The GRAND collaboration is concerned about its environmental impact. Following several discussions about this subject in collaboration meetings, and a “GRAND Carbon Committee” was set up. As the experiment is in its prototyping stage, the time is ripe to take decisions according to environmental criteria. A first step towards taking such measures was to estimate the carbon footprint of the experiment, and assess the major sources of emission. A pioneering study of the global carbon footprint assessment of the GRAND experiment was conducted by Clarisse Aujoux (Institut d’Astrophysique de Paris, ENSTA), Kumiko Kotera (Institut d’Astrophysique de Paris), and Odile Blanchard (Université Grenoble Alpes). A preprint of the paper can be found here: arXiv.
The specificity of the methodology presented in our paper is that it is fully transparent and uses open source data. Hence, the method is replicable to any other scientific consortium. The study focuses on the GHG emissions related to three sources: travel, digital technologies and hardware equipment. Interestingly, it was found that these emission sources have a different impact depending on the stages of the experiment. Digital technologies and travel prevail for the small-scale prototyping phase (GRANDProto300), whereas hardware equipment (material production and transportation) and data transfer/storage largely outweigh the other emission sources in the large-scale phase (GRAND200k). In the mid-scale phase (GRAND10k), the three sources contribute equally.
The study has initiated numerous discussions within the collaboration. Various types of actions may be implemented to mitigate the carbon footprint of GRAND, at all stages of the project deployment.
- Travel emissions may be reduced by encouraging local collaborators to perform the on-site missions or by having international collaborators stay longer on the site of the experiment rather than doing multiple trips, each lasting a few days ; they may also be reduced by optimizing collaboration meetings, through optimizing the location of the meetings, limiting the number of attendees from the collaboration, opting for some virtual meetings, and combining virtual and physical meetings.
- Options to reduce digital emissions include the reduction in the volume of data to be archived. The collaboration is already developing data reduction strategies to reduce the carbon footprint of data transfer and storage by 4 or 5 orders of magnitude. It was also found that shipping regularly the archival data by air mail would be largely less emitting than transferring the data via the internet. As for the emissions from simulations and data analysis, the challenge is to reduce the millions of CPU hours projected to be spent yearly. Incentives to weigh the cost/benefit of the simulation runs may contribute to lower the carbon footprint in the years to come.
- Mitigating the emissions from manufacturing and hauling the hardware equipment will be a top priority for the design of the GRAND200k phase, as these emissions are projected to weigh most in the carbon footprint of GRAND200k phase. It is about optimizing the environmental cost of the materials used for the antennas, the solar panels and the batteries, establishing a recycling plan, and monitoring the transportation from the production sites to the array-sites.
The GRAND collaboration will take several actions in response to this study. The various action plans proposed for each emission source will be documented in a GRAND Green Policy, which each collaboration member will be encouraged to follow, in order to reduce the collective carbon footprint.