Modular LCA approach

Using Modules (formerly called ‘Meta-Processes’) to model life cycle inventories enables:

• modeling life cycle stages based on unit processes from an LCI database
• linking modules to represent complete, possibly new life cycles
• efficient modeling of alternative life cycles
• efficient coupling of LCA and optimization

Modules

Modules can group several life cycle inventories into a single process.

Modules need to have:

• a name
• at least one product output with a user defined name
• at least one activity
• a scaling activity (determined autmatically)

Modules can have:

• additional processes forming the process chain
• multiple outputs
• multiple inputs; product inputs involve a cut-off

Data Format of Modules

Modules can be specified in the format shown below. It is used to define and store modules. All other properties are calculated based on this data, e.g. scaling of edges, LCA results, etc. using the methods of the MetaProcess class.

example_module = {
        'name': 'user defined module name',
        'outputs': [
            (key, 'user defined product name', user defined amount),
        ],
        'chain': [
            (key),
        ],
        'cuts': [
            (parent_key, child_key, 'user defined input product name', amount),
        ],
        'output_based_scaling': True,
}

Notes:

Keys:

• Keys are a tuple composed of two elements, where the first refers to the database and the second to the activity, thus (‘database name’, ‘module name or uuid’)

Output-based scaling:

• The default value is True. If set to False, the scaling activities will be scaled to 1.0 no matter how the product outputs are defined by the user. This can be used to

1. to create artificial outputs that are not part of the original dataset (the user needs to see whether that makes sense)
2. when ecoinvent 2.2 multi-output activities, as imported in brightway2, are used, as these don’t include the output products, which need to be manually defined.

Linked Modules

Linked Module Systems are created by combining modules based on their product inputs and outputs. As shown in the example, the product based linking allows to efficiently specify alternative supply chains.

A detailed description of the math behind modules, its application scope and examples are provided in the following paper (reference will be available soon).