Scientific Software Developement: Lessons from our Emission inventory processing software emiproc

Scientific software often begins as an internal research tool developed by scientists rather than trained software engineers, resulting in limited usability, documentation, and maintainability. emiproc, a tool for processing emission inventories for atmospheric chemistry and transport models, originally followed this trajectory: it grew organically within our laboratory, offered only a command-line interface, and lacked a clear structure, extensibility, and user-oriented documentation. We recently undertook a full modernization of emiproc following the best practices in scientific software development: redesign of the code base into modular components, consistent object oriented Python API, automated testing with continuous integration, extensive documentation for both users and developers and publication in the Journal of Open Source Software. The updated software now supports some of the most widely used emission inventories such as EDGAR and CAMS, and more specific ones like the City of Zurich inventory, and produces output for various transport models like ICON-ART, WRF, or GRAL. We will highlight our approaches for transforming emiproc into a sustainable and user-friendly tool and reflect on the challenges we encountered along the way. By sharing our experience, we aim both to contribute to the discussion on improving scientific software development and to learn from the approaches used by others.