Calculation and results

After you've completed the modeling of your processes, created your product system, it's time to run a calculation.

For demonstration purposes, we create a calculation setup for a product system of an ecoinvent process and run it.

Getting an impact method

The impact method can be retrieved from the database using the db.getForName method:

method = db.getForName(ImpactMethod, "EF v3.1")

The calculation of a product system is done by creating a calculation setup and running the calculate method of the SystemCalculator. The calculation setup is an object that contains all the information needed for the calculation:

the target product system or process,
the amount of the functional unit,
the LCIA method,
the normalization and weighting sets,
the parameter redefinitions,
the allocation method,
with or without costs,
with and without regionalization,
...

setup = CalculationSetup.of(system).withAmount(4.2).withImpactMethod(method)

result = SystemCalculator(db).calculate(setup)

for impact in result.getTotalImpacts():
    print(
        "%s: %.3f %s"
        % (impact.impact().name, impact.value(), impact.impact().referenceUnit)
    )

`LcaResult` object

The result of the calculation is a LcaResult object. It provides an interface for accessing impact factors, total flows, and contributions and many other objects in a structured way. The manual won't cover all the accessible methods of the LcaResult object. For more information, please refer to the class itself.

For the following examples, let's assume we have calculated the results of a product system under the Python variable result.

Specific setup options

Normalization and weighting set

The withNwSet method allows to specify a normalization and weighting set. The normalization and weighting set can be retrieved from the database by using the ImpactMethod object:

nw_sets = method.nwSets
nw_set = next(
    nw_sets for nw_sets in nw_sets if nw_sets.name == "EF v3.1 | Global Reference 2010"
)
setup.withNwSet(nw_set)

Parameter redefinitions

The parameters of a product system can be redefined using the withParameters method. For example, you can replace the value of a global input parameter with a new value:

g = db.getForName(Parameter, "g")
parameters = [ParameterRedef.of(g, 1.62)]
setup.withParameters(parameters)

Parameter redefinition set

You can select one of the product system parameter redefinition sets to use with the in the calculation setup:

assert "Scenario 1" in [p.name for p in system.parameterSets]
setup.withParameterSetName("Scenario 1")

Allocation method

The allocation method can be selected among the following options:

class AllocationMethod:
    USE_DEFAULT,
    CAUSAL,
    ECONOMIC,
    NONE,
    PHYSICAL,

The default allocation method is AllocationMethod.USE_DEFAULT. To use a different allocation method, you can use the withAllocationMethod method:

setup.withAllocationMethod(AllocationMethod.CAUSAL)

Other options

With or without costs

When running an LCC (Life Cycle Costing) calculation on a product system with costs, the costs can be included in the calculation with the withCosts method:

setup.withCosts(True)  # default is False

With or without regionalization

With openLCA you can perform regionalized impact assessment, accounting for specific conditions and characteristics of the location where the processes occur. To enable regionalization, you can use the withRegionalization method:

setup.withRegionalization(True)  # default is False

openLCA Jython Manual