High resolution optical spectroscopy in the mid-infrared (mid-IR) spectral range (3-12 µm wavelength) is an unambiguous way to detect and quantify small traces of greenhouse and toxic gases down to sensitivities of parts-per-billion. Such sensitivities are a prerequisite to safeguard low-pollution and toxic-free environment defined by the EU Action Plan: ""Towards a Zero Pollution for Air, Water and Soil.” However, size, cost, and general complexity of the commercially available instruments limits their use to a small number of highly specialized applications, and prevents their deployment with sufficient coverage e.g. in networks, wearable electronics, etc. Particularly in the context of Internet of Things (IoT) devices, on chip integration of spectroscopic systems would constitute a game changer for mid-IR high-precision and portable sensors. The objective of UNISON is to address this challenge and demonstrate a highly scalable platform for infra-red spectroscopy that has both high-end performance and is compact. UNISON sensing scheme relies on dual comb spectrometers obtained by leveraging on electrically pumped cascade lasers (QCL and ICL) and on silicon-germanium (SiGe) mid-IR photonic circuits to surpass current spectroscopic systems in terms of detection bandwidth, point spacing and system compactness. UNISON is organized around 3 main cornerstones each of them relying on ambitious physical and technological challenges: (i) tunable large bandwidth frequency combs will be generated on SiGe photonics circuits by combining electro-optical comb generation, non-linear effects and dispersion engineering ; (ii) the comb sources will be pumped by novel electrically-driven cascade laser sources integrated with the SiGe photonics circuits ; (iii) compact, broadband, and sensitive interaction region for trace gas detection, designed and optimized for the SiGe platform, will be integrated with the dual comb source to showcase the sensing capability of the spectrometer.