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Comparative LCA Model

Assessment model — instantiates Rebound-Aware Efficiency Governance

Models the full physical resource burden — embodied, operating, replacement, end-of-life — of an efficient option against its counterfactual, per unit of service, so a smaller operating footprint isn't bought with a bigger hidden one.

A Comparative LCA Model traces the physical resource flows of an option across its whole life — raw materials, manufacturing, operation, replacement, end-of-life — and sets them beside the same accounting for a counterfactual option, all normalized to one unit of service. Its purpose in this archetype is to catch burden-shifting: an efficiency improvement that cuts the operating footprint can quietly enlarge the embodied or disposal footprint, so the "greener" option is only greener in the stage you happened to look at. By fixing a system boundary and a functional unit and comparing scenarios stage by stage, it makes the net lifecycle burden visible. Unlike full-cost accounting it works in physical units — energy, water, materials, emissions — not money; and unlike a monitoring dashboard it is a forward-looking, design-time comparison, not a live readout of what is actually happening.

Example

A fleet buyer compares an electric delivery van against a diesel one. At the operating stage the electric van wins handily. But the model, following the lifecycle stages of the ISO 14040 framework, adds the columns the operating figure omits: battery and vehicle manufacturing (embodied energy and materials), the grid mix that charges it, and end-of-life recycling — all normalized to one functional unit, say a tonne-kilometre of delivery over the vehicle's service life. Against the diesel counterfactual the electric van still comes out lower over the full life, but the crossover only arrives after a break-in distance, because it starts with a larger embodied debt to work off. That comparison — not the flattering operating number — is what tells the buyer the efficient option is genuinely better, and after how long it becomes so.

How it works

The model's discipline is comparison on a fixed basis. It draws a system boundary that fixes which lifecycle stages are counted, picks a functional unit so that two options delivering the same service can be set side by side, inventories the physical flows at each stage, and reports the difference between the efficient option and its counterfactual. The whole result hangs on those two upfront choices — boundary and functional unit — because they decide what is compared and against what. Get them honest and the embodied debt that efficiency stories skip becomes plain; get them convenient and the model will confirm whatever was wanted.

Tuning parameters

  • System boundary — cradle-to-gate, cradle-to-grave, or something between. Extending the boundary to disposal is exactly what surfaces end-of-life burden-shift.
  • Functional unit — the unit of service everything is normalized to. Choose it loosely and two options that don't deliver the same service get compared as if they did.
  • Impact categories — which physical burdens are tracked (energy, water, materials, emissions, land). Tracking one can hide a shift into another.
  • Data source and quality — primary measurements versus generic database averages. Cheap data widens the uncertainty the comparison can bear.
  • Allocation method — how burdens shared across co-products are split. A defensible comparison states its allocation rule rather than burying it.

When it helps, and when it misleads

Its strength is catching burden-shift before a decision is locked in: it grounds the comparison in physical reality, forces a functional unit so the options are truly apples-to-apples, and surfaces the embodied debt an operating-only efficiency claim ignores. When the question is whether an efficient design is genuinely lighter over its whole life, this is the tool that answers it.

It misleads when the boundary or functional unit is drawn to suit. Both choices swing the result, so the same two options can be made to trade places by an analyst who wants them to.[1] Data gaps widen the honest uncertainty; tracking too few impact categories lets a burden slip from a counted column into an uncounted one. And crucially, an LCA models the product, not the market — it says nothing about the induced demand a cheaper efficient option unleashes, which is the behavioral rebound this archetype most fears. The classic misuse is to gerrymander the boundary or unit until the preferred option wins. The discipline is a transparent boundary with sensitivity analysis, adherence to a recognized standard, and pairing the physical model with a demand-side rebound estimate for the part it cannot see.

How it implements the components

  • lifecycle_scope_boundary — the model's defining act is drawing the system boundary that fixes which lifecycle stages are counted.
  • service_output_and_functional_unit — it normalizes every option to one functional unit of service, the basis that makes a comparison legitimate.
  • baseline_and_counterfactual_measure — it compares the efficient option against an explicit counterfactual scenario, reporting the difference rather than an absolute.

It works in physical units and does not monetize the burdens into a cost ledger — that is Full-Cost Accounting, which consumes this model's flows — nor does it track live use over time, which is Resource Monitoring Dashboard.

References

[1] Burden shifting is the LCA term for a change that reduces one impact (or lifecycle stage) while increasing another — cutting operating energy at the price of higher embodied energy, say. Catching it is the reason an assessment spans the whole life and multiple impact categories rather than optimizing a single stage. ↩