Nanocatalysts and their integration into biomass have gained importance over the past few years. This research gave insights on impregnation of Ni salts in bagasse and mosambi peels with the variation of pH at 30 degrees C for 48 h. The highest loading was attained at pH 6.5 for bagasse and 5.2 for mosambi peels. The impregnated metal biomass samples were subjected to in situ hydrothermal gasification over the temperature range 300-500 degrees C. The transition of Ni2+ to metal nickel nanoparticles during in situ hydrothermal treatment was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. Maximum yields of H-2, 13.82 mmol/g of bagasse and 9.52 mmol/g of mosambi peel, were attained at the operated temperature of 500 degrees C and 1:8 biomass to water ratio with carbon gasification efficiency approaching 73.7 and 60.6% for bagasse and mosambi peels, respectively. The performance of hydrothermal gasification of impregnated biomass was compared with Raney Ni and washed samples at the above operated supercritical temperature and biomass to water ratio. The results conveyed that in situ gasification of Ni2+ impregnated biomass enhanced not only H-2 yields but also improved overall gas yields contributing to the carbon gasification efficiency of both feedstocks.