Geopolymer-based concretes have been elaborated among others for their potential to lower the environmental impact of the construction sector. The rheology and workability of fresh geopolymers make them suitable for new applications such as 3D printing. In this paper, we aim to develop a potassium silicate-and metakaolin-based geopolymer mortar with sand and local earth additions suited for 3D printing and an environmental assessment framework for this material. The methodology aims at the optimization of both the granular skeleton and the geopolymer matrix for the development of a low-environmental-impact material suited for 3D printing. Using this approach, various metakaolin/earth geopolymer mortars are explored from a mechanical and environmental point of view. The environmental assessment of the lab-scale process shows an improvement for the climate change category but a degradation of other indicators, compared to Portland-cementbased concrete. Several promising options exist to further optimize the process and decrease its environmental impacts. This constitutes the main research perspective of this work.