When complex calculations have to be made, and when LCIs of other background databases have to be applied, it is important to understand the structure of the LCIs.
In practice, the lists of LCIs (Life Cycle Inventories) are never given “from cradle to grave” in these databases, since that is not practical because of the many variations of the total chain of one product. LCA practitioners compile a life cycle chain by combining the LCIs of the subsystems (as shown at the previous webpage Fast Track LCA, example of the truck + trailer)
A LCI of a subsystem comprises a list of “inputs” and a list of “outputs”.
Inputs are materials, heat, electricity and transport which are required in the system, as well as production processes and end-of-life processes. These data can be found in the Idemat excel files at webpage data
Most data on “inputs” in the Ecocosts 2017 LCA databases are “from cradle to gate” where the gate is in Rotterdam, unless it is obvious that it is otherwise (for Processing in the Production Phase, the Use Phase and the End of Life Phase).
There are two types of output:
- the emissions to air, water and ground; the eco-costs of these meissions can be found at the excel files “eco-costs 2022 midpoint tables” at webpage data
- the product or function of the subsystem, also called the “reference flow” (with the quantity and the dimension).
When electricity and/or heat is generated as a by-product (output) of the system, it is given as an negative input.
The are three types of LCIs:
- the LCI of the subsystem only (the Unit, U), i.e. from “gate to gate”; these are processes like drilling, welding, extrusion, molding. Processes in the Use Phase are also gate to gate (e.g. cooking, driving, transport)
- the LCI of a “cradle to gate” sub-system, including upstream subsystems of all inputs (e.g. materials, fuels, electricity and heat)