# Regionalization in Brightway2¶

bw2regional is a separate library that extends the Brightway LCA framework to do regionalized LCA calculations.

It is easy to do regionalized LCA incorrectly. This package tries to make it at least a bit easier to do regionalization correctly, for at least some definitions of correct.

bw2regional supports the following regionalization calculations:

1. Inventory database and impact assessment method share the same spatial scale (Shared spatial scale)
2. Inventory and impact assessment have different spatial scales (Two spatial scales)
4. Inventory and impact assessment have different spatial scales, with extension tables used as a third spatial scale to allocate impact assessment units to inventory units.

In addition to making regionalized LCA calculations, maps of regionalized impact can be exported from methods 2-4.

Each separate spatial scale is stored as a geocollection. The relationships between spatial scales (i.e. how much area of unit a in spatial scale 1 intersects unit b in spatial scale 2) is stored as an Intersection. Areal intersection calculations are done using the separate utility pandarus, a library for matching spatial data sets and calculating their mutual intersected areas. Impact assessment methods store characterization factors per biosphere flow and spatial unit. Each organization unit is described in more detail below.

bw2regional is part of a family of software libraries - see Regionalization libraries for more information.

# Lifecycle of a regionalized LCA calculation¶

A new project is created, and bw2setup() is run. Background databases are imported, and some foreground data in added. bw2regionalsetup() is run (see Base data needed for regionalized calculations for more information), and the function fix_ecoinvent_database() is run for each inventory database which uses ecoinvent-specific location codes.

A regionalized LCIA method is chosen. One or more geocollections are created for the LCIA method, including specifying filepaths to the raster or vector datasets which define these geocollections and characterization factors. Regionalized characterization factors are imported from the spatial datasets using the function import_regionalized_cfs().

Most of the time, a third spatial scale is created, either a Loading or ExtensionTable. This third scale defines activity intensities within the larger inventory locations. Another geocollection is created for this third spatial scale, which includes specifying another spatial data file.

A functional unit for analysis is chosen, and the function check_needed_intersections() is called to get all necessary Intersection datasets. Most of the time, some intersections will need to be calculated, and the method remote.get_needed_intersections() can be called to do all necessary GIS calculations remotely. This step may take some time.

Finally, an LCA object is created. Depending on the study, and whether a third spatial scale was added, this will be an instance of OneSpatialScaleLCA, TwoSpatialScalesLCA, TwoSpatialScalesWithGenericLoadingLCA, or ExtensionTablesLCA. Regionalized results can be summarized numerically, or exported to maps using methods like write_results_to_ia_map(), write_results_to_inv_map(), and write_results_to_xtable_map().

# Project setup¶

Please run the utility function bw2regionalsetup() in each new project that will do regionalized LCA calculations.

Any version of ecoinvent will need to be processed with the utility function fix_ecoinvent_database("some ecoinvent database name"). This function will do the following:

• Convert any Rest-of-World locations into actual world regions and subsequently relabel them.
• Relabel any ecoinvent-specific locations names to place them inside the ecoinvent geocollection.

# Spatial scales (geocollections)¶

A geocollection is a container for a set of locations. For example, the world geocollection contains a political version of the world, while other geocollections could list the watersheds or ecoregions of the world. A geocollection can be as simple as just a name, but if you want to be able to export maps or import characterization factors, the following fields should be provided:

• filepath: The absolute filepath to the vector or raster dataset.
• field: The unique field that identifies each feature, e.g. name for countries.
• layer: The name of the layer. Only needed for vector datasets with more than one layer.
• encoding: The text encoding. Only needed for shapefiles.
• vfs: For shapefiles stored in zip archives, this is the virtual file system string, e.g. vfs="zip:///path/to/file/ne_50m_admin_0_countries.zip". Note that with a vfs, you must spcify the filepath within the zip archive, e.g. filepath="/ne_50m_admin_0_countries.shp". See also the fiona manual.

Example creation of a geocollection:

from bw2regional import *
geocollections['water cfs'] = {'filepath': '/my/favorite/directory/some-raster-dataset.tiff'}


## Default geocollections¶

The setup function bw2regionalsetup creates the following geocollections:

• world: All countries in the world, as well as the global location GLO, which has no spatial definition.
• ecoinvent: Ecoinvent-specific locations, including UN regions and subregions, composite geographies, and other ecoinvent-specific locations. See the ecoinvent geography report for more information.

## Topocollections¶

For performance reasons, calculations done using large-scale and overlapping geocollections can be split into many smaller topological faces. Brightway2-regional will perform such splitting automatically for calculations using most LCI databases. See the technical documentation for more details.

# Intersections¶

An Intersection is a dataset that shows the areal intersections between the spatial units of two geocollections. For example, if the world geocollection had the location “Netherlands”, and the watersheds geocollection had the location “Rhine watershed”, then the intersection (“world”, “watersheds”) would include the line ((“world”, “Netherlands”), (“watersheds”, “Rhine watershed”)): 423.7, though this number is made up. Areal intersections can be calculated using whatever GIS software and projection that you want, but brightway2-regional is designed to work seamlessly with pandarus, which can quickly and painlessly do these areal intersection calculations and write data in a data format brightway2-regional understands.

An Intersection object does not have its own name, but rather is defined by the two geocollections which are intersected.

pandarus /Users/somebody/some-raster.tiff /Users/somebody/some-shapefile.shp --field2=name foo.bar


This would create the file foo.bar.json.bz2.

Example import of pandarus output data:

Note

You should create the geocollections first before creating an Intersection between them.

from bw2regional import *
geocollections['some-raster'] = {'filepath': u'/Users/somebody/some-raster.tiff'}
geocollections['some-shapefile'] = {
'filepath': u'/Users/somebody/some-shapefile.shp',
'field': 'name'
}
Intersection(('some-raster', 'some-shapefile')).import_from_pandarus('foo.bar.json.bz2')


Contents:

# Development¶

bw2regional is developed by Chris Mutel, previously during his work as a postdoctoral assistant in the Ecological Systems Design group at ETH Zürich, and currently as a scientist in the Technology Assessment group at the Paul Scherrer Institute.

Source code is available on bitbucket.