Environmental Impact of CI/CD Pipelines

TL;DR

This study addresses the environmental impact of CI/CD pipelines by quantifying the carbon and water footprints ($CWF$) of GitHub Actions in 2024. It adopts a Cloud Carbon Footprint–based methodology, combining operational and embodied emissions with region-specific energy-intensity data and a large-scale dataset of over $2.2$ million workflow runs from more than $18{,}000$ repositories. The authors estimate the number of active public repositories using GitHub Actions ($R_{GA}$) and derive per-repository footprints under Baseline, High Usage, and Low Usage scenarios, reporting a most likely carbon footprint of $\$456.9\,\text{MTCO2e}$ and a water footprint of $5{,}738.2\,\text{kiloliters}$ for 2024, with regional variation. They further propose mitigation strategies—region-aware runner placement, scheduling alignment with low-carbon periods, disclosure of footprints, and reducing repository sizes—that can materially reduce environmental impact while informing providers and developers. The work highlights the significant share of emissions from network transfers and scheduled runs, and underscores the potential benefits of transparency and policy adjustments to promote greener CI/CD practices.

Abstract

CI/CD pipelines are widely used in software development, yet their environmental impact, particularly carbon and water footprints (CWF), remains largely unknown to developers, as CI service providers typically do not disclose such information. With the growing environmental impact of cloud computing, understanding the CWF of CI/CD services has become increasingly important. This work investigates the CWF of using GitHub Actions, focusing on open-source repositories where usage is free and unlimited for standard runners. We build upon a methodology from the Cloud Carbon Footprint framework and we use the largest dataset of workflow runs reported in the literature to date, comprising over 2.2 million workflow runs from more than 18,000 repositories. Our analysis reveals that the GitHub Actions ecosystem results in a substantial CWF. Our estimates for the carbon footprint in 2024 range from 150.5 MTCO2e in the most optimistic scenario to 994.9 MTCO2e in the most pessimistic scenario, while the water footprint ranges from 1,989.6 to 37,664.5 kiloliters. The most likely scenario estimates are 456.9 MTCO2e for carbon footprint and 5,738.2 kiloliters for water footprint. To provide perspective, the carbon footprint in the most likely scenario is equivalent to the carbon captured by 7,615 urban trees in a year, and the water footprint is comparable to the water consumed by an average American family over 5,053 years. We explore strategies to mitigate this impact, primarily by reducing wasted computational resources. Key recommendations include deploying runners in regions whose energy production has a low environmental impact such as France and the United Kingdom, implementing stricter deactivation policies for scheduled runs and aligning their execution with periods when the regional energy mix is more environmentally favorable, and reducing the size of repositories.

Figures (9)

• Figure 1: Comparison between the yearly carbon emissions of the GitHub Actions ecosystem and the emissions of quotidian activities EPA-2024baumeister2017eachRousseau_2022.
• Figure 2: Comparison between the yearly water waste of the GitHub Actions ecosystem and the water usage of quotidian activities EPA-2025aEPA-2025b.
• Figure 3: Simplified version of the workflow defined to test Flacoco, a fault localization tool for Java.
• Figure 4: Overview of the methodology to calculate the carbon and water footprints of the GitHub Actions Ecosystem.
• Figure 5: Distribution of stars for repositories in our 2024 GitHub Actions sample. The y-axis uses a logarithmic scale, while the x-axis combines a linear scale up to 1 and a logarithmic scale beyond that point.