Emerging Trends in Alternative Energy Sources: A Review of Hydrogen, Bioelectrochemical Systems, and Advanced Biofuels

The increasing demand for sustainable energy and the urgent need to reduce greenhouse gas emissions have intensified global efforts to develop renewable alternatives to fossil fuels. Hydrogen, bioelectrochemical systems (BES), and advanced biofuels have emerged as promising technologies capable of supporting the transition toward a low-carbon and energy-secure future. This review critically examines recent developments in these alternative energy sources, highlighting their production technologies, environmental benefits, technical limitations, and prospects. Hydrogen is recognized as a clean energy carrier with high energy density and broad applications in transportation, power generation, and industrial processes. However, challenges related to cost-effective production, storage, transportation, and infrastructure development continue to limit its widespread adoption. Bioelectrochemical systems represent an innovative approach for simultaneous renewable energy generation and wastewater treatment, offering environmental and economic advantages. Nevertheless, their commercialization is constrained by low power output, limited scalability, and the high cost of electrode materials. Advanced biofuels, produced from lignocellulosic biomass, algae, and other non-food feedstocks, provide a practical solution for reducing greenhouse gas emissions while remaining compatible with existing fuel infrastructure. Despite these advantages, feedstock availability, conversion efficiency, and production costs remain significant challenges. Comparative analysis indicates that hydrogen is most suitable for long-term energy storage and industrial decarbonization; BES is particularly effective for decentralized waste-to-energy applications, and advanced biofuels provide an immediate pathway for decarbonizing the transportation sector. Overall, these technologies should be viewed as complementary rather than competing solutions. Continued research, technological innovation, supportive policy frameworks, and strategic investments are essential to overcome existing barriers and accelerate the deployment of sustainable energy systems capable of meeting future global energy demands while mitigating climate change.