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4 | 4 | > Please help us improve the wiki by reading our |
5 | 5 | > [contributing guidelines](https://github.com/LCA-ActivityBrowser/activity-browser/blob/main/CONTRIBUTING.md#wiki). |
6 | 6 |
|
7 | | -# Overview |
| 7 | +## Overview |
8 | 8 |
|
9 | | -# Contribution Analysis |
| 9 | +### Inventory |
10 | 10 |
|
11 | | -# Sankey |
| 11 | +### LCA overview results |
12 | 12 |
|
13 | | -# Scenarios |
| 13 | +### Score matrix |
| 14 | + |
| 15 | +## Contribution Analysis |
| 16 | +### Differences between approaches |
| 17 | +Activity Browser has two contribution analysis approaches available to assess results, |
| 18 | +`Elementary Flow (EF) Contributions` and `Process contributions`. |
| 19 | + |
| 20 | +Before we discuss the different approaches, we introduce a small example for the production of _'steel'_: |
| 21 | + |
| 22 | + |
| 23 | + |
| 24 | +The amounts we use are: |
| 25 | + |
| 26 | +| activity | product | technosphere exchanges | biosphere exchanges | |
| 27 | +|------------------------|--------------------|---------------------------------|--------------------------| |
| 28 | +| coal production | 10 kg coal | | 0.02 kg CH<sub>4</sub> | |
| 29 | +| electricity production | 10 kWh electricity | 10 kg coal | 10.808 kg CO<sub>2</sub> | |
| 30 | +| steel production | 10 kg steel | 5 kWh electricity<br/>5 kg coal | 10 kg CO<sub>2</sub> | |
| 31 | + |
| 32 | +<sub> |
| 33 | +<b>Note:</b> These numbers are used for ease of understanding, not for realism. |
| 34 | +</sub> |
| 35 | + |
| 36 | +To produce 1 kg of steel, we get a climate change impact of 1.6 kg CO2 eq with the _'IPCC 2021'_ impact category. |
| 37 | +In the way Brightway (and thus Activity Browser) calculate results, a _contribution matrix_ is calculated with |
| 38 | +all impacts _from_ all EFs and all activities. |
| 39 | +For the system and functional unit above, this would be: |
| 40 | + |
| 41 | +| | coal prod. | elec. prod. | steel prod. | |
| 42 | +|-----------------------|------------|-------------|-------------| |
| 43 | +| <b>CO<sub>2</sub></b> | - | 0.5404... | 1 | |
| 44 | +| <b>CH<sub>4</sub></b> | 0.0596... | - | - | |
| 45 | + |
| 46 | +The _contribution matrix_ show the dis-aggregated results for each individual biosphere flow for each activity. |
| 47 | + |
| 48 | +#### EF contributions |
| 49 | +If we take sum the _rows_ to one row, we get the EF contributions |
| 50 | +(the contribution of all CO<sub>2</sub> and CH<sub>4</sub> impacts together). |
| 51 | +In the case above, the EF contributions are: |
| 52 | +- CO<sub>2</sub>: 1.5404... (96.3%) |
| 53 | +- CH<sub>4</sub>: 0.0596... (3.7%) |
| 54 | + |
| 55 | +#### Process contributions |
| 56 | +If we take the sum of the _columns_ to one column, we get the process contributions |
| 57 | +(the contribution of all coal, electricity and steel production impacts together). |
| 58 | +In the case above, the process contributions are: |
| 59 | +- coal production: 0.0596... (3.7%) |
| 60 | +- electricity production: 0.5404... (62.5%) |
| 61 | +- steel production: 1 (33.8%) |
| 62 | + |
| 63 | +To summarize, the difference between EF and process contributions is the direction the contribution matrix is summed. |
| 64 | + |
| 65 | +### Manipulating results |
| 66 | +In this section we generalize a little bit for the different contribution approaches, |
| 67 | +we call the _from_ part of the contributions (the EFs or activities above) _entities_. |
| 68 | + |
| 69 | +There are several ways Activity Browser manipulates your results by default. |
| 70 | +- The results are **sorted** so that the largest (absolute) values are shown first |
| 71 | +- A `cut-off` of 5% is applied to group all entities with an impact below that value. |
| 72 | +- The contributions are _normalized_ to the impact of that reference flow, meaning they are show as a percentage, |
| 73 | + counting up to 100% |
| 74 | + |
| 75 | +These actions are taken to show you the most relevant results. |
| 76 | + |
| 77 | +You can manually manipulate the contribution results in the next menu, which we explain bit by bit below. |
| 78 | + |
| 79 | + |
| 80 | +#### Cut-off |
| 81 | +You can manually change the `cut-off` of the results in two ways, `Relative` or `Top #`. |
| 82 | +The `Relative` option shows contributions _from_ entities of _x_% or higher. |
| 83 | +The `Top #` options shows contributions from the _x_ entities that contribute the most (as absolute). |
| 84 | + |
| 85 | +You can change the value of the cut-off in the menu shown below. |
| 86 | + |
| 87 | +#### Compare |
| 88 | +The `Compare` menu allows you to compare different dimensions of results. |
| 89 | +You can compare between: |
| 90 | +- _Reference flows_ |
| 91 | +- _Impact categories_ |
| 92 | +- _Scenarios_ (only available in scenario LCA, see [scenarios](#scenarios)) |
| 93 | + |
| 94 | +The compare mode defines what is shown in the figure. |
| 95 | + |
| 96 | +#### Aggregation |
| 97 | +The `Aggregate by` menu can be used to _group_ results based on field names. |
| 98 | +As an example, EF contributions can be grouped on the name, |
| 99 | +for example to group all flows with the same name. |
| 100 | +Another example for process contributions can be grouped based on their reference product name. |
| 101 | + |
| 102 | +#### Plot and Table |
| 103 | +By default, Activity Browser shows a plot and a table. |
| 104 | +You can disable one of them if you want to focus on one of them. |
| 105 | + |
| 106 | +#### Relative and Absolute |
| 107 | +Finally, you can choose between `Relative` and `Absolute` results. |
| 108 | +The `Relative` results will sum to 100%, the `Absolute` results will sum to the impact score. |
| 109 | + |
| 110 | +## Sankey |
| 111 | +The `Sankey` tab shows results from [graph traversal](https://docs.brightway.dev/projects/graphtools/en/latest/index.html). |
| 112 | +Graph traversal calculates results step-by-step for _nodes_ (activites) in the _graph_ (supply chain/product system). |
| 113 | + |
| 114 | +### Sankey configuration |
| 115 | +In the `Sankey` tab, you can configure, you can set the |
| 116 | +Reference flow, Impact category and Scenario (only available in scenario LCA, see [scenarios](#scenarios)) to be shown. |
| 117 | +you can also set a `cutoff` and `calculation depth` setting. |
| 118 | + |
| 119 | +The `cutoff` setting will stop traversing the supply chain once the impact is below the percentage specified. |
| 120 | +The `calculation depth` will stop traversing the supply chain once that number of calculations have been performed. |
| 121 | + |
| 122 | +### Sankey results |
| 123 | +In the Sankey, the red arrows show the _cumulative_ impact of the _product_ flow |
| 124 | +(_direct_ from that process and _indirect_ from all upstream processes involved in producing that product), |
| 125 | +the boxes show the _direct_ (process contribution) impact of that process. |
| 126 | + |
| 127 | +Using the example above in the [contribution analysis](#contribution-analysis) section, we show the sankey below. |
| 128 | +The [process contribution](#process-contributions) results are also shown in the boxes below. |
| 129 | + |
| 130 | + |
| 131 | + |
| 132 | +## Other Results tabs |
| 133 | +The Monte Carlo and Senstivity Analysis tabs are explained on the [Uncertainty](Uncertainty) page. |
| 134 | + |
| 135 | +## Scenarios |
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