The goal of our study is to assess the environmental impact of the installation and use of the Giant Radio Array for Neutrino Detection (GRAND) prototype detection units, based on the life cycle assessment (LCA) methodology, and to propose recommendations that contribute to reduce the environmental impacts of the project at later stages. The functional unit, namely the quantified description of the studied system and of the performance requirements it fulfils, is to detect radio signals autonomously during 20 years, with 300 detection units deployed over 200 km${}^2$ in the Gansu province in China (corresponding to the prototype GRANDProto300). We consider four main phases: the extraction of the materials and the production of the detection units (upstream phases), the use and the end-of-life phases (downstream phases), with transportation between each step. An inventory analysis is performed for the seven components of each detection unit, based on transparent assumptions. Most of the inventory data are taken from the Idemat2021 database (Industrial Design & Engineering Materials). Our results show that the components with the highest environmental impact are the antenna structure and the battery. The most pregnant indicators are ‘resource use’, mineral and metals’; ‘resource use, fossils’; ‘ionizing radiation, human health’; ‘climate change’; and ‘acidification’. Therefore, the actions that we recommend in the first place aim at reducing the impact of these components. They include limiting the mass of the raw material used in the antenna, changing the alloy of the antenna, considering another type of battery with an extended useful life, and the use of recycled materials for construction. As a pioneering study applying the LCA methodology to a large-scale physics experiment, this work can serve as a basis for future assessments by other collaborations.