By capturing waste heat in manufacturing or heating processes, thermoelectric generators (TEGs) can directly convert temperature gradients into electricity, enabling green energy harvesting. Nevertheless, rare and toxic raw minerals (e.g. tellurium) are generally used in TEGs production. These critical raw materials can be potentially substituted by secondary raw materials, as in the case of waste sulphides of the tetrahedrite series ((Cu,Fe)12Sb4S13). The EU-funded START project aims at using tetrahedrite, extracted from deactivated mine dumps in Europe, to develop innovative components of TEGs. In this paper, we present the preliminary results of the life cycle assessment (LCA) of these tetrahedrite-based TEGs, with the aim of understanding their environmental sustainability. Data associated to raw material extraction, mineral processing and TEGs production and assembly were considered. Materials use (e.g. tetrahedrite, reagents, TEG components, etc.) and energy consumption (in the mining, production or assembly phases) were adopted as input of the model. Results showed that the adoption of tetrahedrite-based TEGs can reduce wastes and air emissions, when compared to commercially used TEGs (e.g. tellurium-based devices). It is worth noting that mineral concentration and preparation (e.g. magnetic separation, drying), as well as leg production (e.g. powder technology, solidification, layer deposition, etc.) are necessary to obtain high-purity tetrahedrite, efficient legs and suitable TEGs, significantly increasing energy consumption. Ongoing developments on the START TEGs will allow a further optimization of the LCA model. Additional data on the use, repair and maintenance, and end-of-life (disposal or recycling) of the devices can also implement the eco-design of the devices.