The bioenergy production and their by-products valorization is a valuable strategy to the sustainability enhanced targets. The present work integrates valorization of thermochemical conversion of residual biomass rice husk and corn cob, focusing on biogenic oxide production from biochar. The bioenergy analysis and biochar properties allowed to establish a specific energy potential SEP up to 7.47 kWhe-kgOxi-1 and preliminary gas emission factor GHG down to 0.562 KgCO2eq kgOxid-1 for the production of biochar oxide's. A comparative study of the biogenic nanoporous recovery from biochar was done; four biochar samples come from different thermochemical conversions of rice husk, and corncob were treated by hydrochloric acid concentration between 0 to 10% w/w and subsequently oxidized at a temperature between 350-750°C. The biochar and biochar oxides' physicochemical characteristics were realized employing ultimate analysis, specific surface ABET, NLDFT pore size distribution, XRF, and SEM micrograph analysis with EDS. The biochar treatment allowed 55.5% and 41.2% of raw biogenic nanostructure recovery with a specific surface area up to 132 m2 g-1 and 25 m2 g-1 from the rice husk and corncob biochar, respectively. The biochar oxidation temperature was the most relevant factor for controlling oxides' nanoporosity from biochar, reducing mesopores volume in both cases. However, the hydrochloric acid concentration in leaching favors residual carbon removal and ensures nanostructure preservation of biogenic nanopores.