Real-world examples of green coding achievements

Responsibility

Software engineers have many responsibilities, including > social and environmental concerns.
Green coding should be part of every software project.

Measured software

So far the environmental footprint of a software product is only known of a few:
Software applications with measured environmental footprint

Reduction of 59 t CO2 per month by removing a 20 kB JavaScript dependency

In January 2020 Danny van Kooten removed a 20 kB JavaScript dependency in Mailchimp for WordPress. He estimated that this removal saves an estimated 59,000 kg CO2 per month.

https://www.dannyvankooten.com/blog/2020/website-carbon-emissions/

Note on the calculation:
Danny used the factor 0.5 kWh/GB data transfer, sourced from the study @Pihkola.etal.2018.EvaluatingEnergyConsumption. 0.5 kWh/GB is the estimated average energy consumption of a 4G LTE network in Finland in 2016. As Danny himself admits in the blog post, it is "hard to come up with a good estimate that works globally". Nevertheless, it is important to note that kWh/GB is a bad metric in general.

Image optimization on a UK local authority website

By reducing their front page from 20 MB to 2.6 MB just by doing some quick image optimization, they estimated that it saved 1.2 tones of CO2 per year or the same as boiling water for 57,000 cups of tea.

https://open-innovations.org/blog/2021-05-28-council-website-emissions

Note on the calculation:
The estimation used websitecarbon.com in 2021.

Sunsetting PHP library Faker

François Zaninotto (marmelab) was sunsetting the PHP library fzaninotto/Faker in October 2020. One reason was, that he released Faker has probably emitted more than 11 Metric tons of CO2 over the years.

https://marmelab.com/blog/2020/10/21/sunsetting-faker.html

Image from Wikipedia was downloaded 78 Mio times per day by accident

The mysterious photo of a purple flower that receives 78 million hits each day - Rest of World

Switch of the keyboard on Android saves 18 %

It is possible to save nearly 18% of energy by replacing the most used keyboard in Android by the most efficient one.

Greenspecting Android virtual keyboards | Proceedings of the IEEE/ACM 7th International Conference on Mobile Software Engineering and Systems