The main purpose of the article is to present a comprehensive and critical review of the challenges and risks associated with the use of green ammonia as an alternative fuel in land transport. The review is motivated by the clear trend toward phasing out fossil fuel vehicles and replacing them with emission-free alternatives. Topics covered include safety aspects such as safety of powering of vehicles, the production of green ammonia, the use of ammonia in the context of various fuel solutions (combustion engines and fuel cell engines), and the discussion of ammonia-powered vehicles in the context of air pollution. The paper offers new insights into identifying the challenges and obstacles that may arise in the case of the massive use of green ammonia as a fuel for land transport. In addition, the review presents the latest information on the technological readiness of the necessary infrastructure for the production, transport, storage, and utilization of green ammonia in internal combustion or electric engines.

Liquefied natural gas (LNG) is one of the most influential fuels of the 21st century, especially in terms of the global economy. The demand for LNG is forecasted to reach 400 million tonnes by 2020, increasing up to 500 million tonnes in 2030. Due to its high mass and volumetric energy density, LNG is the perfect fuel for long-distance transport, as well as for use in mobile applications. It is also characterized by low levels of emissions, which is why it has been officially approved for use as a marine fuel in Emission Control Areas (ECAs) where stricter controls have been established to minimize the airborne emissions produced by ships. LNG is also an emerging fuel in heavy road and rail transport. As a cryogenic fuel that is characterized by a boiling temperature of about 120 K (−153 °C), LNG requires the special construction of cryogenic mobile installations to fulfill conflicting requirements, such as a robust mechanical construction and a low number of heat leaks to colder parts of the system under high safety standards. This paper provides a profound review of LNG applications in waterborne and land transport. Exemplary constructions of LNG engine supply systems are presented and discussed from the mechanical and thermodynamic points of view. Physical exergy recovery during LNG regasification is analyzed, and different methods of the process are both analytically and experimentally compared. The issues that surround two-phase flows and phase change processes in LNG regasification and recondensation are addressed, and technical solutions for boil-off gas recondensation are proposed. The paper also looks at the problems surrounding LNG installation data acquisition and control systems, concluding with a discussion of the impact of LNG technologies on future trends in low-emission transport.

Natural gas is the primary source of energy, accounting for around 20% of the world’s energy production. It is also a key element in reducing CO₂ emissions due to its key role in stabilizing renewable energy sources. At the same time, natural gas as a fossil fuel that emits CO₂ should be limited. A natural candidate that can ensure the stabilization of RES and at the same time reduce the demand for fossil fuels is biogas. Successful use of biogas requires a thorough understanding of the potential, structure, and specifics of its sources and production technology. The presented study provides a perspective and a brief overview of the existing potential of biogas production. Poland was chosen as the case study and it was shown that almost 90% of the Polish biogas potential comes from sources with a capacity below 100 Nm³/h, which is the current minimum commercially available capacity of the biogas purification and liquefaction technologies. Consequently, full utilization of these sources would require a downsizing of these technologies.

The liquid natural gas (LNG) boiling process concerns most LNG applications due to a need for regasification. Depending on the pressure, the equilibrium temperature of LNG is 112–160 K. The low boiling temperature of LNG makes the vaporization process challenging because of a large temperature difference between the heating medium and LNG. A significant risk included in the regasification process is related to the possibility of solid phase formation (freezing of the heating fluid). A solid phase formation can lead to an increase in pressure loss, deterioration in heat transfer, or even to the destruction of the heat exchanger. This prompts the need for a better understanding of the heat transfer during the regasification process to help avoid a solid phase formation. The present research is focused on the investigation of the mutual interactions between several parameters, which play a significant role in the regasification process. The research is based on a zero-dimensional (0D) model, which was validated through the comparison with a state-of-the-art Computational Fluid Dynamics (CFD) model. This made fast calculations and the study of the risk of freezing for a wide range of parameter space possible, including the LNG boiling regime. The boiling regime of LNG was shown to be a key factor in determining the risk of freezing.