Allocating burdens to products

Calculating what share of the process inputs and emissions are allocated to each product.

In the FunctionalSqliteBackend, multifunctional processes use products and elementary flows (defined through technosphere and biosphere edges) and produce products (defined through production edges). In the end to create a square technosphere matrix, we need to allocate the inputs and emissions of the process to its product nodes.

For this FunctionalSqliteBackend expects that for each product the allocation_factor property is set to a numerical value. This value defines the relative share of the process inputs and emissions (burdens) that are allocated to this product.

Setting allocation factors

In the Activity Browser 3, there are multiple ways to set allocation factors for products:

• Equal burdens are distributed equally among all products.
• By property burdens are distributed according to a specific product property (e.g. mass, price).
• Manually you can set the allocation factor for each product manually.

You can choose from the available options in the Allocation dropdown in the header of the Process details. allocation_factor values are automatically updated when you select one of the options.

Using product properties for allocation

You can only use product properties for allocation if all the products of the process have the same property defined. For example, if you want to allocate by mass, all products need to have a mass property defined. If one or more products do not have the property defined, the option will not be available in the dropdown.

Allocation factors are calculated as such:

allocation_factor = property.amount / sum([property.amount for product of process])

Normalized properties

If you defined a product property with the normalize option enabled, the property value will be multiplied by the production amount of the product before being used for allocation. This is useful if you want to allocate by a property that is dependent on the production amount, e.g. price or revenue.

allocation_factor = (property.amount * product.amount) / sum([property.amount * product.amount for product of process])

Because most properties are defined as being a value per unit of product (e.g. price per kg), properties are normalized by default in bw-functional.