The global energy system needs to undergo a profound transformation, from a system based on fossil fuels, to an efficient and renewable low-carbon system. Given the importance of this transition towards more sustainable models, hydrogen presents itself as a renewable energy source with high capacity to enable this green future. Therefore, the importance of developing studies that contribute to the analysis and optimization of production processes and ways of using this source of energy is evident. Thus, this work consists of an exploratory bibliographic review about the fundamental points related to the production and use of hydrogen and its position in the current energy market. This study focused on the evaluation of gray, brown, blue and green hydrogen. During the literature review, emissions data in kgCO2eq were collected from life cycle assessments with similar and comparable assessment perimeters. At the end of the study, simulations of the relative reduction of greenhouse gases emissions are carried out in the scenarios of electricity production and road transport, when hydrogen from different routes is used as a substitute for fossil fuels. For the national electricity generation scenario, where 15% of the matrix is still produced from natural gas and coal, the simulation results indicated reductions of up to 40% in the carbon footprint of the Sistema Interligado Nacional, replacing both with blue hydrogen. For the scenario of road transport, greater potential gains were found to be made possible through green hydrogen. Internal combustion engine (ICE) with mix of natural gas + green hydrogen and diesel + green hydrogen, up to approximately 34% and 31% were found, respectively, and proton exchange membrane fuel cell (PEMFC) with green hydrogen, reductions of up to 70% were found in comparison with natural gas. But due to the green hydrogen economic competitiveness difficulties, the blue hydrogen reduction results of both scenarios generate optimism for its use as a means of boosting the hydrogen economy and already acting now in the decarbonization of these sectors. Cases using ICE with mix of diesel + blue hydrogen and ICE with mix of natural gas and blue hydrogen from natural gas showed emission reductions of up to 18% and 23% respectively. With PEMFC cars with blue hydrogen from natural gas, reductions reached up to 48% when replacing diesel.