Calculating recipe environmental impact

The calculation of the environmental impact of a recipe is done by RecipeImpactCalculator or its wrapper impact_from_recipe(). It is calculated by doing a sum of the ingredients masses weighted by their environmental impact. For more information about how the environmental impact of ingredients is collected, see Characterizing ingredients.

Ingredients impacts definition

The first step of recipe environmental impact calculation is to define the impact of the ingredients composing the recipe.

Example of ingredient description in ingredients_data.json

 {
   "en:foo": {
     "id": "en:foo",
     "environmental_impact_data_sources": [
       {
         "database": "agribalyse",
         "entry": "Foo, production process A"
       },
       {
         "database": "agribalyse",
         "entry": "Foo, production process B"
       }
     ],
     "impacts": {
       "Score unique EF": {
         "unit": "mPt",
         "amount": 1.46,
         "uncertainty_distributions": [
           {
             "distribution": "uniform",
             "minimum": 0.83,
             "maximum": 1.76
           },
           {
             "distribution": "normal",
             "mean": 1.62,
             "standard deviation": 0.257
           }
         ]
       }
     }
   }
 }

Without uncertainty

If RecipeImpactCalculator is instantiated with use_uncertainty=False (by default), the impact of the ingredients will be the one specified in the amount attribute of the environmental impact in ingredients_data.json.

With uncertainty

If RecipeImpactCalculator is instantiated with use_uncertainty=True, the ingredients impacts will be defined using one randomly chosen distribution among the uncertainty distributions specified in the uncertainty_distributions attribute of the environmental impact in ingredients_data.json. This allows to use the LCA data uncertainty and to link several possible LCA processes to one ingredient.

Warning

Multiple calls of impact_from_recipe() with use_uncertainty=True may result in different outputs.

Recipe impact and ingredient impact share

Once the ingredients impacts have been defined (with _define_ingredients_impacts() automatically called at initialization), the recipe environmental impact can be returned by get_recipe_impact(), as well as the ingredients shares of the recipe’s impact with get_ingredient_impact_share().