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SCI-M: embodied carbon

Software systems cause emissions through the hardware that they operate on, both through the energy that the physical hardware consumes and the emissions associated with manufacturing the hardware. Embodied carbon refers to the carbon emitted during the manufacture and eventual disposal of a component. It is added to the operational carbon (carbon emitted when a component is used) to give an overall SCI score.

Read more on embodied carbon

Parameters

Plugin config

Not Needed

Inputs

  • device/emissions-embodied: the sum of Life Cycle Assessment (LCA) emissions for the component
  • device/expected-lifespan: the length of time, in seconds, between a component's manufacture and its disposal
  • resources-reserved: the number of resources reserved for use by the software
  • resources-total: the total number of resources available
  • duration: the amount of time covered by an observation, in this context it is used as the share of the total life span of the hardware reserved for use by an application, in seconds.

Note that if you have a plugin pipeline that adds vcpus-allocated and vcpus-total to each observation, such as the cloud-metadata plugin, those values will be used in preference to the given resources-reserved and resources-total fields.

Returns

  • carbon-embodied: the carbon emitted in manufacturing and disposing of a component, in gCO2eq

Calculation

To calculate the embodied carbon, m for a software application, use the equation:

m = te * ts * rs

Where:

  • device/emissions-embodied = Total embodied emissions; the sum of Life Cycle Assessment (LCA) emissions for the component.

  • timeShare = Time-share; the share of the total life span of the hardware reserved for use by an application.

    • timeShare is calculated as duration/'device/expected-lifespan', where:
      • duration = the length of time the hardware is reserved for use by the software.
      • device/expected-lifespan = Expected lifespan: the length of time, in seconds, between a component's manufacture and its disposal.

  • resourceShare = Resource-share; the share of the total available resources of the hardware reserved for use by an application.

    • resourceShare is calculated as resources-reserved/resources-total, where:
      • resources-reserved = Resources reserved; the number of resources reserved for use by the software.
      • resources-total = Total Resources; the total number of resources available.

Implementation

IF implements the plugin based on the logic described above. To run the plugin, you must first create an instance of SciM method. Then, you can call execute() to return m.

Usage

The following snippet demonstrates how to call the sci-m plugin from Typescript.

import {SciM} from '@grnsft/if-plugins';

const sciM = SciM();
const results = await sciM.execute([
  {
    'device/emissions-embodied': 200, // in gCO2e for total resource units
    duration: 60 * 60 * 24 * 30, // time reserved in seconds, can point to another field "duration"
    'device/expected-lifespan': 60 * 60 * 24 * 365 * 4, // lifespan in seconds (4 years)
    'resources-reserved': 1, // resource units reserved / used
    'resources-total': 1, // total resource units available
  },
]);

Example manifest

IF users will typically call the plugin as part of a pipeline defined in a manifest file. In this case, instantiating the plugin is handled by ie and does not have to be done explicitly by the user. The following is an example manifest that calls sci-m:

name: sci-m
description: simple demo invoking sci-m
tags:
initialize:
  outputs:
    - yaml
  plugins:
    sci-m:
      method: SciM
      path: '@grnsft/if-plugins'
tree:
  children:
    child:
      pipeline:
        - sci-m # duration & config -> embodied
      defaults:
        device/emissions-embodied: 1533.120 # gCO2eq
        device/expected-lifespan: 3 # 3 years in seconds
        resources-reserved: 1
        resources-total: 8
      inputs:
        - timestamp: 2023-07-06T00:00
          duration: 3600

You can run this example manifest by executing the following command from the project root:

npm i -g @grnsft/if
npm i -g @grnsft/if-plugins
ie --manifest ./examples/manifests/test/sci-m.yml --output ./examples/outputs/sci-m.yml

The results will be saved to a new yaml file in ./examples/outputs.