Comparative evaluation of biochar produced from laboratory waste media using different thermochemical methods and its potential in plant growth promoting properties

The disposal of laboratory waste, especially microbiology media, is a growing concern due to its potential environmental impact. In this study, the conversion of laboratory waste, specifically nutrient agar media, into biochar using three different pyrolysis methods: conventional tube pyrolysis, biomass gasification, and microwave-assisted pyrolysis has been explored. Microwave pyrolysis of biomass resulted in higher biochar yield (63.85%) than conventional pyrolysis (58.16%) and gasification (32.18%). The obtained biochar has been subjected to different analytical techniques to understand the comparative differences in characteristics. Conventional pyrolysis yields the most negative zeta potential (−27.5 mV), whereas biomass gasification results in −16.7 mV, and microwave-derived biochar produces −7.5 mV to −4.8 mV, indicating diverse colloidal stability, anionic character, and potential for tailored soil applications. In plant growth experiments, the application of conventionally pyrolyzed biochar demonstrated superior performance, with the highest germination percentage (84.62%) and significantly longer shoot lengths ( p < 0.001) revealing its potential environmental benefits. In summary, the research has broad implications, ranging from waste management and biochar production efficiency to potential applications in soil improvement and environmental remediation. Further, it contributes to the ongoing efforts to develop sustainable solutions for waste disposal and environmental conservation.