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The global warming is directly related to the increased greenhouse gas emissions from both natural and anthropogenic origins. There has been a drastic rise in the concentration of CO 2 and other greenhouse gases since the industrial revolution primarily due to the intensifying consumption of fossil fuels. With the need to reduce carbon emissions and mitigate global warming certain strategies relating to carbon capturing and sequestration are indispensable. This paper comprehensively describes several physicochemical, biological and geological routes for carbon capture and sequestration. The trend of the increase in greenhouse gases over the years is illustrated along with the global statistics for fossil fuels usage and biofuels production. The physicochemical carbon capturing technologies discussed include absorption, adsorption, membrane separation and cryogenic distillation. The algal and bacterial systems, dedicated energy crops and coalbed methanogenesis have been vividly explained as the biological routes for carbon sequestration. The geological carbon sequestering route centers on biochar application and oceanic carbon storage. A systematic survey has been made on the origin and impact of greenhouse gases along with the potential for sequestration based on some fast-track and long-term sequestration technologies. 100

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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 °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 °C. The transition of Ni 2+ 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 °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 Ni 2+ impregnated biomass enhanced not only H 2 yields but also improved overall gas yields contributing to the carbon gasification efficiency of both feedstocks.