Greenhouse gas emissions, primarily from fossil fuels and other human activities, have been driving the worsening climate crisis. Prompt action is imperative to transition away from carbon-intensive energy sources and adopt sustainable energy alternatives to mitigate the impact of climate change. This chapter explores the classification of fossil-based power generation technologies, including coal, natural gas, and oil, and discusses their characteristics, including environmental impacts. It also examines two decarbonization strategies, emphasizing the replacement of power generation technology and the importance of alternative energy sources using biomass and hydrogen-based fuels. Hydrogen's potential as a clean and versatile energy carrier offers a promising candidate for reducing emissions from existing power generation facilities. However, hydrogen storage and transportation challenges have also sparked interest in using ammonia as an efficient hydrogen carrier. During utilization, ammonia can be decomposed to release hydrogen or directly burned, replacing solid fuels such as coal or gaseous fuels such as natural gas. This combination makes alternative fuels such as biomass, hydrogen, and ammonia versatile for application in existing power generation technologies typically used for fossil-based fuels.