Handling multifunctional activities in the Brightway LCA software framework.
Multifunctional activities can lead to linear algebra problems which don't have exactly one solution. Therefore, we commonly need to apply a handling function to either partition such activities, or otherwise manipulate their data such that they allow for the creation of a non-singular, square technosphere matrix.
This library is designed around the following workflow:
- A multifunctional activity is created and saved to the database by a user. A multifunctional activity is any activity with multiple functional flows, either outputs (e.g. products) or input (e.g. wastes).
- The user provides a handling function of this activity, such as substitution, allocation, etc.
- When this database is processed, this library will apply the handling function, and create a square matrix for the database.
More functionality is planned; see limitations.
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LCA distinguishes processes and products. brightway introduces a new classification at the product level where products are either defined as goods or wastes. This classification is consistently maintained within a project, meaning that the same product cannot be classified as a good in one process and as a waste in another process. Or in other words, all intermediate flows of the same product carry the same classification (good OR waste).
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brightway determines functional flows based on the good/waste classification of the flows of a process. Functional flows are defined as process outputs that are goods and process inputs that are wastes.
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Adding a functional flow exchange will automatically create a new
productnode in the supply chain graph (if necessary). -
Multi-functional processes are handled by handler functions. Handler functions are mapped in
multifunctional.handler_mapping. This library provides a default set of handling functions (see below); users may also add custom handlers. -
When the database is processed, the handler functions are executed, and if necessary, virtual activities are created. The processed array will create a square matrix.
- Users specify products to be either goods or wastes when creating them the first time (this can be changed later, but may lead to changes in multiple processes):
product['waste'] = False. - Users need to specify which allocation method is to be used to resolve multi-functionality (e.g. economic allocation or substitution) and users need to provide the required data (e.g. prices or substitute product) so that multi-functionality can be resolved by one of the handlers.
Users give multifunctional activities a handler function label:
activity_instance['handler'] = 'some_handler_function_label'. Handler function labels are strings.
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This library currently only supports one handler for multifunctional activities. Support for variable handlers will be added in a later release.
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This library is not yet integrated with
bw2data- therefore, multifunctional activities must be manually converted:
import brightway2 as bw
import multifunctional as mf
mf.convert_multifunctional_activity(
activity=bw.get_activity(("some", "activity")),
handler="some_handling_function_label",
)- This library current only works with the default SQlite backend
Install via conda or pip.
Your contribution is welcome! Please follow the pull request workflow, even for minor changes.
When contributing to this repository with a major change, please first discuss the change you wish to make via issue, email, or any other method with the owners of this repository.
Please note we have a code of conduct, please follow it in all your interactions with the project.
BSD-3-Clause. Copyright 2020 Chris Mutel.