Abstract
Global interest in alternative fuels as alternatives to traditional fossil fuels has increased due to strict pollution restrictions and the increasing need for sustainable energy systems. The main alternative fuels—ethanol, biodiesel, dimethyl ether (DME), hydrogen, and ammonia—are thoroughly reviewed and compared in this article, with particular attention paid to their production processes, physicochemical characteristics, engine performance and durability, emission characteristics, infrastructure needs, economic viability, and policy frameworks. Due to their compatibility with current internal combustion engines, established feedstock availability, and relatively mature production technologies, biofuels like ethanol, biodiesel, and DME are recognized as near-term transition fuels. Depending on the feedstock and conversion method, these fuels can reduce greenhouse gas emissions over the course of their lifecycle by 20–70 %. As long-term energy sources with almost negligible carbon combustion potential and suitable for heavy-duty and high-power applications, hydrogen and ammonia are investigated. These fuels have a high gravimetric energy content, but they are hindered by poor volumetric energy density, high production and storage costs, safety concerns, and inadequate infrastructure for recharging. The review emphasizes how regional resource availability, engine technology readiness, and policy support mechanisms have a significant impact on fuel adoption outcomes. No single alternative fuel offers a complete solution, according to a systems-level synthesis; instead, hybrid energy pathways that combine biofuels with power-to-fuel technologies, renewable electricity, and bio-hydrogen coupling can increase overall energy efficiency by 15–30 % while boosting economic viability. In order to overcome market barriers, policy research emphasizes the significance of long-term regulatory stability, carbon price, blending regulations, and targeted financial incentives. In order to help researchers, industry stakeholders, and policymakers achieve a resilient and low-carbon energy transition, the article concludes with a phased deployment roadmap that aligns short-term biofuel utilization with long-term hydrogen and ammonia integration.