虽然氢正在成为一种清洁的替代汽车燃料和储能介质，但在实施过程中仍存在许多挑战，例如氢气生产和部署的经济性、昂贵的储存材料、能源密集型压缩或液化工艺，以及有限的试验应用。另一方面，近一个世纪以来，合成氨的生产一直处于工业规模。氨是全球交易量最大的商品之一，也是仅次于硫酸的第二大合成化学品。作为一种能量载体，它通过将氢原子与大气中的氮结合，实现了化学形式的有效储氢。 虽然氨作为一种燃料仍处于起步阶段，但其独特的性能使其成为汽车工业脱碳的潜在可行候选。然而，缺乏针对汽车应用的法规和标准、技术成熟度，以及两种氢原料都依赖天然气来生成氨并促进氢和氮转化为液氨，这给使用场景增加了额外的不确定性。 关于在地面车辆中使用绿色氨燃料的未解决问题汇集了关于在地面车辆中使用氨的当前和未来前景的知识，包括这种新型清洁燃料的技术和监管挑战。

While hydrogen is emerging as a clean alternative automotive fuel and energy storage medium, there are still numerous challenges to implementation, such as the economy of hydrogen production and deployment, expensive storage materials, energy intensive compression or liquefaction processes, and limited trial applications. Synthetic ammonia production, on the other hand, has been available on an industrial scale for nearly a century. Ammonia is one of the most-traded commodities globally and the second most-produced synthetic chemical after sulfuric acid. As an energy carrier, it enables effective hydrogen storage in chemical form by binding hydrogen atoms to atmospheric nitrogen. While ammonia as a fuel is still in its infancy, its unique properties render it as a potentially viable candidate for decarbonizing the automotive industry. Yet, lack of regulation and standards for automotive applications, technology readiness, and reliance on natural gas for both hydrogen feedstocks to generate the ammonia and facilitate hydrogen and nitrogen conversion into liquid ammonia add extra uncertainty to use scenarios. Unsettled Issues Concerning the Use of Green Ammonia Fuel in Ground Vehicles brings together collected knowledge on current and future prospects for the application of ammonia in ground vehicles, including the technological and regulatory challenges for this new type of clean fuel.