime and service-sharing rules. See Allocation and sharing. A separately replaced assembly needs its own replacement assumption.
Assumptions and limitations
Working assumptions
An explicit, justified residual is preferable to silent omission. Structural contributions belong to the equipment inventory and inherit its allocation. Their evidence quality depends on available configuration data.
Known limitations
Boards and auxiliary assemblies are not uniformly documented. The principal risk is combining a complete archetype with a component sum that covers the same parts. A residual's uncertainty cannot be inferred merely from its percentage of the total.
Improvements
Reusable reference models require residual factors documented by equipment class, linked to complete product inventories and calibrated at compatible boundaries. A standalone validated structural simulator is not claimed here.
Interactive example
The structural residual adds only items not already covered by inventoried components. The example varies this residual and shows its share of the equipment and annual allocation.
Applications
Equipment modelling, terminals, and servers with partial inventories.