Ammonia is inevitable for modern human lives as an artificial nitrogen fertilizer and is the second most common chemical produced worldwide. Ammonia production is more than 182 million tonnes in 2019 and is expected to increase by 4% during the next four years. The ammonia synthesis occupies 1-2% of the whole energy consumption of human beings, indicating the enormous energy-consuming process. Currently, hydrogen and energy sources for industrial ammonia production are fossil fuels. Thus, for a sustainable society in the future, "green ammonia" should be synthesized from the hydrogen gas prepared by water electrolysis based on renewable energy. Furthermore, ammonia is promising as a renewable energy carrier because it readily becomes a liquid state under less than 10 bar at room temperature, and liquid ammonia has a high energy density in weight and volume. Ammonia-fueled power generation technology is being established. The smaller volume results in less space in the fuel tank, and the smaller weight requires less energy to transport fuels together. Furthermore, product of ammonia after usage is nitrogen gas, which can be emitted into the air without pollution. And also, nitrogen gas can be obtained everywhere from the air. It means, after the utilization of ammonia, no need to recover and send back nitrogen gas to the location that generates hydrogen from renewable energy, which omits the cost and energy for recovery and transportation. Moreover, a product of ammonia after usage is nitrogen gas, which can be emitted into the air without pollution. And also, nitrogen gas can be obtained everywhere from the air. It means, after utilizing ammonia, no need to recover and send back nitrogen gas to the location that generates hydrogen from renewable energy, which omits the cost and energy for recovery and transportation. Therefore, liquid ammonia is suitable as a portable fuel and is beneficial to compensate for the power in the transport sector, accounting for roughly 30% of the world's energy consumption. The market size of ammonia has an enormous potential to expand in the near future. Ammonia is produced through the following exothermic reaction: N2 + 3H2 → 2NH3 ΔH = -92 kJ/mol. Therefore, the lower temperature and higher pressure are favorable in equilibrium. However, the temperature must be elevated to accelerate the reaction at extremely high pressure: 350-525 °C and 100-300 bar. Then, the equipment, including reactors and compressors, is much more expensive to endure the severe condition. These costs are usually reduced by the economy of scale, and thus the ammonia production plant has been generally large, e.g., 1000 tonnes/day. The business model of centralized production and distribution to local areas has been successful for a long time. However, poor infrastructure for transport, such as feeders roads linking main cities to other regions of Zambia, Tanzania, Ghana, and Nigeria, increases the transaction cost, and farmers in these areas cannot obtain ammonia at an affordable price. It results in low efficiency of food production and increases hunger.