The conversion of hazardous bio-resources into valuable carbon materials is instrumental in sustainable material manufacturing and green electronics. The present work discourses the transformation of an invasive alien plant species (IAPS), Prosopis juliflora leaves, into a valuable biomass carbon. The characteristics and implications of Prosopis juliflora biomass carbon (PJBMC) are studied in detail. Further, biomass carbon nanocomposites are prepared by decorating SnO2 nanoparticles on the PJBMC, and it is evaluated for hazardous NO2 gas sensing applications. The PJBMC/SnO2 nanocomposite is assessed against varying concentrations of NO2 gas and shows a maximum sensitivity of 31.0 ± 0.9% for 90 ppm of the target gas. The uniform distribution of SnO2 nanoparticles on the biomass carbon support enabled the adsorption/desorption of target gas on the surface of the nanocomposite. The gas sensing mechanism of biomass nanocomposite material is discussed in detail, and a real-time NO2 gas leak detector with a warning LED system is demonstrated. In summary, this work reinforces sustainable growth by reporting the conversion and usage of IAPS Prosopis juliflora as one of the potential carbon materials in sensing applications. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.